p o n en t . Th is im p o ses ad d it io n al d em an d s o n t h e fu n ct io n s o f t h e p ress, in p art icu lar o n t h e sp eed o f t h e slid e. Th is calls fo r t h e u se o f sp ecial
co n t ro l syst em s cf. Sect . 3.3.3
. W h en p ressin g t h erm o p last ics in refrigerat ed d ies, fo rm in g m u st be
p erfo rm ed q u ickly, an d t h e co o lin g p ro cess m u st t ake p lace at a co m - p let e st an d st ill an d wit h o p t im u m p arallelism o f t h e t wo d ie h alves.
In t h e case o f t h erm o set p last ics, a layered m at is in sert ed in t h e d ie. Th e co m p o u n d m at erial – glass fiber an d resin – m u st be p ressed
acco rd in g t o a p recisely sp ecified sp eed p at t ern wit h p recise p arallelism o f t h e t wo d ie h alves, in o rd er t o avo id fiber o rien t at io n . Th e m at erial
h ard en s as h eat is ap p lied . In o rd er t o ach ieve a u n ifo rm p art t h ickn ess, t h e slid e m u st be kep t 0.1 m m m p arallel. Th ese p ro cess p aram et ers
are essen t ial fo r t h e p ro d u ct io n o f h igh -grad e SMC p art s an d can o n ly be im p lem en t ed u sin g a h yd rau lic p ress wit h m u lt ip le axis co n t ro l. Th e
t ech n o lo gical req u irem en t s – fast clo su re, in o rd er t o m in im ize h eat t ran sfer bet ween t h e wo rk-
p iece m at erial an d t h e d ie befo re fo rm in g, – p ressin g at t h e sp ecified sp eed p at t ern t o en su re u n ifo rm fro n t flo w
beh avio r, – p ressin g wit h t h e sp ecified fo rce p at t ern t o en su re ap p licat io n o f t h e
sp ecial p ressu re level req u ired fo r p recise fo rm in g, – h o ld in g t h e p ressu re at a p rescribed level wh ile t h e wo rkp iece h ard -
en s at t h e p recisely p arallel p o sit io n o f t h e t wo d ie h alves, – co n t ro lled o p en in g m o t io n t o avo id d am age t o t h e wo rkp iece
can o n ly be ach ieved u sin g a h yd rau lic p ress. Th e d rive syst em is bu ffered by p ressu re accu m u lat o rs in o rd er t o assu re t h at t h e req u ired
d ifferen t o il vo lu m es are available cf. Table 3.3.1
. Th e slid e o p erat es in a clo sed co n t ro l lo o p , m o n it o red by sen so rs an d co n t ro lled by servo
valves. Th e p arallelism o f t h e slid e is m ain t ain ed wit h in ext rem ely clo se t o leran ces by fo u r cylin d ers act in g o n t h e slid e co rn ers cf.
Fig. 3.3.5 .
4.4.10 Stacking units for finished parts
Fin ish ed p art s leavin g t h e p ress are p allet ized eit h er m an u ally o r wit h t h e aid o f an au t o m at ic st ackin g u n it t o p erm it t h eir st o rage o r t ran s-
p o rt at io n . It is o ft en u n eco n o m ical t o co n vert t h e u n it fo r wid ely vary-
252
Sheet metal forming and blanking
Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998
in g p art s, as t h e st ackin g u n it wo u ld h ave t o be reset at t h e sam e sp eed as t h e fo rm in g lin e, i. e. in 10 m in o r less. Th is wo u ld n ecessit at e a fu l-
ly au t o m at ic reset t in g p ro cess. In ad d it io n , t h e st ackin g p o sit io n in t ran sp o rt co n t ain ers o ft en varies co n sid erably fo r d ifferen t p art s.
Acco rd in gly, st ackin g u n it s fo r fin ish ed p art s o n ly m ake sen se wh ere very sim ilar p art s are p ro cessed . Th e u n it illu st rat ed in
Fig. 4.4.41 , fo r
in st an ce, st acks o n ly sim ilar p assen ger car d o o rs. Th ere are t wo d iffer- en t t yp es o f syst em fo r st ackin g fin ish ed p art s: u sin g an o verh ead feed -
er syst em o r u sin g in d u st rial ro bo t s. Th e d est ackin g feed er o f t h e p ress p laces t h e sh eet m et al p art s o n t h e
p art lift in g an d lo cat in g d evice, wh ich p o sit io n s t h em o n syn ch ro n ized in t erm ed iat e d ep o sit st at io n s o r belt co n veyo rs. Th e p art s t ravel
t h ro u gh a t est an d in sp ect io n st at io n , at t h e en d o f wh ich t h ey are t ran sferred t o an o t h er p art lift in g an d lo cat in g d evice, align ed an d
m o ved in t o t h e st ackin g p o sit io n . In syst em s wit h o verh ead feed er, d ep en d in g o n p art size an d t h e
p ress cycle rat e, o n e o r t wo CNC feed ers en gage t wo , fo u r o r eigh t p art s, o rien t t h em as req u ired an d st ack t h em in t h e t ran sp o rt co n t ain ers.
253
Sheet metal forming lines
Fig. 4.4.41
Stacking unit for passenger car doors
part lifting and locating device
belt conveyor CNC feeder in lifting position
CNC feeder in deposit position
stack of finished parts lifting device
Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998
Tran sp o rt co n t ain ers wit h st ack lat ch es p erm it in d ivid u al rem o val by in d u st rial ro bo t s. Th e u n it is also eq u ip p ed wit h a d et ect io n syst em fo r
t ran sp o rt co n t ain ers an d wit h an elect rical an d m ech an ical co n t ro l sys- t em fo r t h e st ack lat ch es. Th is en su res t h at t h e t ran sp o rt co n t ain ers
belo n gin g t o t h e vario u s fin ish ed p art s are m ad e read y an d t h at t h e st ack lat ch es are ad ju st ed t o t h e geo m et ry o f t h e fo rm ed sh eet m et al
p art s. Th e t ran sp o rt co n t ain ers arran ged o n bo t h sid es o f t h e co n veyo r belt
gu aran t ee co n t in u o u s st ackin g even d u rin g co n t ain er ch an geo ver. A su p p lem en t ary co n veyo r belt can be u sed t o t ran sp o rt p art s o u t o f t h e
p ress in t h e even t o f a m alfu n ct io n in t h e st ackin g u n it o r fo r in sp ec- t io n p u rp o ses wit h o u t in t erru p t in g t h e p ress o p erat io n .
In ad d it io n t o t h e so lu t io n u sin g o verh ead feed ers, in d u st rial ro bo t s wit h six axes can be u sed fo r rem o val an d st ackin g o f fin ish ed p art s.
Th is t yp e o f au t o m at io n co n cep t m akes p art icu lar sen se wh en t h e p art s are p laced t o be read y in t h e assem bly p o sit io n by t h e h an d lin g d evice,
n ecessit at in g an ad d it io n al ro t at in g o r t ilt in g m o vem en t . Th is t yp e o f co n cep t is fo u n d n o t o n ly in p resses bu t also fo r flan gin g an d weld in g
o p erat io n s u sed in p lan t co n st ru ct io n ap p licat io n s cf. Sect . 4.6.5
.
4.4.11 Control systems for large-panel transfer presses
