High-speed blanking lines Shearing lines .1 Slitting lines

4.6.3 High-speed blanking lines

Blan ked an d stam p ed p arts m ad e from th icker sh eet m etal su ch as ch ain lin k p lates, cu p sp rin gs, alu m in iu m an d coin blan ks cf. Fig. 6.8.7 as well as sh eet m etals u sed in electric m otors Fig. 4.6.20 are m an u factu red in large q u an tities, callin g for h igh -p erform an ce lin es with h igh strokin g rates – so-called h igh -sp eed blan kin g lin es Fig. 4.6.6 . In t h is t yp e o f p ress, t h e blan kin g p ro cess cau ses su d d en ch an ges in p ress fo rces d u e t o t h e rap id n at u re o f m at erial breakt h ro u gh wh en t h e sh ear st ren gt h o f t h e m at erial is exceed ed . Th ese fo rces can resu lt in m ajo r d yn am ic d isp lacem en t in t h e d ies Fig. 4.6.7 . Becau se o f p o ssible n egat ive effect s o n p art q u alit y an d o n service life o f t h e d ies, h igh - sp eed p resses are su bject t o p art icu larly h igh p recisio n req u irem en t s Fig. 4.6.8 . 291 Shearing lines Fig. 4.6.6 Blanking line w ith 1,250 kN high-speed press and die changing cart for automatic die change long version Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 Th e p ro d u ct ivit y o f t h e blan kin g lin e is d et erm in ed by t h e m ech a- n ism u sed fo r sh eet m et al feed , t h e efficien cy o f t h e p ress it self, wo rk- p iece rem o val an d t h e eq u ip m en t u sed fo r reset t in g. Th e co il m at erial is fed by a co il lin e wh o se co il sp eed is au t o m at ically ad ju st ed in lin e wit h t h e blan kin g rat e o f t h e p ress cf. Sect . 4.3 . To p ro d u ce co in blan ks, an ad d it io n al coil thickness unit is req u ired cf. Fig. 6.8.23 . Th e sh eet t h ickn ess is co n t in u o u sly m easu red by a sen - so r an d , wh ere ap p ro p riat e, a co m m an d is t ran sm it t ed t o t h e co n t ro l syst em o f t h e h igh -sp eed blan kin g lin e, allo win g fau lt y p art s t o be d is- card ed au t o m at ically. A m ajo r crit erio n wh en it co m es t o ach ievin g h igh o u t p u t is t h e effi- cien cy o f t h e feed syst em by m ean s o f ro ller feed . Mean feed rat es o f u p t o 100 m m in are ach ieved wh ere co n t in u o u s ad ju st m en t o f t h e feed len gt h is p o ssible fo r a rat io o f 1 : 10. Th e ad ju st m en t p ro cess is m o t o r p o wered an d can also be carried o u t d u rin g p ress o p erat io n . Th e feed len gt h is eit h er m an u ally p reselect ed at t h e keybo ard an d d igit ally d is- p layed , o r wh ere an au t o m at ic t o o l ch an ge syst em is u sed , it is accessed by t h e p ress co n t ro l syst em d ep en d in g o n t h e d ie set in u se. 292 Sheet metal forming and blanking Fig. 4.6.7 Force-time curve for blanking of sheet metal stripper force time t force F material flow vibration decay breakthrough Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 An o t h er im p o rt an t asp ect d et erm in in g t h e o u t p u t o f a h igh -sp eed blan kin g lin e is it s st ro kin g rat e. High st ro kin g rat es can o n ly be ach ieved wh ere t h ere is a counterbalance of m asses creat ed by t h e h o ri- zo n t al an d vert ical fo rces Fig. 4.6.8 . Co u n t erbalan ce syst em s in wh ich t h e fo rces o f t h e slid e an d u p p er d ie are co m p let ely elim in at ed by d irect ly o p p o sin g m asses h ave p ro ved p art icu larly ben eficial. Th e m ass co m p en sat io n o