wh ich o ccu r bet ween t h e in n er an d o u t er slit co ils wit h each revo lu t io n o f t h e d eco iler. Th e reaso n fo r t h ese d ifferen ces are t h e t h ickn ess varia-
t io n s in t h e st art in g co il m at erial o ver t h e co il wid t h . Th e p ro d u ct io n sp eed ach ieved by slit t in g lin es ran ges fro m 100 t o
500 m m in . Th e reset t in g o f blad es, as well as t h e rem o val an d h o o p in g o f t h e slit co ils wit h p ackagin g t ap e can lead t o syst em bo t t len ecks.
Im p ro ved cap acit y u t ilizat io n can be ach ieved by u sin g au t o m at ic exch an ge o f blad es an d by reco ilin g o u t sid e t h e lin e it self.
4.6.2 Blanking lines
Sh eet m et al p art s wit h m ed iu m an d large su rface areas are n o t p ro d u ced d irect ly o ff t h e co il, bu t fro m st acked blan ks fed au t o m at ically in t o t h e
fo rm in g p ress. Th ese blan ks are p ro d u ced in blanking lines with cut-to- length shears or blanking presses.
Blan kin g lin es co n sist o f t h e fo llo win g co m p o n en t s: – co il lin e cf.
Sect . 4.3 – sh ear o r blan kin g p ress
– st ackin g lin e
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Sheet metal forming and blanking
Fig. 4.6.2
Circular shears rolling ring
circular blade distance sleeve
frame sheet metal strip
Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998
Th e blan kin g p ro cess u sed Fig. 4.6.3
d ep en d s o n t h e p ro d u ct io n vo lu m e an d t h e d egree o f m at erial u t ilizat io n . Rect an gu lar blan ks can
be p ro d u ced u sin g sim p le cu t -t o -len gt h lin es. Trap ezo id al an d p arallel- o gram sh ap ed blan ks req u ire a swivel m o u n t ed sh ear o r a swivellin g d ie
in t h e blan kin g p ress, wh ich m o ve t h e sh ear o r t h e d ie t o t h e o t h er swivel p o sit io n resp ect ively d u rin g each feed m o vem en t . Th e feed u n it
is d riven eit h er h yd rau lically o r u sin g p ro gram -co n t ro lled servo m o t o rs. Clo sed co n t o u rs can o n ly be p ro d u ced o n p resses wit h blan kin g d ies cf.
Fig. 2.1.29 .
Lines for cut-to-length shearing In cut-to-length lines, t h e co il st o ck is cu t by m ean s o f st at io n ary, flyin g
o r ro t at in g sh ears. In lin es wit h st at io n ary sh ears, t h e ro ller feed in d exes t h e co il st o ck
fo rward o n e st ep at a t im e. Cu t t in g t akes p lace wh en t h e m at erial is st a- t io n ary
Fig. 4.6.4 . Th is rep resen t s t h e lo west co st so lu t io n an d u ses a
fixed o r swivel-m o u n t ed sh ear. Flying shears are accelerat ed briefly t o m at ch t h e sp eed o f t h e co il fo r
sh earin g. Aft er co m p let in g t h e cu t , t h e sh ear ret u rn s t o it s st art in g p o si- t io n . Th e ben efit s o f t h is d esign are co n t in u o u s feed wit h a co n st an t
st raigh t en in g m ach in e sp eed an d elim in at io n o f t h e p it t o acco m m o - d at e t h e co il lo o p , so en su rin g t h at t h e m at erial is n o t ben t again aft er
287
Shearing lines
Fig. 4.6.3
Blank geometries, arranged according to the type of blanking line straight
shear sw ivel-mounted
fixed shear sw ivel-mounted shear,
moving during feed stop contoured
blanking die
Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998
st raigh t en in g cf. Sect . 4.8.3
. As t h e sh eared blan k also m o ves at t h e sam e sp eed as t h e co il, t h ere is n o n eed t o accelerat e t h e blan k as it is
t h e case wh en u sin g st at io n ary sh earin g m et h o d s. Co m p ared t o t h e st o p an d go m et h o d u sed wit h ro ller feed an d st at io n ary sh ears, t h e
ret u rn m o vem en t in vo lved in t h e flyin g sh ear m et h o d resu lt s in a sligh t ly lo wer o u t p u t wh en wo rkin g wit h sh o rt cu t len gt h s.
Rotating shears ach ieve th e h igh est n u m ber of cu ttin g op eration s. Th eir ou tp u t lies at over 150 p arts p er m in u te, m akin g th em twice as
p rod u ctive as a blan kin g p ress. In th e case of rotatin g sh ears, th e coil m aterial ru n s at a con stan t sp eed between two cu ttin g tools m ovin g in
op p osite d irection s. Th e cu ttin g tools are arran ged over th e com p lete coil m aterial wid th at righ t an gles to th e feed d irection , so th at th e sh eet
m etal is sep arated tran sversely to th e feed d irection wh en it m akes con - tact with th e cu ttin g tools. W h en u sin g th is p rocess, th e su rface ed ge
sp eed of th e cu ttin g tools an d th e sp eed of th e coil stock m u st m atch at th e m om en t of sh earin g. W h ile th e cu ttin g tools are n ot en gaged , th eir
rotation sp eed is accelerated or red u ced by th e d rive system in ord er to p rod u ce th e req u ired blan k len gth s.
