NASA Contractor Report 187114

/// -.CJ0

Study of Orifice FabricationTechnologies for theLiquid Droplet Radiator

David B. Wallace, Donald J. Hayes,and J. Michael Bush

MicroFab Technologies, Inc.Piano, Texas

May 1991

Prepared forLewis Research CenterUnder Contract NAS3-25275

National Aeronautics and

Space Administration

(NASA-CR-IB7]!G) STUDY OF ORIFICE

FABRICATIQN TECHNOLOGIES FOR THE LIQUID

DROPLET RADIATOR Final Report (Microfab

Technologies) 55 p CSCL 20D

G3/20

N91-22372

Unclas

0011697

https://ntrs.nasa.gov/search.jsp?R=19910013059 2020-01-10T20:38:25+00:00Z

Report Documentation PageNahonal Al_rOmJ_lhCS ano

Space Admmlstrahon

1. Report No. 2, Government Accession No. 3. Recipient's Catalog No.

NASA CR-187114

4, Title and Subtitle

Study of Orifice FabricationLiquid Droplet Radiator

Technologies for the

7. Author(s)

David B. WallaceDonald J. HayesJ. Michael Bush

9. Performing Organization Name and Address11.

MicroFab Technologies, Inc.1104 Summit Avenue, Suite II0

Piano, Texas 75074 13.

12. Sponsoring Agency Name and Address

National Aeronautics and Space AdministrationLewis Research Center

Cleveland, Ohio 44135

5. Report Date

May 1991

I 6. Performing Organization Code

8. Performing Organization Report No,

10, Work Unit NO.

506-41-51

Contr"ct or Grant No,

NAS3-25275

Type of Report and Period Covered

Contractor Report Final

14. Sponsoring Agency Code

15. Supplementa_ Notes

Project Manager, K. Alan White,NASA Lewis Research Center

Power Technology Division,

16. Abstract

Eleven orifice fabrication technologies potentially applicable for a liquid droplet radiator are discussed. Theevaluation is focused on technologies capable of yielding 25-150p.m diameter orifices with trajectoryaccuracies below 5 milliradians, ultimately in arrays of up to 4000 orifices. An initial analytical screeningconsidering factors such as trajectory accuracy, manufacturability, and hydrodynamics of orifice flow ispresented. Based on this screening, four technologies were selected for experimental evaluation. A jetstraightness system used to test 50oorifice arrays made by electro-discharge machining (EDM), Fotoceram,and mechanical drilling is discussed. Measurements on orifice diameter control and jet trajectory accuracyare presented and discussed. Trajectory standard deviations are in the 4.6-10.0 milliradian range.Electroforming and EDM appear to have the greatest potential for Liquid Droplet Radiator applications.Finally, the direction of a future development effort is discussed.

' 17. Key Words (Suggest_ by Author(s))

Orifice Fabrication;

Radiator; RadiatorLiquid Droplet

18. Distribution Statement

Unclassified - Unlimited

Subject Categories 20, 31

19. Security Classif, (of this report) 20. Security Class#. (of this page) 21. No of pages

Unclassified Unclassified 55

NASA FORM 1626 OCT 86 "For sale by the National Technical Information Service, Springfield, Virginia 22161

22, Price"

A04

Table of Contents

Table of Contents ...................................................... iii

1.0 Summary ....................................................... 1

2.0 Introduction ...................................................... 1

3.0 Phase I: Analytical Evaluation of Jet Straightness Effects, Pressure Drop Considera-tions, Fabrication Methods Survey, and Vendor Survey ...................... 33.1 Analytical Evaluation of Jet Straightness Effects ....................... 3

3.1.1 Structurally Induced Straightness Effects ....................... 33.1.2 Hydrodynamically Dependent Straightness Effects ................ 7

3.2 Pressure Drop Considerations ................................... 103.3 Fabrication Methods Evaluation .................................. 10

3.3.1 Electroform - Plating ................... . ................. 103.3.2 Chemical Milling ........................................ 123.3.3 Laser Drilling ............................. .............. 133.3.4 Electro-Discharge Machining ............................... 143.3.5 Mechanical Punching (or Broaching) ......................... 163.3.6 Mechanical Drilling ...................................... 173.3.7 Soluble Core Glass Fibers ................................. 183.3.8 Microchannel Plates ..................................... 193.3.9 Electron Beam Machining ................................. 203.3.10 Ion Milling ............................................ 213.3.11 Fotoceram ............................................ 23

3.4 Ranking of Fabrication Methods ................................. 243.5 Vendor Evaluation ........................................... 243.6 Recommendations ........................................... 25

4.0 Phase I1:Orifice Plate Design; Test System Design and Fabrication; and Orifice PlateExperimental Evaluation ............................................ 274.14.24.34.44.54.64.74.84.94.104.114.124.13

Orifice Plate Design .......................................... 27Orifice Plate Vendor Quotations and Orders ......................... 28Drop Generator Design ........................................ 28Orifice Plate Assembly Process .................................. 28Jet Straightness Test System ................................... 29Stork-Veto (Electroform) Orifice Plates ............................ 31Buckbee Mears (Electroform) Orifice Plates ......................... 33Coming (Fotoceram) Orifice .................................... 38Creare (EDM) orifice Plates .................................... 41Lee (Etched Sandwich) Orifice Plates ............................. 43Galileo (Multichannel) Orifice Plates .............................. 45NASA (Mechanically Drilled) Orifice Plates .......................... 45Summary of Orifice Plate Testing Result ........................... 47

5.0 Discussion and Conclusions ......................................... 49

6.0 Recommendations ................................................ 49

7.0 References ..................................................... 50

Appendix I: Vendor List ................................................ 51

iii

PRECEDING PAGE BLANK NOT FILMED

1.0 SummaryEleven (11) fabrication methods were identified, de-scribed, and evaluated for their suitability to fabricatethe large scale (105-106 holes per system) orifice arraysrequired for an operational Liquid Droplet Radiator(LDR). The methods were ranked based on past exper-ience with jet straightness, projected experience,manufacturability, pressure drop, hydrodynamic charac-teristics, and diameter control. When various finishingprocesses were factored into the evaluation, the resul-ting rankings were as follows:

I. Electroform2. Soluble Core Glass Fibers3. Fotoceram4. Microchannel Plates5. Punching

Chemical Milling7. Mechanical Drilling and Finishing8. Laser Drilling and Finishing

Mechanical Drilling10. Laser Drilling

EDM and Finishing12. EDM13. E-Beam Drilling

Based on the results of the evaluation, four (4) methods(and five vendors) were selected for experimentalevaluation. An orifice plate was designed and partswere purchased from the five vendors. During theevaluation of these orifice plates, two more vendors andfabrication methods were added to the experimentalstudy, bringing the totals to six (6) methods and seven(7) vendors.

A drop generator and jet straightness test system weredesigned and fabricated. All seven orifice plate typeswere evaluated for orifice diameter control and jetstraightness performance. Twenty-one (21) orificeplates were measured for orifice diameter control,nineteen (19) were qualitatively evaluated for jetstraightness performance, and eleven (11) were quan-titatively evaluated for jet straightness performance.Best overall results were obtained with the Stork-Vecoelectroform orifice plates. The Creare EDM and NASAmechanically drilled results were almost as good as theStork-Veco results. Recommendations are made for

further development efforts and specific Phase Iii tasksare described.

2.0 Introduction

Before the Liquid Droplet Radiator (LDR) can bedemonstrated, a successful method of orifice arrayfabrication must be developed. Liquid Droplet Radiatorsare expected to have a very large number of individualstreams in their final configuration. Straightness of thestreams is very critical and even a few misdirected jetscan result in serious fluid loss. The straightness re-quired will not allow any jet to be 5mrad or more out ofstraightness. Even though jet straightness is the mostdifficult specification, the arrays must meet otherrequirements. To date, almost all of the LDR work hasbeen focused on the heat transfer performance ofLDR's. The objective of this study is to evaluate existingorifice fabrication methods, and to recommend themethod or methods most suitable for production of LDRorifice plates.

In order for a fabrication technology to be acceptable,it must satisfy a number of requirements. These re-quirements can be broken into three main areas:functionality, reliability, and manufacturabiJity. Func-tionally, the orifice array must be able to meet the dropsize, frequency and straightness requirements. It mustperform acceptably over the required temperaturerange. It must be made of a material that is inert to thefluids jetted, Reliability requirements demand that nodegradation of the functionality be observable over thelife of the LDR. This puts additional requirements onthe design and materials. Since an LDR system maycontain up to several million orifices, a fabricationprocess that can be scaled up to volume production isrequired.

Typical specifications for an orifice array are given inTable I. The actual requirements will vary from oneapplication to another. The goal is to find one or moreorifice array technologies that will satisfy all of therequirements.

Table hTypical Orifice Array Specifications

Diameter 50 - 200t_mDiameter Tolerances -5%No. of Orifices 12 rows X 400

Typical 20 rows X 250Temperature Range 25°C to 425°CJet Straightness <5 mradc to c spacings >5 x diameterPlugged holes <1%

An evaluation and testing program comprises a systemof criteria and tests which will measure the orificearrays against the specification. Jet straightness is themost critical performance criterion and is also the mostdifficult to test. Therefore jet straightness performancewas the focus for both analytical and experimentalevaluations.

Some of the factors that affect jet straightness includeorifice shape, surface finish, flow characteristics in theorifice area, rigidity of the substrate, particle generationand cleaning, and surface wetting characteristics. Someof these are discussed in detail below.

Phase I of this effort reviewed orifice array fabricationtechnologies, structural and hydrodynamic influences onjet straightness, testing and selection criterion, andvendor evaluations and recommendations. In Phase II,vendors were selected, orifice plates designed andpurchased, a drop generator was designed and fabri-cated, and orifice plates tested for jet straightness.

2

3.0 Phase I: Analytical Evaluation of Jet Straight-ness Effects, Pressure Drop Considerations,Fabrication Methods Survey, and VendorSurvey

3.1 Analytical Evaluation of Jet StraightnessEffects

Even if an orifice array is fabricated such that all of theorifices are geometrically equivalent and each orifice isperfectly symmetric, errors in jet straightness can occurdue to structurally and hydrodynamically inducedeffects. The general nature of these errors are dis-cussed below and their relation to specific orifice arrayfabrication methods is discussed in section 3.3.

3.1.1 Structurally Induced Straightness EffectsIt is highly desirable to use multiple row orifice plates ina Liquid Droplet Radiator in order to minimize radiatorand catcher size and weight. Heat transfer analysisindicates that up to twenty (20) rows of orifices could beemployed and not materially degrade heat transfer ef-ficiency. However, bending of the orifice plate will causea row-to-row jet straightness error to occur. The mag-nitude of this error will depend on the operating con-ditions of the array (i.e. pressure), and will be a sig-nificant factor in determining the choice of an orificeplate fabrication method and/or the number of rows inan orifice plate.

the shape of the beam exists. The angle of rotation ofthe beam as a function of position is given in equation(1). 1

0 = _--_(-xL2+3x_L-2x _)

G = absolute angle of beam at xW = unifom pressure valueE = beam material elastic modulusL = beam length

(1)

Figure 1 shows a schematic of the structural analysisconfiguration and shows the general shape of thebeam.

For a multiple row orifice plate, the beam length (whichwould probably be referred to as the orifice plate width)would be a function of the number of rows and theorifice diameter. From heat transfer considerations, thecenter-to-center distance between orifices, or the pitch,P, must be greater than or equal to 5 times the orificediameter. For this analysis, a ratio of pitch to orificediameter of 5 will be utilized. This represents a bes._.!case from a structurally induced straightness effectsstandpoint.

The analysis discussed here is presented in non-dimensional form in order to be useful for any operatingcondition, material property, platethickness, and number of rows.General conclusions resulting fromthis analysis will be discussed in thissection. In the sections on the indivi-dual orifice plate fabrication methods,specific results will be pointed out.

Analytical DevelopmentThe deviation from perfect straight-ness of a multi-row array of jets due tobending of the orifice plate undermanifold pressure was examined bymodeling the orifice plate as a uniformbeam clamped at both ends andunder a uniformly distributed load.Initially, the effect of the holes wasignored, both in determining the loadand the strength of the beam. Theeffect of the holes will be discussed atthe end of this section.

In addition to the distance between orifice rows, theremust be some distance between the outside rows and

i_" Xmax =I -'_ P_'- -,_ 8_-N max_

Using the assumptions in the previousparagraph, an analytical solution of

Figure 1: Structurally Induced Straightness EffectsAnalysis Configuration

3

the end of the plate.Thisdistance,referredto as themargin,a, wassettotwicethepitchinthisanalysis.

Overallbeamlength(platewidth)isthengivenbyequation(2).

Usingthevaluesfor pitchandmargindiscussedabove,the lengthof thebeammaybeexpressedasafunctionoforifice diameter. Dividing both sidesof equation (2) by the orifice diameter,d, equation (3) is obtained in non-dimensional form.

Using the values discussed above forthe pitch and margin (shown in equa-tions (4) and (5)), and substituting inequation (3), equation (6) is obtained.

120-

ii0-

I00

90-

80-70-

60-

_ 50-40-

30-

20 _

10-

01

• L/d

....W-'_4'''-'+'''-4- +. W- "P 4- 4.- + "''-'+'°'-4-''-+'''-4-'--4-''-'f'''_4-'°-

.--4

Number of Orifice Rows

Figure 2 shows the value of L/d as afunction of the number of orifice rowson the plate. To use equation (6) in e-quation (1), the beam length must beexpressed in terms of the plate thickness, as in e-quation (7).

L = 2a + [N,_-I]

Figure 2: Plate Length and Location of Maximum Anglevs. Number of Orifice Rows

LL _ 15+5N,_

w

t t td d

(7)

(2)L = beam length(plate width)a = margin(distance from edge

of plate to 1"' rowP = pitch(distance between orifice rows)

-- = + [N,_-I]d d

(3)

P_ = 5.0 (4)d

a_ = 10o (5)d

L " 5[n,o_-1 ] = 15 + 5N,_ (6)-- = 20 +d

Equations (6) and (7) may now be used in equation (1)to evaluate beam deflection as a function of thickness

ratio (t/d), number of rows (N,oJ, load to strength ratio(W/E).

From a system design viewpoint, only the maximumangle of the beam is of interest: more precisely, themaximum absolute angle of one of the orifice rows. Thelocation of the maximum absolute angle is given as inequation (8).

x_._ 0.511+0.577] (8)L

The smaller of the two maxima is shown in Figure 2 asa function of the number of orifice rows.

x. = a +

XN = location of i;_,i;o,, = row number

(9)

In general, there will not be an orifice located at themaximum angle location. Solving equations (1), (6), and

4

(7) at the locations of the orifice rows,an expression (equation (9)) for therow number with the maximum ab-solute angle is obtained. Figure 3shows this row number as a functionof the number of orifice rows in the

array.

4

• 3

2

J

Parametric EvaluationA parametric evaluation of structurallyinduced jet straightness effects wasperformed over the range of expectedvalues of t/d, W/E, and N,o,,.The maxi-mum number of rows is limited to

approximately 20 by heat transferconsiderations. Orifice plate thickness

ratio (t/d) for the manufacturing pro- ocesses considered ranged from 0.4 to z10. Operating pressures wereassumed to be in the 20 to 100 psirange. Elastic moduli for the manufac-turing processes considered rangefrom 8xl06psi (glass) to 28x108psi(steel). Given these ranges, equations(1), (6), and (7) were solved for the maximum absoluteangle at an orifice row location using the values shownbelow.

N,_ = 1,2,3,4,5,6,,7 ..... 18,19,20t/d = 0.4,0.6,1,2,4,7,10W/E = 0.000001,0.000004,0.000007

The results of the evaluation are shown in Figure 4through Figure 9. Note that there are two figures foreach W/E case and the only difference between themis the maximum angle scale.

