Crossbar transfer presses Sheet metal forming lines .1 Universal presses

Th ese co m p o n en t s are sep arat ed fro m t h e p art o f t h e rail wh ich rem ain s in t h e p ress by m ean s o f an au t o m at ic co u p lin g d evice, an d d ep o sit ed o n t h e m o vin g bo lst er. Aft er releasin g t h e p o wer co n n ect io n s, t h e m o vin g bo lst er wit h t h e d ie an d p art -sp ecific accesso ries t ravels t o o n e sid e o u t o f t h e p ress, wh ile t h e slid in g bo lst er wit h t h e n ext d ie en t ers fro m t h e o t h er sid e Fig. 4.4.27 . Aft er au t o m at ic co u p lin g o f t h e grip p er rails an d p o wer co n n ect io n s, t h e d ie d at a su ch as p ressu re levels an d p o sit io n s are accessed fro m t h e d at a m em o ry an d au t o m at ically set . W h en t h e m o v- in g bo lst er wit h a n ew d ie set is set u p o u t sid e t h e p ress, all t h e p art -sp e- cific d evices su ch as grip p ers an d co n t o u red n est s are exch an ged an d p rep ared fo r t h e n ext p ro d u ct io n p ro cess. A ch aract erist ic feat u re o f large-p an el t ran sfer p resses is t h eir h igh p ro d u ct ivit y wit h an o u t st an d in g d egree o f flexibilit y m ad e p o ssible by sh o rt set -u p t im es. Th e au t o m at ic d ie ch an ge p ro cess p o ssible in large- p an el t ran sfer p resses can be co m p let ed in less t h an 5 m in . Th u s, a m ajo r p reco n d it io n is sat isfied fo r t h e red u ct io n o f cap it al co st s an d o f t h e n eed fo r in t erm ed iat e st o rage o f fin ish ed p art s bet ween t h e st am p - in g p lan t an d t h e bo d y assem bly p lan t . Th is m ean s t h at , d ep en d in g o n bat ch size, it m ay be p o ssible t o p erfo rm several d ie ch an ges p er p ro - d u ct io n sh ift cf. Sect . 4.9.2. Dep en d in g on th e p ress op eratin g p eriod , on a large-p an el tran sfer p ress between 5 an d 30 d ifferen t d ie sets are u sed with batch sizes of 3,000 to 10,000 p an els. To en su re econ om ic u tilization of th e p ress, p arts with n early id en tical form an d size an d a sim ilar d egree of form in g com - p lexity sh ou ld be grou p ed to create fam ilies of p arts cf. Fig. 4.9.2 an d 4.9.3 .

4.4.8 Crossbar transfer presses

W h ere large p an els fro m aro u n d 2.5 3 1.5 m in size are p ro cessed , t h e lo w in h eren t st abilit y o f t h e p art s d u rin g t ran sp o rt at io n calls fo r sp ecial m easu res. Co n ven t io n al grip p er rails wh ich o n ly grip o r h o ld t h e p art s aro u n d t h eir o u t er p erip h ery Fig. 4.4.29 are n o t su it able. Part icu larly large u n st able p art s su ch as ro o fs, fu ll bo d y sid e p an els o r flo o r assem - blies are acco rd in gly p ro d u ced u sin g cro ssbar t ran sfer p resses. Th e ap p licat io n o f t h is t yp e o f p ress also co vers t h e d u al p ro d u ct io n o f 243 Sheet metal forming lines Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 m ed iu m -sized p art s, in wh ich t wo p art s are fo rm ed fro m o n e blan k o r t wo ad jacen t blan ks Fig. 4.4.34 an d cf. Fig. 4.9.2 . Do u ble p art s p ro - d u ced fro m a sin gle blan k are sep arat ed as req u ired in a su bseq u en t o p erat io n . Th e p ro d u ct io n o f d o u ble p art s co u ld refer t o an y su it able p art s, fo r exam p le p assen ger car d o o rs. Th is kin d o f p ro d u ct io n d o u bles t h e o u t p u t p er p ress st ro ke an d in creases co n sid erably t h e eco n o m y o f t h e syst em , co m p ared t o grip p er rail t ran sfer syst em s. Mo reo ver, d u al p ro d u ct io n h elp s t o bet t er u t ilize t h e p ress lo ad cap acit y wh en fo rm in g a sin gle large an d u n st able p art d o es n o t fu lly req u ire t h e available p ress lo ad . Large-p an el cro ssbar t ran sfer p resses can be st ru ct u red in d ifferen t ways. Id eally, each d ie sh o u ld be assign ed t o a sep arat e