Lines for the production of electric motor laminations

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

Ro t o rs an d st at o rs in elect ric m o t o rs an d iro n co res in t ran sfo rm ers are m ad e fro m in d ivid u al layered p ieces o f sh eet m et al ran gin g fro m 0.5 t o 1 m m in t h ickn ess, in o rd er t o red u ce ed d y cu rren t lo ss Fig. 4.6.11 . Th e st art in g m at erial u sed fo r t h is t yp e o f ap p licat io n is silico n - allo yed iro n sh eet o r sem i-fin ish sh eet , wh ich is available in co il fo rm 296 Sheet metal forming and blanking Fig. 4.6.10 Effect of penetration depth control on the increase in penetration depth Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 in wid t h s o f u p t o 1,300 m m . Ro t o r an d st at o r sh eet lam in at io n s can acco rd in gly be p ro d u ced fro m a sin gle p iece o n ly u p t o a m axim u m o u t sid e d iam et er o f 1,300 m m . All larger d iam et ers are co m p o sed o f segm en t s wh ich can be u sed t o p ro d u ce st acks fo r elect rical m ach in es o f an y o p t io n al size. Dep en d in g o n t h e geo m et rical sh ap e an d p ro d u ct io n lo t size, t h e eco n o m ical p ro d u ct io n o f lam in at io n s fo r elect ric m o t o rs calls fo r a variet y o f d ie an d m ach in e t ech n o lo gies. Figure 4.6.12 in d icat es t h e field s o f ap p licat io n fo r sin gle n o t ch , co m p let e blan kin g an d p ro gres- sive d ies. To m an u fact u re ro t o r an d st at o r lam in at io n s in larger lo t sizes, u p t o a circu lar blan k d iam et er o f 600 m m , co m p o u n d d ies are u sed in h igh -sp eed blan kin g lin es. Fo r d iam et ers u p t o 1,300 m m , co m - p let e blan kin g d ies are u sed in st raigh t -sid ed p resses Fig. 4.6.13 . W h ere sm aller lo t sizes are in vo lved , t h e lam in at io n s are p ro d u ced fro m circu lar blan ks o n n o t ch in g m ach in es u sin g t h e sin gle n o t ch blan kin g m et h o d . N otching m achines No t ch in g m ach in es are gen erally o p en -fro n t p resses wit h m ech an ical d rive syst em s. Th e p ress is m o u n t ed in ad ju st able ro ller bearin gs o n a 297 Shearing lines Fig. 4.6.11 Rotor and stator blank of an electric motor Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 m ach in e bed . An im p o rt an t elem en t o f every n o t ch in g m ach in e is t h e in d exin g d evice wh ich is also lo cat ed o n t h e m ach in e bed . Th is gen er- at es t h e req u ired n o t ch in g p it ch , i. e. t h e n u m ber o f n o t ch es p er blan k. Th e p u n ch in g rad iu s is select ed by ad ju st in g t h e d ist an ce bet ween t h e p ress an d t h e in d exin g d evice. In sem i-autom atic notching m achines, th e blan kin g p rocess is p erform ed au tom atically, wh ile feed an d d isch arge are m an u al p rocesses. Th e in d ex- in g u n it is eith er m ech an ically or n u m erically con trolled Fig. 4.6.14 . Th e m ech an ical con trol d evice op erates with a cam trip p in g gear an d gears th at are exch an geable for obtain in g d ifferen t n otch in g p itch es. W h en u sin g circu lar blan k d iam eters between 800 an d 1,000 m m , th ese low-cost d evices ach ieve a h igh er ou tp u t th an n u m erically con trolled system s. In con trast, h owever, n u m erically con trolled solu tion s offer greater flexibility: Th e n otch in g p itch can be varied as req u ired , m akin g th is typ e of system id eally su ited for m ore com p lex n otch geom etries su ch as m agn et wh eels, p ole lam in ation s, rotor rim p u n ch in gs or seg- m en ts Fig. 4.6.15 below. With th e aid of con trollable d ies, it is p ossible 298 Sheet metal forming and blanking Fig. 4.6.12 Die engineering methods for electric laminations no. of pieces per year and type [parts a] outsi