Destackers and blank turnover stations

4.4.4 Destackers and blank turnover stations

Destackers Dest ackers sep arat e t h e blan ks an d feed t h em in t o t h e p ress in syn - ch ro n izat io n wit h t h e p ress cycle. W h ere lo w st ro kin g rat es are in vo lved , t h e d est ackin g an d feed in g o p erat io n is p erfo rm ed by feed ers. In t h e case o f h igh er st ro kin g rat es, aft er d est ackin g t h e blan k is t ran s- ferred o n t o m agn et ic belt s wh ich t ran sp o rt t h em in t o t h e cen t erin g st a- t io n , fo r exam p le t h e p ick u p p o sit io n o f t h e p ress t ran sfer. Destackers with feeder and suction cup tooling In t h e case o f p ress lin es cf. Sect . 4.4.5 wit h a st ro kin g rat e o f abo u t 10 t o 12 p art s p er m in u t e an d wh ere su it able blan k sh ap es are bein g p ro cessed , feed er syst em s are u sed . In case o f a d ie ch an ge, t h e en t ire t o o lin g is rep laced t o get h er wit h t h e at t ach ed su ct io n cu p s. Du rin g d est ackin g, t h e t o o lin g su ct io n cu p s p ick u p t h e t o p blan k fro m a st ack. Th e o p erat io n is su p p o rt ed by fan n in g m agn et s wh o se m agn et ic field fan s t h e t o p -m o st blan ks in o rd er t o p reven t t h e blan ks fro m st ickin g t o each o t h er. Th e m agn et s can be p o sit io n ed m an u ally o r au t o m at ically n ear t h e st ack. Bo t h p erm an en t fan n in g m agn et s an d elect rically p u l- sat in g m agn et s are u sed . W h en p ro cessin g n o n -m agn et ic m at erials, e. g. blan ks fro m alu m in i- u m o r st ain less st eel, o n ly su ct io n cu p s can be u sed . In t h is case, co m - p ressed air is blo wn in fro m t h e sid e o f t h e st ack t o en h an ce t h e sep a- rat io n o f t h e in d ivid u al blan ks. Destackers with m agnetic belts Th is d esign is eq u ip p ed wit h o n e o r t wo cylin d er-act u at ed d est ackin g u n it s p ro vid ed wit h vacu u m cu p s o r m agn et s Fig. 4.4.15 . Th ese are lo wered bet ween t h e m agn et belt s o n t h e t o p -m o st blan k o f t h e resp ec- t ive st ack, an d t h en raise an d t ran sfer t h e su sp en d ed blan k t o t h e m ag- n et ic belt co n veyo r. Here, t o o , fan n in g m agn et s are u sed t o su p p o rt t h e rem o val o f in d ivid u al blan ks. Usin g t h ese syst em s, u p t o 25 relat ively sm all an d u p t o 15 larger p art s p er m in u t e can be fed in t o t h e p ress. To en su re th at th e p ress is able to op erate con tin u ou sly wh en ch an g- in g from on e stack to th e n ext, eith er two d estackin g station s or system s with a reserve m agazin e are u sed . In th e case of d u al stackin g feed ers, switch over from th e fin ish ed to th e n ew stack takes p lace au tom atically. 217 Sheet metal forming lines Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 An o t h er p o ssibilit y is t o wo rk wit h a reserve m agazin e. Here, t h e rem ain d er o f t h e st ack is su p p o rt ed an d d est acked o ff t h e reserve fo rks wh ile a n ew st ack is ad d ed t o it fro m u n d ern eat h . Do u ble blan ks are d et ect ed elect ro n ically an d au t o m at ically sep arat ed o u t o f t h e syst em wit h o u t brin gin g t h e en t ire lin e t o a st an d st ill. In th e case of n on -m agn etic m aterials, an in tegrated feed er with su c- tion cu p s is u sed . Here, after d estackin g, th e top -m ost blan k is p osition ed from above on to a con veyor belt. A lower cycle rate is exp ected wh en u sin g th is typ e of h an d lin g system . An o t h er co n figu rat io n u sed t o t ran sp o rt m ed iu m -sized p art s in vo lves t h e u se o f m agn et ic belt s m o u n t ed o n a lift in g brid ge, wh ich are lo wered o n t o t h e st ack o f blan ks. Th u s, t h e t o p -m o st blan k o f t h e st ack is p icked u p . Th is t yp e o f syst em is d riven by m ean s o f a cran k m ech an ism Fig. 4.4.16 . Th e m axim u m ach ievable cycle rat e wit h t h is m et h o d is abo u t 16 p art s p er m in u t e. Prio r t o t h e fo rm in g o p erat io n , freq u en t ly t h e blan ks m u st be wash ed , lu bricat ed , cen t ered an d o rien t ed . Th ese o p erat io n s are in d e- p en d en t o f t h e select ed d est ackin g m et h o d . 