' _ ' _ ' -_ ' $ ' £1' {3 ' is ' _ ' _9Numberof Rowsof Orifices

Figure 3: Row Number of Maximum Anglevs. Number of Orifice Rows

previous experience with orifice plate tolerance al-locations, it is likely that 10-20% of the total error wouldbe allocated to structurally induced effects. Assuming a20% allocation, an allowable error of 1 mrad would beassigned to structurally induced effects if the totalallowed error is 5 mrad, and 0.2 mrad if the totalallowed error is 1 mrad. These are the values indicatedon Figure 4 through Figure 9 as the maximum allow-able error.

By examining Figure 4 through Figure 9, severalgeneral conclusions may be made:

Discussion (1)The results of the parametric evaluation study areshown in Figure 4 through Figure 9 using two sets ofscales to illustrate the magnitude of structurally inducedstraightness effects relative to two maximum overall jetstraightness criteria: 5 mrad and 1 mrad. Since otherfactors will contribute to the overall jet straightness, theallowable error due to structural effects must be lessthan the total error. Because the error is coherent (i.e., (2)all jets in that row will have the same structurallyinduced jet straightness error), it will add arithmeticallyto all the other jet straightness error sources, ratherthan adding statistically if it were a random error (3)source. This implies that structurally induced straight-ness errors must be much less than the total

straightness criterion. Depending on the magnitude ofthe other sources of error, the allowable structurally in- (4)duced error could vary significantly. However, based on

Even for a low loading/high stiffness/largestraightness error case (W/E=0.000001, H_.,_=5mrad), only the highest thickness ratios (t/d=7and t/d=10) would allow 20 orifice rows to beemployed. For the lower straightness criteria andlow loading/high stiffness, only a t/d=10 wouldallow 20 orifice rows.

Orifice plates with thickness ratios less than 1can only be employed in single row con-figurations.

For a high loading/low stiffness case at the lowerstraightness criterion, the number of rows will belimited to 10 or less.

Thickness ratio dominates the structurally in-duced straightness error because of its cubic

5

relationtoH,asopposed to thelinear effect of W/E. However,in the real case, an increase inorifice plate thickness wouldprobably increase the operatingpressure required to produce agiven jet velocity, so some ofthe benefit of a thicker platewould be lost. This would be anespecially important effect fororifice plate types that wouldadd the additional thickness byincreasing the length of theminimum diameter section. Fora given orifice type, the depen-dence of operating pressure onthickness could be modeledand an optimum thickness ob-tained.

Effect of Holes

The placement of holes in the orificeplate reduces the stiffness of thebeam from the value used in derivingequation (1). However, the loading ofthe beam is reduced. For this analy-sis, it will be assumed that to firstorder the reduced "stiffness and the

reduced pressure offset one another.

The stresses in the plate, however,are much more influenced by theholes than is the deflection. For abeam under uniform load, the momentdistribution is given by equation (10))The maximum moment occurs at x=0.The maximum bending stress at anylocation on the beam is given in e-quation (11).

The stress calculated using equation(11) will be increased due to stressconcentration around the holes. Thestress for a single row of holes isincreased by a factor of k/{1-d/P},where k ranges from 1.1 to 1.85 asa/b increases from 0 to 0.7.2

• t/d=0.6

E 4-1 I / f + t/d-z.o$ t I k / o t/_-=.o

_=3t t / _ x ,/,-7.0

' -I I t / .u,,.._=_ ,_1ow,=1..,,;_ _o_/II I /r- s ,_adto=aZst,_ighu_es./

I1/ / \ _,,=,,oo

a 3 s _ 9 az 13 is a'7 a9Number of Rows of Orifices

== _igure 4: Maximum Absolute Jet Angle vs. Numberof Orifice Rows: P/d=5, a/d=10, W/E=10 "6

0.9 6

_- IJ _ t / J o t/d-2.o

° 11/ / / -,>,:;o°'11/ I / 1_/_-_.0

" osJIl 1 /

"'"]11 / /v zo,I_ad tot,1 . /

/ / / ,,,s,..,,,,,,,,...

1 3 5 7 Ii 13 15 17 19

Number of Rows of Orifices

Figure 5: Maximum Absolute Jet Angle vs. Numberof Orifice Rows: P/d=5, a/d=10, W/E=10 "6

M = l_[6Lx-6x2-L2]

M = moment at location x

Mt W 6Lx_6x2_L 2](10) _ = -_'[ (11)

I = moment of inertia

6

For a matrix of holes, two types arerelevant to stress concentration analy-

sis: rectangular and triangular. 5 / / / /Figure 10 illustrates the two types of "_ • t/d=O.6

'tlt /From stress concentration factors "_ // I / /ot/_-=.0determined for plates under tension '¢ || t / / , t/d-_.o(as opposed to bending), the rectan- _ 3 1) _ /* /" x t/d-7.o

gular array results in less stress con- i It/ / / vt/d-lo.ocentration than the triangular array, 2 -_which would have a better view factor < /// _ J ,u_-t_ azlo_l, or_o_/for radiation heat transfer. Both have _ III _ /_-_o= 5 ,_,,d tot=z /

...........a minimum factor of 4. For a rectan- 1 .......................

gu_with closely spaced holes, I V/__" "the stress concentration factor may beas high as 10 and for a triangular o __ ; _ _ _--r .... • ,array as high as 25. Thus, stress 1 3 s 7 9 1_ 13 15 _7 _9concentration effects will probably Number of Rows of Orifices

dominate any fatigue failure analysis. - - F]'gure 6: Maximum Absolute Jet Angle vs. Number

of Orifice Rows: P/d=5, a/d=10, W/E=4xl0"3.1.2. Hydrodynamically Dependent

Straightness EffectsIf an orifice plate manufacturing pro-cess could produce orifices whose

side walls were all parallel, the resul- E :LII J / /" t/d-C.6 Iting jets would not necessarily all be _ o.9

parallel. The phenomena that would _ 0"81/ / 1 / I* tld'1.0 1

cause the jets to be non-parallel will _ o.?tJ / / / Io t/d-2.0 /be referred to here as hydro-dynamically induced straightness el- _ -_ l / / l, t/d-_.o // 1 / Ifects.These in general are caused in 0 t/ / / / I /"10.01four ways:

(1) Asymmetric surface finish/- . ggest:ed alroughness. E 0.3-'_ / / /x ___ error for 1 mrad total I

......./- ......................(2) Misalignment of two parts (i.e. =E °'zl/____-__ _ ._ Iorifice plate and back-up plate)

or two processes (e.g. drilling ° _ 3 11 13 15 17 _9the cone in a mechanical Number of Rows of Orificesbroaching process).

(3) Asymmetric flow separation Figure 7: Maximum Absolute Jet Angle vs. Numberfrom symmetric geometries, of Orifice Rows: P/d=5, a/d=10, W/E=4xl0 4

(4) Asymmetric wetting of the exterior surface of theorifice plate.

The importance of all four of the above phenomena isa function of the flow passage geometry and Reynoldsnumber. In general, the liquid metal LDR configurationswill have much higher Reynolds numbers, but given thenumber of working fluids under consideration, the pos-

sible Reynolds number range is distributed over threeorders of magnitude. Table IP shows the properties forsix fluids and the Reynolds number for each for a10m/s jet exiting from a 0.004 inch (1001_m) orifice.

Asymmetric Surface Finish/RoughnessAsymmetric surface roughness will cause the velocityprofile across the flow at the exit of the orifice to be

asymmetric,whichin turncan causethe average of the velocity componentnormal to the desired flight path to benon-zero. After separation from theorifice, the momentum of the fluid inthe jet will redistribute and the jet willhave a component of velocity normalto the desired flight path, directedaway from the maximum roughnesssurface.

At very high Reynolds numbers vis-cous effects will not be important, andat very low Reynolds numbers, theflow at the exit of the orifice will beparallel, even if it is asymmetric. Bothvery high and very low Reynolds num-bers result in the component of velo-city normal to the flight path beingzero.

For the case where the Reynoldsnumber is such that the boundarylayer is approaching the diameter ofthe flow channel, the effect of non-uniform roughness, whether distrib-uted or discrete, will be a maximum.This will occur when the I/d of theconstant diameter section is equal toapproximately 0.02*Re, and thus willprobably be important only for theapplications using low vapor pressureoils.

Misali,qnment of Two Part or TwoProcess Orifice PlatesIf an orifice plate assembly is made oftwo parts, such as a pure Ni electro-form or a low t/d thickness ratio sol-uble core glass orifice plate bonded toa relatively thick backup plate, or if theorifice plate is made by a two stepprocess, such as the pre-drilling of thecone in the mechanical broaching anddrilling processes, there will be somemisalignment between the two parts or

-- _ t/d-4.0

Jl/ / \" 7 iJJ

1 3 s NTumbe_ofRow%of 83rificeis iv 19 II3

"-- Figure 8: Maximum Absolute Jet Angle vs. Numberof Orifice Rows: P/d=5, a/d=10, W/E=7xl0 e

i II I _ su,g,_t_ ,11o,,_,_1e7 /I ]

9 error for 1 mradt / /tll 0.tl [ /°"'t ° / /I II

0.7

._ 0.6

_ 0.5 ___

0.4 • t/d-0.6

+ t/d-l. 0

_ 0.3

E 24_ ......... A t/d-4.0 I IIo.11-/.........7 .............................x• v t/d-lO=01 _,' /_/_

Number of Rows of Orifices II

JJFigure 9: Maximum Absolute Jet Angle vs. Number

of Orifice Rows: P/d=5, a/d=10, W/E=7xl0"

process steps. This misalignment will result in anasymmetry in the flow due to inertial and/or viscouseffects.

Misalignment of the two parts or processes wouldcause the mean flow to negotiate a pair of turns thatwould result in a velocity component normal to thedesired flight path downstream of the final turn. At very

high Reynolds numbers this effect would be compen-sated for if the section downstream of the turning isstraight: the longer the Vd of this section, the less theeffect of the turning will be "remembered" at the exit ofthe orifice. Since inertial effects dominate at highReynolds number, the decay of the effects of turningwould be similar to the decay of a disturbance in anyfield described by an elliptic partial differential equation.

d

/O

O

0 0 0

0 0 0 0

Rectangular Array

O O

O O

o/ \

,,,' ',

0 0 0 0

Triangular Array

Figure 10: Multiple Row Array Configurations

Therefore, downstream I/d's of greater than 2-3 shouldminimize this effect.

Asymmetric Flow Separation from Symmetric Geome-trie.__ssEven in a perfectly symmetric channel, the flow can benon-uniform. This is usually illustrated by the unstableor mufti-stable flow in a diffuser where the flow separ-ates from one or both walls. Many of the orifice plateprocesses considered here produce very sharp cornersat the entry to the orifice plate and asymmetric separa-tion downstream of these corners, even if the orificegeometry is perfectly symmetric.

This phenomenon will be significant at moderate to highReynolds numbers, since the corner will be smoothedby a viscous layer that is large enough. At theReynolds numbers expected with some of the liquidmetals (10,000 to 40,000) this phenomenon could besignificant and therefore should be investigated analy-tically for the configurations of interest.

Asymmetric Wettin.q of the Exterior Surface of theOrifice PlateAs with the above phenomenon, asymmetric wetting ofthe exterior surface of the orifice plate can cause anotherwise perfectly straight flow to be deflected. Thiscan conceivably occur even if the surface finish isuniform due to the hysteresis between leading andlagging contact angles. In practice, a non-uniformsurface finish is usually the cause.

Previous experience with soluble core glass orificeplates at a Weber number of around 50 indicates thatthis phenomenon can be very important, especiallywhen a high surface energy material like glass is theorifice plate material.

At moderate Reynolds numberswhere the boundary layer is lessthan the channel width, but signifi-cant enough to affect the meanflow, the asymmetric distribution ofviscous effects will interact with theinertial effects. In addition, this non-uniform distribution of viscous ef-fects will be "remembered" down-stream of the turning for a distancethat depends on Reynolds number.Again, a straight section down-stream of turning, on the order of 2-4 diameters, will decrease the ef-fect of the misalignment. Quanti-fying this effect is obviously highlydependent on the geometry andReynolds number.

Table Ih Fluid Properties, Reynolds Number andWeber Number for Candidate LDR Fluids

Fluid

AbsoluteViscosity

(poise)Density(kg/m 3)

Surface TypicalTension Reynolds

(N/m) Number

TypicalWeberNum-ber

Dow 705 0.24 1090 0.037 45 300

Lithium 0.0055 500 0.35 900 14

Gallium 0.0016 6092 0.718 38,000 85

Aluminum 0.029 2300 0.90 770 25

Tin 0.012 6800 0.515 5,500 132

7550.0025 0.110 3,000NaK 7O

9

3.2 Pressure Drop Considerations

Both power consumption and structural weight areaffected by viscosity induced pressure losses. As withhydrodynamically induced straightness effects, 'herelative importance of viscosity induced pressure losseswill be a function of passage geometry and Reynoldsnumber.

The typical Reynolds numbers listed in Section 2.4.0 forthe candidate liquid metals are all greater than 700. Atthese Reynolds numbers almost all the viscous losswould be due to entry flow effects, so the pressure losswould be affected strongly by entrance geometry andonly weakly by the length (i.e, thickness) of the flowpassage.

Systems that use low vapo, pressure oils (typicalReynolds number of 45) would have a much greaterinteraction between orifice shape and viscous loss thanwould liquid metal systems because of the muchsmaller Reynolds number. In order to quantify thisvariation in viscous losses between different orificeplate types, a pressure loss coefficient was estimatedfor each type of plate using the orifice flow modelshown in (12). 4

,,/ K / 64/ ,c. -- t,.,, +..fi.+._a.j

actual pressureCp- /deal"

I = length at diameter dd = orifice diameter

Re = Reynolds number based ond and average jet velocity

K, K _ = loss constants

(12)

For the Reynolds number range of interest, the termwith K' can be neglected. For each orifice plate type, an//d equal to average of the minimum and maximumvalues possible was used in Equation (13). For smoothand continuous contractions, K was estimated as 1.5sFor sudden contractions (I/d = 0), K was estimated tobe 2.3.e The pressure coefficient computed from (12)was multiplied by ten and used as ranking for thepressure drop category.

3.3 Fabrication Methods EvaluationBased upon prior experience at both Microfab andNASA and upon initial literature searches, elevenfabrication methods were investigated during Phase I ofthis effort. The methods selected are shown in Table IIIand will be discussed in detail in Section 3 of this

report. Some of the fabrication methods investigated

Table II1: Orifice FabricationMethods Investigated

Electroform- PlatingChemical MillingLaser DnllingElectro-Discharge MachiningMechanical Punching (or broaching)Mechanical DrillingSoluble Core Glass FibersMultichannel Plates

Electron Beam MachiningIon DrillingFotoceram

have more than one process flow and/or design con-figuration option. Moreover, the addition of a finishingprocess to some of the mechanical and thermalmaterial removal processes will be necessary oradvantageous to enhance the manufacturability of thenozzle arrays. In this section the eleven fabricationmethods are discussed in detail. Specific informationincludes:

Description of MethodGeometric SketchMaterials

Structurally Induced Straightness EffectsHydrodynamically Induced Straightness EffectsPast Experience at Achieving 5 mrad StraightnessStraightness EstimateDirection of Effort to Improve Straightness

3.3.1 Eiectroform - PlatingDescription of MethodFigure 11 outlines the typical process steps for theelectroform process. The starting material can be purelya mandrel where the Ni nozzles are electroformed andthen removed, or in some cases, the Ni is electro-formed onto Cu, BeCu or other starting material to forma bimetallic nozzle structure. In either case, the electro-form metal (for orifice plates this is usually Ni or a Nirich alloy) is plated onto the substrate or mandrel. Thisprocess begins by using a photolithography techniqueto define a pattern of circular disks of photoresist on ametal substrate.

