M echanical presses Presses used for solid forming .1 Choice of press

A n u m ber o f d ifferen t p resses u sed fo r so lid fo rm in g are p resen t ed in t h e fo llo win g. Fo r a d escrip t io n o f t h e fu n d am en t al p rin cip les o f p ress d esign , p lease refer t o Sect s. 3.1 t o 3.3 .

6.8.2 M echanical presses

Mech an ical p resses are u sed p rim arily in co n ju n ct io n wit h au t o m at ic feed syst em s fo r large p ro d u ct io n series o f o ver 1.5 m illio n p art s p er year an d bat ch sizes o f m o re t h an 10,000 p art s. Bo t h vert ical an d h o ri- zo n t al p ress d esign s are u sed . Ho u rly p ro d u ct io n rat es, ach ieved u sin g vert ical syst em s, ran ge bet ween 1,800 an d 3,600, wh ile t h e co rresp o n d - in g figu re fo r h o rizo n t al p resses lies bet ween 3,600 an d 9,000. Th e sys- t em s t h at are m o st wid ely u sed are d iscu ssed belo w. Knuckle-joint presses with bottom drive Th e p rin cip le layo u t o f t h is t yp e o f p ress wit h n o m in al p ress fo rces fro m 1,600 kN is d escribed in sect io n 3.2.2 cf. Fig. 3.2.5 . Figure 6.8.2 illu s- 507 Presses used for solid forming Fig. 6.8.1 Guideline values for press force requirement pressed part diameter [mm] 10 20 30 40 50 60 70 80 90 100 110 120 1 000 2 000 2 000 3 000 4 000 4 000 5 000 6 000 6 000 7 000 8 000 8 000 9 000 10000 10000 11000 12000 12000 13000 14000 20000 22000 24000 18000 16000 14000 15000 42CrM o4 cold forming C10 cold forming C10 hot forming Cf53 100Cr6 hot forming m ul tip le -s te p fo rm in g pr es s fo rc e pr es s fo rc e si ng le -s te p fo rm in g [k N ] [k N ] Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 t rat es a t yp ical p ress. Here, t h e p ress fram e m o ves t h e u p p er d ie u p an d d o wn . In t h e case o f sin gle-st at io n d ies, p art t ran sfer t akes p lace fro m t h e back t o ward s t h e fro n t o r vice-versa. Fo r m u lt ip le-st age d ies, t h e p ress fram e in co rp o rat es lat eral o p en in gs wh ich p ro vid es sp ace fo r t h e rails o f t h e t ran sfer syst em an d fo r p art feed . O n e o f t h e ben efit s o ffered by t h is d esign p rin cip le is t h e lo w cen t er o f gravit y, an d t h e m in im al m ach in e weigh t . Th ese fact o rs resu lt in lo wer cap it al in vest m en t co m p ared t o p resses, o fferin g sim ilar cap a- bilit ies, bu t wit h t h e t o p d rive. Slid e st ro kes are in t h e ran ge o f 150 t o 250 m m in sp ecial d esign s u p t o 450 m m an d t h ey are su bst an t ially larger t h an t h o se available in co in in g o r blan kin g p resses. Multiple-station presses with m odified top knuckle-joint drive system Th e m ain ch aracteristic of th is typ e of p ress with rated p ress forces from 4,000 kN is its m od ified kn u ckle-join t d rive cf. sect. 3.2.2 . In ad d ition to th e ad van tages m en tion ed above, th is d esign p rin cip le offers th e ben - efit of a p rocess-ad ju sted low slid e velocity in th e work ran ge Fig. 6.8.3 508 Solid forming Forging Fig. 6.8.2 Knuckle-joint press w ith bottom drive nominal press force 6,300 kN, four stations w ith transfer feed Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 an d cf. Fig. 3.2.3 . Th is is su p p lem en ted by acceleration of th e slid e d own ward an d u p ward to ach ieve an overall h igh er strokin g rate. As a resu lt , t h e velo cit y o f t h e slid e wh en im p act in g t h e wo rkp iece m at erial is red u ced an d rem ain s ap p ro xim at ely co n st an t d u rin g fo rm in g. As a resu lt , t h e d yn am ic lo ad s o n t h e p