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111111111111111~1~1~11~1~~I~II~II~lnl~1111111111111111 *30000002103418*
UNlVERSITI TUN HUSSEIN ONN MALAYSIA
BORANG PENGESAHAN STATUS TESIS·
1111\ I.. PREDICTION OF PUNCHING LIFE SPAN FOR PHOSPHOR BRONZE STAMPING OPERATION
SESI l'ENGAjIA:\i: _______ _
~,I\.I MOHO F ADZIL MUIN BIN HASHIM (HlIRllf IlESAK)
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No 7 lalan Wira 2 , Taman Wjra, J>t 86400 Pt Raja , Batu Pahat, lohor
"I hereby declared that I have read this thesis and in my opinion this thesis in terms
of contents and quality requirements fulfill the purpose for the award of the
Master of Mechanical Engineering".
Signature
Name of Supervisor PROF. DR. SULAIMAN BIN HASSAN
Date ·······7!:/~~/~1.: ................... .
PRJEDJICTJION OF PlUNCJB[][NG lLJIFE SPAN FOR PHOSPHOR BRONZE STAMPJING OPERATJION
MOHID 18' ADZJIlL MIDN 3JIN HASHJIM
Thesis submitted in fulfillment of the requirements for the award of Master of Mechanical Engineering
Faculty of Mechanical and Manufacturing Universiti Tun Hussein Onn Malaysia
AUGUST 2007
Thesis submitted in fulfillment of the requirements
for the award of
Master of Mechanical Engineering.
"I hereby declare that the work in this thesis is my own except for quotations and summaries which have been duly acknowledged"
Signature
Name of Student MOHD F ADZIL MUIN BIN HASHIM
Date 9., b/([)~1 Q:j 'f ................... 7. .. ~ ............................................... .
11
To my dear wife, Zohaida, the most positive person I know and a constant
source of encouragement. She believed in me before I believed in myself
iii
To my dear children Firdaus, Iman, Naeem, and Syifa. Also to my dear parents.
They would have been pleased and proud to see the results of this undertaking.
Acknowledgements
Praise be to Him only, with His Grace and Mercy, He had given me the strength and courage to do and complete this project.
iv
Firstly I want to thank my supervisor Prof. Dr Sulaiman Hj. Hassan from
UTHM for his support and guidance during the project period.
Special thanks to Mr. Takahiro Yoshiike who is a stamping die designer and
had supported me. Also special thanks to small group of skillful world class die
maintenance technicians with dedicated production staffs and subordinates who had
worked together with me to achieve these results.
I want to thank Vba programmers who have guided me to write a customized
program for punch re-sharpening level using advanced Vba source codes world wide
especially John Walken Bach (USA). In addition, thanks to Krueger from UK for the
opens source Constrained Cubic Spline Vba subroutine. Finally, to countless friends,
local and international who had guided me directly or indirectly.
v
ABSTRAK
Meramal hayat mata alat punch adalah kritikal untuk produk kerana ianya
akan menyebabkan kualiti produk menjadi kurang baik, merendahkan kadar
pengeluaran dan membazir masa bagi proses penajaman. Mata alat perlu diasah
selepas digunakan beberapa kali kerana dimensinya akan merosot dan ini
menyebabkan ketidak tepatan yang akan menyebabkan dimensi produk tidak
mengikut yang ditentukan. Salah satu kaedah yang digunakan bagi penentuan masa
penajaman mata alat ialah melalui anggaran kasar mengunakan unit kshots.