As is t h e case wit h flyin g sh ears, t h e feed rat e an d co n seq u en t ly also t h e o u t p u t o f ro t at in g sh ears d ep en d h eavily o n t h e blan k len gt h s. Fo r
bo t h sh ear t yp es, it is n ecessary t o h ave t h e su p p ly lo o p fo r co il m at er- ial an d t h e p it req u ired t o acco m m o d at e it , as sh o wn in
Fig. 4.6.4 . Lin es
wit h co n t in u o u s feed are co n seq u en t ly sh o rt er in co m p ariso n t o co il lin es eq u ip p ed wit h st at io n ary sh ears.
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Sheet metal forming and blanking
Fig. 4.6.4
Cut-to-length lines: coil line, cut-to-length shear and stacking line
decoiler w ith coil
cropping shear straightener
roller feed and cut-to-length shear
threading unit scrap container coil loop
infeed area w ith lateral coil guidance
blank stacking cart
Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998
Blanking presses for contoured blanks Contoured blanks h ave a co m p lex clo sed co n t o u r cf.
Fig. 2.1.29 an d can
co n t ain h o les. Th ese blan ks are m an u fact u red o n blan kin g p resses, also kn o wn as co n t o u r blan kin g lin es
Fig. 4.6.5 . Blan kin g p resses are
h igh -sp eed eccen t ric o r lin k d rive p resses sim ilar t o sin gle-act io n car bo d y p resses wit h a m axim u m o f 80 st ro kes p er m in u t e cf.
Fig. 4.1.19 right an d
Fig. 4.6.8 . Th ey feat u re a h igh d egree o f rigid it y as well as
sm all bearin g an d gib clearan ces. Th e slid e – gen erally wit h a m axi- m u m st ro ke o f 300 t o 450 m m – is m o u n t ed u sin g eigh t gu id e gibs cf.
Fig. 3.1.5 .
Blan kin g p resses req u ire p art icu lar at t en t io n t o noise reduction. Blan k- in g n o ise d ep en d s o n a n u m ber o f fact o rs, in clu d in g t h e im p act sp eed
o f t h e p u n ch o n t h e sh eet m et al, an d acco rd in gly also t h e slid e velo ci- t y in t h e wo rk area. In vest igat io n s h ave p ro ven t h at n o ise em issio n s
can be red u ced by aro u n d 6 d BA by h alvin g t h e slid e velo cit y. In t h e case o f link drive system s, t h e im p act sp eed reach ed is o n ly 30 t h at o f
289
Shearing lines
Fig. 4.6.5
Contour blanking line w ith nominal press force of 8,000 kN six-link drive
Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998
eccen t ric p resses, rep resen t in g a red u ct io n in t h e n o ise level o f so m e 12 d BA cf.
Fig. 3.2.3 . In ad d it io n , seco n d ary m easu res are ap p lied t o
red u ce t h e n o ise em issio n fro m blan kin g sh o ck in p resses, fo r exam p le by p ro vid in g a so u n d en clo su re. Th is can serve t o red u ce n o ise by as
m u ch as 25 d BA. As a ru le, m o d ern p resses are m o u n t ed on rocker elem ents in o rd er t o
red u ce flo o r vibrat io n s. Wit h a n at u ral lin e freq u en cy o f so m e 3 Hz, t h is t yp e o f so lu t io n ach ieves an iso lat in g efficien cy o f aro u n d 80 .
To allo w blan kin g p resses t o also p ro d u ce st raigh t an d t rap ezo id al blan ks, swivel d ies are u sed . Th ese are gen erally co n figu red in t h e fo rm
o f im p act d ies. Vert ical gu id an ce o f t h e u p p er d ie is in t egrat ed d irect ly in t o t h e d ie set . Th e swivel m o vem en t is gen erat ed by h yd rau lic cylin -
d ers o r elect ric m o t o rs, n o wad ays gen erally u sin g servo m o t o rs an d gear d rive. Th e PLC co n t ro l sp ecifies t h e swivel an gle.
Stacking lines Bo t h in t h e case o f co n t o u r blan kin g lin es an d cu t -t o -len gt h lin es, t h e
p ro d u ced blan ks are st acked o n t o p allet s by au t o m at ic st ackin g u n it s Fig. 4.6.4
. Conveyor belts arran ged cro sswise o r len gt h wise, relat ive t o t h e lo n git u d in al axis o f t h e p ress, t ran sp o rt t h e blan ks eit h er lyin g o r
h an gin g o u t o f t h e blan kin g lin e u p t o t h e ad ju st able st o p s, wh ere t h ey are lo cat ed an d eject ed o n t o p allet s. Th e p allet s are p u t o n st ackin g
cart s eq u ip p ed wit h lift in g d evices wh ich are lo wered co n t in u o u sly in o rd er t o p erm it p recise st ackin g. Usin g t wo stacking carts in each st ack-
in g d evice, co n t in u o u s o p erat io n is p o ssible. Die change
In blan kin g p resses, d ie ch an ge is p erform ed fu lly au tom atically u sin g two m ovin g bolsters cf.
Fig. 3.4.3 . Th e m oving bolsters m ove ou t of th e
p ress toward s th e op eratin g sid e an d are arran ged in th e form of T-tracks cf.
Fig. 3.4.4 . Position in g takes p lace au tom atically in th e m ach in e, on
th e set-u p station an d in th e exch an ge p osition . Th is con figu ration allows to ach ieve d ie ch an ge tim es of u n d er 5 m in .
Mo d ern coil lines are also au t o m at ically reset cf. Sect . 4.3
. Th e co n - t ro l syst em au t o m at ically execu t es t h e seq u en ces “fet ch in g t h e co il”,
“d ep o sit in g t h e co il”, “co il in sert io n ”, “fin ish p ro cessin g o f t h e co il”, “weld in g seam d isp o sal” an d “scrap m et al d isp o sal”.
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Sheet metal forming and blanking
Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998
4.6.3 High-speed blanking lines