ress an d d ie are red u ced . Fo r ext ru - sio n p ro cesses p art icu larly, t h is h elp s t o ext en d t h e service life o f d ies an d red u ce t h e st ress o n t h e d rive syst em . An o t h er p o sit ive sid e-effect is a red u ct io n o f n o ise d evelo p m en t by abo u t 6 t o 8 d BA. A fu rt h er ben efit in co m p ariso n t o co n ven t io n al d rive syst em s is a t h ree t o fo u r-fo ld in crease in t h e d efo rm at io n st ro ke, wit h a d rive t o rq u e valu e co m p arable t o t h at o f co n ven t io n al m ech an ical p resses. Th is m akes p ro d u ct io n o f p ress p art s, req u irin g a h igh level o f d efo r- m at io n en ergy an d a large n o m in al wo rkin g st ro ke 20 m m very eco - n o m ical cf. Sect . 3.2.1 . Th e eigh t -t rack slid e gib o p erat es acco rd in g t o t h e “fixed -lo o se bearin g” p rin cip le, t h u s co m p en sat in g fo r t h erm al exp an sio n in t h e slid e. Th is m akes t h is p ress id eally su it ed fo r warm an d h ot form in g cf. Fig. 3.1.7 . Th e slid e stroke ran ges between 250 an d 400 m m sp ecial d esign s u p to 520 m m Fig. 6.8.4 . 509 Presses used for solid forming Fig. 6.8.3 Slide velocity curves for mechanical cold forging presses ° 90 ° 180 ° 270 ° 360 ° crank angle [ ° ] -70 -60 -50 -40 -30 -20 -10 10 20 30 40 50 eccentric drive modified knuckle-joint drive knuckle-joint drive sl id e ve lo ci ty [m m in ] slide stroke 315 mm stroking rate 40min Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 Multiple-station presses with eccentric drive Th e m ain field o f ap p licat io n fo r t h ese p resses wit h n o m in al p ress fo rces fro m 6,300 kN lies in warm fo rm in g 680 t o 820 °C an d au t o - m at ed flash less fo rgin g Fig. 6.8.5 . Du e t o t h eir large slid e st ro ke o f 630 t o 800 m m , t h ese p resses are also id eally su it ed fo r co ld fo rm in g o f lo n g, sh aft -t yp e p ressed p art s. Th e slid e is gu id ed in t h e sam e gib sys- t em as illu st rat ed in Fig. 3.1.7 . Th is gu id an ce co n cep t also p erm it s n ar- ro w gib clearan ces in warm an d h o t fo rm in g ap p licat io n s, m ean in g t h at it is n o lo n ger n ecessary t o p ro vid e fo r an ad d it io n al clearan ce t o co m p en sat e fo r t h e u n avo id able t h erm al exp an sio n o f t h e slid e. 510 Solid forming Forging Fig. 6.8.4 M ultiple-station press w ith modified knuckle-joint top drive nominal press force 10,000kN, four stations, loading system and transfer feed Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 Co n seq u en t ly, ext rem ely p recise p ressed p art s can be p ro d u ced . Cen - t ral o ffset , in p art icu lar, is co n sid erably lo wer t h an wh en u sin g co n ven - tion al gib system s. As a resu lt, ad d ition al m easu res su ch as lateral p u n ch ad ju stm en ts or colu m n gibs can be elim in ated . In warm an d h o t fo rm in g ap p licat io n s, t h is co n cep t is su p p lem en t ed by h igh ly efficien t co o lin g syst em s wh ich su bst an t ially red u ce t h e o ver- all h eat gen erat io n in t h e d ies. Horizontal m ultiple-station presses for m anufacture of pressed parts m ade of wire Th e m ajo r ben efit o f h o rizo n t al m u lt ip le-st at io n p resses is t h at wire, su it ably p re-t reat ed fo r co ld fo rm in g, can be u sed . Th u s, t h e m an u fac- t u re o f largely co ld p ressed co n t o u red p art s is p o ssible wit h o u t ad d i- 511 Presses used for solid forming Fig. 6.8.5 Warm forming line comprising a multiple-station press w ith eccentric drive nominal press force 20,000 kN, induction furnace, transfer feed and die change support Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 t io n al ch em ical o r t h erm al t reat m en t . Th e wire is d rawn an d st raigh t - en ed by a wire feed d evice. An in t egrat ed sh earin g syst em wit h clo sed sh earin g d ies is u sed t o p ro d u ce vo lu m et rically p recise slu gs. Th e sp e- cial grip p er t ran sfer syst em t ran sfers t h e p art s fro m o n e st at io n t o t h e n ext cf. Sect . 