Fine blanking materials, forces, quality characteristics and part variety

Steel group Group Abbreviation M aterial no. as per DIN as per EURO standard soft, unalloyed steels hot strip 1614 StW22 1.0332 FeP11 EN111 metal sheet 1623 St14 1.0338 FeP04 EN10130 cold strip 1624 St4 1.0338 general structural steels 17 100 St37-3N 1.0116 Fe360D1 EN10025 St44-3N 1.0144 Fe430D1 EN10025 fine-grain structural steels 17 102 StE420 1.8902 S420N EN10113-2 StE460 1.8905 P460N EN10028-3 case hardening steels 17 210 Ck15 1.1141 16M nCr5 1.7131 heat-treatable steels 17 221 Ck45 1.1191 2C45 EN10083-1 17 222 41Cr4 1.7035 41Cr4 EN10083-1 17 200 42CrM o4 1.7223 42CrM o4 EN10083-1 tool steels 17 350 100Cr6 1.2067 C85W 1.1830 stainless steels 17 440 ferritic X6Cr13 1.4000 X30Cr13 1.4028 austenitic X5CrNi18.10 1.4301 Aluminium and aluminium alloys Copper and copper alloys Abbreviation M aterial no. as per DIN Abbreviation M aterial no. as per DIN AlM g3 3.3535 1745 CuZn37 2.0321 17670 AlM gSi1 3.2315 1745 CuSn8 2.1030 17670 CuNi25 2.0830 17670 ap p roxim ately vertical relative to th e su rface of th e sh eet m etal. Th e fin e blan ked p art is also flat t er t h an a st an d ard blan ked p art .

4.7.2 Fine blanking materials, forces, quality characteristics and part variety

Material selection St eel is t h e m o st co m m o n ly u sed m at erial in t h e field o f fin e blan kin g t ech n o lo gy. No n -ferro u s m et als su ch as co p p er, alu m in iu m an d t h eir allo ys acco u n t fo r n o m o re t h an 10 , alt h o u gh t h e t en d en cy t o u se t h ese is o n t h e in crease. Du e t o t h e h igh p ro p o rt io n o f st eel m at erials u sed , t h ese are d escribed in great er d et ail h ere. Th e st eel t yp es u sed are bro ken d o wn in t o a n u m ber o f gro u p s: so ft u n allo yed st eels, gen eral st ru ct u ral st eels, fin e-grain ed st ru ct u ral st eels, 338 Sheet metal forming and blanking Table 4.7.1: Selection of fine blanking materials Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 case h ard en in g n itrited steel, h eat-treatable steel, tool steel, ru st-p roof ferritic steels, ru st-p roof au sten itic steels an d sp ecial steels cf. Sect.4.2.2 . Th ese steels can be p rocessed in th e form of h ot or cold strip or flat bar steel. Flat p rod u cts m u st be free of scale Table 4.7.1 . Material stress and properties Th ere is an u n d erlyin g d ifferen ce in t h e m at erial st ress wh ich o ccu rs d u rin g fin e blan kin g an d st an d ard blan kin g. Th is co rresp o n d s t o a flo w sh earin g p ro cess wh ich is o n ly p o ssible if cert ain sp ecific m at erial p ro p - ert ies are fu lfilled . Th e grain s o f t h e m et al m icro st ru ct u re are su bject ed t o a m arked co ld fo rm in g p ro cess by t h e blan kin g p u n ch p rio r t o t h e p o in t o f sep arat io n . Th is grain d efo rm at io n calls fo r a fo rm able m at eri- al wit h a h igh fo rm abilit y, i. e. wit h a h igh d egree o f u lt im at e elo n ga- t io n an d fract u re n eckin g. Th e flo w p ro cesses t akin g p lace in t h e sh earin g zo n e an d t h e wo rk h ard en in g are illu st rat ed in Fig. 4.7.9 . Th e co ld fo rm in g o f t h e grain s in creases fro m t h e d ie-ro ll t o t h e bu rr sid e o f t h e p art , an d d ecreases fro m t h e cu t su rface t o ward s t h e cen t er o f t h e wo rkp iece. At a cert ain d ist an ce fro m t h e su rface, t h e grain s wh ich m ake u p t h e m icro st ru ct u re are n o lo n ger affect ed by t h e fin e blan kin g p ro cess. Th e fin e blan kin g cap abilit y o f st eels