de di ameter of the el ectri cal machi ne [mm] 6 6 3 6 7 single notching die complete blanking die progressi e die segment blanks rotor stator blanks Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 to gen erat e co n t ou rs, several rows of n otch es in a sin gle clam p in g o p er- at io n , u n co m m o n n o t ch in g p it ch es relat ive t o 360° an d p art icu larly wid e n o t ch es u sin g d o u ble p u n ch es. In autom atic notching m achines and flexible notching system s, t h e u n n o t ch ed b lan ks are rem o ved fu lly au t o m at ically fro m a st ack o f blan ks an d fed in to th e n otch in g m ach in e. Followin g th e n otch in g o p erat io n , t h e blan ks are rem o ved , also fu lly au t o m at ically, an d d ep o sit ed o n a st ack. Th e lo ad in g an d d isch arge o p erat io n s are p er- fo rm ed eit h er by a slewin g rin g, a lin ear t ran sfer syst em o r a ro bo t . Th e six arm s o f t h e slewing ring of an autom atic notching m achine, wh ich o p erat e u sin g a circu lar in d exin g t ech n iq u e, are eq u ip p ed wit h cen t ral- ly ad ju stable tran sp ort m agn ets. Alth ou gh th is p rocess p erm its th e sh ortest p ossible in d exin g tim es, it on ly allows th e p rocessin g of rou n d or p olygon al blan ks. In th e stan d ard version , th e blan ks are tran sp orted 299 Shearing lines Fig. 4.6.13 Complete blanking die set Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 fro m o n e st ackin g m an d rel t o t h e n ext . Wit h sp ecial at t ach m en t s, p al- let s can also be u sed . O n au t o m at ic n o t ch in g syst em s wit h o n e n o t ch in g m ach in e, it is p o ssible t o carry o u t eit h er – sim u lt an eo u s n o t ch in g an d p art in g o p erat io n s o r – o n ly n o t ch in g o p erat io n s o r – first st at o r n o t ch in g an d p art in g an d t h en ro t o r n o t ch in g in t wo p asses. Ho wever, ro t o r an d st at o r lam in at io n s can be p ro d u ced in a sin gle p ass o n a lin e wit h t wo n o t ch in g m ach in es Fig. 4.6.16 . In t h e first case, ad d it io n al sh aft h o le p u n ch es are in sert ed in an em p t y st at io n , in t h e seco n d case, t h e blan ks are p o sit io n ed in t h e sixt h st at io n an d p assed o u t ward s t o t h e sh aft h o le n o t ch in g d evice. Slewin g arm s are t h e m o st eco n o m ical an d m o st efficien t way o f au t o m at in g n o t ch in g m ach in es fo r t h e p ro d u ct io n o f st an d ard lam in at io n s. 300 Sheet metal forming and blanking Fig. 4.6.14 Notching machine for circular blanks w ith numerical indexing drive system nominal press force 250 kN Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 Dep en d in g o n t h e b lan k geo m et ry, flexible notching system s wo rk wit h transfers or robots. In t h is case, t ran sp o rt always t akes p lace fro m o n e p allet t o t h e n ext Fig. 4.6.17 . Th e st an d ard n u m b er o f five st a- t io n s can b e ext en d ed at will. As fo r sem i-au t o m at ic n o t ch in g m a- ch in es wit h n u m erical co n t ro l, flexib le au t o m at ic n o t ch in g lin es are p art icu larly su it ed fo r t h e m an u fact u re o f co m p lex b lan ks: Th e sam e select io n crit eria ap p ly co n cern in g co n t ro llab le d ies. At a h igh er level o f au t o m at io n , au t o m at ic n o t ch in g m ach in es can b e in d ivid u ally ad ju st ed t o sp ecific p ro d u ct io n p ro cesses. O n e su ch d evice jo in s baked enam el-coated lam inations t o creat e a co m p let e lam ination stack o f t h e t yp e u sed in elect ric m o t o rs. Th e st at o r b lan ks are in d ivid u ally h eat ed , in sert ed in a b asket -like d evice. Pressu re is ap p lied o n t o t h e co m p let e st ack wit h each in sert ed lam in at io n . A m easu