4.1.2 Die development
Trad it io n ally t h e bu sin ess o f d ie en gin eerin g h as been in flu en ced by t h e au t o m o t ive in d u st ry. Th e fo llo win g o bservat io n s abo u t t h e d ie
d evelo p m en t are m o st ly relat ed t o bo d y p an el d ie co n st ru ct io n . Es- sen t ial st at em en t s are, h o wever, m ad e in a fu n d am en t al co n t ext , so
t h at t h ey are ap p licable t o all areas in vo lved wit h t h e p ro d u ct io n o f sh eet -m et al fo rm in g an d blan kin g d ies.
Tim ing cycle for a m ass produced car body panel Un til th e en d of th e 1980s som e car m od els were still bein g p rod u ced for
six to eigh t years m ore or less u n ch an ged or in sligh tly m od ified form . Tod ay, h owever, p rod u ction tim e cycles are set for on ly five years or less
Fig. 4.1.6 . Followin g th e n ew d ifferen t m od el p olicy, th e d em an d s on
d ie m akers h ave also ch an ged fu n d am en tally. Com p reh en sive con tracts of m u ch greater scop e su ch as Sim u ltan eou s En gin eerin g SE con tracts
are becom in g in creasin gly com m on . As a resu lt, th e d ie m aker is often in volved at th e in itial d evelop m en t p h ase of th e m etal p art as well as
in th e p lan n in g p h ase for th e p rod u ction p rocess. Th erefore, a m u ch broad er in volvem en t is establish ed well before th e actu al d ie d evelop -
m en t is in itiated .
128
Sheet metal forming and blanking
Fig. 4.1.5
A pressed part w ith an integrated
punched nut
Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998
129
Principles of die manufacture
Fig. 4.1.6
Time schedule for a mass produced car body panel 2-3 year period
go-ahead for a new model
trend and market research
concept phase
participation of the toolmaker in the development and production process styling phase
design of the outer c ar
bodyw ork design of the bodyw ork
reinforcement
prototype parts pilot series parts
various try-out phases w ith prototype
parts
various try-out phases w ith pilot series parts
start of series production
period up to production stop
start on development of follow -up model
Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998
T he tim etable of an SE project Wit h in t h e co n t ext o f t h e p ro d u ct io n p ro cess fo r car bo d y p an els, o n ly
a m in im al am o u n t o f t im e is allo cat ed t o allo w fo r t h e m an u fact u re o f t h e d ies. Wit h large scale d ies t h ere is a ru n -u p p erio d o f abo u t 10
m o n t h s in wh ich d esign an d d ie t ry-o u t are in clu d ed . In co m p lex SE p ro ject s, wh ich h ave t o be co m p let ed in 1.5 t o 2 years, p arallel t asks
m u st be carried o u t . Fu rt h erm o re, ad d it io n al reso u rces m u st be p ro vid - ed befo re an d aft er d elivery o f t h e d ies. Th ese sh o rt p erio d s call fo r p re-
cise p lan n in g, sp ecific kn o w-h o w, available cap acit y an d t h e u se o f t h e lat est t ech n o lo gical an d co m m u n icat io n s syst em s. Th e t im et able sh o ws
t h e in d ivid u al act ivit ies d u rin g t h e m an u fact u rin g o f t h e d ies fo r t h e p ro d u ct io n o f t h e sh eet m et al p art s
Fig. 4.1.7 . Th e t im e p h ases fo r
large scale d ies are m o re o r less sim ilar so t h at t h is t im et able can be co n - sid ered t o be valid in gen eral.
