su bseq u en t ly q u en ch ed an d t em p ered . Gear t eet h an d vario u s ch ain wh eels can also be h igh ly eco n o m ically fin e blan ked .
4.7.3 Fine blanking tools
Tool types In t ern ally an d ext ern ally co n t o u red p art s are p ro d u ced in a sin gle
st ro ke o f t h e slid e u sin g com plete blanking dies. Th e blan kin g bu rr is lo cat ed o n t h e sam e sid e fo r bo t h t h e in sid e an d o u t sid e co n t o u r. Part s
m an u fact u red in t h is way exh ibit a h igh d egree o f flat n ess. Th e d im en - sio n al t o leran ces o f t h e p art s d ep en d largely o n t h e m an u fact u rin g
q u alit y o f t h e d ie. To leran ces in t h e co il feed d o n o t in flu en ce t h e d im en sio n al t o leran ces o f t h e blan k.
Du e t o t h e co m p lex p art geo m et ries in vo lved , in t h e case o f progres- sive blanking d ies, blan kin g o f p art co n t o u rs t akes p lace in a n u m ber o f
st ages cf. Sect . 4.1.1
. Fo r in t ern al t ran sfer fro m o n e st at io n t o t h e n ext wit h in t h e d ie, t h e p art rem ain s in t h e st rip o r scrap web. Th ese are
referred t o as p re-p iercin g d ies wh ereby t h e p re-p iercin g p ro cess can t ake p lace in o n e o r m o re st ages an d is p erfo rm ed p rio r t o blan kin g o f
t h e o u t sid e co n t o u r. Here, t h e d ifferen ces in feed exert an in flu en ce o n
351
Fine blanking
Fig. 4.7.20
Fine blanked parts used in the automobile industry
Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998
t h e p o sit io n o f t h e in sid e co n t o u rs relat ive t o t h e o u t sid e co n t o u r. Th e blan kin g bu rr o n t h e in sid e co n t o u rs is lo cat ed o n t h e o p p o sit e sid e t o
t h at o f t h e o u t sid e co n t o u r. Th e co m p o u n d p ro gressive d ie also p erm it s form in g op eration s su ch as ben d in g, offsettin g, d rawin g, etc. in th e con -
secu tive station s Fig 4.7.21
an d 4.7.22
. Com p ared to com p lete blan k- in g, p arts p rod u ced u sin g th is m eth od exh ibit gen erally larger d im en -
sion ed toleran ces an d lower flatn ess. In t h e case o f t ran sfer d ies, t h e p art is n o t h eld in t h e scrap web. Th e
blan ks are t ran sp o rt ed fro m o n e wo rkp iece st at io n t o t h e n ext by m ean s o f a grip p er rail, wh ich is freq u en t ly co u p led t o t h e p ress cf.
Fig. 4.4.24 o r as illu st rat ed in
4.7.22 , by m ean s o f a t ran sverse feed er.
Die system s In fin e blan kin g t ech n o lo gy, t h e d ies belo n gin g t o t h e vario u s d ie t yp es
are su bd ivid ed in t o “m o vin g p u n ch ” an d “fixed p u n ch ” syst em s. Th e system m akin g u se of a m ovin g p u n ch is u sed m ain ly for com -
p lete blan kin g d ies in th e p rod u ction of sm all to m ed iu m -sized p arts with few in n er form s
Fig. 4.7.23 . Th e blan kin g p late 2 is m ou n ted in th e
u p p er d ie-set 16 on th e d ie block. For th e p u rp ose of p osition in g, it is p osition ed an d fasten ed an d ad d ition ally su p p orted by th e base p late 14,
p iercin g p u n ch retain in g p late 10, back-u p p late 8 an d h old in g rin g 9.
352
Sheet metal forming and blanking
Fig. 4.7.21 Tw o-station compound
progressive fine blanking die: 1
st
station: semi-piercing from below and hole punching,
2
nd
station: embossing the cylin- drical countersinks at the inside
hole, blanking the slots and outside contour.