is d et erm in ed o n t h e basis o f t h eir ch em ical co m p o sit io n , t h eir d egree o f p u rit y, t h eir m icro st ru ct u re, t h eir t reat m en t an d t h e p revailin g m ech an ical an d t ech n o lo gical co n - 339 Fine blanking Fig. 4.7.9 M aterial flow left and w ork hardening right in the shearing zone 1 2 3 4 0.05 mm 0.30 mm 0.15 mm di st an ce fr om c ut s ur fa ce 0.50 mm 1.00 mm 0 100 200 300 400 hardness [HV 0.2] die-roll side burr side sheet metal thickness s he et m et al th ic kn es s [m m ] Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 d it io n s. St art in g wit h so ft , u n allo yed st eels wit h a lo w carbo n co n t en t , fin e blan kin g cap abilit y in creases o n p rin cip le wit h an in creasin g p ro - p o rt io n o f carbo n an d a h igh er allo y co n t en t . Th ere is n o p recise lim it based o n t h e co n t en t o f carbo n an d allo y m at erials fro m wh ich fin e blan kin g cap abilit y can be said n o t t o exist . Th e m icrostru ctu re of a m aterial h as a p articu larly m arked in flu en ce on th e p rop erties of th e cu t su rface, th e dim en sion al stability of th e p art an d th e service life of dies. Th e illu stration on th e top righ t of Fig. 4.7.10 is a sch em atic rep resen tation of th e m icrostru ctu re of a C45 steel wh ich h as 340 Sheet metal forming and blanking Fig. 4.7.10 Schematic representation of the fine blanking process w ith a suitable left and unsuitable right material microstructure microstructure suitable microstructure unsuitable blanking process blanking process fine blanked surface, free of fracture and tear fine blanked surface with tears Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 n ot been soft an n ealed : Th e m icrostru ctu re com p rises ferrite an d p erlite. Th e h ard cem en tite p lates h ave to be broken th rou gh wh en th e blan kin g p u n ch p en etrates th e m aterial. Th e resu lt is tearin g of th e cu t su rface. Th e illu st rat io n at t h e t o p left o f Fig. 4.7.10 sh o ws t h e C45 in a so ft an n ealed st at e, sp h ero id ized : Th e m icro st ru ct u re co m p rises a ferrit e m at rix wit h sp h ero id al cem en t it e em bed d ed in it . Here, t h e sp h ero id al cem en t it e grain s are n o t d ivid ed d u rin g t h e blan kin g p ro cess, bu t p ressed in t o t h e so ft ferrit e m at rix: Th e blan kin g p ro cess t akes p lace wit h o u t t ear fo rm at io n . Wit h an in creasin g carbo n an d allo y co n t en t , t h e t en sile st ren gt h o f t h e m at erial in t h e n o n -an n ealed an d so ft -an n ealed st at e Fig. 4.7.11 in creases. C45 wh ich is n o t so ft -an n ealed h as a h o t fo rm in g m icro st ru c- t u re wit h a st ren gt h o f aro u n d 700 N m m 2 . W h ere C45 h as an o p t i- m u m so ft an n ealin g m icro st ru ct u re, i. e. ext ra so ft sp h ero id ized , it s t en - sile st ren gt h lies at aro u n d 480 N m m 2 , wh ile t h e co rresp o n d in g valu e fo r t h e st an d ard sp h ero id ized q u alit y m o re co m m o n ly u sed fo r fin e blan kin g is 540 N m m 2 . 341 Fine blanking Fig. 4.7.11 Dependency of tensile strength upon the proportion of carbonalloys in unannealed a and annealed b steels te ns ile s tr en gt h R m [] C content 350 400 450 500 550 600 650 700 750 850 0 0.2 0.4 0.6 0.8 1 1.4 1.2 16 Cr 3 16 N i1 4 16 M nC r5 25C rM o4 34Cr4 a: normalized steel b: steel w ith 90-100 spheroidal cementite N mm 2 [ ] Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 Determ ining the degree of difficulty Th e slid e fo rce F St [N] d u rin g fin e blan kin g is wit h t h e blan kin g fo rce F S [N]: To calcu lat e t h e blan kin g fo rce, t h e sh eet m et al t h ickn ess s [m m ], t h e t en sile st ren gt h o f t h e m at erial R m [N m m 2 ] an d t h e len gt h o f t h e cu t co n t o u r l s [m m ] is req u ired cf. Sect . 