f p resses wit h st ro ke ad ju st m en t , wh ich are also su it - able fo r sm aller fo rm in g o p erat io n s, is au t o m at ically ad ju st ed t o get h er wit h t h e st ro ke. Mass co u n t erbalan ce is an essen t ial p rereq u isit e fo r su bcrit ical arran gem en t o f t h e p ress o n ro cker elem en t s, wh ich en su res t h at t h e vibrat io n s in it iat ed by t h e st am p in g p ro cess are t ran sm it t ed o n ly m in im ally t o t h e fo u n d at io n . Th e syst em s o f part rem oval, t ran sp o rt an d in t erlin kin g wit h t h e d o wn st ream p ro d u ct io n p ro cess in crease in sign ifican ce as t h e p ress 293 Shearing lines Fig. 4.6.8 Construction of a high-speed press short version roller bearing mass counterbalance eccentric shaft hydraulic brake feed drive feed press body spring body variable DC drive flyw heel hydraulic coupling double fork connecting rod penetration depth control device pressure point slide gib slide bed plate Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 an d d ie o u t p u t in creases. Co n veyo r belt s fo r t ran sp o rt at io n o f blan ked p art s are freq u en t ly arran ged u n d er t h e p ress. Th e p art s d ro p o u t o f t h e fem ale d ie o n t o an eject io n ch an n el, wh ich is freq u en t ly o rien t ed , o n t o t h e co n veyo r belt s. Th ere is a sep arat o r in t egrat ed in t h e eject io n ch an - n el wh ich segregat es d efect ive p art s fro m t h e st art o f t h e co il, t h e en d o f t h e co il o r p art s o f t h e co il wh ich lie o u t sid e t h e sp ecified t o leran ces. Lin k-u p bet ween t h is d evice an d t h e d o wn st ream p ro cessin g st at io n s fo r wash in g, an n ealin g, p o lish in g, in sp ect io n , co at in g o r p ackagin g o f p art s is in creasin gly im p lem en t ed u sin g co n veyo r belt s o r h an d lin g d evices cf. Sect . 4.6.4 . Stam ping scrap is o ft en co llect ed in bo xes an d t ran sp o rt ed away. Mo re sat isfact o ry t h an t h is m et h o d is co n t in u o u s d isp o sal by m ean s o f co n - veyo r belt s p o sit io n ed u n d ern eat h t h e p ress. Th e scrap can eit h er be fed away d irect ly t h ro u gh t h e fem ale d ie o r o u t sid e t h e d ie by m ean s o f scrap ch u t es. If a scrap web is creat ed , t h is is gen erally ch o p p ed by a sh ear at t h e o u t feed sid e o f t h e p ress. In o rd er t o red u ce st o rage o f m at erial an d cap it al t ie-u p t o a m in i- m u m , sm all bat ch sizes also h ave t o be p ro d u ced eco n o m ically o n h igh - sp eed blan kin g lin es. Sh o rt d ie ch an ge an d reset t in g t im es are an essen - t ial req u irem en t h ere. Resetting fo r t h e m an u fact u re o f a d ifferen t p art in clu d es set -u p o f t h e feed an d rem o val d evices, t h e p rep arat io n o f d ies, d ie ch an ge, co n versio n o f t h e p ress an d a fin al ch eck o f d ie an d p ress set t in g d at a cf. Sect . 