Dep en din g on th e sh eet m etal th ickn ess an d m aterial stren gth , th e oil is su bjected to differen t p ressu re an d tem p eratu re levels. Th e oil m u st be
cap able of with stan din g th ese levels of stress to th e exten t th at th e lu bri- can t film rem ain s in tact du rin g th e blan kin g p rocess. A low viscosity oil,
for exam p le, is su itable for low m aterial stren gth s of 400 N m m
2
u p to a th ickn ess of 3 m m , wh ile for m aterials with a stren gth of 600 N m m
2
th e sam e oil wou ld on ly be su itable u p to a sh eet th ickn ess of 1 m m . A h igh -viscosity oil can be u sed for a blan k th ickn ess of 14 m m an d a
stren gth of 400 N m m
2
, or for a th ickn ess of 10 m m with a stren gth of 600 N m m
2
. In th e p ast, organ ic ch lorid e com p ou n d s were u sed as extrem e p res-
su re EP ad d itives in fin e blan kin g oils. However, d u e to th e toxicologi- cal effects of th e ch lorin e ad d itives, ch lorin e-free oils are n ow in creas-
in gly u sed . Th e p resen t d evelop m en ts in th is field on ly p erm it th is req u irem en t to be fu lfilled u p to a sh eet m etal th ickn ess of arou n d
6 m m an d a stren gth of arou n d 450 N m m
2
with ou t d etrim en t to th e service life of d ies. W h ere h igh tem p eratu res an d p ressu re levels occu r,
th e u se of ch lorin e-free oils in volves a sign ifican t com p rom ise in term s of tool life, alth ou gh coatin g th e active d ie elem en ts can h elp to cou n -
teract th is effect.
4.7.4 Fine blanking presses and lines
Requirem ents Fin e blan kin g is o n ly p o ssible t h ro u gh t h e effect o f t h ree fo rces: t h e
blan kin g fo rce, t h e vee-rin g fo rce an d t h e co u n t erfo rce Fig. 4.7.3
. Acco rd in gly, sp ecial t rip le-act io n p resses are u sed fo r fin e blan kin g
359
Fine blanking
Fig. 4.7.26
Formation of the lubricant film in the die 4
1 2
5 lubricant
vee-ring plate blanking punch
ejector blanking plate inner form ejector
inner form punch lubrication pockets
recesses
Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998
op eration s. Th e m ach in es req u ire a con trolled m ovem en t seq u en ce with a p recise top d ead cen ter
Fig. 4.7.4 . Th e n arrow blan kin g clear-
an ce of th e d ies m u st n ot ch an ge even u n d er h igh levels of stress. Fin e blan kin g p resses are, th erefore, req u ired to com p ly with strin gen t p reci-
sion req u irem en ts for exam p le regard in g slid e gibs, h igh fram e rigid ity an d th e p arallelism of d ie clam p in g su rfaces. Both m ech an ical an d
h yd rau lic system s are u sed for th e m ain slid e d rive. Machine layout and drive system
In stan dard con figu ration , m ech an ical presses Fig. 4.7.27
are equ ipped with a “com bin ation bed” for th e tool system s of m ovin g an d fixed pu n ch
Fig. 4.7.23 an d
4.7.24 . Makin g u se of th e straigh t-side prin ciple, th e
m on obloc p ress fram e as a welded con stru ction offers good dim en sion al rigidity an d freedom from vibration s cf.
Fig. 3.1.1 . A clearan ce-free, p re-
ten sion ed slide gib is u sed cf. Fig. 3.1.5
. A cen tral su p p ort in th e u p p er an d lower die clam p in g p late en su res op tim u m die su p p ort an d in trodu c-
tion of forces to th e die. A con trolled, in fin itely variable DC m otor drives th e p ress via th e flywh eel, a disk clu tch an d a worm gear p air on two syn -
ch ron ou sly ru n n in g cran ksh afts with differen t eccen tricity Fig. 4.7.27
. Th e cran ksh afts drive a dou ble kn u ckle-join t system wh ich gen erates th e
m ovem en t seq u en ce of th e slide req u ired for fin e blan kin g. Th is d rive syst em is p art icu larly su it ed fo r m at erial t h ickn esses
bet ween ap p ro x. 1 an d 8 m m , an d t o t al p ress fo rces o f u p t o 2,500 kN. Th e vee-rin g fo rce an d co u n t erfo rce are ap p lied by h yd rau lic syst em s.
