– p resses fo r so lid fo rm in g, su ch as fo rgin g, ext ru sio n an d co in in g p resses cf. Sect . 6.8,
– p resses fo r in t ern al h igh -p ressu re fo rm in g cf. Sect . 5.6, – p ressu re fo rm in g, st ret ch in g an d st am p in g p resses.
Sh ears are also co m m o n ly u sed , gen erally in sep arat e lin es, fo r t h e m an - u fact u re o f sh eet m et al blan ks cf. Sect s. 4.6.1 an d 4.6.2.
3.1.1 Press frame
Th e fu n ct io n o f t h e p ress fram e is t o abso rb fo rces, t o p ro vid e a p recise slid e gu id an ce an d t o su p p o rt t h e d rive syst em an d o t h er au xiliary
u n it s. Th e st ru ct u ral d esign o f t h e fram e d ep en d s o n – t h e p ressin g fo rce – t h is d et erm in es t h e req u ired rigid it y,
– t h e d im en sio n s o f d ies in flu en cin g t h e size o f t h e t o o l area, – wo rk area accessibilit y t h at d et erm in es o n t h e sh ap e o f t h e p ress
fram e, – t h e d egree o f gu id an ce p recisio n . Th is in flu en ces bo t h t h e sh ap e an d
t h e rigid it y o f t h e fram e. Presses wit h relat ively lo w p ress fo rces, u p t o 2,500 kN, freq u en t ly m ake
u se o f t h e open-front press d esign cf. Fig. 4.6.14
. Th is co n st ru ct io n is ch aract erized p art icu larly by t h e easy access t o t h e t o o l area. Ho wever,
it s d rawback lies in t h e asym m et rical d eflect io n o f t h e fram e, wh ich co n t ribu t es t o red u ct io n s in p art accu racy an d d ie life, p art icu larly in
blan kin g ap p licat io n s. In clin ed o r h o rizo n t al d esign s p erm it fast er p art ejection m akin g u se of gravity followin g th e form in g p rocess, for exam -
p le wh en forgin g or coin in g cf. Fig. 6.8.20
. As a ru le, op en -fron t p resses are u sed in con ju n ction with sin gle d ies.
Presses wit h a n o m in al p ressin g fo rce o ver 4,000 kN are co n st ru ct ed exclu sively in a gan t ry-t yp e d esign . Th ese are kn o wn as straight-side
presses Fig. 3.1.1
. In t h is p ress t yp e, t h e p ress bed wit h t h e bed p lat e, t h e t wo u p righ t s an d t h e cro wn fo rm t h e fram e. Th e ap p licat io n sp ec-
t ru m o f st raigh t -sid e p resses ran ges fro m sm all p art s p ro d u ced u sin g p ro gressio n d ies, co m p o u n d p ro gressio n d ies o r t ran sfer d ies t h ro u gh t o
in d ivid u al d ies fo r varyin g p art sizes cf. Sect . 4.1.1
. W h en u sin g p ro - gressio n t o o ls, t h e p art s are co n veyed by t h e sh eet st rip it self. Co n -
34
Fundamentals of press design
Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998
versely, wh en u sin g in d ivid u al d ies, an ad d it io n al grip p er rail is gen er- ally in t egrat ed in t h e p ress. A p art icu larly eco n o m ical p ro d u ct io n
p ro cess can be ach ieved by acco m m o d at in g in d ivid u al resp . t ran sfer d ies in o n e an d t h e sam e p ress. W h en au t o m at ed , u sin g a t ran sfer sys-
t em , t h is t yp e o f lin e is kn o wn as a transfer press. O rigin ally, p ress fram es were p ro d u ced o f gray cast iro n . Pro gress
m ad e in t h e field o f weld in g t ech n o lo gy su bseq u en t ly allo wed t h ick
35
Press types and press construction
gib surface cylinder bridge
upright clearance bridge for the
draw cushion bed plate
press bed press crown
slide
tie rod uprights
tie rod nut
monoblock frame multiple-part frame
Fig. 3.1.1
Design of a straight-side press frame
Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998
p lat e m et al t o be reliably jo in ed t o get h er, o p en in g u p a h igh d egree o f d esign flexibilit y. Th u s, p resses wit h weld ed fram es can be co n st ru ct ed
p recisely fo r in d ivid u al req u irem en t s. Com p ou n d d esign s in tegratin g weld ed an d cast com p on en ts are also
p ossible. Sm all straigh t-sid e p resses are bu ilt exclu sively u sin g th e weld - ed m onoblock fram e typ e, wh ile larger d esign s u se a m ultiple-part fram e
con stru ction wh ich effectively lim it th e size of com p on en ts to facilitate both p rocessin g an d tran sp ort. Th e in d ivid u al com p on en ts are assem -
bled togeth er u sin g tie rod s wh ich gen erally reach alon g th e en tire h eigh t of th e p ress, an d p re-ten sion ed to a d eterm in ed force
Fig. 3.1.1 .
Carefu l configuration of the fram e is essen tial, as it is su bjected to stress both by th e d rive elem en ts an d au xiliary u n its, an d is also req u ired to
en su re p recise gu id an ce of th e p ress slid e. Care m u st be taken n ot to exceed th e load an d elastic d eform ation lim it of th e fram e. To satisfy
th ese com p lex d esign req u irem en ts, p ress fram es are op tim ized with th e aid of th e Finite Elem ent Method FEM. Th is in volves th e com p u tation
an d d ep iction of stresses also u n d er eccen tric load s Fig. 3.1.2
. By en su r-
36
Fundamentals of press design
Fig. 3.1.2
FEM optimization of the press frame: Distribution of stresses under off-center load
Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998
in g th e correct d istribu tion of m aterial an d con figu ration of tran sition al rad ii between th e bed an d u p righ ts, as well as between th e u p righ ts an d
p ress crown , it is p ossible to avoid exceed in g th e m axim u m p erm issible stress levels, also at rated force. An oth er ben efit of FEM-calcu lated com -
p on en ts is th e ability to save on m aterial n ot n eed ed to en su re rigid ity. On top of th e press bed lies th e bed p late bolster p late u sed to cen ter
an d h old d own th e lower h alf of th e d ie Fig. 3.1.1
an d cf. Sect. 3.4
. Th e bolster p lates on th e p ress bed an d th e slid e are screwed in to p lace to
allow sim p le rem oval, for exam p le to alter th e T-n otch con figu ration , to retrofit h yd rau lic clam p in g d evices or to ad ap t th e op en in gs to n ew
p ressin g req u irem en ts.
3.1.2 Slide drive