Data record and part drawing Th e d at a reco rd an d t h e p art d rawin g serve as t h e basis fo r all su bse-
q u en t p ro cessin g st ep s. Th ey d escribe all t h e d et ails o f t h e p art s t o be
130
Sheet metal forming and blanking
Fig. 4.1.7
Timetable for an SE project production release
specifications
st ar
t o f S
E pr
oj ec
t
milestones: purchasing release
pre-production series pilot series series
pre-planning
process planning CAD data
prototype parts draw development
project planning
die design casting models
machining casting
bench w ork home try-out
series try-out
design die production die development
Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998
p ro d u ced . Th e in fo rm at io n given in t h e p art d rawin g in clu d es: p art id en t ificat io n , p art n u m berin g, sh eet m et al t h ickn ess, sh eet m et al q u al-
it y, t o leran ces o f t h e fin ish ed p art et c. cf. Fig. 4.7.17
. To avoid th e p rod u ction of p h ysical m od els m aster p attern s, th e
CAD d ata sh ou ld d escribe th e geom etry of th e p art com p letely by m ean s of lin e, su rface or volu m e m od els. As a gen eral ru le, h igh q u ality su rface
d ata with a com p letely filleted an d closed su rface geom etry m u st be m ad e available to all th e p articip an ts in a p roject as early as p ossible.
Process plan and draw developm ent Th e p ro cess p lan , wh ich m ean s t h e o p erat io n al seq u en ce t o be fo llo wed
in t h e p ro d u ct io n o f t h e sh eet m et al co m p o n en t , is d evelo p ed fro m t h e d at a reco rd o f t h e fin ish ed p art cf.
Fig. 4.1.1 . Alread y at t h is p o in t in
t im e, vario u s bo u n d ary co n d it io n s m u st be t aken in t o acco u n t : t h e sh eet m et al m at erial, t h e p ress t o be u sed , t ran sfer o f t h e p art s in t o t h e
p ress, t h e t ran sp o rt at io n o f scrap m at erials, t h e u n d ercu t s as well as t h e slid in g p in in st allat io n s an d t h eir ad ju st m en t .
Th e d raw d evelo p m en t , i. e. t h e co m p u t er aid ed d esign an d layo u t o f t h e blan k h o ld er area o f t h e p art in t h e first fo rm in g st age – if n eed be
also t h e seco n d st age –, req u ires a p ro cess p lan n er wit h co n sid erable exp erien ce
Fig. 4.1.8 . In o rd er t o reco gn ize an d avo id p ro blem s in
areas wh ich are d ifficu lt t o d raw, it is n ecessary t o m an u fact u re a p h ys- ical an alysis m o d el o f t h e d raw d evelo p m en t . Wit h t h is m o d el, t h e
fo rm in g co n d it io n s o f t h e d rawn p art can be reviewed an d fin al m o d i- ficat io n s in t ro d u ced , wh ich are even t u ally in co rp o rat ed in t o t h e d at a
reco rd Fig. 4.1.9
. Th is p rocess is bein g rep laced to som e exten t by in telligen t sim u lation
m eth od s, th rou gh wh ich th e p oten tial d efects of th e form ed com p on en t can be p red icted an d an alysed in teractively on th e com p u ter d isp lay.
Die design After release of th e p rocess p lan an d d raw d evelop m en t an d th e p ress,
th e d esign of th e d ie can be started . As a ru le, at th is stage, th e stan d ard s an d m an u factu rin g sp ecification s req u ired by th e clien t m u st be con sid -
ered . Th u s, it is p ossible to obtain a u n ified d ie d esign an d to con sid er th e p articu lar req u ests of th e cu stom er related to wareh ou sin g of stan -
d ard , rep lacem en t an d wear p arts. Man y d ies n eed to be d esign ed so th at th ey can be in stalled in d ifferen t typ es of p resses. Dies are freq u en tly
131
Principles of die manufacture
Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998
in st alled bo t h in a p ro d u ct io n p ress as well as in t wo d ifferen t sep arat e back-u p p resses. In t h is co n t ext , t h e layo u t o f t h e d ie clam p in g ele-
m en t s, p ressu re p in s an d scrap d isp o sal ch an n els o n d ifferen t p resses m u st be t aken in t o acco u n t . Fu rt h erm o re, it m u st be n o t ed t h at d raw-
in g d ies wo rkin g in a sin gle-act io n p ress m ay be in st alled in a d o u ble- act io n p ress cf.