Selalunya anggaran ini tidak tepat dan ianya menyebabkan proses penajaman dan
proses mencetak yang tidak ekonomi. Kajian ini dilakukan untuk mengatasi
kelemahan ini. Mata alat yang digunakan dalam kajian ini adalah dari jenis
Cementite Tungsten Carbide dan bahan keIja yang digunakan ialah Phosphor Bronze
Strip. DaIjah kekerasan relatifbahan adalah lebih kurang 6.3. Proses pencetakan
yang digunakan ialah proses pencetakan progresif dan ianya dijalankan di sebuah
kilang elektronik yang termuka. Untuk kadar kshots yang tertentu, profil kehausan
mata alat diukur dan ketidak tepatan dimensi produk dikaji. Peningkatan burr pad a
produk juga dikaji pad a setiap 4000 unit produk. Hayat mata alat adalah ditentukan
apabila produk yang dihasilkan rosak. Semasa ini, mata alat akan membulat,
kehausan dapat dikenalpasti dan kerekahan pada hujung mata alat dilihat. Dapatan
dari kajian ini ialah hubungan kadar kehausan berkadar terns kepada kshots dan ini
memudahkan algorithma bagi penentuan hayat mata alat dibuat. Model simulasi
dicipta dengan mengunakan 'Constraint Cubic Spline algorithm', pengkaji telah
dapat meramal keturnpulan dan kehausan mata alat dengan lebih tepat. Walau
bagaimanapun bentuk dan bahan mata alat serta kekerasan relatif akan
mempengaruhi algorithma ini. Kajian ini menjimatkan kos proses pencetakan
melalui mengurangkan ketidak tepatan ramalan kehausan dan hayat mata alat yang
seternsnya mengurangkan kerosakan produk, mengurangkan burr dan membolehkan
penajaman dibuat dengan lebih tepat. Secara keseluruhan, algorithma yang didapati
dapat menambah baik kecekapan dan menambah produktiviti.
VI
ABSTRACT
Predictions of punching life span for stamping process is critical since affect the
quality of product, the production rate and cause waste in time and cost. The punch
need to be sharpened correctly after a number of punches since its dimensional
accuracy will deteriorate and cause inaccuracy in the dimensions of the product and
thus do not satisfy the quality requirements. One of the method that are normally
used to determine the point where re-sharpening should be carried out is through
estimating the number of shots or unit kshots that will produce products that are
dimensionally inaccurate and the occurrence of burr on the product. The research
was carried out to overcome this problem. The punch that was used is made of
Cementite Tungsten Carbide and the work piece is Phosphor Bronze Strip. The
relative hardness is about 6.3. The stamping process is a progressive stamping
process carried out in a well known electronic factory. The profile of the wear of the
punch is measured and the error in product dimension is identified. The increase
presence of burr is also studied and identified for every 4000 product. The end of
punch life span is determined when there is a dimensional inaccuracy on the product
and the product is rejected. This research found that at this point punch is rounded,
wear is present and cracks occurred at the cutting edge of the tool. As a result of this
research, relation between the punch wear and kshots are found to be proportionate
and this enable an algorithm to be formulated. Simulation model is built to enable
more accurate algorithm is developed. The simulation model used 'Constraint Cubic
Spline algorithm'. The researcher is able to forecast a more accurately the kshots that
relates to punch wear and thus save products dimensional inaccuracy and product
rejects. An improved sharpening process is also possible and this provide accurate rc-
sharpening work. The accuracy of the sharpening prediction also reduce burr and
have enhance the efficiency of the resharpening process. In conclusion, the algorithm
has improved productivity and save cost to the company.
