Quality assurance through quality control

398 Sheet metal forming and blanking Exa m ple: A p ro d u ct io n u n it h as t o be co n figu red in wh ich 44 p ressed p art s – p rim arily A p art s – h ave t o be p ro d u ced every year fo r 100,000 veh icles. Th e u n it co m p rises a blan kin g lin e, a cro ssbar t ran sfer p ress an d a t ri-axis t ran sfer p ress. A p o ssible co n figu rat io n o f t h is st am p in g p lan t wit h o p t im ized m at erial flo w an d p erip h - eral d evices is illu st rat ed in Fig. 4.9.6 . Th e m at erial is su p p lied in t h e fo rm o f co il st o ck an d st o red in t h e co il st o rage, fro m wh ere it is fed t o t h e blan kin g lin e. Th is su p p lies t h ro u gh t h e blan k st o rage bo t h large-p an el t ran sfer p resses wit h a t o t al o f 4 m illio n blan ks a year. Fo llo win g p ro d u ct io n o n t h e t ran sfer p resses, t h e p art s are t ran sp o rt ed in p art -sp ecific racks t o t h e in t erm ed iat e st o rage fo r fin ish ed p art s. Table 4.9.3 list s t h e p art sp ect ru m fo r bo t h fo rm in g p resses. Th e cro ssbar t ran s- fer p ress is ru n u sin g eigh t in d ivid u al an d eigh t d o u ble d ie set s, wh ereby t h e d o u ble d ies in t h is exam p le always p ro d u ce t wo d ifferen t p art s. Th eir d ie ch an ge t im e am o u n t s t o 10 m in . Th e t ri-axis t ran sfer p ress m an u fact u res 20 d if- feren t p art s u sin g 20 d ie set s. Th e d ie ch an ge t im e is also 10 m in . O verall, t h e 44 p art s are p ro d u ced u sin g 36 set s o f d ies – 20 o n t h e t ri-axis t ran sfer p ress, an d 24 o n t h e cro ssbar t ran sfer p ress. If 222 wo rkin g d ays are available p er year, p art s fo r 450 veh icles m u st be p ro - d u ced every d ay. In t h ree-sh ift o p erat io n wit h wo rkin g p erio d s o f 1,260 m in p er d ay, t h e t o t al o f ap p ro x. 4.8 m illio n p art s in d icat ed in Table 4.9.2 ach ieved wit h 3.9 m illio n st ro kes can be p ro d u ced every year o n t h e t ran sfer p resses. Th is is based o n a p lan n ed cap acit y u t ilizat io n o f 80 . Th ree d ays are select ed as a p ro d u ct io n cycle. If we t ake t h e sim p lified assu m p t io n t h at every p art is o n ly ru n o n ce p er cycle, t h ree t im es 450 p art s m u st be p ro d u ced p er cycle. Th e in t erm ed iat e st o rage fo r fin ish ed p art s h as a t h eo ret ical m axim u m in ven t o ry o f 1,800 p ressed p art s o f each p art t yp e: 1,350 p art s fro m ru n n in g p ro d u ct io n p lu s 450 p art s as a m in im u m safet y in ven t o ry. O n average, h o wever, as bo d y-in - wh it e p ro d u ct io n ru n s o n a p arallel basis, o n ly aro u n d h alf o f t h e p art s are lo cat ed in t h e in t erm ed iat e st o rage. At an y p o in t in t im e, t h e in ven t o ry co m - p rises 900 3 44, i. e. ap p ro x. 40,000 p art s. As a resu lt , t h e p art st o rage an d t h e cap it al in vest m en t t h is in vo lves are co n sid erably lo wer t h an wh en p ro d u cin g o n co n ven t io n al p ress lin es.