Tooling system ” fixed punch” , four- column steel frame w ith ball gibs,
active elements are constructed and coated in segments
Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998
Th e eject o r 3 is gu id ed in t h e blan kin g p lat e. Th e eject o r in t u rn gu id es t h e in n er fo rm p u n ch 5. Via p ressu re p in s 7 an d p ressu re p ad 11, co u n -
t erp ressu re, i. e. eject io n fo rce, is ap p lied t o t h e eject o r 3. In lo wer d ie-set 17, t h e gu id e p lat e o r vee-rin g p lat e 4 is m o u n t ed
d irect ly o n t h e fram e, p o sit io n ed an d fast en ed . Th e m o vin g p u n ch 1, wh ich is co n n ect ed t o t h e p ress via t h e p u n ch base 12, ru n s in gu id e
p lat e 4. Th e in n er fo rm slu gs are eject ed by t h e p ress h yd rau lic syst em via p ressu re p in s 7 o f eject o r brid ge 13, an d t h e in n er fo rm eject o r p in
6 fro m p u n ch 1. Th e u p p er d ie-set 16 an d lo wer d ie-set 17 are p recisely
353
Fine blanking
Fig. 4.7.22
Tw o-station compound progressive fine blanking die w ith part transport by means of transverse shear pusher:
1
st
station: processing sequence in vertical direction – cup draw ing by blanking and draw ing
2
nd
station: processing sequence in vertical direction – setting cup radii, piercing inner form, trimming outside toothing. Active elements are structured in ring for-
mation and coated
Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998
p o sit io n ed by m ean s o f t h e p ress fram es co lu m n gib 18. Th e blan kin g an d gu id e p lat e are fixed u sin g t h e lat ch bo lt 15.
Th e fixed punch system is su itable for all d ie typ es – in p articu lar for th e m an u factu re of th ick, large p arts
Fig. 4.7.24 . Th e blan kin g p u n ch 1 is
p osition ed on a h ard en ed p ressu re p late 9 on th e u p p er d ie-set 16, an d is p erm an en tly p osition ed an d fasten ed to th e u p p er d ie-set 16. Th e p re-
cisely fitted gu id e p late 15 an d th e vee-rin g p late 8, wh ich bear th e latch bolts 14, gu aran tee th e fittin g p recision of th e blan kin g p u n ch 1 relative
to th e blan kin g p late 2 by m ean s of th e colu m n gib u n it 18 of th e fram e. Th e in n er fo rm slu gs are st rip p ed fro m t h e blan kin g p u n ch 1 by t h e
in n er fo rm eject o rs 6 an d 7. Pressu re is ap p lied o n t h e eject o rs 6 an d 7 an d t h e vee-rin g p lat e 8 by t h e vee-rin g p ist o n o f t h e p ress via p ressu re
p in s 13. Pressu re p in s 13 t ran sm it t h e fo rce o f t h e vee-rin g d u rin g t h e blan kin g p ro cess an d t h e st rip p in g fo rce d u rin g t h e st rip p in g cycle.
354
Sheet metal forming and blanking
Fig. 4.7.23
M oving punch system, complete blanking die: 1 blanking punch; 2 blanking plate; 3 ejector; 4 guidevee-ring plate;
5 inner form punch; 6 inner form ejector pin; 7 pressure pins; 8 back-up plate; 9 holding ring; 10 piercing punch retaining plate; 11 pressure pad;
12 punch base; 13 ejector bridge; 14 base plate; 15 latch bolt; 16 upper frame; 17 low er frame; 18 gib unit
1 2
3 4
5
6 7
7
7 7
8 9
1 0
11
1 2 1 3
1 4
1 5 1 6
1 7 1 8
1 8 1 1
Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998
Blan kin g p late 2 is located , p osition ed an d fasten ed on th e lower d ie- set 17. In sp ecial cases, for exam p le wh ere a sp lit blan kin g p late is u sed or
extrem ely th ick m aterials are bein g p rocessed , th e blan kin g p late 2 accom m od ates a sh rin k rin g 19. Th e ejector 3, wh ich is gu id ed in th e
blan kin g p late 2, is also resp on sible for gu id in g th e in n er form p u n ch es 4, an d tran sm its th e cou n terp ressu re an d ejection force from th e cou n -
terp ressu re p iston of th e p ress via th e p ressu re p in s 13. Th e in n er form p u n ch es 4 are m ou n ted on th e p iercin g p u n ch retain in g p late 10 an d
su p p orted by th e back-u p p late 12. Th e u n d erlyin g p rin cip le of th e fixed -p u n ch d ie system is also u sed
for p rogressive blan kin g d ies, com p ou n d p rogressive d ies an d tran sfer d ies
Fig. 4.7.25 . In th e case of p rogressive an d com p ou n d d ies, an ad d i-