Th e m ech an ical d rive syst em is ch aract erized by t h e fo llo win g fact o rs: – a fixed slid e m o vem en t seq u en ce wit h co n st an t st ro ke an d p recise
p o sit io n o f t h e t o p an d bo t t o m d ead cen t er, – lo w en ergy co n su m p t io n ,
– h igh o u t p u t d ep en d in g o n t h e size o f t h e p ress wit h st ro kin g rat es o f u p t o 140 m in ,
– m in im al set t in g an d m ain t en an ce in p u t . Th e p ress bo d y o f hydraulic presses co m p rises a ro bu st m o n o blo c weld ed
straigh t-sid e con stru ction with h igh rigid ity Fig. 4.7.28
an d cf. Fig. 3.1.1
. Th is is ach ieved by im p lem en tin g su itable d esign m easu res su ch as selec-
t io n o f large u p righ t cro ss-sect io n s an d large ribs. Th e slid e an d m ain p ist o n t o get h er fo rm a u n it wh ich is in t egrat ed in t h e p ress bed . Th e
slid e is gu id ed in t h e p ress bo d y an d t h e lo wer p art o f t h e slid e p ist o n .
360
Sheet metal forming and blanking
Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998
Th e gib geo m et ry co m p rises a h igh -p recisio n eigh t -t rack slid in g gib. Th is co n st ru ct io n is able t o largely elim in at e slid e t ilt in g even u n d er
m ajo r eccen t ric lo ad s. Efficien t h yd rau lic fin e blan kin g p resses with a total force ran gin g
between 2,500 an d 14,000 kN are eq u ip p ed with a p ressu re accu m u lator d rive. Th e cou n terp ressu re p iston is in tegrated in th e slid e, an d th e vee-
rin g p iston is m ou n ted in th e p ress crown . Both p iston s are eq u ip p ed with su p p ort bolts, in ord er to p rovid e su p p ort over th e en tire su rface of
th e d ies. Hyd rau lic fin e blan kin g p resses are ch aracterized by: – ap p licat io n o f fo rce in d ep en d en t o f slid e p o sit io n ,
– p ro cessin g o f m at erial t h ickn esses u p t o 12 m m , – in t egrat io n o f fo rm in g o p erat io n s in t o co m p o u n d p ro gressive an d
t ran sfer d ies, – a h igh d egree o f o p erat io n al reliabilit y in t h e wo rk p ro cess.
361
Fine blanking
Fig. 4.7.27
Layout of a mechanical fine blanking press vee-ring
piston die height
adjustment lubrication system
infeed roll counterforce
piston central support
punch tightening rod for mo ing
punch system
double knuckle-
joint w orm gear
dri e slide
outfeed roll w ith scrap w eb shear
cropping shear
Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998
Du e t o t h e d esign p rin cip le o f t h e fin e blan kin g d ies, n o t o n ly t h e blan k it self bu t also all t rim m in gs an d in n er fo rm slu gs are eject ed o r st rip p ed
o f t h e d ie in t o t h e d ie area. Th e wo rkp ieces an d scrap are t h en rem o ved fro m t h e d ie m o u n t in g area by m ean s o f air jet s o r rem o val arm s. If
t h ere are p art s st ill rem ain in g in t h e d ie area befo re t h e n ext blan kin g cycle, t h e slid e m o vem en t m u st be h alt ed in t im e t o avo id d am age t o
t h e d ie. Fo r t h is p u rp o se, fin e blan kin g p resses are eq u ip p ed wit h tool breakage safety system s. Syst em s u sed in clu d e d ie st ro ke-d ep en d en t sen -
so rs, d ie-in d ep en d en t sen so rs in m ech an ical p resses an d d ie-in d ep en - d en t p ressu re sen sin g in h yd rau lic p resses.
