Progressive Dies: Principles and Practices of Design and Construction

468 Pages·163.039 MB·English

Dies
Progressive
Principl.es
and Practices
of Design
and Construction
Second Edition
F|Fndt\ Society of Manufacturing Engineers
trffiw in cooperation with the Forming
Technologies Association of StulE
One SME Drive, P.O. Box 930
Dearborn, Michigan 481 2'n
Based on
Frogressive Dies: Design and Manufacture
By Daniel B. Dallas
Copyright @ 1.994 by Society of ManuJacturing Engineers
Second Edition
987654
All rights reserved, including those of translation. This book, or parts thereof,
may not be reproduced in anyform or by any means, including photocopying,
recording, or microfilming, or by any information storage and relrieval
"yrtu*,
without permission in writing of the copyright owners.
No liabilitlr is assumed by the publisher with respect to the use of information
contained herein. while every precaution has been taken in the preparation of
this book, the pubrisher ass,r^i, no responsibility for errorc or i^iirions. publi-
cation of any data in this book does not constitute a recommendation or endorse-
ment of any patent, proprietary right, or product that may be involved.
Library of Congress Catalog Card Numb er:94465575
trnternational Standard Book Numb er 0-87263448-5
Additional copies may be obtained by contacting:
Society of Manufacluring Engineers
Customer Service
One SME Drive
Dearborn, Michigan 4fi121
1,-800-733-4763
SME staff who participated in producing this book:
Donald A. Peterson, Senior Editor
Dorothy M. Wylo, Production Secretary
Frances M. Kania, Production Secretary
Rosemary K. Csizmadia, Operations Administrator
Robert A. Ankrapp, FTA/SME Association Manager
Judy D. Munrq Manager, Graphic Services
Cover design by Barbara L. Sierp
Table of Contents
Preface........
.....................vii
Introduction..................
.......................1
Chapter 1 - Punches and Dies.....
Pilots
Chapter 2 - Stock Guides, Strippers, and ......:..............31
Sta9es.........
Chapter 3 - Cam ...........55
Selection
Chapter 4 - Press ...................................55
Operations
Chapter 5 - Grinding ........................87
Developn'1ent................
Chapter 6 - Blank ........ 119
Typ"t..........
Chapter 7 - Basic ........ 141
Chapter I - Strip and Stamping Design ...........163
Dies...
Chapter 9 - Conventional Progressive ..:.....................183
Chapter 10 - Progressive Transfer Dies
Dies............
Chapter 11 - Carbide Progressive ......................215
Selection.
Chapter 12 - Materials ...;...................225
Chapter 13 - Die Engineering - Planning and Design .......-.....:............255
Practice......
Chapter 14 - Design ........................277
Chapter 15 - EDM and Progressive Dies....
ChapterlS-ProgressiveDieMathematics.................. .........327
Chapter 17 - Progressive and Tiansfer Die Lubrication..........................353
Protection
Chapter 18 - Electronic Sensors and Die ............38X
Chapter19.QuickDieChange....'.........'.....'
Glossary.....
.,................Mg
Bibliography.......l...........
Index........... .....................
..................:....................461
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il| Tilll
Punches and Dies
Introduction
The words "punch" and "die" haVe accruecl a number of meanings in the
industry that have caused no small amount of confusion. The term ".dies,"
for example, has been used to refer to the entire press tool. It also has been
used to refer to the lower half of the press tool or the unit clamped to the
bolster plate of the press.
The word "purich" has come to refer variously to the entire upper half of
the press tool and, more specifically, to any so-called male section that
punches or forms metal within a female section, the female being called the
die section. Although this array of definitions stands up quite well in most
die work, it falters when specifics are described. For example, in a com-
pound die, the punch section is mounted in the die and the die section is
mounted in the punch.
In the interest of clarity, throughout this book the punch is a rnale
member, a die section a female member, and the press tool itself will be
referred to as a progressive die. A progressive die is a press tool which
performs a series of sequential operations on a piece of metal. Each part of
the die performing an operation is referred to as a stage or as a station, terms
used interchangeably.
Part Size
One of the fundamental rules of diemaking practice is the punch deter-
mines the hole size and the die deterlmines the blank sfue. This is because a part
tapers according to the clearance, as shown in Figure 1-1. The clearance is
the amount of space between the punch and the die on one side anci is
dependent on the type of materialbeing perforated, as well as.onpunch-to-
hole ratio.
Pr@ressire Dies
Figure 1-1. .Aagnlar'edge part breaknge in a blanking operation. Ot't'-center ejector pinbreal<s ztacuum
betwetn punch and stamping.
Vacuum
Slugs of all sizes have a tendency to stick to their punches, creating a
hurdle for all die designers to overcome: The most universally accepted way
to "shed" the slug is with an ejector, or "kicker,,, pin, shown in Figure 1-1.
Ejector pins work very well, are simple and inexpensive, and are difficult to
impJrove upon.
