I ff/ut-'/etfrl,A Penton Publ icat ion

www.americanmachinist .com

October 2001

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techn i c l ue tha t repo r ted l v e l im i -l t i . l te s nt i tn\ ' sec()nrl l rn' r l :rcl ' r ining opcr-

art i t l r rs . Whi le e converr t ior i r l s tanr l . r ine t r p ica l lv has one-tb i rc l shcrr r arr r l tu 'o- th i r -c ls c l ic [ r rca l i , th is r rcrv technic lueproci r rccs srnooth (no tc i r r ) , r 'c r t ica l , i lccLrr r r tc s ic les thr 'ough-or- r t t l re crr t i rc p. r r t t l - r ic l . r rcss.

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Gripflow stampingsel iminate the need

for costly secondarymach in ing

operations such asmi l l ing , g r ind ing ,dr i l l i ng , reaming,

countersinking, andcounterboring.

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press tonnage as material is cut, and the reten-tion of the stamping throughout the cutting cy-cle. The results are a stamping that meets tighttolerances and the option of producing morethan one part per press stroke by increasing theore cavliles.

Gripflow, developed by EBway Corp. of Ft.Lauderdale, F la. , works against a mater ia l 'syield point, while conventional blanking dieswork against tensi le s t rength. And s ince theyield point is lower than the tensile strength, the

techn ique requ i resless tonnage than con-ven t i ona l s tamp ing .Resul ts wi l l vary be-tween different mate-r i a l s , bu t t he be t te rthe co ld -work ingproperties of the ma-ter ia l . the more con-ducive and productiveit is with Gripflow.

Init ially, most peo-ple think Gripflow isf i n e b l a n k i n g . T h equa l i t y i s equ i va len t ,but the processes aredifferent. One notice-able difference is therequ i red tonnage .F ineb lank ing needsm o r e D e c a u s e l t r e -q u i r e s a n i m p i n g e -m e n t r i n g - a V -shaped ring that sinksinto the scrap skele-ton a round the con -t o u r o f a p a r t . A c -co rd ing to Te r r y'STa l ke r

o f EBway ,t h i s r i n g m a y s t e a laway as much as 40oZo f t h e b l a n k i n g t o n -n a g e . B e c a u s e aGripflow tool does nothave an impingementr ing, i t involves lesstonnage, which lowers

the cost of the requireds tamp ing p .es i . AGripflow press can alsoaccommodate conven-t i ona l t oo l i ng , wh i l efineblanking presses doonly fineblanking.

In most cases, Gripflow stampings fulfill theneed for parts that require tight tolerances (min-imum of 80"/" shear) in holes andlor criticalprofile areas. The press-working technique can

also put these smooths t ra igh t edges on l ywhere the customer re-quires them, further re-duc ing pa r t cos t .F ineblanking, on theo the r hand , has d i f f i -cu l t y p rov id ing on l yselect oar t areas wi thfull shelr zones.

F ineb lank ing andGripflow are similar intha t t hey bo th e l im i -nate cost ly secondaryo p e r a t i o n s s u c h a ss h a v i n g , b r o a c h i n g ,

For patts such as thisautomotive seat-adjustermechanism, Gripflowstampings provide tighttolerances in holes andcritical profile areas.

mill ing, grinding, dri l l ing, reaming, counter-sinking, and counterboring. Both techniquesroutinely hold accuracies of 0.001 in. on partthicknesses under 0.090 in.; 0.002 in. on partsunder 0.225 in.; and 0.003 in. on parts under0.300 in. And, the typical surface finish on thepart edge is 16 to 32 rms.

Part f latness for both techniques can be asmuch as one-fifth better than that of a conven-t ional s tamping - 0.001 to 0.001S/ l inear in .for parts up to 5-in. long, says \X/alker. Parts areflatter because they are always clamped withinthe die during the blanking process.'When

it comes to the treatment of slugs, aGripflow die passes them through the way con-ven t i ona l t oo l i ng does . Th i s i s because theGripflow press has a traditional design. Its ramis on the top of the die, unlike fineblanking,which typically has the ram on the bottom un-derneath the tool, so its slugs have to be blownout of the tool with the part.

Press operationPC controls simplify a Gripflow press's opera-

t ion. Shops can regulate the ram force at a l lpoints in the press cycle (tonnage); adjust the ramspeed during cutting and non-cutting; control theamount and duration of hold-down pressure toensure material set-time when coining is control-lable; and operate all external press equipmentfrom one control panel. Basically, press opera-tors can tune the pressto suit the die.

Gr ip f l ow p ressesmoun t on s tanda rd6- in. - th ick f la t con-c re te f l oo rs - nop i t s a r e r e q u i r e d .P r e s s o p e r a t i o n i snormal ly quiet , Iesst h a n 8 5 d B , a n dshock-free with littleor no vibration. a

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Unlike conventionalstamping, Gripflowworks against amaterial's yield point,and it does not requirean impingement ring asin fineblanking.

Conventiona I

Gripflow