Sect . 3.1.3 an d
Fig. 4.1.16 .
In t h e d esign an d sizin g o f t h e d ie, it is p art icu larly im p o rt an t t o co n - sid er t h e freed o m o f m o vem en t o f t h e grip p er rail an d t h e cro ssbar
t ran sfer elem en t s cf. Sect . 4.1.6
. Th ese d escribe t h e relat ive m o ve- m en t s bet ween t h e co m p o n en t s o f t h e p ress t ran sfer syst em an d t h e d ie
co m p o n en t s d u rin g a co m p let e p ress wo rkin g st ro ke. Th e lift in g m o ve- m en t o f t h e p ress slid e, t h e o p en in g an d clo sin g m o vem en t s o f t h e grip -
p er rails an d t h e len gt h wise m o vem en t o f t h e wh o le t ran sfer are all su p erim p o sed . Th e d ies are d esign ed so t h at co llisio n s are avo id ed an d
a m in im u m clearan ce o f abo u t 20 m m is set bet ween all t h e m o vin g p art s.
132
Sheet metal forming and blanking
Fig. 4.1.8
CAD data record for a draw development
Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998
Gu id es o f t h e u p p er an d lo wer d ies m u st carry t h e sh earin g fo rces an d be sized acco rd in g t o t h e calcu lat ed an d an t icip at ed fo rces an d
fu n ct io n s. Large scale gibs sh o w n early n o lat eral d isp lacem en t an d a co n sist en t , u n ch an gin g p ressu re p at t ern o f t h e o p erat io n al d ie
cf. Sect . 4.1.5
. Fu rt h erm o re, t h ey red u ce t h e t ilt in g o f t h e d ie an d t h e p ress slid es
Fig. 4.1.10 . Th u s, a co n sist en t o verall h igh q u alit y o f
p ressed p art s is ach ieved . In o rd er t o avo id erro rs an d p o t en t ial p ro blem areas lat er in p ro d u c-
t io n , t h e so -called FMEA Failu re Mo d e an d Effect s An alysis is u sed wit h p ro ven su ccess d u rin g t h e d esign st age wit h t h e clo se co llabo ra-
t io n o f all t h o se in vo lved wit h t h e p ro ject . Th e d esign o f t h e p ressed p art s an d t h eir arran gem en t an d p o sit io n in g in t h e d ies h ave a great
in flu en ce o n p ro d u ct io n safet y. In sh eet m et al fo rm in g well-d esign ed p ress co m p o n en t s will lead t o sim p le, p ro d u ct io n -frien d ly an d lo w co st
t o o ls. Difficu lt t o fo rm p ress p art s, o n t h e o t h er h an d , in vo lve exp en - sive, co m p licat ed an d h igh co st d ies, wh ich are less easily in t egrat ed
133
Principles of die manufacture
Fig. 4.1.9
Physical analysis model of a draw development
Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998
in t o t h e p ro d u ct io n p ro cess. Tilt in g o f t h e p art s in t h e d ies can co m - p en sat e t h e n egat ive asp ect s o f an u n favo rable p art geo m et ry. Fo r
exam p le, fo r flan gin g an d blan kin g a sh eet m et al p art can be so ro t at ed t h at t h e wo rk d irect io n co rresp o n d s t o t h e d irect io n o f t h e flan gin g
o p erat io n e. g. t h e m o vem en t o f t h e blan kin g p u n ch Fig. 4.1.11
. Ho wever, it is o ft en t h en n ecessary t o in crease t h e n u m ber o f d ies,
wh ich resu lt s in p ro d u ct io n co st in creases. To m eet d ead lin es, t h e fo rm in g d ies m u st be d esign ed first so t h at t h e
cast in g p at t ern s an d t h e fin ish ed cast in gs are available fo r u se as so o n as p o ssible. Aft er m ach in in g an d t ry-o u t , d ies can p ro d u ce st am p in gs
t h at are laser t rim m ed an d u sed in p ro t o t yp e p re-p ro d u ct io n assem blies Fig. 4.1.7
. Th e u se of CAD system s for d ie d esign h as becom e in creasin gly com -
m on Fig. 4.1.12
even th ou gh con ven tion al d rawin g board d esign m ay often be m ore cost effective. Th e reason s for th is are th at th e d rawin g
system is n ot yet p erfected , d ata ban ks are in com p lete an d workstation screen s on ly allow a p ersp ective view in th e ratio of 1 : 5 u p to 1 : 10.