tion al coil gu id an ce system 1, an in itial blan kin g stop 3, as well as p ilot
355
Fine blanking
Fig. 4.7.24
Fixed punch system, complete blanking die: 1 blanking punch; 2 blanking plate; 3 ejector; 4 inner form punch;
5 piercing punch; 6 inner form ejector; 7 ejector pins; 8 vee-ring plate; 9 pressure plate; 10 piercing punch retaining plate; 11 intermediate plate;
12 back-up plate; 13 pressure pins; 14 latch bolt; 15 guide plate; 16 upper frame; 17 low er frame; 18 gib unit; 19 shrink ring
8 2
6 4
5 1 0
1 2 1 3
1 4 1 8
1 3 1 3
1 3
7 9
1 6
1 7 1 5
1 9 1 1
1
3
Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998
p in s 7 8 an d p ositive p ress-off p in s 4 are req u ired . Th e coil gu id e n ot on ly en su res coil gu id an ce bu t also strip p in g of th e scrap web from th e
p ilot p in s 7 8. Th e in itial blan kin g stop 3 en su res p recise in itial blan kin g of th e sh eet m etal at th e start of a coil or strip . Th e p ilot p in s 7 8 are
resp on sible for p recisely p osition in g th e sh eet m etal in each d ie station , i. e. en su rin g th at th e p rescribed feed step is ad h ered to p recisely. Th e
task of th e p ositive p ress-off p in s 4 is to com p en sate for th e cou n ter- p ressu re so th at it d oes n ot h ave to be absorbed fu lly by th e in d ivid u al
p iercin g p u n ch es 6 d u rin g in itial blan kin g in th e first d ie station . Die design
Th e fact o rs wh ich d et erm in e t h e d esign layo u t o f a fin e blan kin g d ie are t h e geo m et rical sh ap e an d size o f t h e p art an d t h e t yp e an d t h ickn ess o f
t h e sh eet m et al bein g p ro cessed . Th ese p aram et ers d et erm in e bo t h t h e t yp e o f d ie u sed an d also t h e d ie syst em in gen eral.
Fu rt h er d efin it io n o f t h e t yp e o f d ie d esign m u st be carried o u t acco rd in g t o t h e fo llo win g co n d it io n s, wh ich are basically t h e sam e as
t h o se also valid in st an d ard blan kin g. In o rd er t o ach ieve o p t im u m blan kin g co n d it io n s, t h e lin e o f ap p licat io n o f t h e slid e fo rce m u st
co in cid e as far as p o ssible wit h t h at o f t h e blan kin g o r fo rm in g fo rce cf. Sect . 4.5
. Th e m o re p recisely t h is co n d it io n is co m p lied wit h , t h e bet - t er t h e blan kin g resu lt an d t h e lo wer t h e d egree o f d ie wear.
Th e p art d rawin g m u st co n t ain all t h e d im en sio n an d t o leran ce sp ec- ificat io n s, an d t h e cu t su rface p ro p ert ies o f t h e p art m u st be in d icat ed
Fig. 4.7.17 . Dep en d in g o n t h e t yp e o f d ie u sed , t h e st rip layo u t m u st
in d icat e t h e p o sit io n o f t h e p art in t h e sh eet m et al o r t h e p ro cessin g seq u en ce
Fig. 4.7.2 an d cf.
Sect . 4.1.1 . Th e m o st im p o rt an t asp ect o f
t h e st rip layo u t o n t h e sh eet m et al is always t h e ach ievem en t o f o p t i- m u m m at erial u t ilizat io n cf.
Fig. 4.5.2 t o
4.5.7 . Th e st rip layo u t is also
u sed t o d efin e t h e st rip wid t h an d feed st ep . Calculation of press forces
Th e fo llo win g fo rces are exert ed d u rin g fin e blan kin g: t h e blan kin g fo rce, vee-rin g fo rce, co u n t erfo rce, st rip p in g fo rce an d eject io n fo rce
Fig. 4.7.3 . Th e first t h ree fo rces d et erm in e t h e co n figu rat io n o f t h e
p ress, ad d in g u p t o creat e t h e t o t al m ach in e fo rce:
356
Sheet metal forming and blanking
F F
F F
N
Ges S R G
= +
+
[ ]
Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998
Th e blan kin g force F
S
[N] an d th e cou n terforce F
G
[N] were alread y calcu lated wh en establish in g th e d egree of d ifficu lty. Th e vee-rin g force
F
R
[N] d ep en d s on th e ten sile stren gth of th e m aterial R
m
[N m m
2
], th e len gt h l
R
[m m ] an d t h e h eigh t h
R
resp . H
R
[m m ] o f t h e vee-rin g Fig. 4.7.7
as well as an o ffset fact o r f
2
[–]:
For f
2
, exp erim en ts h ave p rod u ced th e valu e 4. Th is valu e on ly ap p lies in cases wh ere th e geom etrical con d ition s of th e vee-rin g d escribed in
sect. 4.7.1 , are ad h ered to.