4.5. Fo r circu lar h o le p u n ch in g, fo r exam p le t h e fo llo win g resu lt s: Dep en d in g on th e p revailin g con d ition s, factor f 1 [–] can flu ctu ate between 0.6 an d 1.2. In ord er to en su re a su fficien t blan kin g force, in p ractice 0.9 is taken for f 1 . Th is takes in to con sid eration th e in flu en ces of blan kin g ed ge p rop erties blu n tin g an d su rface rou gh n ess of th e blan k- in g elem en ts, sh eet m etal th ickn ess toleran ce an d alteration of th e blan k- in g clearan ce as a resu lt of abrasive wear. Th e co u n t erfo rce F G [N] is calcu lat ed fro m t h e su rface area A G [m m 2 ] u n d er p ressu re by t h e eject o r an d t h e co u n t erp ressu re q G [N m m 2 ]: Th e valu e q G lies bet ween 20 N m m 2 fo r t h in p art s wit h a sm all su rface area an d 70 N m m 2 fo r larger p art s. Th e co u n t erfo rce F G m u st be select - ed in su ch a way t h at t h e req u ired cu t su rface q u alit y an d o p t im u m even n ess o f t h e p art are ach ieved . As t h e co u n t erfo rce m u st be o ver- co m e d irect ly by t h e blan kin g fo rce, an excessively h igh co u n t erfo rce exercises t h e sam e effect as if t h e sh eet were o f a h igh er st ren gt h level o r t h ickn ess. In t h is way, t h e h igh co u n t erfo rce also in flu en ces t h e ser- vice life o f t h e d ie. Th e p u n ch st ress an d t h e fo rce exert ed by t h e p u n ch bo t h in crease. Dep en d in g o n t h e p art geo m et ry, t h e co u n t erfo rce am o u n t s t o bet ween 10 an d 25 o f t h e blan kin g fo rce. Wit h t h e h elp o f t h is in fo rm at io n an d t h e su rface area A st [m m 2 ] o f t h e h o le p u n ch wit h t h e d iam et er d [m m ], wh ich is: 342 Sheet metal forming and blanking F F F N St S G = + [ ] , F l s R f N S S m = ⋅ ⋅ ⋅ [ ] 1 l d mm S = ⋅ [ ] π F A q N G G G = ⋅ [ ] A d mm St = ⋅ [ ] 2 2 4 π , Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 it is also p o ssible t o d et erm in e t h e m ean p ressu re p m [N m m 2 ] ap - p lied o n t h e p u n ch : o r wh en p u n ch in g a h o le, wh ereby t h e co u n t erfo rce is gen erally t ak- en as 10 o f t h e p u n ch fo rce: Th e m ean p ressu re p m m u st n ot exceed th e 0.2 com p ression lim it R p0.2 [N m m 2 ] of th e p erforatin g p u n ch p m R p0.2 . Accordin gly, on th e basis of th e p reviou s eq u ation for th e m axim u m ratio of sh eet m etal th ickn ess s to p erforatin g p u n ch diam eter d, th e followin g eq u ation resu lts: If we assu m e t h at t h e p erfo rat in g p u n ch is m ad e o f h igh -sp eed st eel S6-5-2 wit h R p 0.2 = 3,000 N m m 2 an d HRC 63-64 an d t h at t h e t en sile st ren gt h o f t h e fin e blan kin g m at erial is 500 N m m 2 , t h e fo llo win g s d rat io resu lt s wh en blan kin g wit h co u n t erp ressu re: an d wh en blan kin g wit h o u t co u n t erp ressu re: Th is m axim u m s d rat io is gen erally assu m ed t o be 1 in n o rm al sh ear- in g p ract ice. Part configuration: flat and form ed Th e geom etric sh ap e of a p art, th e th ickn ess of th e sh eet m etal an d th e ch aracteristics of th e m aterial d eterm in e th e p rod u ction p ossibilities available by fin e blan kin g. In ord er to ascertain wh eth er a p art can be m an u factu red u sin g fin e blan kin g, its d egree of d ifficu lty is d eterm in ed : S1 easy, S2 m ed iu m , an d S3 d ifficu lt. Here, th e variou s form ed ele- m en ts su ch as slot wid th s, section wid th s, h ole d iam eters, tooth form s, corn er an gles an d rad iu s m u st be evalu ated with th e aid of Fig. 4.7.12 . 