Perforating presses Shearing lines .1 Slitting lines

4.6.6 Perforating presses

Perfo rat ed sh eet s are in wid esp read u se in alm o st every sect o r o f in d u s- t ry: in t h e fo rm o f sieves an d filt ers in t h e fo o d in d u st ry, in m in in g an d gravel p it s, as p ro t ect ive co vers in t h e elect rical in d u st ry, in bu ild in g m ach in ery an d m ach in e t o o ls, as p art it io n s an d fo r d eco rat ive p u rp o s- es, in h o u seh o ld ap p lian ces, o ffice fu rn it u re, aircraft an d in d u st rial co n - st ru ct io n . Th e n u m ber of p u n ch con tou rs an d h ole p attern s is alm ost in fin ite. Steel, NF m etals or com bin ation s are am on g th e m aterials u sed , an d sh eet th ickn esses can ran ge an ywh ere between 0.3 an d 30 m m . Perforated sh eet m etal is m an u factu red eith er off th e coil or in p late form . Basically, two m ain m eth od s are u sed : Con tin u ou s or p eriod ically in terru p ted h ole p at- tern s are m an u factu red in large series from coil or p late stock on all-across p erforatin g p resses, wh ile strip p erforatin g p resses are u sed for th e sm all- series p rod u ction of op tion al h ole p attern s from p late m aterial. Bo t h m ach in e syst em s can be eq u ip p ed wit h u n it s fo r au t o m at ic sh eet m et al feed , fo r rem o val o f fin ish ed p art s, n o t ch in g, sep arat in g an d sp lit t in g, an d wit h q u ick-act io n d ie ch an gin g d evices, d ie m o n it o r- in g syst em s an d so u n d en clo su res. All-across perforating presses Sh eet m et al wit h co n t in u o u s o r p erio d ically rep eat ed h o le p at t ern s are m an u fact u red o n all-acro ss p erfo rat in g p resses Fig. 4.6.28 . Th ese p resses p ro cess bo t h co il an d p lat e st o ck u p t o a t h ickn ess o f aro u n d 6 m m . Th e sh eet m et al ru n s t h ro u gh t h e p ress o n ly in t h e feed d irect io n an d is n o rm ally p erfo rat ed in a sin gle wo rkin g st ro ke o ver t h e en t ire wid t h . Th e n o m in al p ress fo rce lies bet ween 800 an d 5,000 kN, t h e m axim u m m at erial wid t h bet ween 1,000 an d 1,600 m m . Dep en d in g o n t h e p ress size an d feed syst em , all-acro ss p erfo rat in g p resses o p erat e at u p t o 800 st ro kes p er m in u t e. Th e p ress fram e is con figu red as a m on obloc Fig. 4.6.29 . Th e slid e ru n s in clearan ce-free h ard en ed roller gibs cf. Fig. 3.1.6 via two colu m n s, an d is d riven by a DC or th reep h ase con trol m otor via a flywh eel, eccen - tric sh aft an d two con n ectin g rod s. Th is con figu ration gu aran tees a lon g d ie life. Sh ort switch in g tim es, sh ort stroke len gth s an d h igh resistan ce to wear are ach ieved th rou gh th e u se of a q u ick-action clu tch -brake com bi- n at io n cf. Fig. 3.2.8 . 314 Sheet metal forming and blanking Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 In con trast to con ven tion al p erforatin g p resses with a n on -ad ju stable, rigid sh eet m etal strip p er, in all-across p erforatin g p resses th e strip p er is d riven by an eccen tric sh aft Fig. 4.6.30 . Th u s, th e strip p er an d slid e m ovem en t are ou t of p h ase so th at th e strip p er p late rem ain s at th e bot- tom d ead cen ter Fig. 4.6.31 wh ile th e slid e travels u p ward s. Th e slid e stroke can be in creased , so exten d in g th e feed p h ase an d in creasin g th e feed ou tp u t. Like th e slid e, th e strip p er is m ou n ted in clearan ce-free h ard en ed roller gibs at two colu m n s, in ord er to en su re p articu larly p re- cise p u n ch gu id an ce. A m ajor ben efit of th e m ovin g strip p er p late is its addition al blan k h older fu n ction . Th e strip p er force an d strip p er stroke can be adju sted to th e sh eet m etal th ickn ess with th e aid of th e adju stable strip p er lin kage or a variable bed p