However, con sid erin g th e total p rod u ction costs, h igh q u ality CAD p rod u ced d ie d esign s an d d ie castin g p attern d ata are p rovid ed as a by-
p rod u ct. Sh rin kage an d exp an sion allowan ces can be d eterm in ed by com p u ter an d u sed for NC m ach in in g of castin g m od els, an econ om ic
altern ative to NC m ach in in g of castin gs. A fu rth er ad van tage of CAD d esign , in so far as it is based on a volu m e m od el, is th e p ossibility
134
Sheet metal forming and blanking
Fig. 4.1.10
Influence of the guidance system on the reduction of slide tilting and offset
58 64
75 82
85
5,9 6
6,5 13,5
10,5
3 6
7
offset [ ]
columns 6 mm
[ columns
6 mm [
lugs polyamid
mm columns
mm [
without gibs
lugs brass
mm
reduction of slide tilt
Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998
135
Principles of die manufacture
Fig. 4.1.12
CAD design of pivoting blanking tool
Fig. 4.1.11
Improvement to the positioning of the part by means of sw ivel movement in the folding operation:
a
simple die construction for press parts w ith simple geometry;
b
complex high cost die construction w ith a sliding element for difficult press part geometry;
c
simple die construction via appropriate sw ivelling of the pressed part in an improved w orking position
a b
c
Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998
of on goin g collision testin g, wh ich clearly con tribu tes to th e red u ction of errors. Jaw layou t p lan s, d ie con stru ction p lan s an d sin gle p art d raw-
in gs can be m ad e available by th is system . Th e gen eral u se of CAD CAM system s in tool m akin g h ave m an y in h eren t ad van tages th at are lin ked
to th e p rocess. Th erefore, in th e m ed iu m term , CAD CAM tech n iq u es will be in creasin gly u sed to in crease th e total cost effectiven ess of p art
p rod u ction . Mechanical processing
To d ay’s t ech n ical p o ssibilit ies in NC p ro cessin g req u ire ever m o re easy t o m an u fact u re d esign s fro m t h e d ie d esign er. In p art icu lar t h e u se o f
five-axis m illin g m ach in es allo ws t o m ach in e co m p let ely co m p lex cast in gs wit h a sin gle fixt u rin g o p erat io n . In t h e p ast , becau se o f
rest rict ed co n d it io n s, ext en d ed o p erat in g an d assem bly act ivit ies were carried o u t wit h fixt u res an d ad d it io n al clearan ces. To d ay, fo r exam p le,
t h ree-d im en sio n ally lo cat ed slid in g an d gu id in g co m p o n en t s can be cast
Fig. 4.1.17 .
High sp eed m illin g HSM is u sed in creasin gly fo r m ach in in g o f scu lp t u red su rfaces in wh ich eco n o m ical cu t t in g sp eed s o f 2,000
m m in are at t ain able. Even st ro n gly p at t ern ed su rfaces fo r in n er p art s can st ill be m ach in ed wit h m ed iu m feed rat es o f aro u n d 5 m m in .
Cerm et s an d sp ecial PVD-co at ed carbid es are cap able o f at t ain in g su r- face q u alit ies o f R
t
= 10 m m , wh ich red u ces t h e n eed fo r seco n d ary m an - u al p o lish in g t o a m in im u m .
