Press lines Sheet metal forming lines .1 Universal presses

en gage bet ween t h e p allet an d t h e st ack. Th e fo rks clo se an d t h e st o p s au t o m at ically co m e t o rest again st t h e st ack. A ro t at io n aro u n d t h e h o r- izo n t al axis o f t h e t u rn in g d evice m o ves t h e st ack o f blan ks t o t h e d esired p o sit io n fo r u p lift in g. Aft er t h e fo rks are o p en ed , a seco n d car- riage wit h t h e p allet t akes o ver t h e st ack. Fu lly au t o m at ic ch an geo ver o f t h e p allet su rface an d t h e t ran sp o rt d irect io n s en su res fast set -u p an d also allo ws t o p o sit io n several st acks o f blan ks o n o n e p allet . Here, t h e st acks are t u rn ed o ver in seq u en ce an d d ep o sit ed back o n t o t h e p allet in a d efin ed p o sit io n .

4.4.5 Press lines

As a ru le, series p ro d u ct io n o f m ed iu m -sized an d large sh eet m et al p art s is p erfo rm ed o n p ress lin es o r large-p an el t ran sfer p resses. Th e fo rm er co n sist o f a series o f m ech an ical Fig. 4.4.19 o r h yd rau lic Fig. 4.4.20 222 Sheet metal forming and blanking Fig. 4.4.18 Blank turning device for multiple stacks Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 in d ivid u al p resses arran ged in seq u en ce an d in t erlin ked by m ean s o f h an d lin g d evices. In m an y cases, p ress lin es are bein g rep laced by large- p an el t ran sfer p resses. Ho wever, t h eir h igh d egree o f flexibilit y assu res t h at au t o m at ed p ress lin es st ill p lay a m ajo r ro le in t h e p ro cessin g o f co m p lex p art s wh ich d o n o t co n fo rm t o an y p art icu lar p art fam ily an d wh ich call fo r a h igh st an d ard o f q u alit y. Th ese in clu d e, fo r in st an ce, p art s req u irin g large d raw d ep t h s, co m p lex d ies wit h cam act io n cf. Fig. 4.1.17 o r p art s t h at req u ire m ajo r rep o sit io n in g bet ween t wo su ccessive o p erat io n s cf. Fig. 4.1.11 . Mo d ern p ress lin es are exp ect ed t o sat isfy t h e st rin gen t d em an d s co n cern in g o u t p u t , p art accu racy, d ie service life, eq u ip m en t u p t im e an d flexibilit y. Th ese d em an d s can be fu lly sat isfied u sin g m ech an ical d riven p resses wit h lin k d rive syst em s. Th e u se o f lin k d rive h elp s t o red u ce t h e im p act sp eed d u rin g d ie clo su re t o aro u n d o n e t h ird o f a co m p arable eccen t ric d rive syst em cf. Fig. 3.2.3 . Th is h as m ajo r ad van - t ages t o o ffer fo r t h e p ro d u ct io n p ro cess: Wit h t h e sam e n o m in al p ress 223 Sheet metal forming lines Fig. 4.4.19 M echanical press line w ith noise protection double-action lead press, nominal press force 20,000 kN, follow -on single-action presses, nominal press force 15,000 kN Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 fo rce an d fo rce-d isp lacem en t , a lin k-d riven p ress can be lo ad ed wit h in t h e wo rk ran ge co n sid erably h igh er an d fu rt h er away fro m t h e BDC t h an co m p arable eccen t ric p resses, becau se t h e lin k-d riven p ress h as a st eep er fo rce-d isp lacem en t cu rve t o rq u e ch aract erist ic. Co n seq u en t ly, a lin k-d riven p ress can ach ieve h igh er st ro kin g rat es t h an an eccen t ric p ress d ep en d in g o n t h e d rawin g d ep t h – t h e great er t h e d rawin g d ep t h , t h e great er t h e in crease. If t h e st ro kin g rat e is n o t in creased , t h e lo wer im p act sp eed resu lt s in im p ro ved d rawin g co n d i- t io n s. Even lo w grad e sh eet m et als can be su ccessfu lly p ro cessed . In ad d it io n , t h ere is less wear an d t ear o n t h e d ie an d d raw cu sh io n , as well as o n t h e clu t ch an d brake. Un d er p ract ical co n d it io n s, t h e m o t io n cu rve o f a lin k-d riven p ress wit h au t o m at ic p art t ran sp o rt is co n figu red so as t o red u ce t h e im p act sp eed . Th erefo re, an d also d u e t o t h e u se o f d o u ble-h elical gears in t h e d rive syst em , n o ise is ad d it io n ally red u ced by u p t o 8 d BA. N um ber of presses Th e n u m ber o f p resses wh ich m ake u p a lin e d ep en d s o n t h e n u m ber o f o p erat io n s req u ired t o p ro cess t h e p art in q u est io n cf. Sect . 4.1.1 . In gen eral t erm s, an at t em p t is m ad e t o red u ce t h e n u m ber o f p resses an d t h u s also t h e n u m ber o f n ecessary d ies. 224 Sheet metal forming and blanking Fig. 4.4.20 Hydraulic press line automated by robots Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 As early as in t h e p art d esign st age, t h ro u gh clo se co o p erat io n wit h t h e co m p o n en t d esign an d p ro d u ct io n d ep art m en t s, p art sim p lifica- t io n can lead t o a sit u at io n wh ere several d ifferen t fo rm in g o r blan kin g o p erat io n s can be gro u p ed t o get h er in a sin gle fo rm in g st at io n . Th e m o re o p erat io n s can be co m bin ed in t h is way, h o wever, t h e m o re co m - p lex t h e d ie it self beco m es. Th is m ay lead t o h igh er co st s, red u ct io n o f wo rkin g sp eed an d h igh er su scep t ibilit y t o m alfu n ct io n s. Th erefo re, an id eal co m p ro m ise h as t o be fo u n d wh en d efin in g t h e n u m ber o f fo rm - in g p ro cesses o r p resses in a p ro d u ct io n lin e. Press lin es co n sist o f fo u r t o eigh t p resses, alt h o u gh , d ep en d in g o n t h e ran ge o f p ro d u ced p art s, fo u r t o six p resses are m o st co m m o n ly u sed . Lead press: blank holder slide or draw cushion W h ile t h e lead p ress is freq u en t ly sp ecified as a d o u ble-act io n p ress, t h e d o wn st ream p resses are sin gle-act io n , so m e o f t h em in co rp o rat in g a d raw cu sh io n in t h e p ress bed . In t h e case o f d o u ble-act io n lead p ress- es, sep arat e d raw an d blan k h o ld er slid es are available an d t h ey are d ri- ven eit h er m ech an ically o r h yd rau lically fro m abo ve cf. Fig. 3.1.8 an d 3.2.4 . Th e blan k h o ld er slid e co n t act s an d h o ld s t h e blan k firm ly at t h e o u t er co n t o u r p rio r t o t h e in it iat io n o f t h e fo rm in g p ro cess by t h e d raw slid e cf. Fig. 4.2.2 . In o rd er t o avo id wrin kle fo rm at io n , t h e fo u r p res- su re p o in t s can be sep arat ely co n t ro lled , i. e. d ifferen t blan k h o ld er fo rces can be set at t h e fo u r co rn ers. In cert ain lin es, it is p o ssible t o vary th e blan k h old er forces d u rin g th e d rawin g p rocess u sin g th e p in ch con - trol cf. sect. 3.2.8 . Th ese m easu res h elp to red u ce th e try-ou t p eriod req u ired fo r a n ew set o f d ies, an d also im p ro ves d rawin g resu lt s. Th e d o u ble-act io n d esign o f t h e p resses allo ws t h e o p t im u m way t o ach ieve large d raw d ep t h s. Th e d rawback is t h at gen erally t h e p art h as t o be t u rn ed o ver fo r t h e su bseq u en t o p erat io n . Th e t u rn o ver st at io n req u ired aft er t h e first p ress lim it s t h e o verall o u t p u t rat e o f t h e p ress lin e Fig. 4.4.21 . New CNC-co n t ro lled h yd rau lic d raw cu sh io n s wh ich sim u lat e t h e fu n ct io n o f t h e blan k h o ld er slid e h ave been d evelo p ed . Th ese cu sh io n s allo w t o fo rm sim ilarly d eep an d co m p lex p ressed p art s o n sin gle-act io n m ech an ical o r h yd rau lic lead p resses cf. Sect . 