slid e t o en su re o p t im u m p erip h eral co n d it io n s fo r t h e d ie an d fo r t h e fo rm in g p ro cess. Th e d esign is based o n a m o d u lar st ru ct u re co m p risin g in d ivid u al m ach in es in wh ich all t h e d rive syst em s are co n n ect ed t o t h e m ain p ress d rive syst em by m ean s o f cen t ral lo n git u d in al d rive sh aft an d in t erm ed iat e co u p lin gs cf. Fig. 3.2.9 . Th is en su res syn ch ro n o u s ru n - n in g o f all t h e st at io n s: Th e t ran sp o rt syst em can be o p erat ed by a co n - t in u o u s t ran sfer wit h o n ly a m in im al safet y clearan ce t o t h e t o p d ie. To tran sp ort large u n stable p arts in tran sfer p resses, a two-axis tran s- fer system eq u ip p ed with crossbars an d su ction cu p s is u sed Fig. 4.4.34 . Un like th e off-cen ter p osition in g of p arts on feed er or robot arm s as u sed on p ress lin es Fig. 4.4.35 , h ere th e p arts are h eld d irectly by su ction cu p carriers located above th e p art. Du e to th e sym m etrical arran gem en t of th e su ction cu p s relative to th e cen ter of gravity of th e p arts, h igh er acceleratin g forces actin g on th e p art are p erm issible. In com p arison wit h feed er m ech an ism s, st ro ke rat es can be in creased fro m 13 t o 15 p art s p er m in u t e wit h t ran sp o rt st ep s bet ween 2,000 an d 2,600 m m . Th e cro ssbars are fast en ed o n carriages wh ich execu t e t h e lo n git u d i- n al feed st ep fro m o n e d ie t o t h e n ext . Th e carriages ru n o n t h e t wo lift beam s o f t h e t ran sfer wh ich m o ve in t h e vert ical d irect io n t o raise an d lo wer t h e p art . No su p p lem en t ary aid s, su ch as lift ers o r eject o rs in t h e d ie, are req u ired fo r p art t ran sp o rt . Th e t im e-m o t io n d iagram d iffers m arked ly fro m t h at o f t h e t ri-axis t ran sfer Fig. 4.4.36 . In co n t rast t o a t ri-axis t ran sfer, t h e cro ssbar t ran s- fer can n o t ret u rn d u rin g t h e fo rm in g p ro cess, as t h e cro ssbars are lo cat - ed bet ween t h e d ies. W h en t h e d ies are clo sed t h e cro ssbars are lo cat ed in a p arked p o sit io n o u t sid e t h e d ie area. Th e d ie sp acin g m u st in an y 244 Sheet metal forming and blanking Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 245 Sheet metal forming lines Fig. 4.4.34 Part transport w ith crossbar transfer system in the production of doors using a double die motion curves carriage lift beam crossbar universal station double die part-specific tooling Fig. 4.4.35 Positioning of parts on a feeder or robotic arm of a press line and on a crossbar loading unloading loading and unloading feeder arm of a press line crossbar of a transfer press Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 case be su fficien t ly great t o acco m m o d at e t h e cro ssbars. Wit h a su it able n u m ber an d arran gem en t o f t h e su ct io n cu p s o n t h e cro ssbars, it is p o s- sible t o t ran sp o rt large o n e-p iece bo d y sid e p an els fo r p assen ger cars o r even m in ivan -t yp e veh icles. Th e blan k d im en sio n s fo r t h is t yp e o f sid e p an el can be u p t o 4,200 3 1,900 m m . In o rd er t o ach ieve sm o o t h t ran sfer in co n ju n ct io n wit h m axim u m o u t p u t , t h e m o vem en t seq u en ces are co m p u t er-o p t im ized Fig. 4.4.36 . Co m p o sit e carbo n fiber m at erials are u sed fo r t h e cro ssbars in o rd er t o im p ro ve rigid it y, d am p in g an d t o red u ce m ass. Th is p erm it s m o re reli- able p art t ran sp o rt t o be ach ieved even at h igh st ro kin g rat es. Wit h t h e u se o f u n iversal st at io n s bet ween t h e u p righ t s, it is p o ssible t o ach ieve an o p t im u m d egree o f p ro d u ct io n flexibilit y Fig. 4.4.37 an d 4.4.34 . Pro gram co n t ro l o f u p t o five axes allo ws t h e t ran sp o rt o f p art s in t o t h e id eal p o sit