Figure 11 a shows a substrate material coated on bothsides with a thin layer of photoresist material. A spincoating process is used on small parts and a dipprocess is usually used on large parts.

10

Once the photoresistis ready, a matchedpair of photomasksare aligned aboveand below the sub-strate. The photo-mask contains clearand opaque featuresthat define the patternto be created in thephotoresist layer. Theareas in the photo-resist exposed to theU.V. light are poly-merized and aremade insoluble to aspecific solventknown as a develop-er. This type of photo-resist is known as a

negative photoresist.

After exposure toU.V. light and thedevelopment of theresist, a patternshown in Figure 11cexists. Now the pa'rtis ready for Ni plating.

The plating occurseverywhere exceptwhere the photoresistpattern exists. Toobtain high qualityparts, the plating rate,uniformity, and timemust be controlledvery tightly. Theplating solution,usually a nickel sul-fumate or a Wattsnickel solution, ismonitored for pH and

A. Apply Photoresist to

Substrate Metal

B. Exposure of Photoresist

C. Development,

then Activation

D. Electroforming of Orifice

Inlet and Outlet

E. Strip Away Photoresist

F. Etch Through

Metal Substrate

photoresist

"2

photoresist

UV light

..... _

photozesist

NI

Ni

Ni

for assay of certainchemicals. In doingso, the plater cancontrol the film stresses, surface finish, and platingrates. Figure 1ld shows the part after plating.

Next, the photoresist is removed (see Figure 1le) andNi is used as a mask and the substrate metal is etchedaway inside the cavity as shown in Figure 1lf. The finalorifice geometry obtained is shown in Figure 12.

Figure 11: Electroform Process

MaterialsThe nozzles are typically formed of pure nickel or anickel alloy. The nozzle cavity can be either nickel, ora Bimetallic where Cu or BeCu is used as a startingmaterial. The assay of the nozzles is influenced by thenickel anode material assay, the plating bath chemistryand the mandrel materials.

11

Structurally Induced Straightness EffectsThe two types of electroform orifice plates, pure Ni andbimetallic, would have distinctly different structurallyinduced straightness characteristics. With a modulus ofelasticity approximately half that of steel for both Ni andBe-Cu, the load to strength ratio, W/E, would probablybe close to the middle of the range evaluated. Usingexisting technology, the pure Ni plates would have t/dratios less than two. A method under current develop-ment whereby the photoresist pegs can be made muchlonger than is currently possible would permit plates tobe made with t/d ratios of up to approximately 5. In theformer case, use of the pure Ni plates would be restric-ted to single row configurations. In the latter case, up to4 rows might be possible.

For the bimetallic configuration, a t/d ratio of 5 probablyrepresents a minimum, and ratios well above 10 arepossible. Thus, from a structural standpoint, the bi-metallic configuration is to be preferred since it shouldallow for as many rows as is desired from heat transferconsiderations.

Hydrodynamically Induced Straightness EffectsFrom a hydrodynamic standpoint, the shape of theorifice for electroform orifice plates is probably the worstthat could be imagined: not only must the entry flownegotiate a sharp corner greater than 90 °, but the flowchannel downstream of the corner is divergent andthere is no clearly defined detachment location for thejet. The divergent channel could result in asymmetricflow separation and the lack of a clearly defined detach-ment point could result in non-uniform wetting effects.

The above paragraph indicates that, by inspection,electroform orifice plates could have poor jet straight-ness due to hydrodynamic effects. Experience,however, indicates the opposite. Electroform plates arethe most common type of orifice plate used in ink jetprinting systems, and by implication their jet straight-ness performance is acceptable. Although drop-on-demand systems do not require small values of jetstraightness to produce acceptable print quality, con-tinuous systems do, and the experience of Microfabpersonnel confirms that electroform orifice plates canhave acceptable jet straightness despite the inherentshape. This is probably due to a high degree of unifor-mify, both of the geometry and the surface finish,resulting from the plating process. Also ink jet printingsystems operate at moderate Reynolds and Webernumbers. An obvious area of concern is that electro-

form plate performance would change at the higherReynolds numbers and lower Weber numbers as-sociated with some of the liquid metal applications.

BeCu

Ni

Figure 12: Bimetallic EiectroformedOrifice Geometry

Past Experience At Achieving 5 mrad StraightnessThis method of nozzle fabrication has been used to

produce single nozzles and nozzle arrays at MeadOffice Systems, Xerox, IBM and other companies whichmet straightness conditions of <5 mrad. Our personalexperience at Mead Office Systems includes jetstraightness results of <3 mrad over large numbers ofjets in a single array (>200 nozzles).

Straightness EstimatesGiven the ability to plug 1 to 2 percent of the jets in agiven array, we feel that jet straightness in the 2 to 3mrad range is possible with this fabrication method.

Direction of Effort To Improve StraightnessImprovements to the surface quality of the mandrelmaterials and/or bimetallic starting materials could yielda large number of jets which meet the 2 mrad straight-ness criterion. In addition, improvements of airborneparticulate conditions by changing both filtration andhandling procedures could improve both averagestraightness and the yield of straight jets. Thirdly, theuse of thick liquid photoresist (25-50_m) when creatingthe nozzle mandrels could reduce the nozzle diametertolerance currently experienced.

3.3.2 Chemical MillingDescription of MethodThis process utilizes photolithography (seeFigure 11a,b,c) to create an etchant resist pattern or"mask" on the nozzle starting material. In the electro-form process, the photoresist was used to define theorifice area (Figure 11c) and expose the surrounding

12

Two Side Etching

One Side Etching

Figure 13: Chemical Milling Geometry

metal. In the chemical milling process, the photoresistis used to protect the surrounding metal and expose theorifice area. Chemical etching removes the metal in theorifice as shown in Figure 13. The subsequent etchingprocess is enhanced by using spray etchers, or by ap-plying an electrical potential between the etchantmaterial and the substrate metal. Thus the term "Photo-

chemical Etching" is sometimes used in describing theprocess. By _,arying etchant conditions and the numberof etch passes, some control of nozzle wall angle canbe achieved.

MaterialsThe chemical milling process works quite well with mostmetals. Many formulations of stainless steels would begood candidate materials for producing liquid dropletnozzle arrays.

Structurally Induced Straightness Effe_'tsIf stainless steel is used as the plate material, the loadto strength ratio should be at the low end of the rangeevaluated. The thickness of the plate can be selected,allowing high t/d plates to be used, although there is atrade-off between thickness and production time andcost. Chemical milling should therefore allow thenumber of rows to be selected from heat transferconsiderations.

Hydrodynamically Induced Straightness EffectsThe two principle areas of concern for chemically milledOrifice plates as far as hydrodynamically induced effectsare concerned are the sharp entry flow region and thepoor, and thus potentially non-uniform, surface finish. Along Vd flow channel would probably decrease anyasymmetry associated with the entry flow.

Past Experience at Achieving 5 mrad StraightnessThere is no direct experience or accounts of nozzlearrays being fabricated using this technique.

Straightness EstimatesWe have no available data on the straightness ofchemical milled parts. The quality of the final orificeplates depends on the quality of the starting metalsubstrate (grain structure, defects, etc.), the photolitho-graphy process and the etching process. We feel thatit would be extremely difficult to obtain large chemicalmilled parts with straightness better than 5 mrad.

Direction of Effort To Improve StraightnessImprovements to the surface quality of the startingmaterial would be a good starting point. In addition,improvements of airborne particulate conditions wouldreduce the nozzle defects that are photolithography in-duced.

3.3,3 Laser DrillingDescription of MethodThe output of a pulsed laser is an intense burst ofcoherent monochromatic light. Using values typicallyencountered in pulsed laser drilling, a 1.2 msec pulseof 15J total energy focused on a .005" diameter spotproduces an instantaneous power density in excess of90MW/cm 2. Such an intense pulse will melt and vapor-ize a small portion of the target work piece. The tre-mendous volume expansion of the vaporized materialgenerates pressures sufficient to blow the moltenmaterial out, creating a hole. Multiple shots at a givenspot produce a progressively deeper hole.

The dimensions of a laser drilled hole are a function ofthe material and part configuration, the pulse lengthand energy, the beam focus, and the number of shotstaken per hole.

The characteristic shape of a laser ddlled hole whendrilled at the optimum parameters exhibits a tapered orbell-mouthed entrance followed by a nearly uniformdiameter through the remainder of the hole. The tapermay add 10 percent to the nominal hole diameter. Byaltering the drilling parameters appropriately, the holecan intentionally be made to taper all the way fromentrance to exit or even to have a reverse taper with an

13

materialsaswellasformetalsandceramics.

Structurally Induced Straightness EffectsIf stainless steel is used as the plate material, the loadto strength ratio should be at the low end of the rangeevaluated. However, with a maximum t/d of around 5,the number of rows would probably be restricted to 8 orless.

Hydrodynamically Induced Straightness EffectsThe two principle areas of concern for laser drilledorifice plates are the sharp entry flow region and thepoor, and thus potentially non-uniform, surface finish.The long I/d of the flow channel would probablydecrease any asymmetry associated with the entry flow.

Figure 14: Laser Machined Orifice Geometry

enlarged exit following the bell-mouthed entrance.

Repeatability of hole diameter is a function of theconsistency of the operating parameters, primarilyenergy per shot, focal distance and work piece thick-Bess.

Figure 14 shows how a typical laser drilled hole mightappear in cross section in a metal sample. Uncontrol-lable diameter variations exist, starting with the funnel-shaped entrance to the hole. A thin layer of "recast"clings to the side walls of the hole. This material hasbeen melted and resolidified in such a short time thatthe frozen metal has a different structure than that of

the parent material. Depending on the alloy beingdrilled, this recast is often of considerable hardness andprone to developing micro-cracks.

The build-up of the recast layer can be minimized byoptimizing the operating parameters of the laser. Insome cases, finishing operations can be used toremove this recast layer. Since amorphous materials gofrom the solid phase directly to the vapor phase, theydon't show the same recast effect.

Materials

A wide variety of materials can be machined usinglasers. Neodymium-doped, Yttrium-Aluminum-Garnet(Nd:YAG) lasers are used to drill holes in metallicmaterials. All metals can be drilled, including high con-ductivity onessuch as gold, silver and copper. Stainlesssteel (incl. #316) as well as high melting point metalssuch as tungsten, molybdenum and niobium, can alsobe drilled.

CO 2 lasers can be used to drill holes in ceramics andpolymers. Excimer Lasers can be used for polymer

Past Experience at Achieving mrad StraightnessWe know of no outside groups who have made arraysusing laser drilling. The principals at Microfab have hadsome experience using this technology, but no partswere ever made where the straightness was better than10 mrad.

Straightness EstimatesThese estimates are difficult to make because we feelthat to get the straightness <5 mrad will require postprocessing steps such as electroplating. Based on thisassumption, our estimates are as follows:

1-2 Yr.

Now EffortStandard Materials 10-20 mrad 10 mradAmorphous Materials 5-15 mrad ~5 mradPost Processing ? <5 mrad

Direction of Effort To Improve StraightnessTo improve the quality of laser drilled orifice arrays, anumber of actions should be taken:

,

2.

3.

.

5.

Select a laser system that has extremely goodcontrol over the power levels.Select a high quality optical system that hasbeen designed specifically for this application.Select the best substrate material for the ap-plication and for the ability to obtain clean holes.Amorphous metals may be the best selection.Run designed experiments to study the interac-tion among the various parameters.Develop a finishing process to obtain clean,smooth surfaces.

3.3.4 Electro-Discharge MachiningDescription of MethodElectro-discharge machining, designated EDM, re-moves metal through the action of high-energy electricsparks on the surface of the work piece. The mechan-

14

3 phaseA.C.

servocontrol

rectifier _1 I control

servo

1!

I

PDIELECTRIC

I lit " :: i='_ I

tool

Figure 15: Electro-Discharge Machining (EDM) System

ical setup and the electrical circuit involved are shownin Figure 15. The tool and the work piece are sub-merged in a fluid having poor electrical conductivity-usually a light oil. A very small gap, of approximately25t_m or less, is maintained between the tool and thework piece by means of a servosystem. When thevoltage across the gap becomes sufficiently high,capacitors discharge current across the gap in the formof a spark for an interval of from 10 to 30 msec andwith a current density of the order of 1,500 A/mm 2 (106A/in.2). When the voltage has dropped to about 12volts, the spark discharge is extinguished and thecapacitors start to recharge. This cycle is repeatedthousands of times per second, and thousands ofspark-discharge paths occur between the surface of thetool and its mating work surface. Each dischargeremoves minute amounts of material from both the tooland the work piece. The resulting workpiece surface iscomposed of extremely small craters, so small that asurface finish of about 3.81 microns (150 microinches)is obtained on roughing cuts and about 0.762 microns(30 micro-inches) on finishing cuts. A typical EDMorifice geometry is shown in Figure 16.

The mechanism of metal removal by electro-dischargemachining is not completely understood and appears toinvolve more than one phenomenon. Most of theremoval is by fusion of minute particles of metal that

are thrown from the surface by the thermal actionaccompanying the highly localized heating and coolingof the metal surface as a consequence of the con-centrated release of energy in the spark. However, notall the particles released are fused, particularly in thecase of some metals. It appears that highly localizedthermal stresses also play a role in the metal-removalprocess.

As with the laser drilling process, EDM usually requiressecondary finishing operations to obtain holes adequatefor fluid jet applications. Chemical machining, electro-polish machining, and abrasive flow machining areexamples of secondary finishing operations.

m

.......,_/////////.,_

1.///I/.

Figure 16: Electro-DischargeMachined (EDM) Orifice Geometry

15

Electro-dischargemachiningis best suitedfor holediameters1251_mor above.It is capableof a depthtodiameterratioof 10:1.We havesourcesof precisiontungstenwireof251_m.Tungstenisusuallyusedastheelectrodematerial.

MaterialsElectro-discharge machining works for all metals. Forthis application, a material such as 316 stainless steelis a good selection. The selection process for materialshould take into account the finishing operation.

Structurally Induced Strai.qhtness EffectsAs with the laser drilled plates, if stainless steel is usedas the plate material, the load to strength ratio shouldbe at the low end of the range evaluated. The maxi-mum thickness for EDM plates would be greater thanthe laser drilled plates, allowing thickness ratios of upto 10. This would allow the use of as many rows asdesired from heat transfer considerations. However, theproduction time (and cost) would increase almostdirectly proportionally to the depth to be drilled, makinghigh t/d EDM plates not quite as attractive.

Hydrodynamically Induced St.raightness Eff.ectsAs with the laser drilled orifice plates, the two principleareas of concern for electro-discharged machinedorifice plates as far as hydrodynamically induced effectsare concerned are the sharp entry flow region and thepotentially non-uniform, surface finish. The long Vd ofthe flow channel would probably decrease any asym-metry associated with the entry flow.

Past Experience at Achievin,q 5 mrad StraiqhtnessWe know of no straightness information using electro-discharge machining. Panasonic has sold an electro-discharge machine MG-ED01 for creatingsingle ink-jet orifices. This machine is capableof creating orifices (of good qualify) below251_m.

Straightness EstimateBased upon the quality of holes obtained usingthe Panasonic MG-ED01, good jet straightnesscould be obtained. It should be as good aslaser drilling.

