are ch an ged in so lid fo rm in g cf. Fig. 6.7.1
. Fo r d ies weigh in g u n d er 10 t o 15 kg, t h is is gen erally p erfo rm ed m an u ally. Fo r h eavier d ies, wh en
ch an gin g in d ivid u al d ie blo cks o r fo r h o t fo rm in g, d ie ch an gin g arm s wit h a h o ist in g p o wer o f 50 t o 800 kg are u sed
Fig. 3.4.5 . Th e u p an d
d o wn m o vem en t is p o wered by elect ric m o t o r in m ech an ical p resses, wh ile h yd rau lic p resses are fit t ed wit h h yd rau lic lift in g cylin d ers. Th e
swivel o r t raversin g m o vem en t in t o t h e d ie sp ace can be execu t ed m an - u ally, o r co n t ro lled by p u sh bu t t o n s t o t h e p reselect ed d ie p o sit io n .
Alt ern at ively, fu lly au t o m at ic syst em s are also available.
3.4.2 Die clamping devices
Th e clam p in g of d ies on to th e bed an d slid e clam p in g p lates m u st be p er- form ed as q u ickly an d reliably as p ossible. Clam p in g d evices are eith er
electrically or h yd rau lically p owered , in som e cases also in com bin ation with m an u al actu ation by m ean s of sp rin g p ower, th read ed sp in d les, tog-
gle lever, wed ge action or self-lockin g m ech an ism s. W h ich ever m ean s is u sed , safet y is always a p rio r co n cern
Fig. 3.4.6 . Differen t clam p in g
syst em s are o ft en u sed fo r t h e u p p er an d lo wer d ie, sin ce t h e lo wer d ies
91
Changing dies
Fig. 3.4.5
Die changing arm for solid forming
Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998
are p u sh ed o ver t h e p ress bed , wh ile t h e slid e is lo wered vert ically o n t h e u p p er d ies. Th e t ask o f classifyin g t h e d ifferen t clam p in g syst em s is
excessively co m p lex, as t h e select io n d ep en d s h eavily o n t h e req u ired clam p in g fo rce, t h e t yp e o f d ie an d p ress in vo lved an d t h e d egree o f
p ress au t o m at io n . Sm all d ies are gen erally h eld by p u sh -in clam p s o r clam p in g rails.
Th e rails are fixed o n t h e clam p in g p lat e, wh ile p u sh -in clam p s are in sert ed in t o t h e T-slo t s o n t h e clam p in g p lat e. Th e ad van t age o f wo rk-
in g wit h t h is t yp e o f sm all, ligh t weigh t fixt u re is t h at it rest rict s t h e u sable t able su rface o n ly m in im ally an d p erm it s easy h an d lin g. If t h e
clam p in g fo rce o f t h e p u sh -in clam p s is n o t su fficien t wh en co n n ect ed t o t h e h yd rau lic syst em o f t h e p ress at 250 bar, it can be in creased t o
50 kN by raisin g t h e lin e p ressu re t o 400 bar. T- slo t clam p s are freq u en t ly u sed t o secu re m ed iu m -sized d ies
Fig. 3.4.7 . A p ressu re o f 250 bar is ap p lied t o t h e clam p in g cylin d ers by
t h e p ress h yd rau lic syst em . As a resu lt , a clam p in g fo rce o f u p t o 200 kN can be gen erat ed . Th e clam p s can be released by m ean s o f sp rin g p o w-
er aft er a d ro p in t h e o il p ressu re. Th e safet y o f t h e fixt u re is gu aran t eed by p o sit ive lo ckin g act io n in t h e T-slo t an d m o n it o red by p ressu re sen -
so rs wh ich brin g t h e p ress t o an im m ed iat e st an d st ill in case o f a d ro p in p ressu re. Fo r large d ies wit h d ifferin g wid t h s, it is n ecessary t o u se
92
Fundamentals of press design
Fig. 3.4.6
Different die clamp designs clamped
released sw ivel-pull clamp
hydraulic push-in-clamp
hydraulically hydraulically
electro- mechanically
electro- mechanically
rotary-pull clamp slide
clamping plate
upper die T-slot
Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998
clam p s t h at can be ad ju st ed au t o m at ically t o t h e d im en sio n s o f t h e d ie u sed
Fig. 3.4.8 . Th ese ad ju st able fixt u res can be co m bin ed wit h all
t yp es o f clam p s – h yd rau lic, elect ric an d h yd ro m ech an ical. If t h ere are n o ad ju st in g d evices available, t h e clam p s are m o u n t ed o u t sid e t h e
clam p in g p lat es, an d t h e d ies m u st be ad ju st ed t o t h e clam p sp acin g by u sin g ad ap t er p lat es.
93
Changing dies
Fig. 3.4.7
T-slot clamp for upper and low er tool mechanical release
slide
top die T-slot bar
hydraulic clamping T-slot bar
mechanical release hydraulic clamping
bolster plate
bottom die
Fig. 3.4.8
Automatic die clamping device w ith adjusting facility: electromechanical clamp left, hydraulic clamp right
adjustment spindle upper die
slide clamping plate
largest die smallest die
T-slot
Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998
3 Fundamentals of press design
3.5 Press control systems 3.5.1 Functions of the control system