\'11
CONTENTS
CHAPTER TItLE PAGES
ACKNOWLEDGEMENTS iv
ABSTRACT "i T ABLES OF CONTENTS "II
LtST OF FIGURES xi
LlST OF TABLES X" liST OF SYMBOLS xvi
LiST OF DEFINITION xvii
LlST OF APPENDIXS xxiii
CHAPTER 1 INtRODUCTION
1.1 Needs For Prediction of Punching
Life Span
1.2 Research Motivation 2
1.3 Aim 2
1.4 Research Objectives -. .)
1.5 Research Scope 3
Vlll
CHAPTER 2 LITERATURE REVIEW 4
2.1 Introduction 4 2.2 Punch Wear Characteristics 4 2.3 Wear Mechanism and Quantification 12 2.4 Quantification of Adhesive Wear 14 2.5 Punch Wear At The Cutting Edge 16 2.6 Summary 19
CHAPTER]U THEORY OF STAMPING AND FACTORS 20 THAT ASSOCIATES WITH PUNCHING LIFE SPAN
3.1 Introduction 20 3.2 The Theory of Stamping 20
3.2.1 Classification of Stamping 21 3.2.2 Progressive Stamping 25
3.3 Basic Characteristics of Shear Cutting 26 3.4 Factors For Stamping Accuracy 29
3.4.1 Machine Accuracy 29 3.4.2 Static Accuracy 29 3.4.3 Dynamic Accuracy 30
3.4.4 Die Set Accuracy 31 3.4.5 Influence of punch
die clearance 32 3.4.6 Insufficient Clearance 33 3.4.7 Excessive Clearance 34 3.4.8 Stock Material 35
Accuracy 35
3.4.9 Phosphor Bronze Strip 35 3.5 Summary 36
IX
CHAPTER IV EXPERIMENT AL METHOD 38
4.1 Introduction 38 4.2 Experimental Procedure Flow Chart 39 4.3 Selection Of Punches 40 4.4 Preparation Of Stamping Machine 44 4.5 Stamping Die Set 44
4.6 Equipments 45 4.7 Scientific Imaging Software 47 4.8 Data Analysis Software 47
4.8.1 Interpolation Algorithms 48 4.8.2 Linear Piecewise Interpolation 48
4.8.3 Constrained Cubic Spline
Interpolation 49 4.8.4 Measures For The
Estimation of Predicted 51
Error
4.9 Punching Operation 52
4.10 SEM Micrograph of Punch Dull
Surface 53 4.11 Measuring The Punch Wear 55 4.12 Equation of The Wear Profile 55 4.13 Computation of Punching Life
Span and Wear Characteristics 58
4.14 Summary 59
CHAPTER V RESULTS AND DISCUSSIOl\S
5.1 Introduction
5.2 Punching Life Span
5.3 Validation of Punching Life Span
5.3.1 Validation of Punch SI Life
Span
5.3.2 Validation of Punch S2 Life
Span
5.3.3 Validation of Punch S3 Li fe
Span
5.4 Prediction of Optimum Re-sharpening
Length ofWom Punch Program
5.5 Validation of Punch SI Side Wear
Length
5.6 Validation of Punch S2 Side Wear
Length
5.7 Validation of Punch S3 Side Wear
Length
5.8 Summary
CHAPTER VI CONCLUSION
6.1 Conclusion
6.2 Contribution to Science
6.3 Future Works
REFERENCES
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XI
LIST OF FIGURES
FIGURES TITLE PAGES
2.1 Characteristics factors related to occurrence of 5
burr (After Kanno, 1986)
2.2 Relationship between the surface abrasion of the 6
punch and the occurrence of burr (After
Kanno,1986)
2.3 Schematic area of side wear (Mter Mitsumi 8
Corp,2002)
2.4 Transition of area of side wear (After Mitsumi 8
Corp,2002)
2.5 Transition of burr height with different punch 9
materials (After Mitsumi Corp,2002)
2.6 Transition of burr height with increase in number II
of shots (After Mitsumi Corp,2002)
2.7 Mechanism of adhesive wear by plasticity (After 13
Roberts,2003)
2.8 Model for derivation of Archard wear equation 14
(After Roberts, 2003)
2.9 Forces reacting on tooling surface during 17
punching process (After Lange, I 975)
2.10 Tooling conditions of the shearing process (After 17
Yoshida 2001)
2.11 SEM Micrograph of crack initiation (After 18
Yoshida, 2001)
3.1 Plastic deformations phase (After Lascoe, 1986) 21
XlI
3.2 Penetration deformations phase (After 21
Lascoe,1986)
3.3 Fracture phase (After Lascoe,1986) 22
3.4 Stamping operations using shearing principles 24
(After Lascoe,1986)
3.5 Comparison of cutting off and parting operation 25
(After Lascoe ,1986)
3.6 A progressive stamping skeleton (After 26
Shinano,1985)
3.7 The four basic characteristics of shearing cutting 27
(After Lascoe,1986)
3.8 Theoretical part edge after blanking (After 28
Taupin, ,1996)
3.9 Actual part edge after stamping using phosphor 28
bronze material
3.10 The effects of clearance towards part's e (After 33
David, 2000)
3.11 Effects of insufficient clearance towards facture
zone (After David, 2000) 33
4.1 Flowchart for the experimental procedure 39
4.2 Location of punches in the stamping die 40
4.3 The pilot punch identified as S 1 41
4.4 The oblong pilot punch identified as S2 42
4.5 The punch identified as S3 42
