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Selecting manufacturing processes
Manufacturing process decisions Deformation processes Casting processes Sheet metalworking Polymer processing Machining Finishing Assembly Material compatibilities / Process
capabilities Material costs, Tooling costs, Processing
costs
How would we manufacture a mountain bike ?
TopTube
RearDerailleur
Front Brake
Rear Brake
SaddleSeatPost
Pedal
Handle Bar
DownTube
Fork
(Courtesy of Trek Bicycle, 2002)
Manufacturing process decisions
How do we choose the specific manufacturing processes?
How do the selected materials influence the choice of manufacturing processes?
Would product function or performance issues influence our choice of processes?
What criteria should we use to select processes?
Which criteria are more important? Who will make the final decisions?
Parts undergo sequence of processes
Primary - alter the (“raw”) material’s basic shape or form. Sand castingRollingForgingSheet metalworking
Secondary - add or remove geometric features from the basic forms
Machining of a brake drum casting (flat surfaces)Drilling/punching of refrigerator housings (sheet metal)Trimming of injection molded part flash
Tertiary - surface treatments PolishingPaintingHeat-treatingJoining
Changes?
Part / Mfg. Process Considerations
1. Production Volume2. Part Size (overall)3. Shape Capability (features) boss/depression 1D boss/depression >1D holes undercuts (int./ext.) uniform walls cross sections - uniform/regular rotational symmetry captured cavities
Types of manufacturing processes
E xtrus ionF org ingR o ll ingB ar d raw ingW ire d raw ing
D eform ation
C en trifugalD ie cas t ingInvestm entP erm anen t m o ldS and cas t ing
C ast ing
B end ingB lank ingD raw ingP unch ingS hear ingS p inn ing
S hee tM etal
B low m old ingC ast ingC om press ion m o ld ingE x trus ionIn jec tion M old ingT herm oform ingT ransfe r m o ld ing
P o lym erP rocesses
B oringD ril lingF ac ingG rind ingM ill ingP lan ingT urn ingS aw ingE C M , E D M
M ach in ing
A nod iz ingH on ingP a in tingP la t ingP o lish ing
F in ish ing
A utom atedB ond ingB raz ingM anualR ive tingS o lde r ingW eld ing
A ssem bly
M anufac tu r ingP rocesses
How is the input material
changed?
Investment casting
Wax patternis cast
Wax removedby melting
Molten metal solidifies in cast
Ceramic mold is removed
Ceramic mold(hardened slurry)4-part pattern tree
Blow molding
Extruderair injector
parison
Part isremoved
Airblown into
parison
Mold halvesclose
Molten parison is extruded
Injection molding
Shear-heating
Cavity halfof mold
Core halfof mold
Ejector pins
Moving
Feed hopper
Sprue
Fixed
Barrel
Pellets
Mold closure directionParting
plane/surface
Example of a box …with no undercuts
core
cavity
partingline
mold closure
directionplastic
injection
ejector pins
Solidification processes
Casting ProcessesSand CastingDie CastingInvestment CastingCentrifugal
Polymer ProcessesInjection MoldingBlow MoldingThermoFormingCompression Molding
solid Part molten material freezing
Flow (voids, flash)Cooling time (cycle time)TemperatureMold complexity Warpage Post processing Costs (materials, tooling, processing)
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Machining processes
E xtrus ionF org ingR o ll ingB ar d raw ingW ire d raw ing
D eform ation
C en trifugalD ie cas t ingInvestm entP erm anen t m o ldS and cas t ing
C as t ing
B end ingB lank ingD raw ingP unch ingS hear ingS p inn ing
S hee tM etal
B low m old ingC as t ingC om press ion m o ld ingE x trus ionIn jec tion M old ingT herm oform ingT ransfe r m o ld ing
P o lym erP rocesses
B oringD ril lingF ac ingG rind ingM ill ingP lan ingT urn ingS aw ingE C M , E D M
M ach in ing
A nod iz ingH on ingP a in tingP la t ingP o lish ing
F in ish ing
A utom atedB ond ingB raz ingM anualR ive tingS o lde r ingW eld ing
A ssem bly
M anufac tu r ingP rocesses
Machining – removal of material…
Sawing –using a toothed blade.Milling – from a flat surface by a rotating cutter tool. Planing – using a translating cutter as workpiece feeds.Shaping - from a translating workpiece using a stationary cutter. Boring - increasing diameter of existing hole by rotating the workpiece.Drilling- using a rotating bit forming a cylindrical hole.Reaming – to refine the diameter of an existing hole.Turning - from a rotating workpiece. Facing - from turning workpiece using a radially fed tool. Grinding - from a surface using an abrasive spinning wheel.Electric discharge machining - by means of a spark.
Machining process considerations
sawing, turning, boring, milling, drilling, grinding, ECM
material removed solid material machining
hardness, strength of materialshear forces = strong jigs & fixtures tool/bit wear, replacementsize of workpiece, fit machine?volume removedrate of removal, hp neededtolerances operator skill, CNCcosts (materials, tooling, processing)
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Finishing processes
E xtru s ionF org ingR o ll ingB ar d raw ingW ire d raw ing
D eform a tion
C en trifugalD ie cas t ingInvestm entP e rm anen t m o ldS and cas t ing
C as t ing
B end ingB lank ingD raw ingP unch ingS hea r ingS p inn ing
S hee tM etal
B low m o ld ingC as t ingC om press ion m o ld ingE x tru s ionIn jec tion M old ingT herm oform ingT ransfe r m o ld ing
P o lym erP rocesses
B oringD ril lingF ac ingG rind ingM ill ingP lan ingT urn ingS aw ingE C M , E D M
M ach in ing
A nod iz ingH on ingP a in t ingP la t ingP o lish ing
F in ish ing
A u tom atedB ond ingB raz ingM anualR ive t ingS o lde r ingW eld ing
A ssem bly
M anufac tu r ingP rocesses
protection?