343 Fine blanking p F F A N mm m S G St = +     2 p s R f d N mm m m = ⋅ ⋅ ⋅     4 4 1 2 . s d R R f p m ≤ ⋅ ⋅ [ ] 0 2 1 4 4 . . – s d ≤ ⋅ ⋅ = = 3 000 4 4 500 0 9 3 000 1 980 1 50 , . . , , . s d ≤ ⋅ ⋅ = = 3 000 4 500 0 9 3 000 1 800 1 67 , . , , . Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 Th e h igh est sin gle d egree of d ifficu lty d eterm in es th e overall d ifficu lty level of th e p art. Un d er th e lim itin g lin e S3, fin e blan kin g d oes n ot offer th e n ecessary p rocess reliability u sin g classical toolin g tech n ology. 344 Sheet metal forming and blanking Fig. 4.7.12 Dependency of the degree of difficulty of a fine blanking part upon the thickness geometrical shape: hole diametersection w idth A; tooth module B; slotsection C; radii D d S a S1 degree of difficulty 1 a min. = 0,6 s d min. = 0,6 s S2 degree of difficulty 2 S3 degree of difficulty 3 1 1 0,5 2 3 4 5 6 7 8 9 10 2 3 4 5 6 7 8 9 10 11 12 13 14 15 S2 S3 S1 s 0.1 1 2 3 4 5 6 7 8 9 10 11 0.2 0.3 0.4 0.5 1.0 1.5 2.0 3.0 4.0 6.0 8.0 10.0 to o th m o d u le m S1 S2 S3 S1 degree of difficulty 1 a min. = 0,6 s d min. = 0,6 s I max. = approx. 15 a S2 degree of difficulty 2 S3 degree of difficulty 3 1 1 2 0,6 3 4 5 6 7 8 9 10 11 12 13 14 15 2 3 4 5 6 7 8 9 10 11 12 13 14 15 S1 S2 S3 a b l l b a r i r a R i R = 0.6 R i a r = 0.6 R i a r = R a a r = R i i R a a 1 2 3 4 5 6 7 8 9 10 0.1 0.1 0.5 1.0 1.5 2.0 2.5 3.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 30 ° 60 ° 90 ° S3 S2 S1 r m = 2r z z: no. of teeth A B C D h o le d ia m e te r d , s e c ti o n w id th a [ m m ] sheet metal thickness s [mm] sheet metal thickness s [mm] sheet metal thickness s [mm] sheet metal thickness s [mm] sl ot a , s ec ti on b m m ra d iu s r a R a [ m m ] 120 ° corner angle a Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 Exam p le: We wish t o p ro d u ce an in d ex cam wit h a t h ickn ess o f 4 m m in C15 sp h er- o id ized wit h a t en sile st ren gt h o f 420 N m m 2 Fig. 4.7.13 . Th e fo llo win g fo rm - in g elem en t s are in clu d ed an d assign ed t o t h eir resp ect ive d egrees o f d ifficu lt y in acco rd an ce wit h Fig. 4.7.12 : – h o le d iam et er d m m : 4.1 S1 – sect io n wid t h b m m : 3.5 S3 – m o d u le m : 2.25 S2 – rad iu s R a m m wit h an an gle o f 80°: 0.75 S1 S2 Th e great est d egree o f d ifficu lt y is p resen t ed by t h e sect io n wid t h S3. Th is set s t h e t o t al d egree o f d ifficu lt y o f t h e p art at S3, wh ich m ean s t h at t h e p art can be p ro d u ced . By con stru ctin g com pound progressive dies an d transfer dies with part trans- fer, it is p ossible to com bin e form in g p rocesses su ch as d eep d rawin g, cou n tersin kin g, sem i-p iercin g, offsettin g, ben d in g an d em bossin g on workp ieces with fin e blan kin g Fig. 4.7.14 an d 4.7.15 , cf. Sect. 4.1.1 . 