4.6 Stamping machine 44
4.7 The stamping die set 45
4.8 The Scanning Electron Microscope 46
4.9 Overshooting of Cubic Spline and Smoothness of 51
Constrained Cubic Spline
4.10 Cleaning the punch before analyzing 53
4.11 Mounting the punch on the SEM stage 54
4.12 SEM micrograph of the punch wear cutting edge 54
4.13 Screenshot of SCION imaging software 55
Xlll
4.14 Screenshot of the Excel Function to extract 56
coefficients
4.15 Screenshot of tabulated data points 58
4.16 Equations of punch wear profile after 5.1 Mshots 57
4.17 Screen shot of the computed worn punch loss area 59
5.1 (a) Measured variables of worn punch 62
5.1 (b) Schematic of punch re-sharpening length 63
5.1 (c) Comparison of burr height between (a) sharp 66
punch and a (b) worn punch when life span is
reached
5.1 (d) SEM micrograph of worn punch ex 1200) 67
5.1 (e) SEM micrograph of a failed punch 67
5.2 Comparison between shots-dependent of average 69
area loss on different punches S 1, S2 and S3
5.3 Agreement between shot -dependence on average 72
area loss and recorded area loss of punch S 1 is
reached between 0 Mshots to 4.7 Mshots
5.4 Agreement between shot-dependent average area 73
loss and recorded area loss of punch S2 is reached
between 0 Mshots to 5.2 Mshots
5.5 Agreement between shot-dependent average area 74
loss and recorded area loss of punch S3 is reached
between 0 Mshots to 5.4 Mshots
5.6 Process flow for predicting and validating the side 76
wear length
5.7 Agreement between shot-dependent side wear 78
lengths of recorded and predicted curve of punch
S1 is reached between 0 Mshots to 4.7 Mshots.
5.8 Agreement between shot-dependent side wear 79
lengths of recorded and predicted curve of punch
S2 is reached between 0 Mshots to 4.9 Mshots.
5.9 Agreement between shot-dependent side wear 80
lengths of recorded and predicted curve of punch
S3 is reached between 0 Mshots to 5.4 Mshots
XIV
B.l Recorded data for checking stamping machine 98
dynamic accuracy
E.l A straight is used to approximate the curve f(x) 101
between X 1 and x2
F1.1 Comparison between the cutting edge of the
punch S 1 taken at a different interval
F1.2 Shows the comparison of punch's wear profile at 106
different intervals
F1.3 The CCS interpolation has fitted a smooth line 108
between the observed data points
F1.4 Shows the screenshot of the simulation program 109
01.1 Wear profile of punch SI after run 01 110
01.2 Wear profile of punch SI after run 02 110
01.3 Wear profile of punch SI after run 03 111
01.4 Wear profile of punch Sl after validation process 111
02.1 Wear profile of punch S2 after run 01 112
02.2 Wear profile of punch S2 after run 02 112
02.3 Wear profile of punch S2 after run 03 113
02.4 Wear profile of punch S2 after validation process 113
03.1 Wear profile of punch S3 after run 01 114
03.2 Wear profile of punch S3 after run 02 114
03.3 Wear profile of punch S3 after run 03 115
03.4 Wear profile of punch S3 after validation process 115
H1.1 Samples of punch S 1 micrograph after run 02 116
H1.2 Samples of punch S 1 micrograph after run 03 116
H2.l Samples of punch S2 micrograph after run 02 117
H2.2 Samples of punch S2 micrograph after run 03 117
H3.l Samples of punch S3 micrograph after run 02 118
H3.2 Samples of punch S3 micrograph after run 03 118
xv
LIST OF 'fABLES
TABLES TITLE PAGES
2.1 List of punch material used to determine life span 7
3.1 Classification of stamping operation 23
4.1 The operational conditions of stamping machine 43
5.1 Area loss by worn punches 81,82 and 83 68
5.2 8ummary of observed wear rates between punches 70
81,82 and 83
5.3 Validation results of punches life span and wear 75
rate
5.4 Prediction accuracy and curve validation range 81
Fl.l An extract of the excel formula that generates the 104
coefficients
Fl.2 A detail list of data generated by the polynomial 105
equation of the punch model 81 at the 2nd
repetition of the industrial experiment
Fl.3 Data of punch model 81 107
Fl.4 Data generated by Constrained Cubic 8pline 107
Interpolation
A
H
V
W
Wsp R2
spm
K
K
L
Mshots
LIST OF SYMBOLS
Area loss due to wear at the punch cutting edge
Hardness
Volume loss due to wear at the punch cutting edge
Wear rate of a punch (mm2/Mshots)
Specific Wear Rate (mm2/m/N)
Coefficient of determination.