6.6 . Th e m ain d esign feat u re o f t h e p ress lin e illu st rat ed in Fig. 6.8.6 is t h e lat erally p o sit io n ed d ie m o u n t in g area wh ich is accessible fro m t h e o p erat o r’s sid e. Th is co n cep t p erm it s an ergo n o m ically favo rable t o o l set t in g an d co n ven ien t t o o l ch an ge. O t h er im p o rt an t d esign feat u res in clu d e t h e h igh ly ro bu st slid e gib again st o ff-cen t er lo ad in g, t h e cast m o n o blo c fram e st ru ct u re cf. Fig. 3.1.1 an d in d ivid u ally ad ju st able grip p er an d eject io n syst em s fo r each p ress st at io n . Th e p ro d u ct io n st ro kin g rat es fo r t h is t yp e o f p ress are su bst an t ially h igh er t h an t h at fo u n d in co m p arable vert ical m u lt ip le-st at io n p resses. Th u s, t h e u se o f t h ese p resses is h igh ly eco n o m ical fo r large-scale p ro - 512 Solid forming Forging Fig. 6.8.6 Horizontal multi-station press suitable for fasteners and form parts manufactured from w ire nominal press force 1,300 kN, five stations, quick tool change system, w ire diameter max 18 mm Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 d u ction d esp ite th e h igh in itial in vestm en t costs in volved . By u sin g sem i-au tom atic an d au tom atic d ie resettin g an d d ie ch an ge system s, set- u p tim es can be su bstan tially red u ced , m ean in g th at even m ed iu m batch sizes of 20,000 to 40,000 p arts can be econ om ically m an u factu red cf. Fig. 3.4.5 . Th e p resses are u sed at n om in al p ress forces of between 1,000 an d 6,300 kN for wire d iam eters ran gin g from 10 to 36 m m . Horizontal presses – single-station with knuckle-joint drive Th ese p ress syst em s are u sed m ain ly fo r t h e p ro d u ct io n o f ext ru d ed p art s m ad e o f alu m in iu m an d alu m in iu m allo ys Fig. 6.8.7 : Th ese m ach in es are also id eally su it ed fo r p re-fo rm in g st eel slu gs. Th e p resses are fu lly au t o m at ed an d m ake u se o f sim p le, cam -co n t ro lled p u sh ers fo r p art feed . Th e h o rizo n t al d esign , sim p le p art feed an d d isch arge an d t h e su p erio r fo rm in g ch aract erist ics o f alu m in iu m p erm it h igh st ro kin g rages o f u p t o 300 m in . Co m p ared wit h vert ical p resses, su bst an t ially h igh er st ro kin g rat es also resu lt wh en fo rm in g st eel. No m in al p ress fo rces ran ge bet ween 1,500 an d 12,000 kN. 513 Presses used for solid forming Fig. 6.8.7 Single-station horizontal press w ith knuckle-joint drive nominal press forces 1,500 to 12,000 kN punch slide connecting rod eccentric dri e fi ed link point dri e shaft Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 Horizontal presses with m odified knuckle-joint If lo n ger fo rm in g st ro kes are n ecessary, a m o d ified kn u ckle-jo in t d rive syst em can be u sed as a sp ecial variat io n o f t h e st an d ard kn u ckle-jo in t p o wer u n it . Th e fo rce-st ro ke cu rve an d t h e slid e velo cit y co rresp o n d t o t h e vert ical p ress sh o wn in Fig. 6.8.3 .

6.8.3 Hydraulic presses