4.9.3 Quality assurance through quality control

Th e aim o f ach ievin g zero -d efect p ro d u ct io n calls fo r co n t in u o u s q u al- it y co n t ro l. Th is in vo lves t h e d et ect io n o f an y ch an ges in t h e p ro d u c- t io n p ro cess wh ich co u ld p reced e a d efect , an d t h e segregat io n o f in d i- vid u al d efect ive p art s. Co n ven t io n al m et h o d s o f q u alit y assu ran ce in st am p in g p lan t s in clu d e visu al in sp ect io n s – in t h e case o f d eep d rawn Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 Crossbar transfer press Parts Part require- Part name stroke mentday body side, outer, right 1 450 1350 body side, outer, left 1 450 1350 door, outer, front, right + left 2 450 1350 trunk lid, inner 1 450 1350 roof 1 450 1350 trunk lid, outer 1 450 1350 door, inner, front, right + left 2 450 1350 body side, inner, rear, right + left 2 450 1350 door, outer, rear, right + left 2 450 1350 door, inner, rear,right + left 2 450 1350 hood, outer 1 450 1350 hood, inner 1 450 1350 fender, outer, front, right + left 2 450 1350 w heel house, inner, front, right + left 2 450 1350 floor, mid 1 450 1350 floor, front 2 450 1350 Part batch partscycle 1350 1350 1350 1350 1350 1350 1350 1350 1350 1350 1350 1350 1350 1350 1350 1350 1350 1350 1350 1350 2700 2700 2700 2700 1350 1350 2700 2700 1350 2700 size Part batch size 2700 Tri-axis transfer press Parts Part require- Strokes Strokes Part name Stroke mentday partscycle floor, rear 1 450 1350 lock reinforcement, front, right 1 450 1350 lock reinforcement, rear, right 1 450 1350 rib, reinforcement, rear, right 1 450 1350 hinge pillar, front, right 1 450 1350 hinge reinforcement, front, right 1 450 1350 rib, reinforcement, front, right 1 450 1350 lock reinforcement, front, left 1 450 1350 lock reinforcement, rear, left 1 450 1350 rib, reinforcement, rear, left 1 450 1350 hinge pillar, front, left 1 450 1350 hinge reinforcement, front, left 1 450 1350 rib, reinforcement, front, left 1 450 1350 dash panel 1 450 1350 shelf, rear 1 450 1350 seat, reinforcement, rear 1 450 1350 w heel house inner, rear, left 1 450 1350 w heel house inner, rear, right 1 450 1350 1350 1350 1350 1350 1350 1350 1350 1350 1350 1350 1350 1350 1350 1350 1350 1350 1350 1350 1350 1350 1350 1350 1350 1350 1350 1350 1350 1350 1350 1350 1350 sunroof 1 450 1350 1350 sunroof aperture panel 1 450 1350 1350 Production cycle: 3 days Availability: 70 Die change time min: 10 Die sets: 20 Planned utilization rate: 80 Production cycle: 3 days Availability: 70 Die change time min: 10 Die sets: 16 24 Planned utilization rate: 80 399 Organization of stamping plants Table 4.9.3: Production data for crossbar and tri-axis transfer presses Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 400 Sheet metal forming and blanking p art s, fo r exam p le, fo r wrin kles an d cracks cf. Table 4.2.2 – an d also t h e t est in g o f wo rkp ieces fo r d im en sio n al accu racy u sin g m easu rin g d evices o r gau ges. Ho wever, t h is t yp e o f co n t ro l p ro cess is bo t h t im e- co n su m in g an d labo r in t en sive, an d is gen erally o n ly u sed in t h e case o f large, co m p lex wo rkp ieces su ch as bo d y p an els o r fo r ran d o m sam - p lin g o f sm aller p art s. W h ere sm all p u n ch ed p art s are in vo lved , t h e p referred syst em is o n e o f o n -lin e co n t ro ls in wh ich q u alit y assu ran ce is in t egrat ed in t h e m an - u fact u rin g p ro cess it self, i. e. in t h e p ress. Th is p erm it s m o n it o rin g o f each in d ivid u al p art an d o f p ro cess p aram et ers su ch as d ie wear. Visu al in sp ect io n s o r wo rkp iece