Direction of Effort to Improve StraightnessTo improve the quality of orifice arrays madeby the electro-discharge machine method, anumber of actions should be taken:

,

2.Obtain a Panasonic MG-ED01

Develop an acceptable process usingthe MG-ED01

3. Select the best substrate material for the ap-plication

4. Run designed experiments to optimize theprocess parameters

5. Develop a finishing process to improve thequality of the surfaces

3.3.5 Mechanical Punching (or Broaching)Description of MethodThis technology is used for the manufacture of fibersfor the clothing industry. In that industry, it is referred toas the spinneret technology. The fabrication processconsists of first drilling the taper section of the nozzleand then high speed/high pressure mechanical punch-ing. The surface finish of parts observed has beenoutstanding. It is not known whether secondary opera-tions were performed on those parts. The method hasflexibility in the taper length, taper angle, and the lengthto diameter ratio. Length to diameter ratios from 0.5:1to 5:1 are possible. A typical broached orifice geometryis shown in Figure 17.

MaterialsThe quality of mechanically punched holes dependsupon the mechanical and flow characteristics of themetals. A material of medium hardness is desired.Successful holes are routinely manufactured usingstainless steel (316 is a good choice).

Structurally Induced Straightness EffectsIf stainless steel is used as the plate material inmechanical broaching processes, the load to strengthratio should be at the low end of the range evaluated.The need to predrill the cone forces the plate to highthickness ratios. Therefore, broached plates should

/ -- Drilled Tape/ r

I

Orifice Exit

Figure 17:Mechanically Punched Orifice Geometry

16

allowfortheuseof as many rows as desired from heattransfer considerations.

Hydrodynamically Induced Straightness EffectsMechanical broaching requires the pre-drilling orforming of a cone at the locations where the orifices areto be made. This produces the potential for somemisalignment of the two steps, and thus a flow inducedjet straightness error. Note that any angle between theaxis of the cone and the axis of the broached sectionwill produce a flow pattern similar to a spatial misalign-merit of the two processes.

Past Experience at Achieving 5 mrad StraightnessWe have previously tested 200 jet arrays using platesmade by Kasen. These plates had most of the jets <10mrad, with a few outside this range. Seventy-fivepercent of the jets were within 5 mrad.

Straightness EstimateThe only data we have is 200 orifice arrays where 75%of the orifices were within 5 mrad and 100% werewithin 20 mrad. We feel that this could be improved tothe point where orifice plates with all jets within 8 to 10mrad are possible.

Direction of Effort To Improve StraightnessCompanies such as Celanese, DuPont, etc. use thisspinneret technology to make orifice arrays for pullingfiber consider their processes a trade secret. Since wedo not understand the processes it would be necessaryto rely on these companies for improvements.

Figure 18: Mlcrodrilling Tooling Configuration

shown in Figure 18. Figure 19 shows a typicalmechanically drilled orifice geometry.

3.3.6 Mechanical DrillingDescription of MethodCertain aspects of drilling can cause considerabledifficulty, especially when drilling holes below 0.010" indiameter. Most drilling is done with a tool having twocutting edges, These edges are at the end of a rela-tively flexible tool and the cutting action takes placewithin the work piece. This requires that the chips mustcome out of the hole while the drill is filling a largeportion of it. This especially complicates very small holedrilling, Friction between the body of the drill and thewall of the hole results in additional heating. Problemscan arise from poor heat removal. Lubrication andcooling are difficult because of the counter flow of thechips.

Even though companies manufacture drills down to201_mthe quality of the cutting edges and the strengthof the tools are questionable. High speed drilling isperformed reliably in the PC board manufacturingindustry. Hole sizes range down to .004" to .016" withaspect ratios of 8:1 or more. Tools are configured as

On some of the systems, drilling speeds have reached200 in/rain @ 90,000 RPM. This is in epoxy basedPCB's. Multilayer boards containing 16,000 holes of.006" diameter have been successfully drilled on one ofthese systems. Even though PCB material is notacceptable for the LDR application, these numbers givea sense where the state-of-the-art is.

For the LDR application, small drill bits need to be useddrilling into harder materials. This requires slowerRPM's, lower feed rates and more specialized bits andmachines. Post processing finishing operations mayalso be required.

MaterialsAlmost all metals can be mechanically drilled. Stainlesssteel is a good choice.

Structurally Induced Straightness EffectsAs with mechanical broaching, stainless steel can beused as the plate material in drilling processes so theload to strength ratio should be at the low end of the

17

Figure 19:Mechanically Drilled Orifice Geometries

range evaluated. The need to predrill the cone forcesthe plate to high thickness ratios so that broachedplates should allow for the use of as many rows asdesired from heat transfer considerations.

Hydrodynamically Induced Straightness EffectsAs with mechanical broaching, mechanical drillingrequires the pre-drilling or forming of a cone at thelocations where the orifices are to be made. Thisproduces the potential for some misalignment of the twosteps, and thus a flow induced jet straightness error.Note that any angle between the axis of the cone andthe axis of the broached sec-tion will produce a flow pat-tern similar to a spatial mis-alignment of the two proces-ses. Also, a drilled orificeplate would have the potentialfor non-uniformly distributedburrs.

Past Experience at Achieving5 mrad StraightnessOrifice arrays have beenmanufactured by a group atLawrence Livermore Labora-tories. With an electropolishfinishing operation, they ob-tained jet straightness num-bers <5 mrad. NASA has also

manufactured arrays using the

mechanical drilling approach. To date, their results arenot as encouraging.

Straightness EstimatesWithout finishing operations 10-30 mrad would beexpected.

Direction of Effort To Improve StraightnessThe largest improvements would come from finishingoperations.

3.3.7 Soluble Core Glass FibersDescription of MethodGlass fibers can be manufactured to very high preci-sion. In the fiber optics industry, it is normal to fabri-cate a fiber which has an inner glass (core) differentfrom the outer glass (clad). In optical fibers the intentis to have a different index of refraction in the core andclad glass. By taking advantage of the manufacturingtechnology of fiber optics, fibers have been made inwhich the core glass has a much higher solubility thanthe clad glass in dilute acids. If the core and clad glassare thermally matched, the core-to-clad diameter ratiofor the preform can be reproduced in the fiber. The

fibers are then aligned in parallel grooves and sealedin place, as shown in Figure 20. Once the block andfibers are sealed, the block is cross-sectioned intowafers and these wafers are polished and bonded to asupporting plate.

After bonding, the front surface of the plate is lappedand polished, and finally the core glass is etched out toform the orifices. The final orifice geometry is the sameas for the Microchannel arrays (see Figure 22).

Figure 20: Fabrication of Soluble Core Glass Orifice Array

18

MaterialsSpecial glasses must be fabricated to obtainthe fibers. Special thermal and mechanicalmatching must exist between clad and coreglass. A material such as fotoceram can beused to manufacture the grooved block. Solderglass can be used to seal the fibers in theblock.

Because the center-to-center spacings for theLDR application are not critical, grooves maynot be necessary. This would eliminate theneed for the fotoceram.

Structurally Induced Straightness EffectsWith a modulus of elasticity only one third thatof steel, the load to strength ratio for solublecore glass plates will be at the high end of therange examined. Thus, even though thicknessratios of up to 10 are possible, the number ofrows will probably be limited to 11 or less.

Hydrodynamically Induced Strai,qhtness EffectsSoluble core glass orifice plates have verysharp corners in the entry flow region, but theI/d of the flow channel can be long to compen-sate. Because of the relatively high surfaceenergy of glass, the sharpness of the edge ofthe orifice at the exit and the surface finish ofthe outside of the orifice plate have beenfound by Microfab personnel to be critical to jetstraightness performance.

Past Experience at Achieving 5 mrad Straight-nessArrays with all jets <2 mrad have been ob-tained with this technique.

Straiqhtness EstimatesArrays can be made using this technique withjet straightness better than 2 mrads. Improvingthis would be difficult.

Direction of Effort To Improve StraightnessAt this time, no company is set-up to utilizethis method. The experience base exists atMicroFab.

3.3.8 Mlcrochannel Plates

Description of MethodThe basic steps used are given in Figure 21(courtesy of Galileo Electro Optics Corpora-tion). Single fibers are drawn as solid glass fibershaving two components, an etchable core glass, and aglass cladding which is insoluble in the core glass

Core Glass

Cladding Glass

O---,Single-Fiber

Single-FiberStacked Array

HexagonalMulti-Fiber

Solid GlassBorder

Active Area

MCP Wafer

Figure 21:Fabrication of a Mlcrochannel Orifice Array

etchant. The fibers from this first draw are packedtogether into an array (usually hexagonal), are tackedtogether thermally, and are drawn again into hexagonal

19

Figure22:MicrochannelOrificeGeometry

multifibers. These hexagonal multifibers are thenstacked again and fused within a glass envelope toform a boule. The boule is then sliced usually at a slightangle (8° to 15°) from the normal to the fiber axes. Theresulting wafers then are edged, beveled and polishedinto thin plates. The soluble core glass is then removedby a suitable chemical etchant. A typical MCP orificegeometry is shown in Figure 22.

Materials

The mechanical plates consist entirely of glass for-mulations. Although the composition may be varied, alead oxide glass is most common.

Structurally Induced Straightness EffectsWith a modulus of elasticity only one third that of steel,the load to strength ratio for microchannel plates will beat the high end of the range examined. Thus, eventhough thickness ratios of up to 10 are possible, thenumber of rows will probably be limited to 11 or less.

.Hydrodynamically Induced_Straiqhtness EffectsAs with soluble core glass orificeplates, microchannel orifice plateswould have very sharp corners in theentry flow region, but the I/d of theflow channel can be long to compen-sate. Because of the relatively highsurface energy of glass, the sharp-ness of the edge of the orifice at theexit and the surface finish of the out-side of the orifice plate would be crit-ical to jet straightness performance.

Past Experience at Achieving 5 mradStrai,qhtnessThere is no direct experience or ac-counts of nozzle arrays being fabri-cated using this technique. However,one would expect that the experience

with soluble core fibers at Mead Office Systems, IBMand elsewhere is applicable, due to the process similar-ities.

Straightness EstimatesThis process should yield straightness values as goodas the soluble core glass fiber process (2 mrad).

Direction of Effort To Improve StraightnessImprovements to the current lapping/polishing areneeded because of the small t/d ratios needed for

droplet formation. Typical t/d ratios for microchanneldevices are 50:1 whereas 3:1 to 1:1 is more commonin ink-jet applications.

3.3.9 Electron Beam MachiningDescription Of MethodA beam of electrons (108 to 109 W/cm2) colliding with asurface can transform solid materials into the gaseousphase. In order to avoid molten pools resulting fromthermal conduction, short bursts are used. This processis similar to laser drilling, using electrons instead ofphotons. The process works in the following way:

If electrons collide with a solid material at a certainspeed, their kinetic energy will be immediately con-verted to thermal energy. What happens within thework piece after this initial effect depends not only onthe electron beam parameters such as total power,power density, duration of impact, etc., but also on thethermal properties of the target, such as heat capacity,melting point and vaporization point, thermal conduc-tivity, heat of fusion, etc. The material can be heated,melted or vaporized.

Focused Electron Beam Exposure

Depresslon in the melt allowsbeam to contlnue through material

A capillary Is producedthrough the material

Figure 23: Electron Beam Machining Process

2O

For removingmaterialby ElectronBeammachining,there are two differentmechan-isms.Eitherthematerialisevaporatedor it ismeltedand the liquidphaseis removedbyadditionalforces.

Ingeneral,a combination of fusion and evap-oration is used in such a way that the vaporpressure is used as additional force to removethe liquid material.

The pulse interval and thus the time of impactof the beam on the work piece is between101_sand 10ms. The main task of the processcontroller is to maintain suitable beam parameterswhich allow the shape of the molten volume to becontrolled as well as the position of maximum tempera-ture (the vapor source) so that the liquid material isejected completely and rapidly. The main controlparameters for shaping the hole are the pulse width forthe depth of the hole, the beam current for the diameterof the hole and the power distribution within the beamas well as the position of the focus with respect to thework piece. These parameters can be combined inmany ways and each can be varied with respect totime.

Many of the features of the electron beam machinedhole are similar to that of the laser drilled hole.Figure 23 shows the typical process for e-bearn drilling.In both cases, selection of materials and operatingparameters are important. EBM, like laser drilling, mayrequire secondary finishing operations. A typicalelectron beam machined orifice is shown in Figure 24.

MaterialsA wide variety of materials can be used with thistechnique. All metals can be machined, includingstainless steels and titanium. Since there is a wide

range of choices with this technique, these can beevaluated on the basis of reproducible hole formationand debris formation.

Structurally Induced Strai.qhtness EffectsAs with the EDM plates, if stainless steel is used as theplate material, the load to strength ratio should be atthe low end of the range evaluated. The maximumthickness for e-beam plates should be greater than 10,thus allowing the use of as many rows as desired fromheat transfer considerations. However, the productiontime (and cost) would increase almost directly propor-tionally to the depth to be drilled, making high t/delectron beam plates not quite as attractive.

Exit

Figure 24:Electron Beam Machined Orifice Geometry

Hydrodynamically Induced Straightness EffectsAs with EDM, the two principle areas of concern for e-beam plates are the sharp entry flow region and thepotentially non-uniform, surface finish. The long Vd ofthe flow channel would probably decrease any asym-metry associated with the entry flow.

Past Experience at Achieving <5 mrad StraightnessThere is no direct experience or accounts of nozzlearrays being fabricated using this technique.

Straightness EstimatesThis process has the capability of yielding parts likelaser drilling, except this is not a large industrial effortto drill small, high quality holes with E-beam. Even withpost processing, we feel 5 mrad is out of reach in theforeseeable future.

Direction of Effort To Improve StraightnessThere is a current minimum hole diameter limitation of

approximately .004". Efforts are in progress to get tothe .002" range.

In addition, material choices plus subsequent debrisremoval (chemical polish, etc.) to improve the surfacefinish and nozzle shape are required.

3.3.10 Ion MillingDescription of MethodBeams of ions have been used in two ways to formorifices. First, they can be focused and used in thesame fashion as electron beams in the previoussection, The limited intensity of ion-beam sources havein the past made this method slow. But stable, liquidmetal ion sources are changing this situation. Second,unfocused beams can be used to etch away materialunprotected with a mask. This is shown in Figure 25.This process is referred to as ion milling. It has beenused in the semiconductor related industry for sometime. In this process, a beam of accelerated ions(usually argon) bombards the surfaces and imparts

21

Substrate Atoms Ion Beam

Figure 25: Ion Beam Machining Process

enough energy to the substrate atoms to remove mater-ial. The etching rate is a function of five major variables:acceleration voltage, angle of incidence, type of gasemployed, type of material milled, and reactive gasinfluence. Increasing the acceleration voltage raises themilling rates almost linearly. For most materials, max-imum milling occurs at an angle 40° - 60° from normal.Ion milling etch rates are slow. Using Argon at 500volts, normal incidence, and lmNcm 2 beam currentdensity, the following etch rateshave been obtained:

Structurally Induced StraightnessEffectsBecause of the slow etch rates, onlyvery low t/d plates are practical if theorifices are made entirely using iondrilling. Therefore, only single rowplates could be used. If a secondaryprocess is used to open the entrance,large thickness ratio plates could bemade, allowing heat transfer effects todetermine the number of rows.

Hydrodynamically InducedStraightness EffectsThe combination of low Vd and sharpedge entry flow region would be ofconcern for an entirely ion milledplate. The formation of a taperedentrance by a secondary process

would eliminate entry flow effects, but would create thepotential for misalignment of the two processes. Theshort I/d downstream of the entrance would not be able

to eliminate the effects of misalignment.

Past Experience at Achievin,q 5 mrad StraightnessNo past experience is known.

