Process plan Formed part and process plan

6.4.2 Process plan

Th e fo rm ed p art an d t h e relevan t vo lu m et ric calcu lat io n rep resen t t h e st art in g p o in t fo r d evelo p in g t h e p ro cess p lan . A creat ive p ro cess is in i- t iat ed in wh ich a wid e ran ge o f bo u n d ary co n d it io n s – su ch as st art in g d iam et er, m at erial, p rescribed st ren gt h levels, lo t size, h eat t reat m en t , n u m ber o f st at io n s, d ist an ce bet ween st at io n s, p ress fo rce, o ff-cen t er lo ad cap acit y o f t h e p ress an d in t ern al o p erat in g circu m st an ces – m u st be co n sid ered sim u lt an eo u sly. O n t h e basis o f t h e calcu lat ed vo lu m e, t h e billet d im en sio n s p re- ferred d iam et er an d len gt h are d efin ed . Fo r m an y p art s, p art icu larly ro d -sh ap ed p art s, t h e billet d iam et er is select ed fro m a d iam et er wh ich alread y exist s in t h e p art t o be fo rm ed . Th is m u st t ake in t o acco u n t t h e clearan ce n ecessary t o t ran sp o rt an d lo cat e t h e p art fro m o n e st at io n t o t h e n ext , an d t h e p referred d iam et er. Fo r all flat p art s wh ich are p ro - d u ced by u p set t in g o p erat io n s, t h e u p set rat io an d t h e len gt h d iam et er rat io o f t h e billet m u st be co n sid ered , as t h ese in flu en ce t h e p o ssibilit y o f bu cklin g. St art in g wit h t h e geo m et ry o f t h e fo rm ed p art , d evelo p m en t wo rk p ro ceed s t o d et erm in e t h e p revio u s st ages, wo rkin g backward s t o ward s t h e st art in g billet . In it ially, ro u gh p ro cess p lan alt ern at ives are su ffi- cien t h ere. Th ese p relim in ary p ro cess p lan s are u sed as a basis fo r d efin - in g t h e fo rm in g p ro cesses. Vo lu m et ric ad ju st m en t is n o t yet n ecessary at t h is st age, as o n ly t h e d egree o f t ru e st rain is calcu lat ed an d co m - p ared wit h t h e co rresp o n d in g p ro cess lim it s. If t h e exist in g co n d it io n s are crit ical, it m ay be p o ssible t o alleviat e t h ese by ch an gin g billet d im en sio n s an d t h e seq u en ce o f o p erat in g st at io n s. If t h is is n o t p o ssi- ble, in t erm ed iat e h eat t reat m en t is u n avo id able. If o n e, t wo o r m o re in t erm ed iat e h eat t reat m en t s are n ecessary, warm fo rm in g can o ffer an o t h er m o re eco n o m ical alt ern at ive. O n ce a p ro m isin g p ro cess p lan alt ern at ive h as been fo u n d as a resu lt o f t h is in t u it ive p ro ced u re, vo lu m e calcu lat io n s are carried o u t . Fu rt h erm o re, t h e feasibilit y is verified based o n fo rce an d en ergy calcu - lat io n s an d o n t h e co m p u t at io n o f t h e d ie lo ad . If th e u se of p rocess com bin ation s m ean s th at th ere are several p rocesses bein g p erform ed in a sin gle station , reliable p red iction of th e m aterial flow is d ifficu lt even for exp erien ced form in g en gin eers. In th is case, m etal flow sim u lation with th e aid of a su itable fin ite elem en t p ro- 467 Formed part and process plan Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 gram can serve t o illu st rat e t h e m et al flo w in t h e relevan t fo rm in g p ro cess. Th is allo ws t o p red ict an d elim in at e p ro blem s su ch as crack fo r- m at io n , u n d erfillin g an d excessive d ie lo ad s p rio r t o act u al d ie t ry-o u t Fig. 6.4.1 . 468 Solid forming Forging Fig. 6.4.1 FEM study of material flow for a flange upsetting process w ith relief borehole Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 6 Solid forming Forging

6.5 Force and w ork requirement