gau gin g are in creasin gly bein g rep laced by o p t o elect ro n ic an d im age p ro cessin g syst em s. Sim p le o p t o - Fig. 4.9.6 Layout of a stamping plant w ith material flow 1 coil storage; 2 blanking line; 3 intermediate pallet storage; 4 intermediate blank storage; 5 tri-axis transfer press; 6 die storage for 5; 7 racks for finished parts for 5; 8 crossbar transfer press; 9 die storage for 8; 10 racks for finished parts for 8; 11 to intermediate finished part storage; 12 offices and recreation facilities; 13 die repair and cleaning 1 2 5 7 8 10 11 9 6 4 12 3 13 Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 401 Organization of stamping plants elect ro n ic syst em s are u sed , fo r in st an ce, fo r m easu rin g d isp lacem en t : An LED o r laser so u rce em it s ligh t beam s wh ich are p icked u p by a d et ect o r o n t h e o t h er sid e o f t h e wo rkp iece. Th e received beam s are evalu at ed an d u sed by t h e co m p u t er t o reco gn ize an d in d icat e an y p o s- sible d ie o ffset . Mo re efficien t m o n it o rin g syst em s co n sist o f a vid eo cam era wit h wo rkp iece illu m in at io n , a d igit alizat io n u n it , a co m p u t er fo r im age p ro cessin g an d a screen t o p erm it m o n it o rin g by t h e o p erat o r Fig. 4.9.7 . Th e cam era is lo cat ed at t h e p ress, t h e geo m et ry d at a o f t h e cu rren t p art is co m p ared d u rin g t h e p ro d u ct io n p ro cess wit h t h e sp eci- fied d at a fo r a go o d p art . In t h e case o f d eviat io n s beyo n d a cert ain t o l- eran ce, t h e d efect is d isp layed an d p ro d u ct io n st o p p ed . Th e im age p ro - cessin g syst em is u sed fo r t h e d et ect io n o f wrin kles, scrat ch es, d en t s, bead s, cracks an d also fo r t est in g h o les an d d et erm in in g d im en sio n s. In case o f a grad u al d et erio rat io n o f p art q u alit y, fo r exam p le as a resu lt o f d ie wear, a co n t ro l d evice fo r t h e p ro cess p aram et ers fo rm in g fo rce, blan k h o ld er fo rce, et c. is ben eficial. Fo r t h is p u rp o se, q u alit y m o n it o rin g can be co u p led wit h t h e p ress co n t ro l syst em . An o t h er q u alit y assu ran ce syst em is based o n m o n it o rin g o f t h e p ress fo rce. A sh eet fo rm in g p ro cess always p ro d u ces t h e sam e fo rce t im e cu rve wh en m an u fact u rin g d efect free p art s. Th e fo rm in g fo rce act in g Fig. 4.9.7 Quality assurance through digital image generation and processing press control image evaluation unit w ith control monitor camera w orkpiece press digital image generation illumination outfeed conveyor Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 402 Sheet metal forming and blanking o n t h e p u n ch is o bt ain ed by m easu rin g t h e elast ic d eflect io n o f lo ad ed co m p o n en t s. Lo ad cells o r st rain gages can be lo cat ed d irect ly in t h e p rim ary fo rce p at h o r in d irect ly in t h e seco n d ary fo rce p at h , fo r exam - p le in t h e p ress fram e. Th e p o sit io n in g p o ssibilit ies o f in d ivid u al sen - so rs fo r fo rce, aco u st ic em issio n an d d isp lacem en t m easu rem en t are in d icat ed in Fig. 4.9.8 . A d efect in t h e p ro d u ct io n p ro cess is in d icat ed by a d eviat io n in t h e fo rce cu rve, fo r exam p le a rap id d ro p in t h e fo rm in g fo rce d u rin g t h e d eep d rawin g p ro cess as so o n as a crack ap p ears in t h e sh eet m et al. Fu rt h erm o re, co n t ro llin g t h e blan k h o ld er fo rce d u rin g p ress set t in g also h elp s t o avo id fo rm at io n o f wrin kles in d rawn p art s. A m eth od sim ilar to