rem en t d evice gu aran - t ees a co n sist en t st ack h eigh t . O n ce t h e req u ired st ack h eigh t h as b een reach ed , t h e b asket -like d evice co n t ain in g t h e lam in at ed st ack is swiv- elled o u t . Th e p ressin g p ro cess is carried o u t wh ile t h e n ext st ack is b ein g fo rm ed . Th is cu rin g p erio d allo ws t h e co at in g o n t h e lam in a- 301 Shearing lines Fig. 4.6.15 Complete blanking die for the production of segment blanks Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 t io n s t o h ard en , fu sin g t h e st ack t o get h er. Th e st ack is t h en eject ed o n t o a ro ller co n veyo r. Usin g a p art icu larly flexible au t o m at io n m et h o d , t wo in d ivid u al n o t ch in g m ach in es wit h p allet m agazin es an d p allet st o rage st at io n s are lin ked by m ean s o f a p allet h an d lin g syst em . A h o st co m p u t er is resp o n sible fo r jo in t co n t ro l. Th is allo ws bo t h lin es t o p ro d u ce st at o r an d ro t o r lam in at io n s fo r o n e size elect ric m o t o rs o r fo r d ifferen t in d e- p en d en t sizes. 302 Sheet metal forming and blanking Fig. 4.6.16 Automatic notching line for the production of stator and rotor laminations in tw o passes w ith one notching machine above and in a single pass w ith tw o notching machines below 1 6 5 4 3 2 1 6 7 8 5 4 3 2 position rotor blanks notching machine: notch rotor deposit rotor laminations rotor blanks deposit rotor destack blanks destack blanks destack rotor blanks orientation orientation notching machine: notch stator and separate rotor notching machine: notch stator and separate rotornotch rotor deposit stator blanks deposit stator blanksidle station idle station punch finish shaft hole Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 In gen eral, large-scale sp ecial m otors are cu stom -p rod u ced u sin g blan ks wh ich req u ire u p to seven d ifferen t blan kin g op eration s Fig. 4.6.11 . Th e u n p rod u ctive d own tim e in volved in th is typ e of p ro cess can acco u n t fo r o ver 50 o f t h e t o t al p ro d u ct io n t im e as a resu lt o f t h e reset t in g an d h an d lin g wo rk in vo lved . Fo r t h is reaso n , t h ese blan ks are m o st eco n o m ically p ro d u ced u sin g a flexible production cell wh ich req u ires o n ly a sin gle clam p in g o p erat io n . A cen t ral ro bo t is resp o n sible fo r all h an d lin g fu n ct io n s an d also fo r fu lly au t o m at ic d ie ch an ge. If t h e blan ks an d d ies are p laced read y fo r p ro cessin g d u rin g n o rm al wo rkin g h o u rs, t h e p ro d u ct io n cell is cap able o f o p erat in g u n m an n ed ro u n d t h e clo ck. 303 Shearing lines Fig. 4.6.17 Flexible automatic notching machine w ith robot and pallet magazine nominal press force 250 kN Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 No t ch in g m ach in es can be eq u ip p ed wit h supplem entary attachm ents fo r sp ecial ap p licat io n s. Th ese in clu d e d evices fo r t h e p ro d u ct io n o f – in t erru p t ed h o le p at t ern s, – t ap ered lam in at io n st acks an d – skewed lam in at io n st acks. Blanking lines with com plete blanking dies Med iu m -sized bat ch es o f elect ric m o t o rs, fin ish ed segm en t s, raw seg- m en t s an d p o le blan ks are gen erally p ro d u ced u sin g co m p let e blan kin g d ies Fig. 4.6.13 . Here, t h e ext ern al co n t o u rs, h o les an d n o t ch es are blan ked in a sin gle wo rk p ro cess, gen erally u sin g st raigh t -sid ed p resses cf. Fig. 3.1.1 . Th e p ress co n cep t u sed h ere is sim ilar t o t h at o f u n iver- sal m ech an ical p resses cf. Sect . 