Fo r co ld fo rm in g p ro cesses, t h e grip p er u n it s are m o u n t ed o n clam p - in g rails wh ich are fixed in t u rn o n a base rail
Fig. 6.6.1 . W h en reset -
t in g fo r p ro d u cin g a d ifferen t p art , all t h at h as t o be exch an ged are t h e clam p in g rails in clu d in g t h e p re-set grip p ers. Th e fro n t grip p ers are
eq u ip p ed wit h p ro xim it y swit ch es t o m o n it o r p art t ran sfer. Part s wit h a h igh er L D rat io ap p ro x. 3 t o 8 m u st be t ran sferred
bet ween st at io n s by a 3D t ran sfer. Th is in vo lves t h e u se o f an ad d it io n - al h o rizo n t al p u sh er wh ich m o ves t h e p art t o get h er wit h it s ret ain er
in t o a p o sit io n fro m wh ere it can be raised vert ically. Here, t o o , t h e lev- el o f t h e base p lat e o n wh ich t h e p art s are p o sit io n ed is lo cat ed belo w
t h e t ran sp o rt p lan e. Sh aft -sh ap ed p art s wit h a billet L D rat io o f 6 can also be m o ved in t o t h e u p lift p o sit io n u sin g sp ecial d evices su ch as
ro t at in g sleeve ret ain ers. In warm fo rm in g, t h e lo ad in g st at io n h as t h e ad d it io n al fu n ct io n o f
segregat in g p art s wh ich eit h er h ave n o t been fed in co rrect syn ch ro - n izat io n wit h t h e p ress, o r wh ich h ave an in co rrect t em p erat u re. To
allo w t h ese p art s t o be eject ed , an o p en in g is released in t h e base p lat e o f t h e lo ad in g st at io n t h ro u gh wh ich t h e p art s d ro p d o wn in t o a ch u t e
fo r rem o val.
6.6.2 Transfer study
Before con d u ctin g a tran sfer stu d y, d ata on th e kin em atics of th e slid e m ovem en t m u st be available in th e form of a tim e-d isp lacem en t d ia-
gram . Th e stroke is d efin ed based on th e ran ge of p arts, th e req u ired form in g p rocess an d th e d ie layou t. Th e slid e cu rve is given by th e stroke
h eigh t an d p ress kin em atics eccen tric d rive, kn u ckle-join t d rive, m od i- fied kn u ckle-join t d rive cf.
Fig. 3.2.3 . Th e slid e cu rve, wh ose bottom
d ead cen ter is at 180°, can on ly be d isp laced vertically for tran sfer stu d y. Th e eject o r st ro ke is d et erm in ed by t h e ran ge o f p art s bein g p ro cessed
an d t h e resp ect ive p o sit io n o f t h e fo rm in g st at io n s in t h e d ie. Th e largest n ecessary eject o r st ro ke is eq u al t o t h e su m o f t h e in lay d ep t h o f
t h e p art in t h e d ie an d t h e p art len gt h . Th e eject o r st ro ke can be ach ieved by m ean s o f a m ech an ical an d an ad d it io n al p n eu m at ic d is-
p lacem en t . Th e st ro ke co vered m ech an ically m u st eject t h e p art , wh ich is st u ck in t h e t o o l as a resu lt o f elast ic d eflect io n o f t h e co n t ain er. In
ad d it io n , t h e p n eu m at ically gen erat ed d isp lacem en t is able t o raise t h e
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p art . O u r p resen t exam p le h as a m ech an ical eject o r cu rve wit h a st ro ke o f 200 m m wh ich is t ravelled t h ro u gh at 80° cran k an gle: In t h is case,
n o p n eu m at ic eject o r is req u ired . Th e st art in g p o in t fo r t h e eject o r cu rve can be o p t io n ally select ed , allo win g t h e cu rve in t h e d iagram
Fig. 6.6.2 t o be d isp laced h o rizo n t ally. Th e slo p e o f t h e eject o r cu rve
can be co n figu red in su ch a way t h at it co rresp o n d s ap p ro xim at ely t o t h e lin ear p o rt io n o f t h e slid e cu rve.