force m easu rem en t is acou stic em ission m on itor- in g. Th e d yn am ic p rocesses takin g p lace at th e d ie d u rin g a blan kin g or form in g op eration cau se h igh -freq u en cy acou stic em ission s, so-called stru ctu re-born n oise. Measu rem en ts of th e acou stic em ission are carried ou t by m easu rin g th e d egree of vibration u sin g accelerom eter. In case of trou blefree p rod u ction , always th e sam e vibration cu rve is p rod u ced . Prod u ction of a d efective p art can be d etected by th e p resen ce of an Fig. 4.9.8 Positioning of sensors at the press for process monitoring force displacement acoustic emission press frame connecting rod slide cover plate die Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 u n exp ect ed aco u st ic em issio n sign al. Th e am p lit u d e o f t h e vibrat io n s in creases in co m p ariso n t o t h e u su al vibrat io n cu rve, fo r in st an ce, wh en a crack o ccu rs in a d rawn p art . Mo n it o rin g o f aco u st ic em issio n sign als are u sed m ain ly fo r t h e d et ect io n o f cracks o r p u n ch breakage. Th e efficien cy o f q u alit y assu ran ce syst em s in creases wit h t h e n u m - ber o f sen so rs u sed sim u lt an eo u sly o r by co m bin in g d ifferen t syst em s. W h en u sin g co m bin ed m o n it o rin g syst em s fo r o p erat io n an d su rveil- lan ce, wh en ever p o ssible it is reco m m en d ed t o u t ilize t h e sam e co m - p u t er an d d isp lay u n it . Pro cess d at a acq u isit io n an d d o cu m en t at io n are essen t ial t o en su re co n t in u o u s q u alit y assu ran ce. Syst em s wit h learn in g cap abilit y fo r d iagn o sis an d t h e avo id an ce o f d efect s h ave been sh o wn t o o ffer an o p t im u m so lu t io n . Bibliography Bareis, A., Braun, R., Hoffmann, A.: Hochleistungs-Stanzanlage für die Verarbeitung dickerer Bleche, VDI-Zeitschrift-Special-Rationelle Blechbearbeitung 1990 4. Bareis, A., Dommer, H.-M ., Hoffman, H.: Flexibilität in der Stanztechnik, VDI Journal 131 1989 9. Beisel, O.: Tuschieren und Probieren ohne Produktionsausfall, Werkstatt und Betrieb 1993 10. Birzer, F.: Fine blanking does even better, Sw iss quality production 1993 4. Bräutigam, H.: Richten mit Walzenrichtmaschinen, Eigenverlag, 1987, 2 nd edition Breuer, W.: M ultimediafähiges Informationssystem ergänzt herkömmliche Pressensteuerung, M aschi- nenmarkt 1995 16. DIN 1623: Steel flat products; Cold rolled sheet and strip; technical delivery conditions – part 1 02.83: Cold reduced sheet and strip, part 2 02.86: General purpose structural steels, Beuth Verlag, Berlin. DIN 1745: Wrought aluminium and aluminium alloy plate, sheet and strip greater than 0.35 mm in thick- ness - part 1: Properties, Beuth Verlag, Berlin 02.83. DIN 1788: Wrought aluminium and aluminium alloy sheet and strip w ith thicknesses betw een 0.021 and 0.350 mm, properties, Beuth Verlag, Berlin 02.83. DIN 5512: Werkstoffe für Schienenfahrzeuge; Stähle - Teil 1 02.84: Allgemeine Baustähle - part 2 09.89: Flacherzeugnisse aus unlegierten Stählen bis 3 mm Dicke – part 3 01.91: Flacherzeugnisse aus nichtrostenden Stählen, Beuth Verlag, Berlin. DIN 6935: Cold bending of flat rolled steel products, Beuth Verlag, Berlin 1975 DIN 8586: Fertigungsverfahren Biegeumformen, Beuth Verlag, Berlin 1971. DIN 17 440: Stainless steels; technical delivery conditions for plate and sheet, hot rolled strip, w ire rod, draw n w ire, steel bars, forgings and semi-finished products, Beuth Verlag, Berlin 07.85. DIN 17 441: Stainless steels; technical delivery conditions for cold rolled strip and slit strip and for plate and sheet cut therefrom, Beuth Verlag, Berlin 07.85. DIN 17 670: Wrought copper and copper alloy plate, sheet and strip; - part 1: Properties, Beuth Verlag, Berlin 12.83. DIN 17 860: Sheet and strip of titanium and w rought titanium, Beuth Verlag, Berlin 11.73. Doege, E., Besdo, D., Haferkamp, H., Tönshoff, H. K., Wiendahl, H.