Assem bly and try-out Mo re accu rat e m ach in in g an d fin ish in g o p erat io n s t o get h er wit h t h e
abo ve-m en t io n ed ad van t ages o f a CAD su p p o rt ed d ie d esign , sim p lify t h e assem bly t ask co n sid erably. Th e gen eral p ro cessin g o f d at a gives
access t o fu rt h er t h eo ret ical an d erro r-free blan kin g an d co n t o u r in fo r- m at io n wit h o u t h avin g t o reso rt t o t h e u se o f co st ly aid s. Th e exp ert
kn o wled ge o f t h e q u alified d iem aker is, h o wever, st ill n ecessary. In p ar- t icu lar, in t h e p re-ru n o r t ry-o u t p h ases wh en t h e d ie d evelo p er t ries t o
p ro d u ce a go o d p art aft er t h e in st allat io n o f t h e d ies in t h e p ress, it beco m es evid en t wh et h er o r n o t t h e t h eo ret ical d esign effo rt h as been
co rrect cf. Sect . 4.1.5
. Pro t o t yp e t o o ls o r sim u lat io n m et h o d s p ro vid e, o f co u rse, co n sid erable h elp . Th ere are, h o wever, ad d it io n al fact o rs
wh ich co n t ribu t e t o ward s t h e q u alit y o f t h e st am p in gs o bt ain ed wit h
136
Sheet metal forming and blanking
Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998
t h e p ro d u ct io n d ies. Th e m ach in in g o f t h e d ie su rfaces an d t h e gibs, t h e m illin g o f t h e free fo rm su rface u sin g HSM o p erat io n s an d t h e t ry-
o u t o n a p recisely gu id ed t ry-o u t p ress wit h ad ju st able h yd rau lic d raw cu sh io n s sh o u ld all be carried o u t efficien t ly
Fig. 4.1.19 an d
4.1.20 .
Process control In o rd er t o assu re t h at t h e p art d ep en d en t p ro cess p lan an d t h e
d raw d evelo p m en t are co rrect , p ro t o t yp e d ies o r so ft t o o ls are p ro d u ced Fig. 4.1.13
. In so d o in g, t h e fo rm in g beh avio r o f t h e sh eet m et al m at e- rial, esp ecially wh en t h e p art geo m et ry is co m p lex an d m o re p ro n e t o
failu re, m u st be in vest igat ed at t h e p relim in ary st ages o f t h e d ie d esign . Ho wever, t h e p ract ise o f u sin g so ft t o o ls d ed icat ed exclu sively fo r t h is
p u rp o se is beco m in g less sign ifican t as co m p u t er-aid ed sim u lat io n p ro cesses are bein g in creasin gly u sed fo r d ie d esign an d d evelo p m en t .
Prototype dies Th e p rep arat io n o f p ro t o t yp e o r so ft d ies is, h o wever, wo rt h wh ile if
fu rt h er o bject ives n eed t o be at t ain ed . At a very early p o in t in t h e p ro - d u ct io n p ro cess, t h e sh eet m et al p art s are m ad e available, wh ich can be
u sed , fo r in st an ce, t o co n st ru ct veh icles fo r assem bly an d crash t est p u r-
137
Principles of die manufacture
Fig. 4.1.13
Prototype draw ing die in aluminium for the production of the roof of a station w agon
Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998
p o ses. In cert ain cases, t h ese p art s m ay be u sed as p re-p ro d u ct io n series Fig. 4.1.7
. A fu rt h er co n sid erat io n wh ich ju st ifies t h e p ro d u ct io n o f p ro t o t yp e d ies is wh en t h e t im in g o f t h eir m an u fact u re is clo se t o t h e
sch ed u le fo r t h e begin n in g o f series p ro d u ct io n . Th u s, in fo rm at io n o n t h e fo rm abilit y an d t o leran ces o f t h e p art s can be o bt ain ed , wh ich co n -
t ribu t es t o go al o rien t ed an d co st -effect ive d ie m an u fact u re. Th e fo llo win g are so m e o f t h e p o in t s wh ich m u st be t aken in t o acco u n t
h ere: – t h e d ie m at erial