218 Sheet metal forming and blanking Fig. 4.4.15 Destacker of a large-panel transfer press for maximum blank dimensions of 3,800 3 1,800 mm w ith a destacking bridge Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 W ashing To en su re th e m axim u m p ossible p art q u ality, th e blan ks – p articu larly th ose u sed to p rod u ce visible p arts su ch as d oors an d roofs etc. – are wash ed an d clean ed p rior to form in g. Th e wash in g clean in g p rocess is p erform ed u sin g clean in g em u lsion s or oils in con ju n ction with clean - in g bru sh es. Th e blan ks are fed toward s th e wash in g m ach in e th rou gh a con veyor belt Fig. 4.4.22 . Th e blan k is m ech an ically wash ed in th e wash in g clean in g m ach in e by a p air of roller bru sh es. Du rin g th is p rocess, th e wash in g m ed iu m is con tin u ou sly ap p lied to th e blan k by m ean s of n ozzles. Down stream from th e p air of roller bru sh es is a p air of sq u eezin g rollers m ad e of n on -woven fabric. Th ese red u ce th e clean in g m ed iu m u n iform ly an d assu re th at th ere is on ly a m in im al resid u e. Th e h igh th rou gh feed velocity based on th e cycle rate is u p to 150 m m in . For less com p lex p arts, su bseq u en t lu brication can be elim in ated if th e resid u e of th e wash in g em u lsion is su fficien t for d rawin g, an d th e m ed i- u m u sed is su itable for th is p u rp ose. 219 Sheet metal forming lines Fig. 4.4.16 Destacker w ith magnetic belt for maximum blank dimensions of 2,100 3 750 mm, suitable for coated and non-coated blanks Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 Oilinggreasing For selective lu brication of blan ks, oil sp rayin g an d greasin g d evices are in tegrated in to th e d estacker. Th ese can be u sed to ap p ly th e lu brican t p artially on th e u p p er an d or lower sid e of th e blan k. Mod ern oilin g d evices are com p u ter con trolled an d cap able of p artial greasin g or oilin g of ap p rox. 200 m m len gth at th rou gh feed velocity of u p to 150 m m in . Centeringorientation Befo re t h e blan k can be au t o m at ically t ran sp o rt ed in t o t h e d ie, it m u st be align ed o r cen t ered in lin e wit h t h e req u ired p o sit io n . In accu racies m ay o ccu r wh en p o sit io n in g a blan k. Th ese m ay be d u e t o t h e lo cat io n o n t h e st ack o r t ran sp o rt an d t h ey are co rrect ed by m ean s o f en d st o p s o r lat eral p u sh ers. In o rd er t o o bt ain a h igh d egree o f flexibilit y co n - cern in g t h e d im en sio n s an d geo m et ry o f t h e blan ks, all t h e p o sit io n in g d evices can be p ro gram m ed an d p o wer ad ju st ed . As a resu lt , t h e set -u p t im es are red u ced . Turnover devices for blank stacks Blan ks in t en d ed fo r fu rt h er p ro cessin g in fo rm in g lin es are p art ed fro m t h e co il st o ck o n blan kin g lin es cf. Sect . 4.6.2 an d layered t o blan k st acks. In o rd er t o save t o o l co st s, wh ere sym m et rical p art s are in vo lved , o n ly a sin gle blan kin g d ie is p ro d u ced . Th u s, it is p o ssible, fo r in st an ce, t o u se t h e blan ks fo r t h e left -h an d fen d er also fo r t h e righ t -h an d sid e by sim p ly t u rn in g o ver t h e st ack. A d ist in ct io n is m ad e bet ween t h e fo l- lo win g blan k st ack t u rn o ver co n cep t s: – Frict io n -lo cked st ack t u rn in g d evice: Th e st ack is p ressed wit h su ffi- cien t fo rce so t h at frict io n h o ld s t h e blan ks t o get h er an d t h en it is t u rn ed o ver. – Po sit ive-lo cked st ack t u rn in g d evice: W h en t u rn in g in a d ru m o r fo rk t u rn in g d evice, t h e st acks are m ech an ically su p p o rt ed . Drum turning device: for blanks with com plex geom etries Man y blan ks wit h irregu lar geo m et ry, fo r exam p le t rap ezo id al p art s, m ay slip o u t wh en t h e st ack is bein g t u rn ed o ver. Th erefo re, t h e st ack m u st be su p p o rt ed o n t wo sid es by m ean s o f en d st o p s. In ad d it io n , t u rn in g d evices are o ft en req u ired t o o ccu p y o n ly a m in im al sp ace an d a sin gle lo cat io n t o acco m m o d at e st acks bo t h befo re an d aft er t u rn in g. 220 Sheet metal forming and blanking Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 In t h e u n it illu st rat ed in Fig. 4.4.17 , t h e st ack o f blan ks is d ep o sit ed o n a ro ller co n veyo r wit h o u t u sin g a p allet . Th e st ack is t ran sp o rt ed in t o t h e t u rn o ver d evice u sin g t h is feed in g ro ller co n veyo r an d an o t h er ro ller co n veyo r in t h e t u rn o ver d ru m it self. Th e blan ks are h eld in p lace by ad ju st able st o p s at t wo sid es o f t h e st ack. A t h ird ro ller co n veyo r co m es d o wn o n t o t h e st ack fro m abo ve, an d t h e u n it ro t at es by 180°. Aft er o p en in g t h e t u rn o ver d evice an d releasin g t h e st o p s, t h e st ack is m o ved o u t . Here, t o o , fast set -u p is gu aran t eed as t h e st o p s au t o m at i- cally m o ve t o lean again st t h e st ack. Fork turning device for m ultiple stacks Mu lt ip le st acks o f blan ks wh ich are st acked in a d efin ed p o sit io n o n a p allet an d m u st be p o sit io n ed again exact ly aft er t u rn in g req u ire a h igh ly p recise t u rn o ver syst em Fig. 4.4.18 . Th e st acks are in it ially lo ad ed t o get h er wit h t h e p allet o n a carriage. To raise t h e first st ack, t h e carriage t ravels t o ward s t h e t u rn in g d evice, allo win g t h e lo wer fo rks t o 221 Sheet metal forming lines Fig. 4.4.17 Blank turning device for complex blank geometries Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 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