Production and processing of tailored blanks

4.6.5 Production and processing of tailored blanks

Weld ed blan ks co m p risin g d ifferen t m at erials, t h ickn esses o r co at in gs are kn o wn as t ailo red blan ks. Th e m o st im p o rt an t ben efit s o ffered by t ailo red blan ks are weigh t savin gs an d also red u ct io n o f t h e n u m ber o f p art s req u ired t o fo rm assem blies, fo r exam p le in t h e case o f car bo d y 310 Sheet metal forming and blanking Fig. 4.6.22 Punch-bundled rotor and stator lamination stacks Fig. 4.6.23 Joining laminations by means of punch-bundling punch blank female die punched part w ith cams punched part w ithout cams Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 rein fo rcin g co m p o n en t s Fig. 4.6.24 . In t h e p ro d u ct io n o f co m p let e assem blies, t h is red u ces lead t im es an d t h e su scep t ibilit y t o co rro sio n d u e t o t h e sm aller n u m ber o f weld in g jo in t s. By u sin g scrap p art s fro m p revio u s blan kin g o p erat io n s, fo r m an u - fact u rin g t ailo red blan ks it is p o ssible t o red u ce scrap in t h e st am p in g p lan t . Co st s fo r in p u t m at erials can also be red u ced by u sin g lo wer-co st sh eet m et al grad es fo r lo w-st ress ap p licat io n s. In ad d it io n , t ailo red blan ks can be co n figu red t o sp ecial sh ap es fo r sp ecific cases o f ap p lica- t io n . Su ch sh ap es are gen erally n o t o ffered by st eel m an u fact u rers. Th ese ben efit s h ave led t o t h e wid esp read p ro cessin g o f t ailo red blan ks. Tailored blan ks are m an u factu red on blan k weld in g lin es Fig. 4.6.25 . Th e blan ks p rod u ced on a blan kin g p ress are load ed in stack form , align ed , cen tered an d fed to th e au tom atic weld in g m ach in e. Th e blan ks are th en weld ed by m ean s of resistan ce, laser or in d u ction weld in g m eth od s Fig. 4.6.26 . W h ere resistan ce weld in g is u sed , a con trol system ch ecks th e p rocess, assu m in g h igh ou tp u t an d q u ality. Th e weld in g u n it com p rises two load in g an d cen terin g tables for blan k feed , a traversin g u n it to h old th e 311 Shearing lines Fig. 4.6.24 Passenger car reinforcement formed from a tailored blank Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 overlap p in g blan ks togeth er, an d th e station ary weld in g rolls. Altern a- tively, th e blan ks can be station ary an d th e weld in g rolls m ay m ove. Laser tech n ology u sin g CO 2 or solid lasers h as p roven su ccessfu l as a n ew p rod u ction tech n ology. However, wh en th is m eth od is u sed th e two sh eet m etal ed ges to be weld ed togeth er m u st be p rep ared for th e weld in g p rocess by laser cu ttin g or by h igh -p recision fin e sh earin g. Weld in g itself is p erform ed with th e blan ks station ary an d a m obile laser focu sin g d evice or with m ovin g blan ks an d a station ary focu sin g d evice. Th e workin g sp eed s are com p arable to th ose of a resistan ce weld in g u n it. In th e case of coated sh eet blan ks, it is actu ally p ossible to ach ieve h igh er workin g sp eed s. Th e ben efit of laser weld in g is th at n o weld over- fill occu rs an d even coated blan ks can be p rocessed with ou t p roblem s. A th ird system , wh ich is n ot yet u sed on an in d u strial scale, is eq u ip p ed with an in d u ction weld in g u n it. Th e blan ks are p ressed togeth - er at th e ed ges. Th e weld in g p rocess itself is carried ou t at h igh sp eed , as th e blan ks are join ed over th e en tire len gth of th eir ed ges with in abou t 312 Sheet metal forming and blanking Fig. 4.6.25 Blank w elding line w ith continuous part handling system for the manufacture of w elded side members cf. Fig. 4.4.12 Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 2 s. Th e p rocess can n ot be execu ted on a con tin u ou s basis, as p art tran s- p ort m u st be in terru p ted d u rin g weld in g. After th e weld in g p rocess, th e p arts p ass th rou gh th e m on itorin g station an d th e bead in g an d oilin g u n it. Th e fin ish ed tailored blan ks are th en stacked again an d m ad e read y for fu rth er p rocessin g in th e form in g lin e. W h en d eep d rawin g, d ep en d in g on th e p osition of th e weld ed seam , tailored blan ks beh ave d ifferen tly to con ven tion al p arts. If, for exam p le, th e sh eet m etal th ickn ess d iffers wh ile th e blan k h old er force rem ain s con stan t, wrin kles or tears can occu r in th e form ed p art. In th ese cases, sp ecial blan k h old ers wh ich can be ad ju sted accord in g to th e form ed p rod u ct, are u sed in th e d ie set Fig. 4.6.27 . 313 Shearing lines Fig. 4.6.26 Comparison of the principle layouts of resistance, laser and induction w elding systems F F laser w elding induction w elding resistance w elding blank blank Fig. 4.6.27 M odified blank holder for deep draw ing of tailored blanks height difference of the blank holder die tailored blank segmented blank holder clearance for welding seam Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998

4.6.6 Perforating presses