St art in g wit h t h e t ran sverse m o vem en t o f t h e co n n ect in g ro d , t h e slid e eject o r cu rve is gen erat ed by t h e co rresp o n d in g kin em at ic
Fig. 6.6.2 , dashed line. Fo r t h e t ran sfer st u d y, t h is cu rve can be d is-
p laced o n ly vert ically. Th e cu rve o f t h e p n eu m at ic eject o r, wh o se act u al d ist an ce fro m t h e
slid e cu rve m u st be d et erm in ed wit h t h e t ran sfer st u d y, ru n s p arallel t o t h e slid e cu rve
Fig. 6.6.2 , broken line. Th e slid e eject o r act s m ech an i-
cally briefly aft er t h e bo t t o m d ead cen t er an d can be o p erat ed p n eu - m at ically aft er t h at .
In ad d ition to th ese m ain p ress m otion s, in u n iversal tran sfer d evices th e cu rves for op en in g an d sh u ttin g th e grip p ers are also sign ifican t. Th e
op en in g an d closin g tim es can n orm ally be ad ju sted with in certain lim - its, e. g. with in a 30° ran ge, m akin g th e cu rves h orizon tally d isp laceable
in th e tran sfer stu d y. Th e op en in g stroke is d eterm in ed by th e req u ired d iam eter of th e u p p er d ie
Fig. 6.6.2 , op en in g stroke 100 m m . W h ere
m ostly slen d er p u n ch es are u sed , th is stroke is sm aller th an for fem ale d ies u sed on th e sid e of th e slid e, for exam p le wh en p rod u cin g lon g rod -
sh ap ed p arts or p arts in closin g d evices. Dep en d in g on th e op en in g st ro ke, t h ese m o vem en t s req u ire a sm aller ap p ro x. 30° fo r aro u n d
40 m m o r a larger ap p ro x. 60° fo r aro u n d 100 m m cran k an gle ran ge. Th ro u gh t h e fo rward an d reverse m o vem en t , lat eral t ran sp o rt at io n
t akes p lace. Fo rward m o t io n can be in it iat ed as so o n as t h e grip p ers en gage t h e p art , an d m u st h ave been co m p let ed befo re t h e grip p ers
o p en , i. e. t h e u p p er d ie elem en t s m ake co n t act wit h t h e t ran sp o rt ed p art . Th e fo rward an d ret u rn m o t io n s req u ire a cran k an gle o f ap p ro x.
80 t o 100°. Th e ret u rn m o t io n t akes p lace d u rin g t h e in feed an d p ress- in g cycles.
Tran sp o rt st u d ies o f 3D t ran sfer d evices in vo lve a lift -u p m o t io n in ad d it io n t o t h e m o vem en t s p revio u sly d escribed . Th is m o t io n st art s
briefly aft er t h e eject o r m o vem en t an d aft er t h e clo sin g o f t h e grip p ers. It en d s wit h t h e lo werin g m o t io n wh ich sh o u ld h ave been co m p let ed
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483
Part transfer
Fig. 6.6.2
Tw o-dimensional transfer study: 1 define opening starting point; 2 determine pneumatic spring travel for fed part;
3 define shortening of ejector bolt in the machine and starting point of ejector in bed; 4 define closing end point;
5 determine pneumatic spring travel for ejected part
Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998
ju st befo re t h e o p en in g o f t h e grip p ers. Here, t o o , d ep en d in g o n t h e lift - u p m o t io n , a great er o r sm aller cran k an gle ran ge m ay be req u ired . A
lift -u p m o t io n o f aro u n d 100 m m can req u ire a cran k an gle o f aro u n d 60°. All t h e t ran sp o rt m o t io n s o f t h e p ress an d t ran sfer d evice are lim it -
ed by m axim u m allo wable accelerat io n levels, an d m u st be sep arat ely d esign ed fo r each in d ivid u al case u n d er co n sid erat io n .
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6 Solid forming Forging
6.7 Die design