3.4 . As t h e blan kin g p ro cess is t h e m ajo r fact o r in d et erm in in g t h e preci- sion of punched parts an d also t h e service life o f d ies, st ep s m u st be t aken t o m in im ize t h e vibrat io n o ccu rrin g bet ween t h e p u n ch an d t h e fem ale d ie in t h e vert ical an d h o rizo n t al d irect io n at t h e m o m en t o f sh eet m et - al breakt h ro u gh by execu t in g t h e n ecessary m easu res at t h e m ach in e Fig. 4.6.7 . Vertical vibrations are creat ed as a resu lt o f t h e p lay exist in g in t h e fo rce flo w o f t h e p ress an d o f t h e elast ic p ro p ert ies o f t h e en t ire p ress syst em . Th ey cau se an in crease in t h e p en et rat io n d ep t h o f t h e blan k- in g p u n ch in t h e fem ale d ie, t h e ext en t o f wh ich d ep en d s o n t h e st ro kin g rat e. Th e resu lt is in creased p u n ch wear Fig. 4.6.9 . Co m p ared t o a p ress wit h frict io n bearin gs, vert ical p lay is co n sid er- ably red u ced wh en u sin g an eccen t ric sh aft ru n n in g in ro ller bearin gs Fig. 4.6.8 . In co n ju n ct io n wit h t h e h yd rau lic slid e ad ju st m en t clam p , t h e t o t al vert ical p lay is red u ced t o a m in im u m . A h igh d egree o f vert i- 294 Sheet metal forming and blanking Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 cal rigid ity is p rovid ed by th e solid p ress bod y, by th e slid e d rive system u sin g a d ou ble fork con n ectin g rod in sh ort p resses an d two gen erou sly d im en sion ed con n ectin g rod s in lon g p resses, an d by th e ben d in g resis- tan ce of th e slid e. However, as th e strokin g rate-d ep en d en t in crease in p en etration d ep th h as a p h ysical cau se an d d oes n ot d ep en d on th e sta- tic an d d yn am ic beh avior of th e p ress, a con trol d evice is freq u en tly u sed on h igh -sp eed p resses. Th is d evice d etects th e in crease in p en etra- tion d ep th an d au tom atically corrects it to th e set valu e Fig. 4.6.10 . Even wh en workin g at extrem ely h igh strokin g rates, th is system allows to ach ieve a d ie service life th at is sim ilar to th at ach ieved wh en blan k- in g in th e lower strokin g ran ges. In ad d it io n t o t h e beh avio r o f t h e p ress in t h e vert ical d irect io n , t h e vibration characteristics of the slide in the horizontal direction also in flu en ce d ie life. As t h e blan kin g clearan ce bet ween t h e p u n ch an d fem ale d ie am o u n t s t o o n ly a few h u n d red t h s o f a m illim et er, h igh ly st rin gen t d em an d s are m ad e o n accu racy o f slid e gu id an ce an d o n t h e h o rizo n t al rigid it y o f t h e p ress bo d y. Th e d egree o f h o rizo n t al vibrat io n is also d irect ly in flu en ced by p lay an d by t h e elast ic beh avio r o f t h e p ress. Th e h o rizo n t al p lay can be elim in at ed t h ro u gh t h e u se o f slid e gibs wit h 295 Shearing lines Fig. 4.6.9 Influence of the press stroking rate on the penetration depth of the blanking punch in the female die Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 ro llers, wh ile t h e h o rizo n t al p ress rigid it y is ap p reciably in creased t h ro u gh sp ecial co n figu rat io n o f t h e p ress bo d y. Th e slid e is gu id ed wit h o u t p lay by m ean s o f ro llers at fo u r co lu m n s cf. Fig. 3.1.6 . Th e o p t im u m arran gem en t o f gibs abo ve an d o n t h e blan kin g p lan e, in p art icu lar, serves t o red u ce slid e vibrat io n s co m p ared t o p revio u s slid e gib syst em s so t h at a su bst an t ial in crease in d ie life is ach ieved . In co n t rast t o co n ven t io n al p resses, t h e co n figu rat io n o f t h e p ress bo d y is n o w so co m p act t h at u p righ t d eflect io n u n d er lo ad is n egligi- ble, an d h o rizo n t al fo rces gen erat ed d u rin g blan kin g can be abso rbed even ly o ver t h e en t ire gib area.

4.6.4 Lines for the production of electric motor laminations