Assembly processes – fastening / joining of 2 or more components
E xtru s ionF org ingR o ll ingB ar d raw ingW ire d raw ing
D eform ation
C en trifugalD ie cas t ingInvestm entP erm anen t m o ldS and cas t ing
C as t ing
B end ingB lank ingD raw ingP unch ingS hear ingS p inn ing
S hee tM etal
B low m o ld ingC as t ingC om press ion m o ld ingE x tru s ionIn jec tion M old ingT herm oform ingT ransfe r m o ld ing
P o lym erP rocesses
B oringD ril lingF ac ingG rind ingM ill ingP lan ingT urn ingS aw ingE C M , E D M
M ach in ing
A nod iz ingH on ingP a in t ingP la t ingP o lish ing
F in ish ing
A u tom atedB ond ingB raz ingM anualR ive t ingS o lde r ingW eld ing
A ssem bly
M anufac tu r ingP rocesses
permanent?
Product function is interdependent
Material Properties
ProductFunction
ManufacturingProcesses
ProductGeometry
Are materials compatible with mfg. process?
Material Properties
ManufacturingProcesses
compatiblematerials & processes
Material-Process Compatibility
ME 488 Design for Manufacture & Assembly Materials Compatibility
Processes Sh
ap
e A
ttrib
utes
Cast
Iron
Carbon S
teel
Alloy S
teel
Sta
inle
ss S
teel
Alu
min
um
& a
lloys
Copper &
alloys
Zin
c &
alloys
Magnesiu
m &
alloys
Titaniu
m a
nd a
lloys
Nic
kel &
alloys
Refr
acto
ry m
eta
ls
Therm
opla
stics
therm
osets
Solidification sand castinginvestment castingdie castinginjection moldingstructural foamblow molding - extrblow molding - injrotational molding
Bulk impact extrusionDeformation cold heading
closed die forgingpowder metalhot extrusionrotary swaging
Metal machined from stockRemoval ECM
EDM
Profile Generation Wire EDM
Sheet sheet metal bendingForming thermoforming
metal spinning© R. J. Eggert, BSU (Based on data from Boothroyd, Dewhurst & Knight) pg 47 revision 9/02/03
Legend Normal practiceLess commonNot applicable
Is process capable of producing part geometry?
ManufacturingProcesses
ProductGeometry
“capable”geometry & processes
Process-first selection approach
Part Information1. Production Volume (run qty)2. Part Size (overall)3. Shape Capability (features)
boss/depression 1Dboss/depression >1Dholesundercuts (int./ext.)uniform walls
uniform cross sectionsregular cross sectionsrotational symmetrycaptured cavities
Manufacturing costs
Total Manufacturing Cost = Material + Tooling + Processing
raw mat’ls molds labor fixtures electricity jigs supplies tool bits O/H
(deprec.)
TMC = M + T + P (6.1)
Material costs per part
Let M = total materials costs (raw, bulk) q = production quantity
Then material costs per part, cM is
cM = M/q = (cost/weight x weight) / number of parts
Let’s reorganize the variables in the equation above cM = [cost/weight] [weight/number of parts]
= (cost/weight) (weight/part), and therefore cM = cost/part
Material cost per part (continued)
Let cw = material cost per unit weight, and wp = weight of finished part ww= weight of wasted material, scrap = ratio of wasted material weight / finished weight = ww / wp
Then the material cost per part, cM iscM = cw (wp + ww ) = cw (wp + wp )
(6.2)cM = cw wp (1+ )
(6.3)
e.g. sand casting cM = ($1/lb)(1lb/part)(1+.05) = $1.05/part
Tooling cost per part
Let T= total cost of molds, fixtures per production run q = number of parts per run
Then cT= T/q (6.4)
e.g. sand casting cT = ($10,000/run) / (5000 parts/run) = $2.00/part
Processing cost per part
Letct = cost per hour, (machine rate + labor)t = cycle time (hours per part)
then cP = ct t (6.5)
e.g. sand casting cP = ($30/hr) (0.3 hrs/part) = $9/part
Total cost per part
Cost per part,
c = cM + cT + cP
c = cw wp (1+ ) + T/q + ct t (6.6)
e.g. sand casting
c = $1.05 + $2.00+ $9.00
c = $12.05 / part
1
10
100
1000
0 1000 2000 3000 4000 5000 6000
Production quantity
Cos
t ($
/par
t)
A B C
Run quantity is important!
A-Sand casting B-Inj.Molding C-Machining
How can we lower the cost of parts?
c = cw wp (1+ ) + T/q + ct t (6.6)
1) purchase less expensive materials,2) keep our finished part weight low3) produce little manufactured waste4) design simple parts that result in less expensive
tooling 5) make many parts production run (i.e. batch)6) choose a manufacturing process that has a low
cycle time & cost per hour
Goal: minimize the sum of the terms!(not any one term in particular)