3.1.4 . In t h is case, t h e fo rm ed p art d o es n o t req u ire t u rn in g o ver aft er t h e d rawin g o p erat io n . Co n seq u en t ly, t h e o u t p u t rat e o f a p ress lin e can be en h an ced t h ro u gh t h e u se o f a sin gle-act io n lead p ress wit h d raw cu sh - 225 Sheet metal forming lines Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 io n . Ho wever, in t h is case t h e en ergy req u irem en t is great er co m p ared t o a d o u ble-act io n p ress becau se t h e slid e is ad d it io n ally req u ired t o p ress again st t h e d raw cu sh io n cf. Fig. 4.2.3 . In p ress lin es, t h e d esign o f t h e clu t ch an d brake syst em is im p o rt an t becau se au t o m at ed p ress lin es are freq u en t ly o p erat ed in t h e co n t ro lled sin gle-st ro ke o r in t erm it t en t m o d e. As a resu lt o f d em an d s fo r great er p erfo rm an ce, t h e cycle t im es o f t h e large-p an el p resses are co n t in u o u s- ly bein g in creased an d t o d ay can reach as m an y as 15 st ro kes p er m in u t e. Co n seq u en t ly, h yd rau lically act u at ed clu t ch es an d brakes are freq u en t ly u sed . In co m bin at io n wit h a h eat exch an ger, t h is d esign alt ern at ive can su st ain a h igh er en ergy rat e t h an p n eu m at ically act u at - ed u n it s, resu lt in g in a h igh er st ro kin g rat e wh en o p erat ed in t erm it - t en t ly, in t h e co n t ro lled sin gle st ro ke m o d e. Th e en gagem en t o f h yd rau lic clu t ch es can also be d am p ed in o rd er t o red u ce wear an d t ear o n t h e d rive syst em an d t o red u ce n o ise cf. Sect . 3.2.4 . Autom ation Th e wo rk seq u en ce o f a p ress lin e begin s wit h t h e d est ackin g o f blan ks by t h e d est acker, clean in g, lu bricat io n an d feed o f t h e blan ks t o t h e lead p ress cf. Sect. 4.4.4 . On com p letion of th e form in g op eration , th e p arts are fed fo r fu rt h er p ro cessin g su ch as rest rikin g, t rim m in g, flan gin g o r p iercin g. St ackin g o f t h e fin ish ed p art s t akes p lace at t h e en d o f t h e p ress lin e. 226 Sheet metal forming and blanking Fig. 4.4.21 Interlinkage of presses w ith sw ing arm feeders sw ing arm feeder blank destacker blank feeder intermediate station w ith turnover station intermediate station w ith longitudinal transport Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 In m o d ern p ress lin es, wo rkp iece t ran sp o rt bet ween t h e in d ivid u al p resses as well as blan k feed are au t o m at ically execu t ed . Au t o m at ic st ackin g o f fin ish ed p art s is u sed wh erever ap p ro xim at ely id en t ical st ackin g co n d it io n s, p art sh ap es an d sizes exist Fig. 4.4.41 . A n u m ber o f d ifferen t au t o m at io n syst em s are u sed : swin g arm feed ers, CNC feed - ers o r ro bo t s. Th e t yp e o f au t o m at io n m o st su it able fo r an y p art icu lar lin e d ep en d s o n t h e ran ge o f p art s bein g p ro cessed , t h e st ro kin g rat e an d t h e available sp ace. Swing arm feeders are d riven by elect ric m o t o rs via cam s an d lin ks Fig. 4.4.21 . Th e feed er at t h e rear o f t h e p ress rem o ves t h e d rawn p art , wh ich h as been raised in t h e d ie by eject o rs, by m ean s o f su ct io n cu p s an d a su ct io n cu p carrier an d p laces it o n an in t erm ed iat e st at io n . Fro m h ere, t h e wo rkp iece is t u rn ed o ver if req u ired an d lo ad ed in t o t h e n ext d ie by t h e feed er o f t h e d o wn st ream p ress. Swin g arm feed ers h ave fixed m o t io n cu rves, m akin g t h em su it able fo r sm all p ress d ist an ces, m ed i- u m -sized p art s an d sim ilar p art