4.4.1 . It is also p o ssible t o m an u fact u re circu lar blan ks, wh ich are freq u en t ly u sed fo r fu rt h er p ro cessin g in n o t ch in g m ach in es. Th e wid t h o f t h e in d ivid u al blan ks, st rip s o r co il m at erial can be an ywh ere bet ween 300 an d 1,250 m m . Th ese p resses are co n st ru ct ed fo r blan kin g fo rces ran gin g fro m 1,250 t o 5,000 kN. Th e st ro kin g rat e can be ad ju st ed co n t in u o u sly bet ween 15 an d 150 st ro kes p er m in u t e d ep en d in g o n t h e size o f t h e m ach in e an d t h e p ro cess en gi- n eerin g co n cep t u sed . Th e dies are o ft en co n st ru ct ed in su ch a way t h at t h e p u n ch wit h t h e o u t sid e co n t o u rs is lo cat ed in t h e bo t t o m d ie h o ld er an d t h e fem ale d ie is lo cat ed in t h e u p p er d ie h o ld er. Several p art s can be p ro d u ced sim u l- t an eo u sly. In so m e cases, t h e scrap is p u n ch ed by t h e bo t t o m d ie. Th e sep arat e st rip p er p lat e in t h e bo t t o m d ie st rip s t h e scrap web wh ile t h e eject o r in t h e u p p er d ie eject s t h e fin ish ed p art . Th is req u ires a p lat e o r cro ssbar eject o r in t h e p ress slid e wh ich is act ive n ear t h e t o p d ead cen t er. Th e gib co lu m n s gen erally ext en d o u t o f t h e gib bu sh es wh en t h e d ie o p en s. Th erefo re, t h ey are u su ally m an u fact u red o f st eel, wh ile t h e gib bu sh es are m ad e o f bro n ze. Th e co il gu id in g elem en t s are co m bin ed wit h t h e st rip p er p lat e. As a sin gle-u n it weld ed co n st ru ct io n , t h e p ress bo d y is co n figu red fo r a h igh d egree o f rigid it y. Co n sid erin g t h at h igh -q u alit y blan kin g d ies are u sed , t h e p recisio n o f t h e slid e gib is o f p art icu lar im p o rt an ce. Th e eigh t -t rack ro ller gib syst em h as p ro ven t o be an id eal syst em h ere cf. Fig. 3.1.6 . Th e slid e is eq u ip p ed wit h a t o t al o f 16 ro ller elem en t s, 304 Sheet metal forming and blanking Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 wh ich ru n , backlash -free, alo n g h ard en ed gib rails. Sh o u ld t h e slid e beco m e in ad vert en t ly jam m ed , t h e p ress can be q u ickly released wit h t h e aid o f h yd rau lic o il cu sh io n s u n d er t h e co n n ect in g ro d s. In earlier system s, p resses eq u ip p ed with com p lete blan kin g d ies req u ired freq u en tly m an u al load in g. Now, h owever, autom ated p art tran s- p ort is in creasin gly becom in g a cu stom ary featu re. Bu t th is is on ly p ossi- ble wh ere m ach in es are eq u ip p ed with coil lin es cf. Sect. 4.3 or blan k- load ers cf. Sect. 4.4.4 an d p art d isch arge d evices. Th e p ress d im en sion s are d eterm in ed accord in gly n ot on ly by th e wid th of th e coil stock bein g p rocessed an d th e n ecessary p ress force an d th e d ie d im en sion s, bu t also by th e greater sp ace req u ired to accom m od ate ad d -on u n its. Th e p rocessin g of coil stock u sin g a coil line req u ires th e u se of a d ecoil- er an d straigh ten in g d evice as well as an efficien t feed system at th e p ress. For sm all coil stock wid th s, a d u al d ecoiler is gen erally u sed , wh ile wid er coils are p rocessed by a sin gle d ecoiler with a coil liftin g p latform . A coil load in g car is also cap able of accom m od atin g two or th ree large coils. Th e elect ro n ically co n t ro lled ro ller feed syst em h as p ro ven t o be h igh ly p o p u lar fo r m aterial feed. It is d riven by a t h reep h ase servo m o t o r wit h co n t ro l circu it , wh ich allo ws t h e feed p h ase t o be set d ep en d in g o n t h e slid e st ro ke an d d ie en gin eerin g co n cep t . To d ay, st at e o f t h e art p resses are gen erally eq u ip p ed o n ly wit h o n e feed d evice at t h e m at eri- al in feed sid e. In d ivid u al co m p o n en t s, su ch as u n fin ish ed segm en t s, are in sert ed in