– t h e co m p lexit y o f t h e sh eet m et al p art – t h e blan k m at erial
– t h e d esign o f t h e d raw d evelo p m en t – t h e geo m et rical p aram et ers su ch as d egree o f sh rin kage, cam berin g,
p rest ressin g – t h e p ro cess-relat ed variable su ch as lu bricat io n , blan k h o ld er fo rces,
wo rk-flo w d irect io n , d raw bead s – t h e size an d geo m et ry o f t h e blan ks
– sp ecial fact o rs an d p aram et ers wh ich in flu en ce t h e resu lt s o f t h e st am p in g o p erat io n
Th e t yp e an d d esign o f t h e p ro t o t yp e d ies are in flu en ced by d ifferen t fact o rs. Th e ch o ice o f p ro t o t yp e m at erial will be in lin e wit h t h e sh eet
m et al sp ecificat io n , t h ickn ess an d t h e n u m ber o f p art s t o be p ro d u ced . To d ay, p last ics, alu m in iu m allo ys
Fig. 4.1.13 , d ifferen t q u alit ies o f cast
m et als as well as ro lled st eel can be u sed as p ro t o t yp e o r so ft d ie m at erial. A su m m ary o f t h e ch o ice an d ap p licat io n crit eria is given in
Table 4.1.1 .
Methods of process sim ulation Co m p u t er-aid ed sim u lat io n t ech n iq u es, e. g. t h e an alysis o f t h e fo rm -
in g p ro cess wit h o u t an y p h ysical d ies, will in creasin gly rep lace t h e u se o f p ro t o t yp e an d so ft d ies. Th is d evelo p m en t is beco m in g m o re p ract i-
cal t h ro u gh rap id ly gro win g h ard ware d evelo p m en t s wh ich allo w t h e p ro cessin g o f ever in creasin g am o u n t s o f co m p u t erised d at a in ever
sh o rt er t im e sp an s. In ad d it io n , t h e co m p u t er so ft ware u sed fo r p ro cess sim u lat io n h as beco m e m o re reliable an d m o re u ser frien d ly.
138
Sheet metal forming and blanking
Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998
13 9
Pr in
cip le
s o f d
ie m
an ufa
ctu re
Die type Plastic
Aluminium alloys Iron alloys
w ithout additives alloyed or
Zamak Cerrotru
GSGG cast iron Plate steel
fiber-reinforced M anufacturing
complete structure cast steel frame
model production precise model
model manufacture for punch construction of die
process
in plastic, as basic structure
for punch and manufacture, casting
and female die possibly from plates and jaw s,
cast in layers for plastic panels
female die the punch, insertion
blank holder, casting of screw ed and pinned,
or w ith back as punch, casting of
possibly blank holder, of sheet metal thickness,
models, rew orking of rew orking of functional
the front casting female die shape
casting of models, casting of female
functional surfaces, surfaces, integration
rew orking of die no rew orking
integration of gib elements of gib elements
functional surfaces
Repair and
machinable shape punch shape
w eldable, melt dow n
w elding on, w elding on,
possibility for
or new front machinable, inserts are
inserts machinable existing die
screw -mounted inserts, new jaw s
modification
casting seamlessly glued in,
and recast rew orking by means
or inserts casting of
of milling female die
Range of parts
outer bodyw ork outer bodyw ork parts
outer bodyw ork parts outer bodyw ork parts
reinforcement and reinforcement and
parts in steel and reinforcements in
and reinforcements and easily formable
chassis parts w ith chassis parts
and aluminium steel and aluminium
parts complex shapes
w ith flat shapes
Sheet metal
sheet steel up to up to 2.5 mm
up to 1.5 mm up to 1.2 mm
up to 3 mm up to 3 mm
thickness
2 mm, aluminium up to 4 mm
Piece numbers
w ith max. sheet metal for outer
easily deform- easily deform-
depending on stress level and sheet metal thickness, extremely