Stainless steelAluminumTitaniumGlass (Na, Ca)

250-275 _min.300-600 ,lVmin.150-350 _min.200-220 Jr_/min.

At 250 _min., it would take ap-proximately 17 hours to drill a251_mdeep hole in stainless steel.This is one of the main drawbacksto ion milling. The second problemis that of finding a masking mater-ial that is much more resistant tothe ion beam than the substratematerial. A typical ion milled ori-fice geometry is shown inFigure 26.

MaterialsAlmost any material can be used.The etch rates are very slow andwhen a mask is used, the etchrate of the mask material must beslower than the substrate.

Nozzle Cross-Section

With Entrance OpeningMade by a Secondary Process

Nozzle Cross-Section

Entirely Ion Milled

Figure 26: Ion Beam Machined Orifice Geometry

t22

Strai.qhtness EstimateThe process combines some form of photolith-ography with ion milling. Both processesshould produce clean, uniform surfaces.Therefore, the potential is good. 5 mrad couldbe achieved if it were not for the processlimitations.

Direction of Effort To Improve StraightnessBecause of the low process speed, thismethod is not recommended.

3.3.11 FotoceramDescription of MethodFotoceram glass has one unique property.Where it is exposed to UV light, it crystallizeswhen heated in a furnace. The use of Foto-ceram glass in orifice plate fabrication is asfollows:

U.V. Light

_Photomask

Only glass

exposed to U.V. light

Figure 27: Fotoceram Orifice Array Fabrication Process

A photomask would be made which exposesonly the areas where the orifices are desired,as shown in Figure 27. A sketch of the typicalprocess flow is shown in Figure 28. Thismaterial is then baked. Crystallization occursin the exposed areas. These crystallized areasare subject to etch rates 15 to 20 times higherthan the uncrystallized material. After etching,the substrate is fired into ceramic form forstrength. The main limitation of this method isthat shrinkage during the firing process cannotbe controlled accurately.

Materials

The starting material is a piece of photosen-sitive glass. It will be fired later to produceFotoform opal or Fotoceram.

Structurally Induced Straightness EffectsAs with microchannel plates, fotoceram plateswould have a modulus of elasticity only onethird that of steel. Thus the load to strengthratio for fotoceram plates will be at the highend of the range examined, and even thoughthickness ratios of up to 10 are possible, thenumber of rows will probably be limited to 11or less.

¸¸ 11----3

Starting Glass

UV Masking Step

Controlled Heat

Treatment

Hydroflouric Etch

uv Expose

Fired to Form Opal orFotoceram

Hydrodynamically Induced Straightness EffectsAs with soluble core glass orifice plates andmicrochannel orifice plates, fotoceram would have verysharp corners in the entry flow region. The I/d of theflow channel is more limited for fotoceram, however,Because of the relatively high surface energy of glass,the sharpness of the edge of the orifice at the exit and

Figure 28: Fotoceram Orifice Array Fabrication Process

the surface finish of the outside of the orifice platewould be critical to jet straightness performance.

Past Experience at Achieving 5 mrad StraiqhtnessNo past experience known.

23

Strai,qhtness EstimateThis process could produce parts today in the 10 to 15mrad range. With further development 5 mrad could beobtained. This would most probably require postprocessing operations.

Direction of Effort To Improve StraightnessWorking closely with Coming will be necessary toobtain acceptable plates. Improved finishing operationsmay need to be developed.

3.4 Ranking of Fabrication MethodsIn order to compare the various methods of orifice arrayfabrication, eight items were identified. These are listedon the left hand side of Table V. The fabricationmethods are listed across the top. Most items wereevaluated on a scale from 1 to 5, where 5 is best.Straightness past experience was weighted by using ascale of 1-10, where 10 is the best. Each of themeasurement criterion is briefly reviewed below.

Straightness: Past ExperienceIf a method has produced arrays with straightnessbetter than 5 mrad, it gets a rating of 5. No experiencegets a 1.

Strai.clhtness: ProjectedThese estimates are applicable after a hypothetical oneyear effort to improve the fabrication processes. Arating of 5 indicates a high probability of meeting the 5mrad specification. A 1 rating indicates a low probabil-ity. In these estimates it is assumed that a smallnumber (-1%) of the holes may be plugged.

ManufacturabilityThis rating gives an indication of the adaptability of themanufacturing process to volume production. A processthat produces all the holes at the same time is pre-ferred over a one-at-a-time process. Tooling wear on aone-at-a-time process is a negative. Cleanliness andsurface finish are also considered.

AvailabilityA good source of qualified vendors yields a 5 rating inthis category.

Mechanical

A good mechanical rating indicates a stiff plate and avery small structurally induced straightness error. Thisusually implies the process allows higher t/d orificeplates.

Pressure DropThe pressure drop rating was obtained by multiplyingthe pressure coefficient (see section 2.5.0) estimated

Etched From Both Sides

Single Sided Etch

Figure 29: Fotoceram Orifice Geometries

for each orifice plate by 10. The maximum possiblerating was 10, but the maximum in value in this studyis 5. Thus a rating of 5 would indicate the lowestpressure drop (best) and a rating of 0 the highest pres-sure drop (worse).

Fluid FlowThis rating contains two characteristics that affecthydrodynamically induced straightness errors. First isthe geometry of the orifice cross section which deter-mines the flow properties. Second is the quality anduniformity of the exit surface. Good ratings for both willgenerate a 5.

Diameter ControlThe specification on diameter is +5%. A process thateasily meets specification gets a 5. A process thatcannot be controlled to meet the specification gets a 1rating.

Rankinq ResultThe results from Table V are summarized below. Past

experience brings electroform and soluble core glassfibers to the top of the list. Fotoceram and microchan-nel plates are rated high because of the orificegeometry, manufacturability, diameter control, and ourprojections. We feel that processes that form orificesone at time (laser, EDM and mechanical drilling) showpotential, but require a finishing process to get clean,smooth surfaces. Using the process described above,the result of ranking of the processes is shown inTable IV.

3.5 Vendor EvaluationOver fifty companies or organizations were identifiedand approximately 70% of those were contacted. A list

24

of thecompaniesidentifiedis shownin AppendixI.Tripsweremadeto visitelevenof thesecompanies.The listof companiesidentifiedis givenby processtype. Wherewe have enoughinformationto rankcompanies in a given process area, the rankings areshown to the left of the company name. Note that therankings are relative to LDR orifice array developmentonly.

3.6 RecommendationsBased on our evaluation of both the orifice arrayfabrication methods and specific vendors, the followingvendors/processes were recommended for experimentalevaluation during Phase I1:

ElectroformBecause of past experience in achieving jet straight-ness <5 mrad, high volume manufacturability, andavailability of competent vendors, this method has to beat the top of the list. Obtaining parts from both Buck-bee-Mears and Stork-Veco was recommended.

FotoceramThis process has the advantage of being capable ofvolume manufacturing. If the material is fired to theceramic form, it has good temperature stability. Theorifice configuration has advantages in the fluid flowcharacteristics ff etched from one side. Obtaining partsfrom Coming Glass was recommend. Obtaining twodifferent configurations was also recommended. Onewould be a single sheet with a cylindrical hole, and thesecond configuration would utilize a backing layer witha larger hole fused to the primary orifice for addedstrength.

Table IV: Ranking of Orifice ArrayFabrication Methods

1. Electroform2. Soluble Core Glass Fibers3. Fotoceram4. Microchannel Plates5. Punching

Chemical Milling7. Mechanical Drilling and Finishing8. Laser Drilling and Finishing

Mechanical Drilling10. Laser Ddlling

EDM and Finishing12. EDM13. E-Beam Drilling

recommended that NASA Lewis make some additionalorifice plates using the techniques developed atLawrence Livermore. We also recommended that anoutside vendor be found to aid in the finishing operation(electro-polishing).

Chemical MillingThis technology has improved greatly over the lastseveral years, driven by the disk drive industry. Stain-less steel prototype parts can be obtained inexpen-sively and manufacturability is very good. We recom-mended obtaining parts from Vaaco or Buckbee-Mears.

Microchannel PlatesMicrochannel plates have very uniform cylindrical holeswith a large t/d ratio. Our past experience has shownthat this results in values of jet straightness much betterthan 5 mrad. Obtaining these parts from GalileoElectro-Optics was recommended because of theirexperience in dealing with many different configurationsand outside customers.

Mechanical PunchingThis process produces stainless steel plates of goodstiffness and flow characteristics. Based on our ex-perience, Kasen has the best quality pads.

Mechanical Drilling and FinishinqBased upon the reports from Lawrence LivermoreNational Laboratories, we felt it important to takeanother look at this process. The advantage of thisprocess is the attendant structural rigidities, the disad-vantages are in the area of manufacturability. We

25

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26

4.0 Phase Ih Orifice Plate Design; Test SystemDesign and Fabrication; and Orifice PlateExperimental Evaluation

Based on the Phase I results and recommendations,NASA decided that four orifice array fabrication meth-ods would be experimentally evaluated for jet straight-ness performance:

,

2.3.4.

Electroform (two vendors)FotoceramMechanically DrillingMicrochannel Plate

In addition, two other processes (Lee Company'setched sandwich process and Creare's EDM) wereevaluated because they were low cost "targets ofopportunity."

4.1 Orifice Plate DesignAn orifice plate with 50 orifices of 75t_m diameter on635_m centers was selected as the nominal design.Fifty (50) orifices were selected to be large enough toprovide meaningful statistics and a reasonable test ofthe fabrication process. At the same time, it was limitedenough to keep the purchase and testing costseconomical.

The 75#m diameter was selected as a compromise.Droplet heat transfer performance increases withdecreasing droplet size. However, pressure dropincreases, the number of orifices required increases,and contamination related failures increase as theorifice diameter decreases. 7,8

The rather large orifice-to-orifice pitch (P/d=8.3) wasselected to produce an overall plate length significantenough to test the fabrication processes. Also, therewas some concern that a smaller pitch would causesome vendors to decline to furnish a quotation.

Figure 30 shows the nominal orifice plate design. Theorifice geometry detail shown is that a typical electro-formed orifice. For processes other than electroform,appropriate details were substituted.

The electroform orifice plates (Stork-Veco and BuckbeeMears), the Fotoceram orifice plates, and the EDMplates (Creare) were supplied in the nominal configura-tion. Galileo attempted to supply a Microchannel orificeplate in the nominal configuration, but failed. Mechani-cally drilled (NASA), Microchannel (Galileo), and etchedsandwich (Lee) orifice arrays were supplied in "non-standard" configurations. The geometries of these

7Sum _

.003

f.//#k//////,//

_ASCA_:NONE

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_1

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Figure 30: Electroform Orifice Array Drawing

m.

.250

; _-.125

._._icroFab

75_ Orifice Pla_e

27

orificearraysaredescribedbelowin thesectionsthatdiscusstheexperimental results.

4.2 Orifice Plate Vendor Quotations and OrdersBased on the result of Phase I, quotations were re-quested from the vendors listed in Table VI (seeAppendix I for full company name and address). Alarger number of orifice plates were ordered for theelectroform and Fotoceram processes because most ofthe cost was related to tooling charges. No quotationswere originally solicited from Lee and Creare since theLee process was not known to us and EDM ranked lowin the Phase I analysis. Both these companies con-tacted MicroFab after Phase II had begun. The CreareEDM process was being developed as a part of anotherNASA heat exchanger development project. Both theCreare and Lee plates represented very low costopportunities to expand the jet-straightness informationbase generated during Phase II.

4.3 Drop Generator DesignBecause of the relatively small size of the orifice platesto be tested, a structurally transmitted stimulationmethod g (as opposed to an acoustic method) was em-ployed. This was accomplished by attaching the orificeplate to an aluminum block that was excited in a lengthmode (normal to the plane of the orifice plate) by twolong aspect ratio piezoelectric sheets attached to eachside of the aluminum block. The block was held at itscenter so as not to restrict the desired motion. A fluidmanifold was machined into the block and fluid connec-

Table Vh Orifice Array Vendors, Quotes & Orders

Vendor OrificePlate Type

Stork-Veco electroform

Litchfield electroform

Buckbee Mears electroform

Coming Fotoceram

Galileo MCP

NASA drilled

Lee sandwich

Creare EDM

QR = quotation receivedPR = number of orifice plates receivedPT = number of orifice plates tested

QR PR PT

Y 15 4

N 0 0

Y 10 4

Y 14 3

Y 4 2

na 3 2

N 2 2

N 2 2

PZT

mountingslot <

_-alignment pinmanifold slot

)O

38.1 mm t_

Figure 31: Drop Generator Design

tors added to both ends. Two fluid connections wereincluded so that high flow rate purging (or cross-flush-ing) of the orifice plate could be used for contaminationcontrol. Alignment pins, corresponding to the alignmentholes in the orifice plates, were pressed into the block.Figure 31 contains a drawing of the drop generatordesign and Figure 32 shows the drop generator inoperation.

4.4 Orifice Plate Assembly ProcessThe orifice plate/drop generator designs require that theorifice plate be attached to the drop generator block.Since the orifice plates are generally very thin, ad-hesive bonding was selected as the attachmentmethod. A B-stage adhesive was selected. An air-brushtype sprayer was used to deposit a thin film (less than15 microns) of epoxy onto the block. The orifice platewas then attached, using the mounting pins forreference. The block with the orifice plate attached wasplaced into a fixture that applied uniform pressure tothe orifice plate. The fixture was then placed in a ovento cure at 170°C for 30 minutes. Operating pressuresof up to 60 psig were used without causing failure ofthe adhesive bond.

28

4.5 Jet Straightness Test SystemTo evaluate jet straightness, a test system wasdesigned to hold the drop generator (withassembled orifice plate) in a fixture so that thejets could be observed through a microscopewith the field of view defined by the plane ofthe jets. Figure 33 illustrates the system. Asillustrated by Figure 32, electronics to drive thepiezoelectric crystals and to stroboscopicallyobserve droplet formation behavior wereintegrated with the test system. However, jetstraightness measurements were made onunstimulated jets. All jet straightness measure-ments were made using deionized water asthe working fluid and a pressure of 35 psig.

0

O

Quantitative jet straightness data was acquiredwith this system as follows. While the jets wereflowing, the image, consisting of 4-6 jets in thefield of view, received by a CCD cameraattached to the microscope, was captured andstored. A Targa M8 video board and the Javaimage analysis system were used to accomp-lish this. The microscope was then traversedto the next field of view, keeping one jet in the field ofview as a reference, where the image was againcaptured and stored. This process was repeated untilthe images of all the jets had been captured andstored. Each orifice plate thus required 10-11 images.

• • 0 • Q

l • l 0 t •• • • • • •

• • • • • O• • • • • •

q

O

&

Figure 32, Drop Generator Operation,Stork-Veco Orifice Array Driven at 40kHz

At this point, the jets were shut off and all data reduc-tion occurred off-line.

First, the individual images of the jets were enhancedto improve measurability. Then the centroid of each jet

DROPGENERATOR

CATCHER N I

• o

r'b-'_ ............. O'b-'}

UICROSCOPE

Figure 33: Jet Straightness test System Utilized in this Study

29

t0-!t

I

=E

L

1

I I [ tfOt_8 _-¢[

Figure 34: Automated, Two Component Jet-Straightness test System

3O

at a distance of 25.4mm (along the jet) from the orificewas determined in each captured field of view using theobject identification function of the image analysissystem. Finally, the locations of each jet at 25.4mmfrom the orifice were computed using the positions calc-ulated in each frame and the jet common to adjacentframes.

The same process of image capture and measurementwas used to determine the locations of the orifices onthe orifice plate. While the orifice locations were beingmeasured, orifice area and effective diameter wasmeasured.