io n fo r su bseq u en t o p erat io n s, t h u s red u cin g t h e exp en se o f t h e d ies an d im p ro vin g t h e reliabilit y o f d ie fu n ct io n s. Fu rt h erm o re, t h e u n iversal st at io n s allo w t h e cro ssbars t o assu m e an asym m et rical p arkin g p o sit io n d u rin g d ie clo su re. Th is m ean s a m arked red u ct io n in t h e len gt h o f t h e p art t ran sfer an d co n seq u en t ly an 246 Sheet metal forming and blanking Fig. 4.4.36 M otion diagram of a crossbar transfer press unloading, parked position loading, parked position slide mo ement slide mo ement slide 1 lift transfer stroke [mm] 2600 2200 1800 1400 1000 600 200 0 30 60 90 120 150 180 210 240 270 300 330 360 return stroke pick up in parking position 2 return stroke to pick up part 3 die parked position uni ersal station 1 2 3 pick up lift pick up lift transport lower return stroke slide 2 to 5 Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 in crease in t h e st ro kin g rat e o f 10 t o 15 wit h o u t gen erat in g h igh fo rces d u rin g p art accelerat io n . Th e m o t io n p at h s an d accelerat io n val- u es are calcu lat ed o n ce t h e p art fam ily h as been d efin ed . Th e p ress co n cep t in wh ich every st at io n is eq u ip p ed wit h a sep arat e slid e Fig. 4.4.38 o ffers cert ain ad van t ages o ver slid es wh ich accep t sev- eral d ies. Fo r exam p le each slid e an d t h erefo re each d ie st at io n can be in d ivid u ally ad ju st ed co n cern in g h eigh t , p ress fo rce an d resp o n se o f t h e o verlo ad syst em . Th e slid e is gen erally su bject ed t o o n -cen t er lo ad s, as t h e in d ivid u al d ie st at io n s d o n o t in flu en ce each o t h er. Fo rces are abso rbed by t h e fo u r co n n ect in g ro d s wit h m in im al t ilt o f t h e slid e. Th e slid es are gu id ed in eigh t -way gibs wh ich red u ce t ilt in g o f t h e slid e cf. Fig. 3.1.5 . Th e d eflect io n in t h e d irect io n o f t ran sp o rt is red u ced in bo t h t h e p ress bed s an d t h e slid es. Th ese feat u res en su re – p art icu larly in t h e case o f large d ies – an ad van t ageo u s effect o n p art q u alit y an d o n t h e service life o f d ies. Mo reo ver, it resu lt s in red u ced d ie t ry-o u t p erio d s an d ru n -in t im es fo r n ew d ie set s u n t il p ro d u ct io n o f t h e first accep t able p art . Sep arate slid es also offer th e ben efit th at th e sp acin g between in d i- vid u al d ies – still with th e ad van tage of red u ced p art tran sfer – in creases. 247 Sheet metal forming lines Fig. 4.4.37 Universal station w ith three to five programmable axes part-dependent contoured template Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 As a resu lt , q u ick d ie clam p s, t o o lin g at t h e t ran sfer an d u n iversal st a- t io n s an d t h e d ies t h em selves are m o re easily accessible, allo win g fo r m o re gen ero u sly d im en sio n ed scrap ch u t es. Malfu n ct io n s are less fre- q u en t an d easier t o lo cat e an d rem ed y. In gen eral, sep arat e slid es h elp t o in crease t h e u t ilizat io n rat e an d eco n o m y o f t h e p ress. In ad d it io n t o cro ssbar p resses wit h sep arat e slid es d escribed h ere, t h is p ress t yp e can alt ern at ively be d esign ed t o accep t several d ies u n d er o n e slid e. Th is rep resen t s a so lu t io n at lo wer cap it al in vest m en t sim ilar t o t h e so lu t io n u sed in a t ri-axis t ran sfer p ress Fig. 4.4.27 . Basically t h is syst em t ran sfers t h e p art s d irect ly fro m o n e d ie t o t h e n ext d ie wit h o u t em p lo yin g u n iversal st at io n s fo r p art rep o sit io n in g in bet ween . Co n seq u en t ly, t h e p art t ran sp o rt n eed s t o co ver t h e d ist an ce bet ween d ie cen t ers wit h t h e in clu sio n o f t h e cro ssbar p arkin g sp ace wh ich resu lt s in abo u t 20 m o re h o rizo n t al t ran