Unit of stamping velocity in strokes per minute.
Wear rate (mm2/m)
Archard wear coefficient
Life of a punch before next re-sharpening
The unit of punch hits through the stock material.
XVI
Abrasion
Abrasive
wear
Adhesion
Adhesive
wear
Blank
: Blanking
xvii
LIST OF DEFINITIONS
A process where hard particles are forced against and
moved along a solid surface.
It is a displacement of material, due to hard particles
or hard protuberances. A hard body plastically
deforms (with or without removal of matter) a softer
body.
(1) The attractive force between adjacent surfaces in a
frictional contact; (2) the state in which interfacial
forces hold two surfaces together.
At a certain moment, the force applied to the contact is
supported by the existing junctions. An adhesive
junction is produced. It is either hardly resistant at all
and the two bodies separate with no change, or the
junctions is relatively resistant, and a crack forms in
the less resistant body.
The piece of sheet or strip metal produced in cutting
dies. The produced pieces are discrete and have no
material carrier.
The process of cutting out a flat piece of the size and
shape necessary to produced the desired part.
Bolster plate
Burr
Burr side
Capacity of a
press
Clearance
Crank press
Die set
Die shoe
The static plate attached to the top of the bed of a
press.
xviii
A rough ridge, edge, protuberance, or area such as that
left on metal after cutting, drilling, punching, etc. In
stamping it occurs in cutting dies because of the
clearance between punch and die.
This term is refers to the side or face of a blank or
other stamping which comes in direct contact with
punch in a blanking operation, and the side or face of a
blank or other stamping which comes in direct contact
with the die in a punching operation.
The related capacity of a press is the pressure, in tons,
which the slide will safely exert at the bottom of the
stroke in doing work within the range of the press.
In punching and shearing dies, the gap between the die
and the punch.
A mechanical press the slide of which is actuated by a
crankshaft.
A tool holder held in alignment by guideposts and
bushings and consisting of a lower shoe, upper shoe or
punch holder, guideposts and bushings.
A plate or blocks which die holder is mounted. A die
shoe functions primarily as a base for the complete die
assembly and, when used, is bolted or clamped to the
bolster plate or face of slide.
Elastic limits
Flank of punch
Metal
Progression
Progressive die
Punch
Punching
XIX
The maximum stress to which a material or body can
be subjected and still return to its original shape and
dimension.
The position at the horizontal plane of punch where it
will shear the stock material.
A group of substance that can conduct electricity and
heat and can be hammered into shape or draw out in
sheets.
The precise linear travel of the stock strip at each press
stroke and is equal to the inter-station distance. Also
called pitch, advance, or feed.
A die with two or more stations arranged in line for
performing two or more operations on a part one
operation usually being performed at each station.
The parts are connected by a carrier strip until final
parting or cutoff operation.
i) The male part of the die, as distinguish the female
part called the die. The punch is the upper member of
the complete die and is mounted on the slide.
ii) The act of piercing or punching a hole. Also
referred to as punching
The die shearing of a closed contour in which the
sheared out sheet metal part is scrap.