-P.: Fortschritte in der Werkzeug- technik, M eisenbach Bamberg Verlag, Hannover, 1995. 403 Organization of stamping plants Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 Fritz, W.: Herstellen einbaufertiger Umformteile aus Stahlblech vom Band, Bänder Bleche Rohre 1994 7-8. Frontzek, H.: Beitrag zur Bestimmung der Reibungsverhältnisse in der Blechumformung, Dissertation, Darmstadt, 1990. Guericke, W.: Theoretische und Experimentelle Untersuchungen der Kräfte und Drehmomente beim Richten von Walzgut auf Rollenrichtmaschinen, Dissertation, M agdeburg 1965. Habig, K.-H.: Verschleiß und Härte von Werkstoffen, Hanser-Verlag, M unich 1980. Hoffmann, H., Bareis, A.: Höhere Teilegenauigkeit – Wirtschaftliches Nuten von Elektroblech, Industrie- Anzeiger 1987 77. Hoffmann, H., Bareis, A.: Rotor- und Statorbleche für Elektromotoren flexibel fertigen, Werkstatt u. Be- trieb 123 1990 7. Hoffmann, H., Bareis, A., Waller, E.: Optimierte Schnelläuferpressen-Regelung der Stempeleintauchtiefe verlängert die Werkzeugstandzeit, Bänder Bleche Rohre 1988 3. Hoffmann, H.: Großteilpressen mit Saugerbrückentransfer, VDI Berichte Nr. 946, VDI-Verlag, Düsseldorf 1982. Hoffmann, H., Schneider, F.: Wirtschaftlich Fertigen auf Großteil-Stufenpressen, Entw icklung, Bauarten, Produktionsmerkmale, Werkstatt und Betrieb 122 1989 5. Hoffmann, H., Schneider. F.: Wirtschaftlich Fertigen auf Großteil-Stufenpressen, Werkstatt und Betrieb 122 1989 6. Kellenbenz, R.: Anforderungen an schnellaufende Schneidpressen bei der Fertigung von Elektroblechen, Neuere Entw icklung in der Blechumformung, DGM Verlag, Oberursel 1990. König, W.: Fertigungsverfahren, Volume 5: Blechumformung, VDI-Verlag, Düsseldorf 1990. Lange, K.: Umformtechnik, Volume 3: Blechbearbeitung, Springer-Verlag, Heidelberg, 1990. Lepper, M .: Flexible automatisierte Blechverarbeitung, Werkstatt und Betrieb 1992 6. Lepper, M .: Robot interlinked press line for car body panels, Sheet M etal Industries 1995 5. M ang, T.: Schmierung in der M etallbearbeitung, Vogel-Verlag, Würzburg 1983. Oehler, G., Kaiser, F.: Schnitt-, Stanz- und Ziehw erkzeuge, 7 th edition, Springer-Verlag, Berlin 1993. Oehler, G.: Biegen, Carl Hanser Verlag, M unich 1963. Pischel, H.: Neue Gesamtfertigung von Längsträgern für LKW-Chassis, Werkstatt und Betrieb 1995 5. Pischel, H.: Pressenstraßen optimieren komplexe Fertigungsabläufe, Werkstatt und Betrieb 1995 3. Reiss, A.: Walzrichten, Eigenverlag, 2 nd edition 1990. Rossner, S.: Vom Blechband zum Kompressor-Gehäuse, Werkstatt und Betrieb 1993 6. Siegert, K.: Innovative Pressentechnik, DGM Verlag, Oberursel 1994. Stahl-Eisen-Werkstoffblatt 093: Kaltgew alztes Band und Blech mit höherer Streckgrenze zum Kaltumformen aus mikrolegierten Stählen, Verein Deutscher Eisenhüttenleute, Verlag Stahleisen, Düsseldorf 2 nd edition 03.87. Stahl-Eisen-Werkstoffblatt 094: Kaltgew alztes Band und Blech mit höherer Streckgrenze, Verein Deut- scher Eisenhüttenleute, Verlag Stahleisen, Düsseldorf 1 st edition 07.87. Tschätsch, H.: Handbuch Umformtechnik, Hoppenstedt Technik Tabellen, Verlag, Darmstadt 1993. Tschätsch, H.: Taschenbuch Umformtechnik, Carl Hanser Verlag, M unich 1977. Weimar, G.: Zum gegenw ärtigen Stand des Walzprofilierens, Bänder Bleche Rohre, 8 1967 5. 404 Sheet metal forming and blanking Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 5 Hydroforming

5.1 General