sp o rt at io n an d co n se- q u en t ly red u ced st ro kin g rat e. Die ch an gin g eq u ip m en t p lays a sign ifican t ro le in red u cin g p ress set -u p t im es. Tran sfer p resses are eq u ip p ed wit h m o vin g bo lst ers 248 Sheet metal forming and blanking Fig. 4.4.38 Crossbar transfer press w ith moving bolsters outside the press nominal press force: 52,000kN; slides: 5; w ork stages: 5; feed pitch: 2,000 mm Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 cf. Fig. 3.4.3 fo r au t o m at ic d ie ch an ge. Fo r each d ie st at io n t h ere are t wo m o vin g bo lst ers. O n e d ie set is u sed fo r p ro d u ct io n in sid e t h e p ress, t h e o t h er set is lo cat ed o u t sid e t h e p ress bein g p rep ared fo r t h e n ext p ro d u ct io n ru n Fig. 4.4.38 an d cf. Fig. 3.4.4 . Th is allo ws t h e d ie an d p art -sp ecific t o o lin g t o be p rep ared wh ile t h e p ress is st ill p ro d u cin g. W h ile th e lift beam s stay in th e p ress, th e crossbars an d th e toolin g are sep arated by au tom atic cou p lin gs from th e lift beam s for d ie ch an ge. Th ey are th en p osition ed on th e m ovin g bolster of th e d ie an d m oved ou t of th e p ress at 90° to th e d irection of p art flow. Every d ie set is eq u ip p ed with its own crossbar an d su ction cu p toolin g. W h en settin g- u p th e m ovin g bolsters ou tsid e th e p ress, th e crossbars assign ed to th e m ovin g bolster are eq u ip p ed with th e toolin g req u ired for th e n ext p art. Th e st ep s p erfo rm ed wh en ch an gin g d ies an d reset t in g all relevan t p aram et ers o f t h e p ress are execu t ed au t o m at ically. Th ese st ep s in clu d e: d ep o sit an d u n clam p in g o f t o p d ies, release o f cro ssbar co u p lin gs, rais- in g o f lift beam s t o clear t raversin g o f m o vin g bo lst ers, exit o f m o vin g bo lst ers; en t ry, lo werin g an d cen t erin g o f n ew bo lst ers, clam p in g o f u p p er d ies, rep lacin g t h e n ext cro ssbars wit h t o o lin g an d co n t o u red n est s o f t h e u n iversal st at io n s. All t h e d ie ch an ge p aram et ers are au t o m at ically set by a p ro gram m a- ble lo gic co n t ro l. Acco rd in gly, all t h e ad ju st able p aram et ers o f t h e p erip h eral p ress syst em s su ch as t h e d est acker o r p art st ackin g are recalled an d au t o m at ically set cf. Sect . 4.4.11 . A co m p let e d ie ch an geo ver req u ires abo u t 10 m in , as vario u s reset - t in g p ro cesses ru n sim u lt an eo u sly. Th e in d ivid u al p h ases o f t h e d ie ch an gin g p ro cess are lo cally an d cen t rally d isp layed o n screen s fo r m o n it o rin g p u rp o ses. W h en m an u fact u rin g large p art s su ch as o n e-p iece bo d y sid es, in p ar- t icu lar, in d ivid u al an d d irect co n t ro l o f t h e blan kh o ld in g fo rces is very im p o rt an t t o ach ieve go o d p art q u alit y. Ju st as in t ri-axis t ran sfer p ress- es, p o wer is t ran sm it t ed via p ressu re cylin d ers t o t h e blan k h o ld er fram e. Gen erally, syst em s wit h fo u r d isp lacem en t cylin d ers are u sed . Th e fu n d am en t al ad van t age o f t h e h yd rau lic d isp lacem en t syst em , co m p ared t o p n eu m at ic d raw cu sh io n s, is t h at t h e d raw cu sh io n fo rce can be o p t io n ally co n t ro lled at each in d ivid u al h yd rau lic cylin d er d u r- in g t h e d rawin g p ro cess by m ean s o f m icro p ro cesso r-co n t ro lled servo valves. Th e p ressu re can be ad ju st ed bet ween 25 an d 100 o f t h e rat ed p ressu re cf. Fig. 3.1.12 . 249 Sheet metal forming lines Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 Do u ble p art s can be m o st su ccessfu lly p ro d u ced Fig. 4.4.39 o n eigh t -cylin d er d raw cu sh io n s wit h a sp lit p ressu re p ad . Th is allo ws in d i- vid u al ad ju st m en t o f fo u r cylin d ers p er p art .

4.4.9 Presses for plastics