t o t h e d ie by a m ech an ically o r elect rically d riven blan klo ad er. Th e ro ller feed fo r t h e co il st o ck an d t h e blankloader can be co m bin ed wit h a vert ical ad ju st er in su ch a way t h at o n e o f t h e t wo is select ed t o be in o p erat io n at an y o n e t im e. Usin g a p lat e-like feed d evice, t h e blan klo ad er t ran sfers t h e blan ks fro m t h e st ack, wh ich is raised by a lift in g p lat fo rm , t o t h e p ress. Th e elect rical d evice is d riven by a t h reep h ase servo m o t o r an d ch ain t ran s- m issio n . O u t p u t is lim it ed t o so m e 20 blan ks p er m in u t e. Mech an ical t ran sfer syst em s d riven d irect ly by t h e eccen t ric sh aft o f t h e p ress via cam in d exin g gears are able t o t ran sp o rt u p t o 40 blan ks p er m in u t e d ep en d in g o n t h e p art size. Rem oval of the scrap web fro m t h e t o o l area is p erfo rm ed b y a p o wer- d riven m agn et ic ro ller. Th e scrap web creat ed b y t h e b lan kin g p ro cess is fin ally ch o p p ed b y a cro p p in g sh ear p o sit io n ed o n t h e o u t feed sid e o f t h e p ress. 305 Shearing lines Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 In th e case of autom atic part discharge, th e stroke of th e p ress slid e lies between 150 an d 300 m m d u e to th e lon g d isch arge p eriod . An ad ju stable slid e stroke offers th e ad van tage th at p rogressive d ies with a sm all stroke of for exam p le 40 m m can be u sed to op tim u m effect cf. Fig. 3.2.13 . Mech an ical d isch arge d evices wh ich are eith er d irectly d ri- ven or con trolled by th e p ress are gen erally u sed . Th e p arts are ejected wh en th e p ress is at its top d ead cen ter an d th ey are collected by discharge plates, wh ich d ep osit th em ou tsid e th e p ress on a m agn etic belt, as illu strated in Fig. 4.6.18 for a fin ish ed segm en t. Dep en d in g on th e p art size, th is m eth od lim its th e strokin g rate of th e p ress to between 20 an d 60 p arts p er m in u te. Th is req u ires a slid e stroke of 150 to 300 m m . Du e to th e lon g slid e stroke req u ired , a p art d isch arge m eth od h as been d evelop ed in wh ich th e p u n ch ed p arts are collected an d p u sh ed ou t by two raised lugs in th e scrap web Fig. 4.6.19 . Th e d ies can be op erated with a su bstan tially sm aller slid e stroke of 70 m m , so 306 Sheet metal forming and blanking Fig. 4.6.18 Discharge plate and destacking magnetic belt for an unfinished segment magnetic belt for finished parts scrap con eyor belt roller feed lifting table finished segment blank discharge belt for unfinished segments discharge plate scrap w eb unfinished segment coil stock scrap chute complete blanking die Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 t h at u p t o 150 st ro kes p er m in u t e can be ach ieved d ep en d in g o n t h e p art size. Th is is o n ly p o ssible u sin g a sp ecial eject o r in t h e slid e, wh ich eject s t h e p art aro u n d 10 m m aft er t h e bo t t o m d ead cen t er an d d ep o sit s it o n t h e scrap web. Du rin g t h e su bseq u en t feed m o vem en t , t h e blan k is en gaged by t h e raised lu gs an d p u sh ed o u t o f t h e d ie. Beh in d t h e d ie is a m agn et ic belt wh ich t akes t h e p art an d t ran sp o rt s it in an o verh ead p o sit io n . Th e scrap web is ch o p p ed eit h er d irect ly beh in d t h e d ie o r u sin g a sep arat e cro p p in g sh ear. In co m p ariso n wit h co n ven t io n al d isch arge syst em s, t h is m et h o d p erm it s t h e o u t p u t t o be d o u bled , so en su rin g t h e eco n o m ical ap p lica- t io n o f co m p let e blan kin g d ies. Ho wever, t h is m et h o d can o n ly be u sed wh en o n ly o n e fin ish ed p art is p ro d u ced at a t im e an d wh ere t h e