late. Th e friction p ath between th e p u n ch an d strip p er p late is also redu ced, as th e down ward m ovem en t of th e p late p artially coin cides with th at of th e p u n ch . Th is syst em h elp s t o red u ce wear an d t h e ret u rn st ro ke fo rce at t h e p u n ch , in creases d ie service life, an d en su res m o re gen t le h an d lin g o f t h e sh eet m et al. W h en p erfo rat in g st ain less st eel sh eet s, p art icu larly, st abilizat io n o f t h e sh eet m et al by t h e st rip p er p lays a m ajo r ro le. 315 Shearing lines Fig. 4.6.28 All-across perforating press nominal press force 1,000 kN Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 316 Sheet metal forming and blanking Fig. 4.6.29 Structure of an all-across perforating press drive shaft slide connecting rod camshaft pressure point stripper slide pressure point, slide column gib punch control unit die beams clamping plate stripper connecting rod stripper slide clamps gear box feed drive Fig. 4.6.30 Section through an all-across perforating press w ith die holding system and sepa- rating shear hydraulic clamp bottom die hydraulic clamp stripper hydraulic cropping shear outfeed roller infeed roller infeed table punch control beam moving stripper press bed slide perforating punch Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 Th e st rip p er p lat e is raised d u rin g t h e feed m o vem en t su fficien t ly t o en su re t h at even co rru gat ed co il st o ck can be t ran sp o rt ed t h ro u gh t h e o p en d ie. Aft er p erfo rat io n , t h e co rru gat ed sh eet m et al can be st raigh t - en ed by t h e st rip p er p lat e. Before an electroh yd rau lically p owered sh ear, m ou n ted at th e ou tfeed roller u p righ t, sep arates th e coil in to p lates, it can be cu t u sin g a su p p le- m en tary slittin g or n otch in g d evice in to variou s wid th s. Th e slittin g or n otch in g d evice is m ou n ted eith er at th e m ain slid e – th e m ore eco- n om ical solu tion – or fasten ed at a slid e d riven sep arately by th e eccen - tric sh aft. In th is case, it m u st be p ossible to m ove th e sep aratin g sh ear ou t of th e way. If th e d evice is m ou n ted at th e m ain slid e, it m u st also be p ossible to rem ove th e ou tfeed system to en su re im p roved accessibility. W h en ch an gin g d ies, th e resettin g tim e req u ired can be red u ced by exch an gin g th e slittin g or n otch in g d evice from th e p ress ou tfeed sid e. Th e p erforatin g d ies can be released by m ean s of h yd rau lic q u ick-action clam p in g d evices an d rem oved com p lete at th e sid e of th e p ress. In d ivid u al o r m u lt ip le ro ws o f p erfo rat in g p u n ch es in t h e d ie can be m o ved in t o p lace, d ep en d in g o n t h e sp ecificat io n s o f t h e p ro gram , u sin g a elect ro h yd rau lically act u at ed slid in g beam . Even at m axim u m 317 Shearing lines Fig. 4.6.31 Stroking curves of the slide and stripper plate w ith a sheet metal thickness of 2 mm sl id es tr o ke[ m m ] stripper stroke [mm] start feed phase 6 ° slide stripper Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 strokin g rates, th e con trol system is able to m ove th e p u n ch in an d ou t of p osition with ou t th e n eed to stop th e p ress. Th e feed d evices arran ged d irectly in fron t of an d beh in d th e tool m ou n tin g area can also be p ro- gram m ed . Th e u p p er an d lower rollers of th e feed u n its are con n ected by m ean s of clearan ce-free m ech an ical in term ed iate gear d rives. Both rollers are su p p orted in several p oin ts, an d th e u p p er rollers are h yd rau lically p ressed d own ward above th e su p p ort in th e area of th e rollers. Th e rollers are lifted m an u ally or by m ean s of p rogram con trol. Th e in feed d evice is rem ovable, th e ou tfeed d evice eith er rem ovable or station