t yp es. Th ey can t ran sp o rt bet ween 10 an d 12 m ed iu m -sized co m p o n en t s a m in u t e. CN C feeders are elect rically co n t ro lled an d as su ch can be freely p ro - gram m ed o n t wo axes an d u sed fo r a wid e variet y o f p art t yp es. Drive is p erfo rm ed by m ean s o f t wo sp in d le m ech an ism s o r t im in g belt -d riven carriages Fig. 4.4.22 . Th ey are able t o rem o ve t h e p art fro m t h e d ie 227 Sheet metal forming lines Fig. 4.4.22 Interlinkage of presses w ith CNC feeders and timing belt-driven carriages washing machine turno er station intermediate station CNC feeder CNC feeder blank feeder Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 wit h o u t t h e n eed fo r an eject o r. Th e o u t p u t o f a p ress lin e m akin g u se o f a CNC feed er is bet ween 8 an d 10 large-sized p art s p er m in u t e. W h en u sin g bo t h , swin g arm an d CNC feed ers, in t erm ed iat e st at io n s are req u ired . Th ese in t erm ed iat e st at io n s are eq u ip p ed wit h t h ree t o five p ro gram m able axes fo r p art t ran sp o rt in t h e lo n git u d in al d irect io n , fo r t ran sverse an d h eigh t ad ju st m en t an d also ad d it io n al t ilt in g m o ve- m en t s. Au t o m at io n u sin g ro bo t s o ffers t h e ad van t age t h at it elim in at es t h e n eed t o d ep o sit p art s bet ween t h e p resses Fig. 4.4.20 . Th e ro bo t ’s grip - p er arm p o sit io n s t h e p art d irect ly fro m t h e d ie o f o n e p ress in t o t h e d ie o f t h e n ext . Th is m ean s t h at o n ly o n e ro bo t is req u ired t o service each p ress wit h o u t t h e n eed fo r in t erm ed iat e st at io n s. Th e m ain d rawback o f ro bo t -lin ked p ress lin es is t h at h eavy p art s can o n ly be t ran sp o rt ed slo wly o r n o t at all d u e t o t h e cen t rifu gal fo rces an d t h e lo n g t ran sp o rt p at h s. Fo r t h is reaso n , o u t p u t is largely d ep en d en t o n p art size an d cu r- ren t ly lies bet ween 6 an d 8 p art s p er m in u t e. Th e freely p ro gram m able axes o f t h e ro bo t arm , in co n t rast , en su re t h at wid ely d ifferin g p art sh ap es can be t ran sp o rt ed in t o m an y d ifferen t p art p o sit io n s. Die change In ad d it io n t o t h e in t erlin kage o f p resses in a lin e, au t o m at ic d ie ch an g- in g syst em s also p lay a m ajo r ro le. Am o n g d ie ch an gin g syst em s fo r p ress lin es, m o vin g bo lst ers wit h left righ t -h an d rails o r T-t racks h ave p ro ved t o be t h e m o st p o p u lar cf. Fig. 3.4.4 . Th e fo rm er req u ire m o re sp ace, bu t o ffer t h e sh o rt est p o ssible d ie ch an gin g t im es. Th e u p p er an d lo wer d ie o f t h e d ie set wh ich is n o lo n ger req u ired are m o ved o u t o f t h e p ress o n m o vin g bo lst ers. Su bseq u en t ly, t h e o p p o sin g bo lst ers m o ve t h e n ew d ie set s in t o t h e p ress. Prep arat io n o f t h e d ies fo r t h e n ext p ro - d u ct io n ru n is p erfo rm ed o u t sid e t h e p ress d u rin g p ro d u ct io n . As a resu lt o f d ie ch an gin g au t o m at io n it is p o ssible t o ach ieve ch an geo ver t im es o f bet ween 10 an d 30 m in d ep en d in g o n t h e wo rkp iece t ran sp o rt syst em . No wad ays, p ress lin es are o ft en en clo sed in o rd er t o en h an ce safet y an d n o ise p ro t ect io n . No ise em issio n s can be red u ced by aro u n d 15 d BA if t h e sp ace bet ween t h e in d ivid u al p resses an d t h e p erip h eral eq u ip m en t is also en clo sed Fig. 4.4.19 . 228 Sheet metal forming and blanking Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998

4.4.6 Transfer presses for small and medium sized parts