Given the starting and ending locations of the jets, therelative jet straightness in th.e plane of the lets wasdetermined. Relative jet straightness is referenced tothe mean directionality of the jets whereas absolute jetstraightness is referenced to some reference plane,usually a mounting surface of the drop generator. Tosave money, a system capable of measuring only oneof the two (vector) components of jet straightness wasemployed in this study.

Before acquiring quantitative jet straightness data asdescribed above, every orifice plate that was assembledto a drop generator housing was qualitatively evaluatedand given a rating of A, B, or C. The grade of A meantthat, at 25.4mm below the surface of the orifice plate,none of the jets merged orcrossed. The grade of B meantthat, at 25.4mm below the surfaceof the orifice plate, <2 jets mergedor crossed. Finally, the grade of Cmeant that, at 25.4mm below thesurface of the orifice plate, two ormore jets merged or crossed.Screening plates in this mannerinsured that the time consumingquantitative measurements weremade on only the best orificeplates.

described below.

The system, illustrated in Figure 34, uses two perpen-dicular collimated light sources to illuminate each jet,one at a time. The resulting diffraction/shadow patternsare then imaged on two separate CCD arrays. Thelocation of the shadow on each CCD array is deter-mined and used, along with the location of the orificeon the array, to determine the vector jet angle. A lineartranslation stage provides coarse motion (+l_m) tolocate each jet at the single focal point defined by theCCD array optics. Location of the orifices can bedetermined by measuring the orifice plate directly or byduplicating the jet location measurement near theorifice plate. An alternate method, made possible byrecent advances in two-dimensional CCD arrays, woulddetermine directionality directly from the shadow/diffrac-tion pattern on the array.

4.6 Stork-Veco (Electroform) Orifice PlatesFifteen (15) electroform orifice plates were receivedfrom Stork-Veco. The overall appearance of the plateswas excellent. All of the orifices were very round withsharp edges and smooth surface. Figure 35 shows anSEM of a typical Stork-Veco orifice.

The orifice diameter distributions on five (5) Stork-Vecoplates were measured using the image analysis systemdescribed above. The results are shown in Figure 36,

In our original proposal, both thelow cost system described above,and a higher cost/performancesystem were proposed as options.The higher cost system wasbased on a system built (byMicroFab personnel) to test ink-jetprinter orifice arrays. For com-pleteness and future reference,the higher cost system, whichwould be required for pilot or pro-duction volume manufacturing, is Figure 35: SEM of a Stork-Veco Electroform Orifice

31

ORIGINAL PAGE IS

OF POOR (_J/LLITY

and are summarized in Table VII. The varia-

tion of orifice diameter within a given plate isvery small (0.3-0.6_m), but the mean orificediameter varies several microns (3.2pro maxi-mum) from plate to plate. This type of behavioris caused by variations in the plating rate,either over time (batch-to-batch) or at differentlocations in the plating bath. Both of thesecauses can be readily addressed by monitor-ing and controlling the process closely.

Judgements about orifice diameter variationmust be made relative to the measurementuncertainty. Repeated orifice diameter mea-surements of orifice

plate SV-14 were

Table VII: Summary of Stork-Veco PlatesOrifice Diameter Measurements

average, p.m

std. dev., pm

std. dev., %

]lsv.,Isv21sv31,,v4IsvsI avg|

69.3 70.5 69.8 I 72.2 67.3 69.8

0.5 0.5 0.6 0.3 0.6 0.5

0.7 0.6 0.8 0.5 0.8 0.7

std. dev. = standard deviation

made and themeasurement stan-dard deviation wasdetermined (with 50degrees of freedom)to be 0.18p.m. Giventhe lack ofsophistication of theedge detectionmethod employed,this is quite good.However, it will be astrong function oforifice plate quality(i.e., surface finishand edge sharpness),as will be seen withthe other orificeplates.

Four (4) Stork-Vecoorifice plates were as-sembled to drop gen-erator housings andinstalled in the jetstraightness testsystem. Orifice platesSV-1, SV-2, and SV-4received an A ratingand plate SV-3 re-ceived a B rating(due to two jets mer-ging) from the quali-tative evaluation.Quantitative measure-ments were thenmade on orifice platesSV-2, SV-3, and

74

73

72

71

70

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07

I SV-1 SV-2 SV-3 SV-4 SV-14 I)<- ....

_.LLLLLIIIIIIIIIIIIIIIIIIIIIIIIII_II/IllilIIIIIIIIIII

1 3 5 7 @ 1113151710212325272031333537304143454740

Orifice Number

SV-4. SV-1 was not Figure 36: Orifice Diameter Distributions, Stork Veco Plates

32

testedbecauseit becamedegradedby a corrosionproblemwiththe systemthatwassubsequentlyrem-edied.

Thequantitativejet straightnesstest results(jetanglefor eachorifice)forthethreeStork-Vecoorificeplatesareshownin Figure37 through Figure39, andaresummarizedinTableVIII.Thedatadoesnotshowanyclearly identifiable trends that might be eliminated orimproved by fabrication process modification and/orcontrol. This is confirmed by the histograms of the jetstraightness data shown in Figure 40 throughFigure 42. Given the numberof data points (50), the jetstraightness distributions for

!sall three orifice plates areapproximately normal.

Only orifice plate SV-2 comesclose to meeting the require-ments for a LDR orifice array:99% of the jets <5 mrad.However, the fact that theresults are fairly close to thedesired goal in the first at-tempt is encouraging.

4.7 Buckbee Mears (Elec-troform) Orifice Plates

Ten (10) orifice plates werereceived from Buckbee

Mears. The overall appear-ance of all the orifice plateswas good, but was consider-ably poorer tnan that of theStork-Veco orifice plates. Theorifices were not as round, theedges of the orifice were notas sharp, and the surface wasnot as smooth. Some of theorifices had "lumps" of mater-ial near the edge. These inter-fered with the orifice diametermeasurements and are a

likely cause of jet straightnessdegradation. It should be re-emphasized that the quality ofthe Buckbee Mears plateswas good, and only sufferfrom the comparison with theexcellent quality of the Stork-Veco orifice plates.

Table VIII: Quantitative Jet StraightnessResults Summary, Stork-Veco Orifice Plates

Standard Deviation ofOrifice Plate Jet Angle, mrad

SV-2 3.4

SV-3 5.6

SV-4 4.9

iaverage, 3 plates 4.6

10

4-5

-1G

-15I I I I I I I I 1 I I I I I I 1 1 I I I I I I ] I I LJ_.JJ_I I I I I I I I J_

5 9 13 17 21 25 29 33 37 41 45 49

Orifice Number

Figure 37: Jet Straightness Distribution, Stork.Veco Orifice Plate SV-2

15

1

-15i 5 9 13 17 21 25 29 33 37 4,1 45 49

10

6 o

Orifice Number

Figure 38: Jet Straightness Distribution, Stork-Veco Orifice Plate SV-3

33

Orificediameterdistributionson five (5) BuckbeeMearsorificeplatesweremeasured.Theresultsfor two(2)of theorificeplates are showninFigure43,andthedataforallfive orificeplates measuredaresummarizedin TableIX.Only two of the five orificediameter distributions areshowninFigure43forclarity•Theother threedistributionsaresimilarto thetwothatareshown.The diametermea-surementdeviationwasdeter-mined(with 50 degreesoffreedom) from repeatedmeasurementsof orificeplateBM-6to be 0.431_m.Thein-creaseinmeasurementdevia-

15

10

'_ 5

-5

-15t I 11 I I [ I I I I I I I I I I I I I I I I I l_J t I I 1 11 I I I I 11 I I I I I I 11 I I I

1 5 9 13 17 21 25 29 33 37 41 45 49

Orifice Number

Figure 39: Jet Straightness Distribution, Stork-Veco Orifice Plate SV-4

I

-20

/

I

-10 0

Jet Straightness, mrad

Percentof Jets

I

2O

28

24

20

- 16

- 12

8

- 4,

z/lll/iz

0 5 I0 15

Jet Straightness, mrad

CumulativePercentof Jets

2O

I00

- 80

60

40

2O

Figure 40: Histogram of Jet Straightness Data, Stork-Veco Orifice Plate SV-2

nf

-20 -10 0

Percentof Jets

I0 20

Jet Straightness, mrad

20

16

12

8

4

z

0 5

Jet Straightness,

_ _ _J_ ....._,_latwu

....... __t_

I0 15 20

mrad

100

8O

60

40

20

Figure 41: Histogram of Jet Straightness Data, Stork-Veco Orifice Plate SV-3

34

I

-20

Percentof Jets

-I0 0 I0 20

Jet Straightness, mrad

30

- V/f__l

I0

0

_ulative!_/'cent

ets_

5 i0 15 20

Jet Straightness, mrad

I00

80

60

40

20

Figure 42: Histogram of Jet Straightness Data, Stork.Veco Orifice Plate SV-4

tion over that of theStock-Veco orificeplates is attributableto the lower quality ofthe orifice plate sur-faces and the less

sharp orifice edgesassociated with theBuckbee-Mears ori-fice plates.

The variation of ori-fice diameter within agiven plate is verysmall (0.6-0.8_m), aswas the case with theStork-Veco orificeplates. Only one ofthe Buckbee Mearsplates had a diametervariation as small asthe worst Stork-Vecoorifice plate. Theaverage diametervariation from plate toplate (2.6t_m maxi-mum) was againgreater than the vari-ation on any givenorifice plate, but wasless than the Stork-Veco plate-to-plateaverage diametervariation. The com-ments pertaining toimprovement in the

79

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-=-==9_-- ----_K----

t )E

Itllillt

I I I I I I I I _.J_Lll III I I fill I illl I I I ] I I I i ] I I I I I IJ__

l 5 9 13 17 21 25 29 33 37 41 45 _,9

Orifice Number

plate-to-plate average Figure 43: Orifice Diameter Distributions, Buckbee Mears Plates (2 of 5)

35

diametervariationmadein thediscussionofthe Stork-Vecoresult also pertain to theBuckbeeMearsorificeplates.

Four(4) BuckbeeMearsorificeplateswereassembledto drop generatorhousingsandinstalledin the jet straightnesstest system.OrificeplateBM-2receivedanA rating,plateBM-1receiveda B rating,and platesBM-3andBM-4receivedC ratings(dueto multiplecrookedjets) fromthequalitativeevaluation.Quantitativemeasurementswerethenmadeon orificeplates BM-1andBM-2.

The quantitativejet straight-nesstestresults(jetangleforeachorifice)forthetwoBuck-bee Mearsorificeplatesareshown in Figure 44 andFigure45, and aresummar-izedinTableX.TheresultfororificeplateBM-2wouldhavebeenasgoodasthoseof thebestStork-Vecoplate(SV-2)if the four endjets had nothad such largeangles.His-togramsofthejetstraightnessdataareshownin Figure46and Figure47.Again,thejetstraightnessdistributionsforbothorificeplatesareapprox-imatelynormal.

On average, the BuckbeeMears orifice plates hadpoorerjetstraightnessperfor-mancecomparedtotheStork-Vecoorificeplates.Theper-formanceof the electroformorificeplatesfromthesetwovendorswas close enough(bothto eachotherandtotheultimate LDR performancegoal,99%of jet <Smrad) thatwe do not advocate selectinga single vendor for futuredevelopment at this time.

Table IX: Summary of Buckbee Mears PlatesOrifice Diameter Measurements

std. dev., %

JlBM'IBM21BM-3IBM-'IBM0Iavg75.4 75.4 78.0 77.4 76.7 76.6

0.8 0.7 0.6 0.8 0.8 0.7

1.1 1.0 0.7 1.0 1.1 1.0

std. dev. = standard deviation

15

10

"_ 5

-5

-10

-15"I I I I | l I I I I I I I I ]._

1 5 9 13 17 21 25 29 33 37 41 45 49

Orifice Number

Figure 44: Jet Straightness Distribution, Buckbee Mears Plate BM-1

15

10

5

-5

-10

-15

"1Jj_LL.L_I 1 I t I I I I i I I I I I I I I I I I I I I I I I I I I I 1 I [ t I I I I 1 I I 1 I I 1

1 5 9 13 17 21 25 29 33 37 41 d5 49

Orifice Number

Figure 45: Jet Straightness Distribution, Buckbee Mears Plate BM-2

36

Table X: Quantitative Jet StraightnessResults Summary, Buckbee Meats Orifice Plates

Standard Deviation of

Orifice Plate Jet Angle, mrad

BM-1 6.6

BM-2 6.0

average, 2 plates 6.3

I I

-20

Percentof Jets

I I

-10 0 10 20

Jet Straightness, mrad

20 F I00

_ Icent

, N ;:::::: .o• _J_/,_///_::::::Z::..........

0 5 I0 15 20

Jet Straightness, mrad

Figure 46: Histogram of Jet Straightness Data, Buckbee Mears Orifice Plate BM-1

Percent_ ofJets

/

-20 -I0 0 i0 20

Jet Straightness, mrad

i16 _ ('um__lativ] Peicent

, <

12 ! °f'let=i

4

, 21 ! .....

0 5 I0 15 20

Jet Straightness, mrad

I00

S 80

6O

4O

20

Figure 47: Histogram of Jet Straightness Data, Buckbee Mears Orifice Plate BM-2

37

4.8 Coming (Fotoceram) OrificeFourteen (14) orifice plates were received fromComing. Visual inspection revealed severalsignificant attributes of these plates.

1. Approximately half the orifices were fairlyround, while the rest had jagged, sawtoothedges. The edges of the orifices wererounded, not sharp.

2. The orifice diameter could be seen (undera microscope, but without the use of ascale) to vary greatly.

3. The minimum diameter on most of theorifices was not atthe orifice exit.

Table Xh Summary of Corning PlatesOrifice Diameter Measurements

average, I_m

std. dev., pm

std. dev., %

std. dev. = standard deviation

IIOOl1oo-21oo-3Ioo,Ioo-+lay°81.7 81.2 84.5 85.6 80.0 82.6

5.7 4.7 4.4 4.4 3.2 4.5

7.0 5.8 5.2 5.1 4.0 5.4

This indicated thatthe orifices wereetched from twosides. Having theminimum diameterin the interior olthe orifice is alikely cause of thepoor straightnessperformance dis-cussed below.

. The surface of the

Fotoceram plateswas granular (aswould be expec-ted with this pro-cess), flat, anduniform. Figure 49shows a SEM of atypical Fotoceramorifice.

Orifice diameter distri-butions on five (5)Cornlng orifice plateswere measured. Thedistribution for one ofthe orifice plates isshown in Figure 48,and the data for all

five orifice platesmeasured are sum-marized in Table Xl.The orifice diameterdistribution for CO-5,shown in Figure 48,

9O

88

86

78

76

74

-oJ

%

cb_

Jtt

)

l

+I+I}IIIIIIIIJ_LIIII+IIIIIIlIIIIIIIIIIIIIII_II}IIII1 5 9 13 17 21 25 29 33 37 41 d5 49

Orifice Number

had the least diam- Figure 48: Orifice Diameter Distributions, Corning Plate CO-5 (1 of 5)

38

ORIGINAL PAGE IS

eter variation of the five platesmeasured. The diameter mea-surement deviation was deter-

mined (with 50 degrees of free-dom) from repeated measure-ments of orifice plate CO-1 to be0.721_m. The large measurementdeviation is caused by the mini-mum diameter occurring interiorto the orifice• Although themeasurement variation is muchlarger than those determined forthe Stork-Veco and BuckbeeMears orifice plates, it is still quitesmall compared to the actualdiameter variation on the Comingorifice plates.