ary. To en su re a p erfect ly p erfo rat ed p at t ern , a p h o t o elect ric cam era m o n - it o rin g syst em is u sed cf. Fig. 4.9.7 . W h ile t h e all-acro ss p erfo rat in g p ress is in t h e set -u p m o d e, t h e d evice is p ro gram m ed u sin g t h e t each - in m o d e. If t h e act u al h o le p at t ern d eviat es fro m t h e p ro gram m ed p at - t ern d u rin g p ro d u ct io n , t h e p ress is au t o m at ically swit ch ed o ff. Strip perforating presses W h ile p erfo rat ed sh eet s are p ro d u ced in m ed iu m an d large-series o n all-acro ss p erfo rat in g p resses, st rip p erfo rat in g p resses are u sed fo r t h e p ro d u ct io n o f in d ivid u al p lat es, p art icu larly wh ere large o r t h ick sh eet m et al m at erials are u sed o r wh ere in d ivid u al h o le p at t ern s are req u ired Fig. 4.6.32 . St rip p erfo rat in g p resses are available wit h n o m in al p ress fo rces ran gin g fro m 500 t o 2,500 kN fo r sh eet m et al p lat es bet ween 1,500 3 3,000 m m an d 2,000 3 6,000 m m wit h a m axim u m t h ickn ess o f 30 m m . Dep en d in g o n t h e sh eet m et al t h ickn ess an d feed st ep , it is p o ssible t o ach ieve bet ween 40 an d 400 st ro kes p er m in u t e. Th e st rip p erfo rat in g p ress co n t ro l syst em p erm it s sim p le p ro gram - m in g o n screen an d st o rage o f co m p lex h o le p at t ern s. Th e st o red d at a reco rd s can be sim p ly accessed if a p art icu lar p ro d u ct io n ru n h as t o be rep eat ed . Th e sh eet m et al p lat es are fast en ed o n a clam p in g p lat e wh ich can be m o ved h o rizo n t ally in t wo axes. Elect rical servo d rive syst em s wit h clearan ce-free in t erm ed iat e gear d rives are u sed t o p o wer t h e feed sys- t em . Th ese p erm it p erfo rat io n t o t ake p lace d u rin g fo rward an d reverse m o vem en t o f t h e m at erial. As is t h e case wit h all-acro ss p erfo rat in g p resses, h ere t o o a sep arat ely m o ved st rip p er p lat e wit h st rip p in g fu n c- t io n can be u sed Fig. 4.6.33 . St at io n ary sin gle p u n ch es o r sm all p u n ch assem blies p erfo rat e t h e sh eet m et al p lat es. W h ere co m p licat ed h o le p at t ern s are in vo lved , t h e 318 Sheet metal forming and blanking Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 p u n ch es can be d riven u sin g t wo ad d it io n al p ro gram m able axes. Par- t icu larly co m p lex geo m et rical sh ap es can also be p ro gram m ed reco rd by reco rd o r u sin g t h e t each -in m o d e, wh ereby t h e p at t ern s bein g p ro - gram m ed can be d isp layed o n screen . Tem p o rary d eact ivat io n o f t h e slid e m o vem en t irresp ect ive o f t h e clam p in g p lat e feed m o vem en t can be u sed t o creat e o p t io n ally in t erru p t ed p at t ern s. 319 Shearing lines Fig. 4.6.32 Examples of hole patterns produced on a strip perforating press Fig. 4.6.33 Die w ith separately controlled stripper plate Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 Th e clam p in g p late is eq u ip p ed with electroh yd rau lically actu ated clam p in g d ogs wh ich are retracted in th e area of a p erforation close to th e m aterial ed ge, so elim in atin g th e n eed to reclam p th e sh eet m etal p late. Su p p ort rails eq u ip p ed with rollers wh ich can be m oved as req u ired on th e clam p in g p late are p osition ed in fron t of an d beh in d th e d ie to p reven t u n wan ted saggin g of th e sh eet m etal p late. Th is system allows to red u ce th e m ass of in ertia to a q u arter of th at of th e old -style solid con stru ction clam p in g p lates. Used in con ju n ction with m od ern op tim ized h igh -p erform an ce actu ators, extrem ely sh ort traversin g p eri- od s of for exam p le 0.2 s with a feed len gth of 80 m m can be ach ieved .

4.6.7 Control systems for blanking presses