Punches that are too small to contain an
ejector pin are sometimes pointed as shown
in Figure 1-2. This design is effective in keep-
ing the slug from returning with the punch, !
but sharpening time is greatly increased.
Flowever, it is recommended that specifica-
F igar e 1, -2. P o int e d pier cin g p un ch fion of this type of punch be left to the discre- Il
Adensgiglnee dis t od le<peeepn sdleugnst oinn l omwaert edfiiea l. tion of the diemaker. If, in tryout, slugs begin
har dnes s and thichtes s. to pull, grinding an angle on punches will
4
f
Purlcttes and,Di€'s
likely rectify the problem. The grinding of this angle is simplified by use of
a device familiarly called a vertical "whirligig." The whirligig is set at one
degree to the back rail, and the punch is fed into the side of the wheel.
Tapered Buttons
Some firms spgcify that die but-
tons be ground with a half-degree
taper, as shown in Figure 1-3. This
forces the slug into an ever-decreas-
ing diameter which holds it from
returning on the punch. Although
effective, such a design should only
be incorporated as a last resort. It is
expensive, the buttons mustbe inter-
nally ground, and. punchbreakage is Figtte L-3. Tapered. die button designed to ret ain
slugs. Taper relief in most cases reduces punch
high. breaknge as it contuols the slug.
Breaking Slug Columns
Small slugs often present a problem in the die itself because of their
inherent tendency to stick together. These columns of slugs should be
broken up. Although rare and quite costly; one of the best ways to do this
is by angling the escape hole through the backing plate, as shown in Figure
14. Slugs emerging from the die set should be kept out of the holes in the
bolster plate by means of a sheet-metal guard. Clearance can be milled or
shaped into the risers and the guard secured by means of flat-headed
screws.
Shear
A punch with shear operates more smoothly than a flat punch and
requires less tonnage. It also minimizes problems of slugs sticking to the
punches. Because in most progressive dies the punch removes metal that is
not wanted, shear is put on the punch - important to bear in mind becatlse
a punch with shear distorts the part it cuts out of the strip.
If a progressive blank die is being built, the situation is reversed because
the finished panel is the part being cut out. In such a case the shear must be
put in the die, generally equal to metal thickness as shown in Figure 1-5.
I}'qgressfir Dles
Die section
Eocking plote
Die shoe
Figure 1-4. Angular hole in backing plate is effectioe in bruking slug columns.
Push-off Pins
Push-off, or ejector, pins have
been mentioned with respect to
slug removal from a punch. But
yet another importantuse of these
pins is shown in Figure 1-6. Illus-
trated is a fypical cutoff punch for
a two-per-stroke progressive
Figure 1-5. Sectional oieu of a blanking punch blank die. The outer die section
showing shear,
(detail 1) is angled at about 30
degrees for blank removai. The push-off pin ensures that the part will start
down the slide.
Push-off pins are occasionally used to complete a "stripping" operatiory
as illustrated in Figure 1'-7. Ona panel such as the one shown, the designer
must ensure that every portion of the stock can be stripped. The stripper, or
knock-off, pin qn this die takes care of the enrire strip except for the final
forrn stage.
t)
-
RJr]ches ond"Dbs
Figtre 14, Push-off pin incorporuteil for par t disposal
Stripper pins
ming punch
Figurrel-7,Push-off pinsusedlor sfipping.Whm afotmingpunch coaers theentirepanel,thestripper
cantnt ftee the part from the punch.
Progressiue Dies
Die Life
The term "diehf.e" refers to a dimensiory specifically, the length of the
land in a cutting edge. This dimension is governed by the number of
stampings expected from the die. Progressive dies are usually built to
produce millions of parts, and it is reasonable to expect that cutting sections
will have to be replaced when they have been ground and shimmed over a
period of tirne. lfowever, the sections should be designed for maximum
possible use a4d, generally speaking, each cutting edge should have at least
a 0.125-inch (3.175-mm) land ending at a two-degree draft.
In truth, itis notimportantwhetherthe angle is one, trvo, or three degrees
because any open angle will permit the slugs to fall through. Flowever, the
designer should specify a certain angle so the diemakerwill notbe tempted
to undercut the c.utting edge, as illustrated in detail 2 of Figure 1-8.
Undercutting the edge is much easier for the diemaker than grinding an
angle, but it steals an eighth of an inch (3.18 mm) or so from the die life of
the section. The dgsigner specifies a two-inch (50.8-mm) angle merely to
rnake sure he gets a draft and not an undercut. If the die is built for a
comparatively short run, however, the cutting sections should be designed
with an undercut instead of a draft as an economy measure.
Figure 1-8. Ttao methods of indicating ilie lit'e. Design at left is preferable inlong-run progressiae dies.
Counterbored Holes
Byno means therarestbutcertainly one of the saddest sights in a die shop
is a cutting section that is completely finished without provision for die life
8