Die-in d ep en d en t p ressu re sen sin g offers th e greatest d egree of safety, bu t can on ly be u sed in h yd rau lic p resses
Fig. 4.7.29 . Th e system works
362
Sheet metal forming and blanking
Fig. 4.7.28
Layout of a hydraulic fine blanking press vee-ring piston
die change clamping table
central support cropping
shear outfeed
roll
counterforce piston slide gib
actuating motor fixed stop
main working piston slide gib
feed height adjustment infeed roll
infeed roll basket
lubrication system
rapid tra erse closing piston
Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998
m easu rin g th e p ressu re in th e rap id traverse closin g cylin d ers. Pressu re is ap p lied to th e rap id traverse closin g cylin d ers from th e low p ressu re
syst em in su ch a way t h at t h e weigh t o f t h e slid e an d t h e bo t t o m d ie can ju st be raised at t racin g sp eed
Fig. 4.7.4 . If t h e o p erat io n is u n in -
t erru p t ed , t h e slid e swit ch act ivat es t h e h igh -p ressu re accu m u lat o r, an d t h e m ain p ist o n in it iat es t h e blan kin g m o vem en t .
If t h ere are fo reign o bject s lo cat ed in t h e d ie, t h e co n t act bet ween t h e fo reign o bject an d sh eet m et al o r u p p er d ie in it iat es an in crease o f p res-
su re in t h e rap id t raverse clo sin g cylin d er befo re t h e slid e swit ch is reach ed . Th e p ressu re in crease – a m axim u m o f 2 bar – is d et ect ed by a
p ressu re swit ch , cau sin g t h e p ress co n t ro l syst em t o in t erru p t t h e clo s- in g m o vem en t im m ed iat ely. Th is safet y syst em o ffers t h e fo llo win g
ad van t ages o ver o t h er syst em s: – st ru ct u rally co st -effect ive so lu t io n ,
– m o n it o rin g o f t h e en t ire d ie sp ace, – n o m o vin g p art s in t h e d ie sp ace,
– t racin g sp eed an d p ressu re can be set d ep en d in g o n p art sen sit ivit y.
363
Fine blanking
Fig. 4.7.29
Die-independent pressure tracing HD
ND foreign object
bottom die slide sw itch resp.
position encoder in numerically controlled
presses
pressure sw itch tracing speed controller
tracing pressure controller
rapid traverse closing piston
Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998
Exam ples of production lines Figure 4.7.30
sh ows a CNC-con trolled h yd rau lic fin e blan kin g p ress with a total p ress force of 4,000 kN. Its m axim u m p art-d ep en d en t strokin g
rate is 50 m in . Figure 4.7.31
illu st rat es an au t o m at ic p ro d u ct io n lin e fo r t h e m an u - fact u re o f syn ch ro n o u s t ap ered p lat es in t h ree st ages. Th e n erve cen t er
o f t h e lin e, wh ich p ro d u ces so m e 4,500 p art s p er sh ift , is a CNC-co n - t ro lled h yd rau lic fin e blan kin g p ress wit h a t o t al fo rce o f 14,000 kN.
Th e co m p let e lin e can be o p erat ed by a sin gle p erso n . Th e blan ks p rod u ced on a blan kin g p ress are stacked on p allets an d
th en d ep osited on th e h eigh t-ad ju stable p allet p latform . From h ere, th e
364
Sheet metal forming and blanking
Fig. 4.7.30
Fine blanking press w ith a nominal press force of 4,000 kN
Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998
p allets reach th e stackin g feed er. An accu m u latin g roller con veyor tran s- p orts th e p re-p erforated blan ks to th e in d exed p ress tran sfer u n it wh ich
tran sp orts th em th rou gh th ree d ie station s. On th e ou tfeed sid e of th e p ress, th e fin ish ed syn ch ron ou s tap ered p lates are fed via a bu ffer con -
veyor toward s th e stackin g u n it an d th e scrap is d isp osed of sep arately. Th e lo ad ed p allet s t h en t ravel via an accu m u lat in g ro ller co n veyo r
t o ward s t h e h eigh t -ad ju st able rem o val p o in t . O u t sid e t h e p ress, t h e d ies are p rep ared o n a d ie ch an ge cart cf.
Fig. 3.4.2 . Th e t h ree in d ivid u al d ie m o d u les are m o u n t ed o n a co m m o n
d ie ch an ge p lat e. Th is syst em p erm it s au t o m at ic d ie ch an ge t o be co m - p let ed in a m at t er o f m in u t es.
365
Fine blanking
Fig. 4.7.31
Overall line for the manufacture of synchronous tapered cups w ith a 14,000 kN CNC controlled fine blanking press
Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998
4 Sheet metal forming and blanking
4.8 Bending 4.8.1 Bending process