bodyw ork able parts
able parts material used, possibly w ith series capability
low piece numbers, parts, up to
up to 100 pieces, up to 50 pieces,
otherw ise suitable 1,000 pieces
complex parts complex parts
for small or pre-series up to 50 pieces
up to 20 pieces
Product. period
2 to 3 w eeks 4 to 6 w eeks
3 to 4 w eeks 2 to 3 w eeks
7 to 10 w eeks 5 to 7 w eeks
Table 4.1.1: Allocation of prototype dies
Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998
Fo r t h e evalu at io n o f t h e geo m et ry d at a, wh ich h as been est ablish ed by t h e p ro cessin g p lan an d t h e d raw d evelo p m en t as well as t h e p ro -
d u ct io n p aram et ers, CAE so lu t io n s are available wh ich are based u p o n m at h em at ical an d p last o -m ech an ical eq u at io n s o r o n exp erim en t ally
p ro ven d at a. An alyt ical an d n u m erical sim u lat io n belo n g t o t h ese so lu - t io n s. Th e n u m erical m et h o d s, an d h ere in p art icu lar t h e Fin it e
Elem en t Met h o d FEM, d eliver t o d ay t h e m o st accu rat e resu lt s. St am p in gs can be alm o st co m p let ely in t eract ively an alysed o n a wo rk-
st at io n in relat io n t o t h e m o st im p o rt an t failu re crit eria. Th e resu lt s are t h e d ist ribu t io n o f st ress t ears
Fig. 4.1.14 , t h e t en d en cy t o ward s
wrin klin g Fig. 4.1.15
an d t h e variat io n o f t h e sh eet m et al t h ickn ess. Th e n ecessary st ep s an d t h e p rereq u isit es fo r a sim u lat io n ru n are as fo l-
lo ws: – p rep arat io n o f CAD d at a fo r t h e p u n ch , fem ale d ie an d blan k h o ld er
as well as t h e t o t al geo m et ry o f t h e d raw d evelo p m en t in t h e wo rk- in g d irect io n
Fig. 4.1.8 ,
– d et erm in at io n an d in p u t o f t h e blan k size cf. Sect . 4.2.1
an d 4.5
, – in p u t o f t h e p ro cess p aram et ers su ch as sh eet m et al m at erial, ro llin g
d irect io n , blan k h o ld er fo rce, frict io n al co n d it io n s, – d efin it io n i. e. est ablish m en t o f t h e FE m esh p art ly au t o m at ic an d
– in it iat io n o f t h e calcu lat io n p ro cess. By varyin g t h e p ro cess an d d ie p aram et ers, t h e sim u lat io n can be
rep eat ed as o ft en as req u ired u n t il a failu re-free d rawin g p art is p ro - d u ced . Th e ad van t age o f t h is p ro cess lies in t h e fact t h at an y o bject ive
an d n ecessary co m p o n en t ch an ges can be in t ro d u ced at an y t im e p rio r t o t h e act u al m an u fact u re o f t h e d ies. Sp ecific m easu res fo r t h e co n t ro l-
lin g m et al flo w, fo r exam p le t h ro u gh t h e sh ap e o f t h e blan k o r t h ro u gh t h e u se o f d raw bead s, can be sim u lat ed . Sim ilarly, calcu lat io n s can be
m ad e t o p red ict an d co m p en sat e fo r sp rin g back cf. Sect . 4.8.1
. Th ro u gh p ro cess sim u lat io n , p ro cess p lan n ers an d d ie d esign ers re-
ceive reliable in fo rm at io n at an early st age in t h e d ie d evelo p m en t , wh ich really co n t ribu t es t o t h e p ro d u ct io n o f fu lly o p erat io n al an d reli-
able d ies.
140
Sheet metal forming and blanking
Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998
141
Principles of die manufacture
1.20 0.00
M aximum strain limit
0.0400 0.0000
Wrinkling
Fig. 4.1.15 Representation
of possible w rinkle
formation by means of FEM
simulation
Fig. 4.1.14 Representation
of stress distribution by
means of FEM simulation
Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998
4.1.3 Die materials
Kategori