The orifice diameter distributionsfor the Coming plates had almostfive times the diameter variation

compared to those of the Stork-Veco and Buckbee Mears (elec-troform) orifice plates. Al-though the amount of vari-ation measured might be Jacceptable for an LDR ap-plication, it is indicative of aprocess that is not undercontrol, possibly an uncontrol-lable process. Future LDRorifice array developmenteffort should try to determine,with Coming, if the currentresults are characteristic of

what Coming can achieve, orif the process can be signifi-cantly improved•

Figure 49: SEM of a Fotoceram Orifice

15

10 -i

-5 -

-10 -

I-15

1

Five (5) Coming orifice plateswere assembled to drop gen-erator housings. All fivecracked during curing(170°C), probably due tothermal expansion coefficientmismatch. However, thecracks on four (4) of the plates were at the edges of theplates (ie., awaY from the orifices), and three (3) ofthese did not leak. The cracks on the three plates thatdid not leak had no effect on jet straightness.

A

II I!l I I ILl I I I I I II I I I I I I I ] [I I L

5 9 13 17 21 25 29 33 37 4145

Orifice Number

Figure 50: Jet Straightness Distribution, Corning Plate CO-3

The three (3) surviving Coming orifice plates/dropgenerator assemblies were installed in the jet straight-ness test system. All three received C ratings from thequalitative evaluation. In order to have some quan-

Table XIh Quantitative Jet StraightnessResults Summary, Cornlng Orifice Plate

Standard Deviation ofOrifice Plate Jet Angle, mrad

CO-1 9.7

39

JPZcg F.7#_

I !

-2O

| I

-10 0 10 20

Jet Straightness, m_ad

8

4f_

"

0 5

"HHHH,

i///////_./ri11H_

2vlzx,_k

9Z//_,:

g41/+;;

.........g_._

_../.:.>>

".?,_,>.."

i

10 15

Jet Straightness, mrad

Nnutlt

.....-.....

20

- i00

80

lyeit

60i

_0

20

Figure 51: Histogram of Jet Straightness Data, Cornlng Orifice Plate 00-3

titative jet straight-ness data base forthe Coming orificeplates, plate CO-3was quantitativelyevaluated for jetstraightness.

The jet straightnessdistribution for CO-1is shown in Figure 50and the overall results

are given inTable XII. Given thelarge variation inorifice diameters and

the negative obser-vations related toorifice shape and thelocation of the mini-mum orifice diameter,it is somewhat sur-prising that the jetstraightness is onlyabout -50% larger(worse) than theaverage of the Buck-bee Mears orifice

plates and -100%larger than the Stork-Veco orifice plates•Figure 51 shows thejet straightness distri-bution for CO-3.

71

70

"i 68

Ill 66

_¢ I I0 10 20

ORIFICE

I CR-1 CR-2 l

<

I I30 _,0 50

Figure 52: Orifice Diameter Distributions, Creare Plates

40

Overall,the Corningorificeplateswere a surprisingdisappointment.If the orificeplateshadbeenetchedfromonesideonly, the minimum diameter would be atthe orifice exit, removing one possible source of jetstraightness error. Before eliminating Corning and/orFotoceram orifice plates from consideration for futureLDR development efforts, discussions should be heldwith Coming to determine the causes the poor orificequality and diameter control. In addition ,the impli-cations of single sided etching should be discussed.

4.9 Cream (EDM) Orifice PlatesElectro-discharge machining(EDM) was not rated veryhighly during Phase land,originalty, there were no plansto evaluate EDM orifice platesin Phase I1. However, Micro-Fab was contacted duringPhase II by Creare Inc. per-sonnel interested in providingorifice plates for our evalua-tion. They had developed anEDM orifice fabrication pro-cess for their High Heat FluxCold Plate for Space Applica-tions project, a Phase II SBIRcontract (NAS9-17574). Twoorifice plates (with the correctnumber of orifices and pitch)were provided free of charge.Since this represented a verylow cost opportunity to in-crease the number of orifice

plate types experimentallyevaluated during Phase II, iboth of the Creare EDMplates were measured for idiameter distribution and jetstraightness performance.

The orifice diameter distribu-tions for the Creare plates areshown in Figure 52 and are

15

10

-51

-10

- 15_--- II0

summarized in Table XIII. Thediameter variation for CR-1was the lowest (best) of the50 hole plates measured inthis study. Taken together, thetwo Creare plates had thelowest diameter variation of

the orifice plate types evaluat-ed in this study, along withthe Stork-Veco (electroform)orifice plates. Diameter mea-

Table Xlll: Summary of Creare PlatesOrifice Diameter Measurements

CR-1 CR-2 avg.

average, _m 69.1 66.1 67.6

std. dev., I_m 0.3 0.7 0.5

std. dev., % 0.4 1.0 0.7

std. dev. = standard deviation

I I I20 30 dO

Orifice Number

Figure 53: Jet Straightness Distribution, Creare Plate CR-1

15

I I , I I ..-150 i0 20 30 40

OrificeNumber

I0

5_

5O

Figure 54: Jet Straightness Distribution, Creare Plate OR-1

5O

41

-20

;$2:; )/;"_

I

-lO 0

Percentof Jets

|

i0

Jet Straightness, mrad2O

24

r-2o

- 16

- 12

- 8

4

l

VIXN

0

PJ_%_i__umulative

._"

5 10 15 20

Jet Straightness, mrad

i00

80

60

40

20

Figure 55: Histogram of Jet Straightness Data, Creare Orifice Plate CR-1

I

-20

J

/

-I0 0

Percent

of Jets

I !

10 20

Jet Straightness, mrad

2_

20 [_/7/./_

16

0 5 I0 15

Jet Straightness, mrad

_ulativeercentJets

1oo

8O

60

_0

20

i

20

Figure 56: Histogram of Jet Straightness Data, Creare Orifice Plate CR-2

surement deviation was not determined for the Creareorifice plates, but based on the quality of the surfacefinish and sharpness of the orifice edges, it is estimatedto be similar to that of the Buckbee Meats orifice plates(0.441_m).

Both Creare orifice plates were mounted to drop gener-ator housings and evaluated for jet straightness. Bothplates received an A qualitative jet straightness. Jetstraightness distributions for the two plates are shownin Figure 53 and Figure 54, and the data are sum-marized in Table XlV. Histograms of the jet straightnessdistributions for both Creare orifice plates are shown inFigure 55 and Figure 56. The average jet straightnessdeviation for the Creare plates was the second lowest(best) of the orifice plate types evaluated and was only0.2% higher (worse) than the Stork-Veco orifice plates.

Table XlV: Quantitative Jet StraightnessResults Summary, Creare Orifice Plates

Standard Deviation ofOrifice Plate Jet Angle, mrad

CR-1 4.9

CR-2 4.6

average, 2 plates 4.8

42

4.10 Lee (Etched Sandwich) Orifice PlatesDuring Phase II, a representative of the Lee Companycontacted NASA and MicroFab regarding their multipleorifice ink-jet bar code printer. The print head has 64orifices on 5081_m (0.020") centers in two rows. Leerepresentatives would not discuss the fabricationprocess, but by observing the orifice plate, the fol-lowing description was surmised.

The orifices are fabricated by joining (method un-known) thin metal plates, each with etched slots. Aphotomasking process is probably used to control theetched geometry. The slots in each plate are offsetfrom each other by half the pitch when the plates arejoined, producing a staggered array. After joining, thefront surface of the orifice plate is lapped, whichremoves any indicationof the parts line. A

joined stainlessplates

etched channels

Figure 57: Lee Sandwich Orifice Plate Configuration

sketch of the orificeplate design is shown inFigure 57.

This fabrication methodwas not known to uspreviously, and was notevaluated in Phase I. Aswith the Creare orificeplates, adding the Leeorifice plates to thePhase II evaluationrepresented a very lowcost opportunity to ex-pand the experimentaljet straightness data-base. Two standardorifice plates were or-dered and received fromLee.

The Lee orifices wererectangular (with a 2:1aspect ratio) and theorifice edges were veryrounded. Both orificeplates were measuredfor orifice diameter distri-bution, and the resultsare shown In Figure 58and summarized inTable XV. The meanorifice diameters areseen to be almostdouble the desired nom-

inal value, 751_m,due to

I I I I

9

1.13o-1 1__-2 1

I I II1 I[I I I II I I I I I 1 1

17 25 33 41

OrificeNumber

I I I I I I I I

4,9 57

the use of a standard Figure 58: Orifice Diameter Distributions, Lee Plates

43

part.Obtaining parts with thedesired orifice diameterwould not have been dif-ficult, if the straightnessresults had been good (theywere not). The diametervariation for one of the twoplates is fairly low (1.5%),while the diameter variationfor the other plate is almost3 times greater.

Table XV: Summary of Lee PlatesOrifice Diameter Measurements

average, I_m

std. dev., p.m

std dev., %

IILee,I'ee21avo137.3 130.1 133.7

2.1 5.3 3.7

1.5 4.1 2.8

std. dev. = standard deviation

Table XVh Quantitative Jet

Straightness Results Summary,Lee Orifice Plate

Orifice PlateStandard

Deviation ofJet Angle,

mrad

iI Lee-1 7.6

Because the Lee orifice

plates came already assem-bled to their own drop gener-

ator housing, a special hol- ' 15I_ _

ding fixture was designed andfabricated to adapt the Lee lodrop generator to the jetstraightness test system. Bothplates were mounted in the jet ._ 5straightness test system and

bothweregivenaCqualita-_'_ ii__

tive jet straightness rating. Forcompleteness, one of the two _,Lee orifice plates was quan-titatively evaluated for jetstraightness. Figure 59 andTable XVI show the jet

straightness test results for -_5_ _Lee-1. Figure 60 gives a his-togram of the jet straightnessdistribution for orifice plate

'°1

! ,I20 30

Orifice Number

@

Ao

I I I40 50 6010

Lee-1. As can be seen, the Figure 59: Jet Straightness Distribution, Lee Plate Lee-1

straightness results were verypoor. Based on our current understanding of the we do not recommend pursuing further developmentfabrication process and on the test results of this study, efforts with the Lee orifice plates.

I I

-20 -10

__ Percentof Jets

{£;

0 10 20

Jet Stmiohtness, mind

20

16

;',tE/////_/t/. ,;//i ,_,

4, p"/,;y//,,/:_,k'/,///_

0 I0 15

Jet Straightness, mrad

rt_ _ve_lt

rJ_J_

2O

t00

80

60

¢0

2O

Figure 60: Histogram of Jet Straightness Data, Lee Orifice Plate Lee-1

44

4,11 Galileo (Multichannel) Orifice PlatesThe Microchannel Plate (MCP) fabrication process de-scribed in section 3.3.8 was developed specifically toproduce a very high density of orifices in a small area.For their normal electronic, optical, and internal hydro-dynamic applications, the high orifice density of MCP'sis very advantageous. However, if used as an orificeplate whose function is to produce distinct jets, as is thecase for this study, the very high orifice density has twodrawbacks. First, jet merging can occur at very shortdistances from the orifice exit, even if the jets are all<5 mrad, making jet identification and straightnessmeasurement difficult, if not impossible. Second,transient wetting of the orifice plate during start-up cancause two or more jets to merge in a pool of fluid at theorifice plate. Some of these jet groups will not separateafter the start-up transient, again making jet identifi-cation and measurement difficult. Both these conditionsare also undesirable for an operational LDR array.

In light of the above, discussions were held with Galileopersonnel to define a configuration that would be bothtestable and manufacturable at a reasonable cost (andtime) in small quantities. To produce a custom orificeplate for this study from stock microchannel material,Galileo planned to mask off most of the fibers beforethe etching process. Only fibers that were approxi-mately in the desired locations would then have thecore glass etched out to produce an orifice. Total costwas quoted at $2,100 per orifice plate. Because of thehigh cost in small quantities, only two orifice plateswere ordered from Galileo.

To insure that a MCP orifice plate would be availablefor testing even if the custom orifice plate was notdelivered, two standard configuration orifice plates(glass capillary arrays in Galileo's terminology) wereordered. The standard configuration arrays (circular)were 13ram in diameter, l mm thick, and contained100_m diameter orifices. The 1001_m diameters were

Table XVII: Summary of NASA PlatesOrifice Diameter Measurements

average, _m 67.3 90.2 na

std. dev., I_m 0.9 1.9 1.4

std. dev., % 1.4 2.1 1.8

std. dev. -- standard deviation

note: 15 orifices per orifice plate

the closest available stock parts. Galileo normallymakes this product in much smaller diameters(10-201_m).

No functional custom parts were received from Galileo,due to problems they had with the etching and lasercutting processes they were using. Four (4) "best effort"parts were received, but after assembling three (3) todrop generator housings, it was discovered that noneof the holes were open. In addition, we noted that theoverall orifice quality was much poorer (out of roundorifices, rounded edges, and large variation on dia-meter) than what we had expected, both from previousexperience and from Galileo's literature. We were in-formed that Galileo uses two types of glass fibers intheir production. The fibers used in the parts sent to us(soda lime glass) do not have the precise diametercontrol that the other fibers have. Any future work withGalileo should specify the type of fiber used and aresultant orifice quality.

Since no custom plates were received from Galileo,special drop generator housings were fabricated for the13mm diameter standard pads. The drop generatorhousing had a slot with dimensions 0.8mm x 32mmover which the array was mounted. It was hoped thata sheet of jets <4-5 jets thick would be produced andsome individual jets would be distinguishable enough tomake jet straightness measurements. However, even at60 psi, no individual jets could be produced using eitherGalileo standard arrays: the jets coalesced immediatelyinto one large "jet."

MicroFab personnel have fabricated soluble core glassarrays, using Galileo optical fibers, with 220 orifices andhaving all the jets <3 mrad. The current results aretherefore both surprising and disappointing. It appearsthat producing quality glass fiber orifice plates forevaluation for an LDR application will require a muchmore time consuming (and expensive) effort thananticipated. Based on the degree of difficulty Galileoexperienced in trying to modify their high density arraysto produce a lower density array, as is required by anLDR application, we recommend that future efforts withsoluble core glass fibers be directed toward arraysfabricated in the manner described in section 3.3.7.

4.12 NASA (Mechanically Drilled) Orifice PlatesThree (3) mechanically drilled orifice plates werereceived from NASA Lewis. Each had only 15-16orifices on 6351_mcenters, due to fabrication difficulties.One of the plates had some form of contamination inseven (7) of the orifices which could not be removed,even with vigorous and extended cleaning. One of thetwo remaining orifice plates had a nominal orifice

45

diameterof 70p.mand theothera nominaldiameterof901_m.Visualinspectionoftheorifice plates indicatedthatthe orificequalitywasgood,with roundholesand sharpedges.

Thetwo (2) uncontaminatedorificeplatesweremeasuredfor diameterdistribution.TheresultsareshowninFigure61and are summarized inTableXVII. The variationindiameterforthemechanicallydrilledorificeplateswasfairlylow (good),but greaterthanthediametervariationfor theelectroformand EDMorificeplates.Becauseof the lownumber of holes (15, as op-posed to 50 on the standardorifice plates), care should betaken in comparing themechanically drilled orificeplate results (both diameterand straightness) with theother orifice plates.

94

90

o 86

r-

._ 69

I I i2 4 6 8 10 12 14

OrificeNumber

1 • i ] I I I I I I I I I I ]2 4 6 8 10 12 14

Orifice Number

Table XVllh QuantitativeJet Straightness

Results Summary,NASA Orifice Plate

OrificePlate

StandardDeviation

of JetAngle,mrad

NASA-1 5.7

NASA-2 4.0

average, 4.92 plates

15

i0

5

-i0

-15

Figure 61: Orifice Diameter Distributions, NASA Plates

I I t f ( | | I ( ( | | | { I

2 4 6 8 I0 12 14

Orifice Number

Figure 62: Jet Straightness Distribution, NASA Plate 1

Both NASA orifice plates were mounted to drop gener-ator housings and evaluated for quantitative jet straight-ness and both received an A qualitative rating. Thestraightness distributions measured for each orifice

plate are given in Figure 62 and Figure 63, and aresummarized in Table XVIII. No histograms of the jetstraightness distributions are given because of the lownumber of jets. Overall, the straightness of the NASA

46

orificeplateswasasgoodasany of the orifice platestested,butthe lownumberofjets tempers this resultsomewhat.