345 Fine blanking Fig. 4.7.13 Indexing cam: fine blanked part w ith differing degrees of difficulty radius R a section b module m hole diameter d Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 Properties of the cut surface Th e cu t su rface o f fin e blan ked p art s can be blan ked sm o o t h o ver t h e en t ire wo rkp iece t h ickn ess 100 o f s. Ho wever, at t im es t earin g an d fract u re m ay o ccu r. W h ile t earin g d ep en d s m ain ly o n t h e m icro st ru c- t u re o f t h e m at erial Fig. 4.7.10 , fract u re beh avio r is in flu en ced by t h e m agn it u d e o f t h e blan kin g clearan ce Fig. 4.7.16 . Fo r co n figu rat io n o f t h e d ies an d o n -lin e in -p ro cess q u alit y co n t ro l, t h e cu t su rfaces o f a p art m u st be d escribed an d d efin ed in acco rd an ce wit h t h e fu n ct io n al req u irem en t s. 346 Sheet metal forming and blanking Fig. 4.7.14 Examples of different forming techniques w hich can be combined w ith fine blanking bevelled cut offsetting bending embossing hole w ith tapered countersink one-sided shearing flanging cylindrical countersink hole w ith countersink on either side hole w ith rounded edges semi-piercing w elded buckle cup draw ing coining Fig. 4.7.15 Fine blanked part featuring the forming processes semi-piercing, offsetting, cup draw ing, coining, bending, taper sinking and flanging Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 In t h e p art d rawin g, t h e d esign er is req u ired t o d efin e t h e n ecessary sm o o t h cu t rat io s, su rface ro u gh n ess ch aract erist ics, ad m issible t earin g, d ie-ro ll h eigh t s an d wid t h s an d also blan kin g bu rr fo rm at io n . Th e sp ec- ificat io n s are m ad e eit h er o n t h e basis o f t h e cu t su rface st an d ard acco rd in g t o VDI 3345 or as p er VDI 2906 p age 5: wh ereby E rep resen ts th e ad m issible d egree o f t earin g acco rd in g t o VDI 3345 in acco rd an ce wit h n o . 1, 2, 3 o r 4. In o rd er t o avo id t h e n eed fo r rep eat ed co m p lex sp ecificat io n s, t h e blan ked su rfaces are m arked wit h sim p le sym bo ls , st art in g wit h t h e last let t er o f t h e alp h abet z. Th e len gt h o f t h e cu t su rface is in d icat ed by a d o t t ed lin e Fig. 4.7.17 . Dim ensional and form tolerances Th e ach ievable t o leran ce levels d ep en d o n t h e m at erial, t h e wo rkp iece t h ickn ess an d geo m et rical sh ap e o f t h e p art . Th e blan kin g p ress, t h e d ie an d t h e lu brican t u sed are also sign ifican t in d et erm in in g t h e ach iev- able p art q u alit y. Th e gu id elin e valu es fo r ach ievable t o leran ces are in d icat ed in Table 4.7.2 . 347 Fine blanking Fig. 4.7.16 Terms defining the fine cut surface: h S1 min. smooth cut section in of the sheet metal thickness s in case of fracture; h S2 min. smooth cut section in of the sheet metal thickness s in case of shell- shaped fracture; b A shell-shaped fracture w idth sum of all b A can be defined as required by the user; h E die-roll height; b E die-roll w idth; E admissible tear in accordance w ith VDI Guidline 33452906 part 5 relative to size no. 1, 2, 3 or 4 s achievable smooth cut ratio tearing E fracture h S2 h E b E h S1 b A h s in S1 h s in S2 100 100 90 90 75 75 50 R a h S h S E 1 2 R ZDIN h s h s E S S 1 2 z y , , … Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 Table 4.7.2: Achieveable tolerances in fine blanking Sheet metal thickness [mm] 0.5 to 1 6 to 7 7 ± 0.01 7 8 ± 0.01 1 to 2 7 7 ± 0.015 7 to 8 8 ± 0.015 2 to 3 7 7 ± 0.02 8 8 ± 0.02 3 to 4 7 8 ± 0.02 8 9 ± 0.03 4 to 5 7 to 8 8 ± 0.03 8 9 ± 0.03 5 to 6 8 9 ± 0.03 8 to 9 9 ± 0.03 6 8 to 9 9 ± 0.03 9 9 ± 0.03 Inside contours ISO quality Outside contours ISO quality Hole distance tolerances [mm] Inside contours ISO quality Outside contours ISO quality Hole distance tolerances [mm] Tensile strength over 500 Nmm 2 Tensile strength up to 500 Nmm 2 Th e die-roll wit h it s wid t h b E an d h eigh t h E d ep en d s o n a variet y o f