Th e st rip p in g fo rce F
Ra
[N] is calcu lat ed fro m t h e blan kin g fo rce an d t h e o ffset fact o r f
3
[–], wh ich lies bet ween 0.1 an d 0.2 : ‘
357
Fine blanking
Fig. 4.7.25
Compound progressive die 1 coil guidance unit; 2 coil guidance bolts; 3 initial blanking stop;
4 positive press-off pins; 5 latch bolts; 6 piercing punch; 7 feed step pilotembossing punch; 8 feed step pilotembossing punch
2 5
6 3
8 4
7 1
F f
l h
R N
R R
R m
= ⋅ ⋅ ⋅
[ ]
2
F F
f N
Ra S
= ⋅
[ ]
3
Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998
Th e eject io n fo rce F
Ga
[N] is ap p ro xim at ely t h e sam e as t h e st rip p in g fo rce:
Wit h a cu t co n t o u r o f t h e sam e len gt h , a t o o t h ed sh ap e req u ires a great er eject o r fo rce t h an a ro u n d co n t o u r. Bo t h fo rces are ad d it io n ally
in flu en ced by t h e lu bricat io n , t h e su rface ro u gh n ess o f t h e blan kin g elem en t s an d t h e elast ic reco very o f t h e sh eet m et al.
Die lubrication Fin e blan kin g is im p ossible to p erform with ou t lu brication . Th e p rocess
wou ld lead to cold weld in g of th e active elem en ts to th e blan k an d rap id wear an d blu n tin g of th e d ie. Accord in gly, th e n ecessary p recau tion s m u st
be taken to en su re th at th e active elem en ts are su p p lied with su fficien t lu brican t at every p oin t of th e cu t con tou r an d form in g areas in th e d ie.
Fin e blan kin g o ils can be ap p lied t o t h e sh eet m at erial u sin g rollers or spray jet s. Bo t h t h e t o p an d t h e bo t t o m su rface o f t h e sh eet m et al m u st
be even ly wet t ed by a film o f lu brican t . Fo r t h is p u rp o se wet t in g su b- st an ces are ad d ed t o t h e fin e blan kin g o ils.
W h ere a sp ray system is u sed , oil m ist is created wh ich m u st be rem oved u sin g a su itable extraction d evice. If h igh -viscosity oils are u sed
for th ick, h igh er stren gth m aterials, it is also p ossible to ap p ly lu brican t th rou gh th e rollers.
To en su re t h at t h e fin e blan kin g o il ap p lied t o t h e sh eet m et al su rface also reach es t h e frict io n p art n ers d u rin g t h e blan kin g p ro cess, sp ecial
d esign m easu res are called fo r at t h e d ie. Th e gu id e p lat e, t h e eject o r an d t h e in n er fo rm eject io n p in s m u st be ch am fered o r p rep ared alo n g
t h e cu t co n t o u rs in o rd er t o creat e lu bricat io n p o cket s Fig. 4.7.26
. Recesses are p ro vid ed t o exp o se t h e vee-rin g an d blan kin g p lat e, so
en su rin g t h at o il-wet t ed sh eet m at erial reach es t h e act ive p art o f t h e d ie wit h each feed st ep . In t h e case o f clo sed d ies, t h e blan kin g o il o n t h e
sh eet m et al is p ressed in t o t h e lu bricat io n p o cket s an d serves as a su p - p ly fo r lu bricat io n o f t h e p u n ch an d blan kin g p lat e.
No u n iversal fin e blan kin g o il exist s wh ich sat isfies eq u ally all req u irem en t s. Th e fin e blan kin g o il u sed in each case m u st be sp ecially
ad ju st ed acco rd in g t o t h e m at erial, t h e t h ickn ess an d st ren gt h o f t h e p art . Th e visco sit y o f t h e o il m u st be co o rd in at ed t o t h e sp ecific t yp es
o f st ress o ccu rrin g d u rin g fin e blan kin g.
358
Sheet metal forming and blanking
F F
f N
Ga S
= ⋅
[ ]
3
Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998
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