4.13 Summary of OrificePlate Testing Results

Diameter measurements for

the seven (7) orifice platesresulted in a very clear dis-tinction between orifice plateswith good orifice diametercontrol and those with poororifice diameter control. Both

types of electroform (Stork-Veco and Buckbee Mears)plates, the EDM (Creare)plates, and the mechanicallydrilled (NASA) plates hadaverage diameter standarddeviations <1.51_m. In con-trast, the Fotoceram(Coming), etched sandwich(Lee), and Microchannel Plate(Galileo) plates all had aver-age standard deviations>3.5t_m for the orifice dia-meters. The orifice diametermeasurement results aresummarized in Table XlX.Note that the Galileo plateswere not actually me'asuredfor orifice diameter and areincluded in the >3.5p.m aver-age standard deviation categ-ory on the basis of visualinspectionof the orifice plates.Also note that inclusion of theNASA orifice plates in < 1,5_maverage standard deviationcategory is based on muchless statistically significantdata (15 orifices per plate asopposed to 50 or greater onthe other orifice plates).

Table XlX: Orifice Diameter Measurements,Summary of Results for All Seven (7) Orifice Plate Types

Orifice Plate Type& Vendor Number of

Plates MeasuredAverage

Diameter, pmi

Electroform, 5 69.8 0.5Stork-Veco

Eiectroform, 5 76.7 0.7Buckbee Mears

Fotoceram, 5 82.6 4.5Corning

EDM, 2 67.6 0.5Creare

Etched 2" 133.7 3.7Sandwich,Lee

Multichannel Plate 0"" na naGalileo

2"" na 1.4MechanicallyDrilled, NASA

TOTAL 21

The jet straightness perfor-mance of the seven (7) orificeplate types generally followedthe orifice diameter results,but did not produce as clear a division in quality. Thebest orifice plates, the Stork-Veco electroform, theCreare EDM, and the NASA mechanically drilled orificeplates, all had average jet straightness standard devia-

AverageStandard

Deviation, pm

* Nonstandard arrays (64 orifices), but very similar to standard array.** Nonstandard, high density orifice arrays.*** Nonstandard arrays, 15jets per, 70pm and 90pm nominal diameters.

Figure 63: Jet Straightness Distribution, NASA Plate 2

tions <5mrad for the one component of jet straightnessmeasured. Although having a one component (_<5mradis respectable for a first attempt, the LDR requirementthat 99% of the jets be <5mrad is equivalent to

47

Table XX: Jet Straightness Measurements,Summary of Results for All Seven (7) Orifice Plate Types

Orifice Plate Type& Vendor

Number of PlatesEvaluated for

Qualitative Jet

Straightness

Qualitative

Ratings

Number ofPlates Evaluatedfor Quantitative

Jet Straightness

AverageStandardDeviation,

mrad

Electroform, 4 3 - A 3 4.6Stork-Veco 1 - B

Electroform, 4 1 - A 6.3Buckbee Mears 1 - B 2

2-C

Fotoceram, 3 3 - C 1 9.7Coming

EDM, 2 2 - A 2 4.8Creare

Etched 2" 2 - C 1 7.6

Sandwich,Lee

Multichannel Plate 2°. 2 - C 0 naGalileo

Mechanically 2"" 2 - A 2 4.9Drilled, NASA

19 11TOTALS

* Nonstandard arrays (64 orifices), but very similar to standard array.** Nonstandard, high density orifice arrays.*** Nonstandard arrays, 15jets per.

<_<l.9mrad for a normal distribution. For a rectangularsheet LDR configuration, 3 only the jet straightnesscomponent normal to the line of centers of the orificerows need be considered for all but the end jets.Therefore, the G<l.9mrad requirement applies to thatcomponent only. For a triangular sheet configuration, 3both components of jet straightness are important andthe c<1.9mrad criterion applies to the total jet straight-ness error. Assuming the two components of jetstraightness are independent, a total c<1.9mrad wouldbe equivalent to each component having _<l.3mrad.Thus, even the best orifice plates in this study have along way to go before achieving the required straight-ness.

The rest of the orifice plates tested fell into two groups:the Buckbee Mears electroform and Lee etched sand-wich orifice plates had straightness standard deviationsin the range 6-8mrad, and the Coming Fotoceram and

Galileo Multichannel plates had straightness standarddeviations >9.Smrad. Although the jet straightness forthe plates in both these categories was poor, theseplates had jet straightness performance as close to theperformance of the best plates as the best plates wereto the ultimate goal, the Galileo plate being the onlyexception!

The jet straightness test results are summarized inTable XX. Note that the Galileo plates were not actuallymeasured for jet straightness and are included in the>9.5mrad average standard deviation category on thebasis of visual observations. Also note that inclusion of

the NASA orifice plates in <5mrad average standarddeviation category is based on much less statisticallysignificant data (15 orifices per plate as opposed to 50or greater on the other orifice plates).

48

5.0 Discussion and ConclusionsThe results of this study would seem to indicate furtherdevelopment efforts be concentrated on electroform,EDM, and possibly mechanically drilled orifice plates.Before proceeding along these lines, the results of thisstudy should be shared and discussed with the ven-dors. Both EDM and mechanical drilling received lowratings for manufacturability in the Phase I evaluationand, unless these vendors have significantly improvedtheir processes, the favorable jet straightness results inPhase II do not in themselves make these processescandidates for further study. When manufacturability isconsidered along with the experimental results, the onlyfabrication process clearly recommended for furtherdevelopment efforts is electroform, with Stork-Vecobeing the preferred vendor.

As discussed above, the results for the Fotoceram(Corning) and Multichannel Plates were extremelydisappointing. The Fotoceram process is one of themost appealing for an LDR array application becauseof its suitability to volume production of large arrays.The Microchannel Plates are the commercially availableprocess closest to the soluble core glass fiber process,which is the only process to have demonstrated theability to produce arrays with 100% of the jets <5mrad(<3mrad in some cases). Therefore, before droppingFotoceram from further consideration, discussionsshould be held with Coming personnel to see if minormodifications to their process can significantly improvejet straightness. In particular, modifications to improvehole quality and to insure the minimum orifice diameteris at the orifice exit should be addressed. In addition,discussions should be held with Galileo personnel toexplore the possibility of their generating a low density,high quality orifice array for the LDR application.

6.0 RecommendationsMost of the orifice arrays evaluated in Phase II weresingle row, 50 hole arrays of 75_m diameter on 625_mcenters (nominally 3.2cm long). As currently envisioned,a subassembly of a Liquid Droplet Radiator (LDR)system will consist of a 4000 hole drop generatorconfigured in a 20x200 array of 75-1001_m diameterwith the orifice pitch/diameter in the 4-6 range. The nextlogical step in.the development of an LDR orifice arraywould be to obtain orifice plates with:

More rows

The most straightforward approach would keep thenumber of orifices at 50, orifice diameter at 751_m,andthe orifice pitch at 625p.m, while increasing the numberof rows to 5. Depending on the response of the vendors

selected and the data obtained from 5 row arrays, thenumber of rows might be increased to 10.

More orifices in one rowThe length of a 200 hole per row array with 751_mdia-meters and a pitch/diameter ratio of 4 (3001_m) wouldbe nominally 6cm. This represents a minimum arraylength because of the small orifice diameter and thelow pitch/diameter. As a first step, this array lengthwould be used with the current 75p.m orifice diameterand 6251_mpitch. Rounding up, this would result in 100holes in a row. As this is not a large increase in the 50holes used in the present study, two rows would bedesirable.

Smaller pitch/diameterThe pitch/diameter ratio affects the overall size, andthus weight, of the drop generator. In addition, struc-turally induced jet straightness effects are a function ofpitch/diameter. In both cases, low values are better, upto the point where heat transfer performance is de-graded. A simple extension of the current work wouldbe to obtain arrays of 100 orifice with 751_mdiameterson 300_m centers. These arrays would require nomodification of the existing jet straightness tester.

Based on the above, the following future effort isrecommended:

Task h Low Pitch/DiameterOrifice Plate Evaluation

From each of 2 vendors, obtain 5-10 single row orificeplates, each with 100 holes with diameters of 75t_m on3001_m centers. Fabricate drop generator housings,measure orifice diameters, assemble the orifice platesto the housings, measure jet straightness, and reduceand analyze the data. Compare the results with thePhase II results with single row, 50 hole plates with751_mdiameters on 300p.m centers.

Task Ih Multiple RowOrifice Plate Evaluation

From each of 2 vendors, obtain 5-10 multiple roworifice plates (4-6 rows, depending on vendor responseto the RFQ), each row having 50 holes with diametersof 75_m on 625_m centers. Design and fabricate dropgenerator housings, design and fabricate modificationsto jet straightness tester mechanical and fluid systems,measure orifice diameters, assemble the orifice platesto the housings, measure jet straightness, and reduceand analyze the data. Compare the results with thePhase II results with single row, 50 hole plates with75pm diameters on 3001_m centers.

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Task II1: Full Length OrificePlate Cost Estimate

From each of 2 vendors, obtain estimates for the costof producing 5-10 orifice plates with 5-10 rows, eachrow having 100 holes with diameters of 751_m on6251_m centers.

7.0 References

1. Roark and Young, Formulas For Stress and Strain, 5th edition, Niagara Hill, New York, 1975.

2. Peterson, R.F., Stress Concentration Factors, John Wiley and Sons, New York, 1974.

,

.

Mankamyer, M.M., R.E. Snyder, R.T. Taussig, "Liquid Droplet Radiator System Investigation,"AFRPL-TR-85-080, November 1985.

Filmore, G.L., "Drop Velocity from an Ink-Jet Nozzle", IEEE Trans. on Ind. App., Vol. 6, pp.1098-1103, Dec. 1983.

.

.

Wallace, D.B., "A Method of Characteristics Model of a Drop-On-Demand Ink-Jet Device Usingan Integral Drop Formation Method," ASME publication 89-WNFE-4, December 1989.

Kretz, M., editor, Mechanical Engineers' Handbook, John Wiley & Sons, New York, pp. 1527-1529, 1986.

.

o

.

K.A. White, "Liquid Droplet Radiator Development Status," 22nd Thermo-physics Conference, AIAA,July 1987.

Mattick, A.T., and A. Hertzberg, "Liquid Droplet Radiators for Heat rejection in Space," Energyto the 21"t Century, Vol. 1, AIAA, New York, 1980. pp. 143-i50.

Braun, H., "Fluid Jet Print Head," U.S. Patent #4,606,104, 1987.

5O

Appendix I: Vendor List

Over fifty companies or organizations were identifiedand approximately 70% of those were contacted. Thelist of companies identified is shown below. Trips weremade to visit eleven of these companies. The list ofcompanies identified is given by process type.

Where we have enough information to rank companiesin a given process area, the rankings are shown to theleft of the company name. Note that the rankings arerelative to LDR orifice array development only.

Electroform - PlatingStork-Veco68 Harvard StreetBrookline, MA 02146

Buckbee Mears245 E. 6th StreetSt. Paul, Minnesota 55164

EMF3025 Janitell RoadColorado Springs, CO 80901

Optical Radiation Corporation1300 Optical DriveAzusa, California 91702

GAR ElectroformingAugusta DriveDanbury, Connecticut 06810

AMT - XeroxJefferson RoadRochester, New York

A.J. Tuck Company10 Tuck RoadBrookfield, Connecticut 06804

GAR ElectroformingAugusta Drive Commerce ParkDanbury, Connecticut 06813

T.V. Jay Company1771 W. Sunnyside AvenueChicago, Illinois 60640

Hanovia100 Chestnut StreetNewark, New Jersey 07105

Chemical MillingOptifab, Inc.1550 W. Van BurenPhoenix, Arizona 85007

Photo Milling Inc.2437 Radley CourtHayward, California 94545

Litchfield Prec. Comp., Inc.

MECH - TRONICS Corp.1635 N. 25th Ave.Melrose Park, Illinois 60160

Photo Fabrication Eng. Inc.2 Granite ParkMillford, Massachusetts 01757

Tech - Etch, Inc.45 Aldrin Road

Plymouth, MA 02360

Vacco Industries10350 Vacco StreetSouth El Monte, CA 91733

Hutchinson Technology Inc.40 West Highland ParkHutchinson, Minnesota 55350

Laser DrillingEBTEC630 Silver RoadAgawam, Massachusetts 01001Laser Fare Ltd., Inc.

f Industrial Drive SouthLan Rex Industrial ParkSmithfield, R.I. 02917

Precision ApertureP.O. Box 10863

Fort Wayne, Ind. 46854

2

Raytheon Company4th Avenue

Burlington, MA 01803

Control Laser7503 Chancellor DriveOrlando, Florida 32809

Chicago Laser Systems, Inc.4034 North Nashville AvenueChicago, Illinois 60634

Lumonics12163 Globe RoadLivonia, MI 48150

Coherent General Inc.1 Picker RoadSturbridge, MS 01566

Image Micro Systems900 Middlesex TurnpikeBillerica, MA 01821

XMR5403 Betsy Ross Dr.Santa Clara, CA 95054-1102

Electro-Dischar,qe MachiningPanasonicOne Panasonic WaySecaucus, New Jersey 07094

CreareEtna Road, P.O. Box 71Hanover, NH 03755

Electrocut - Pacific1058 Terminal WaySan Carlos, California 94070

Aerospace Techniques, Inc.5-A Pasco Hill Rd.Cromwell, CT 06416

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WestHartfordTool& DieCo.840HolmesRoadNewington,Connecticut06111

NewEnglandDieCo.,Inc.49FordAve.Waterbury,Connecticut06111

SpectrumManufacturing,Inc.140HintzRoadWheeling,Illinois60090

F.D.MillerToolCompanyRD1 Box282Brodbecks,Penn.17329

Mechanical Punchin,q/Broachin,qAccurate Products Company404 Hillside AvenueHillside, New Jersey 07205

Chatham Precision Inc.342 Union Street

Stirling, New Jersey 07980

Fairview Machine Company427 Boston StreetTopsfield, MA 01983

Nikkoshi Co., Ltd.151 East Post RoadWhite Plains, New York 10601

Dupont

Celanese

KasenJapan

National Jet

Nippon Nozzles, JapanFrey, GermanCeccheo, Italian

Mechanical DrillingNASALewis Research CenterCleveland, Ohio

1 Lawrence Livermore Labs

National Jet10 Cupler DriveLaVale, Maryland 21502

Ted PeUa Inc.P.O. Box 510Tustin, California 92681

M.A. Ford CompanyDavenport, IA

International CarbideJamesv_le, Wl

Soluble Core Glass FibersNone available

Multichannel PlatesVarian Image Tube DivisionMicrochannel Plate Operation601 California AvenuePalo Alto, California 94303

Galileo Electro-Optics Corp.Galileo ParkSturbridge, MS 01518

Electron Beam Machinin.qM.G. Industries, Systems Div.9427 Fountain Blvd.Memomonee Falls, WI. 53051

Laybold Inc.120 Post RoadEnfield, CT. 06082

Ion DrillingCommonwealth Scientific Corp.500 Pendleton StreetAlexandria Virginia 22314

IICO3350 Scott Blvd.Santa Clara, California 95051

FotoceramComing Glass WorksMP 21- 3- 4

Coming, New York 14831

Hoya GlassJapan

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