blan k an d m at erial-relat ed fact o rs Fig. 4.7.8 , 4.7.16 an d 4.7.18 . Th e an gle an d rad iu s of in ward an d ou tward p oin tin g corn ers, th e m aterial an d th e m icrostru ctu re, stren gth an d sh eet m etal th ickn ess, for in stan ce, exert a con sid erable in flu en ce. Also im p ortan t in d eterm in in g th e d ie- roll am ou n t is th e ed ge p rep aration of th e blan kin g p late an d in n er form 348 Sheet metal forming and blanking Fig. 4.7.17 Example dimensions for a fine blanked part in accordance w ith VDI 3345 Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 p u n ch es, as well as t h e effect o f t h e vee-rin g. Th e d ie-ro ll wid t h b E d ep en d s o n t h e d ie-ro ll h eigh t h E . In m o st cases, t h e fo llo win g ap p lies: Bu rr-free fin e blan kin g is n o t p o ssible. Th e blanking burr is lo cat ed o p p o sit e t o t h e d ie-ro ll, an d o ccu rs as so o n as t h e first p art is blan ked d u e t o ed ge p rep arat io n at t h e blan kin g p lat e an d t h e blan kin g p u n ch . As a resu lt o f wear o f t h e act ive elem en t s, t h e h eigh t an d wid t h o f t h e bu rr in crease wit h t h e in creasin g n u m ber o f blan kin g o p erat io n s. Th e blan kin g bu rr is gen erally rem o ved by belt o r flat grin d in g. Th e cut surfaces are n o t at abso lu t e righ t an gles t o t h e p lan e o f t h e sh eet m et al. Th e o u t sid e co n t o u rs o f a blan k o n t h e bu rr sid e are great er t h an at t h e d ie-ro ll sid e – in n er co n t o u rs are sm aller o n t h e bu rr sid e t h an o n t h e d ie-ro ll sid e. As a gu id elin e, t h e d ifferen ce am o u n t s t o 0.0026 m m p er 1 m m o f blan k t h ickn ess, an d d ep en d s o n a n u m ber o f in flu en cin g variables, su ch as d im en sio n in g o f t h e blan kin g p lat e, co n - figu rat io n o f t h e blan kin g p lat e wit h o r wit h o u t sh rin k rin g, p rep ara- t io n an d co at in g o f act ive elem en t s. Application exam ples Th e fo llo win g p ict u res p ro vid e exam p les o f fin e blan ked p art s. In Fig. 4.7.19 , an au t o m at ic car t ran sm issio n is illu st rat ed t o in d icat e t h e 349 Fine blanking b h mm E E ≈ ⋅ [ ] 5 Fig. 4.7.18 Geometry and die-roll on a fine blanked part: R corner radius; b E die-roll w idth; β corner angle; s blank thickness; h G burr height; h E die-roll height R R h G h G h E h E b E b E s s b b Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 variet y o f fin e blan ked p art s. High d em an d s co n cern in g cu t su rface q u alit y, d im en sio n al t o leran ces an d flat n ess are req u ired fro m t h e lam - in at io n s, d rive bo xes an d in t erm ed iat e p lat es. Ext rem ely sm all h o les in t h e in t erm ed iat e p lat e are also fin e blan ked , alt h o u gh t h e s d rat io lies at aro u n d 2. Several fin e blan ked p art s are also req u ired fo r su bassem blies u sed in t h e brake an d d rive syst em Fig. 4.7. 20 , fo r in st an ce brake d isks wit h t h eir m an y h o les wh ich h ave a d iam et er sm aller t h an h alf t h e sh eet m et al t h ickn ess. Th ese sm all p erfo rat io n s co u ld n o t be execu t ed u sin g st an d ard blan kin g m et h o d s. In ad d it io n , a t ear an d fract u re-free cu t su rface is essen t ial in o rd er t o avo id n o t ch in g effect s, as t h e d isks are 350 Sheet metal forming and blanking Fig. 4.7.19 Fine blanked components in the automatic transmission of a passenger car Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 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