o u t - sid e sh ap e o f t h e p art p erm it s d isch arge u sin g raised lu gs in t h e scrap web. 307 Shearing lines Fig. 4.6.19 Discharge of finished parts by lugs stamped into the sheet metal strip magnetic belt for finished parts scrap con eyor belt roller feed lifting table magnetic roller cropping shear finished part scrap w eb finished blank with shaft hole coil stock complete blanking die scrap chute for shaft hole scrap chute transport lug in the scrap w eb Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 High-speed blanking lines with progressive blanking dies Large series of rotor, stator an d m agn etic lam in ation s are p rod u ced u sin g p rogressive blan kin g d ies on h igh -sp eed blan kin g lin es, in wh ich coil stock feed , p art d isch arge an d freq u en tly also d ie ch an ges are all au tom atic cf. Sect. 4.6.3 . In p rogressive blan kin g d ies, p iercin g an d cu t- ou t are execu ted first for th e rotor an d th en for th e stator Fig. 4.6.20 . At feed rates of u p to 100 m m in over 1,000 p arts p er m in u te can be p u n ch ed . W h ere sm all feed d istan ces are in volved , ou tp u t is lim ited by th e p ress strokin g rate, wh ile in th e case of larger feed step s th e ou tp u t is lim ited by th e feed system . Sm all blan ks are freq u en tly d isch arged u sin g stackin g ch an n els. Often , con sid erable tim e – u p to th ree h ou rs – is req u ired for ch an geover of th e stackin g ch an n els in m agn etic lam in ation p rod u ction . Th erefore, au tom atic d ie ch an ge system s h ave been d evelop ed wh ich p erm it lin es to be au tom atically reset in less th an 10 m in . As a ru le, th ese system s com p rise a d ie ch an ge cart cap able of accom m od atin g two d ies, actu a- tors an d p osition in g d evices for th e axes to be traversed , an d a d ialogu e- orien ted , p rogram m able logic con troller. Th e d ies are exch an ged com - p lete with m ou n ted an d filled stackin g ch an n els Fig. 4.6.21 . After sp ec- ifyin g th e relevan t d ie set, th e com p lete d ie ch an gin g an d resettin g p rocess ru n s fu lly au tom atically. 308 Sheet metal forming and blanking Fig. 4.6.20 Progressive blanking die set for rotor and stator blanks Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 Larger ro t o r an d st at o r lam in at io n s, in co n t rast , are st ill arran ged in acco rd an ce wit h t h eir n o t ch in g p at t ern in t h e d ie, st acked o n m an d rels o r in m agazin es u p t o a p reselect ed st ack h eigh t an d co n veyed o u t o f t h e p ress by m ean s o f t ran sp o rt syst em s. A seq u en ce o f st acks o f vary- in g h eigh t s, fo r exam p le fo r ven t ilat ed m o t o rs, can also be p ro - gram m ed . An o t h er m et h o d fo r t h e o rd ered u n lo ad in g o f elect ric lam in at io n s is by p u n ch -bu n d lin g Fig. 4.6.22 . Fo r t h is p u rp o se, ad d it io n al p u n ch es are lo cat ed in t h e d ie set an d t h ey p u n ch fo r exam p le lu gs, cam s o r n ep s in t o t h e lam in at io n s. Du rin g t h e cu t -o u t p ro cess, t h ese raised areas p ress t h e lam in at io n s in t o t h e co rresp o n d in g recess in t h e p revio u sly p u n ch ed p art Fig. 4.6.23 . O n ce t h e req u ired st ack h eigh t h as been reach ed , t h e fo llo win g lam in at io n is p ierced wh ere t h e raised area is p rio r t o bu n d lin g by m ean s o f a p iercin g h o le p u n ch . Th is en su res t h at t h e p ierced lam in at io n is n o t able t o lin k u p wit h t h e p revio u s lam in a- t io n an d beco m es t h e first lam in at io n o f t h e n ew st ack. 309 Shearing lines Fig. 4.6.21 Automatic die change using a die changeover cart Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998

4.6.5 Production and processing of tailored blanks