Page 20 - MetalForming April 2014

Zig-Zag Servo Feeds
Stamping airbag housings by the thousands has deep-draw specialist Metal Flow Corp. changing servo-press ram speed seven times per stroke, while “bulletproof” rack-and-pinion-driven servo feeds perform tireless work.
BY BRAD F. KUVIN, EDITOR
Support Servo- Press Operations
Deep drawing tightly toleranced high-strength low-alloy steel airbag housings requires the full 13.5 in. of available press stroke. So, why limit press speed to a slower form- ing speed during the portion of the stroke when the tool is not in contact with the workpiece material?
That’s the question deep-draw spe- cialist Metal Flow, Holland, MI, addressed when it acquired a pair of matching 600-ton Aida servo-drive presses—the first in October 2012, the second in December 2013. That invest- ment was followed by a third Aida servo press, this one a 400-ton model, slated to enter production in May of 2014.
Brought in to add horsepower to Metal Flow’s flourishing airbag-housing business, the servo presses, according to manufacturing technical director Jeff Wierenga, allow production output to climb from 21 strokes/min. in a standard mechanical press to 30 strokes/min. And, that includes performing a highly engineered in-die testing sequence on each and every housing.
“We can program 14 different points
Initiating transfer-press operations at this new 600-ton servo press is a zig-zag servo feeder installed with swing-out mounting fixtures to smoothly feed the 11.5-in.-wide strip material from coil stock. Zig-zag movement is programmable in 0.001-in. increments.
18 MetalForming/April 2014
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in the stroke where we can change ram speed,” says Wierenga, “to allow for material feed, in-die testing, part trans- fer etc. We’re changing speed seven times per stroke on the airbag housings. When we’re not touching the part, we can run as quickly as 50 strokes/min.”
Brawny Zig-Zags
The airbag housings are tiny tubes drawn from 0.090-in.-thick steel. Draw depth is 6.5 in.; finished diameter is either 5⁄8 or 1.25 in.
Initiating the transfer-press opera- tions are zig-zag servo feeders (Dallas DRFM ZZ-418 models) installed with swing-out mounting fixtures on each servo press to smoothly feed the 11.5- in.-wide strip material from coil stock. Maximum coil width is 18 in.; max. stock thickness is 1⁄8 in.
Zig-zag movement is 12 in., pro-
grammable in 0.001-in. increments, and the units boast extended lateral travel of 23 to 69 in. for stock-edge positioning from the press centerline. The setup support screen provides the recommended strip-advance length and lateral movement based on oper- ator entry of pattern, blank diameter and web thickness. The servo-feed index cycle occurs simultaneously with cross-slide lateral travel to produce diagonal stock movement with one-, two- or three-out capability.
Directing the feeders and closely synchronizing their motion to that of the servo press: Dallas’ ServoPressSe- lect feed control, a variation on its Pro- fileSelect controls designed to provide a smooth sinusoidal feed profile that minimizes stress on the feed’s mechan- ics while using 100 percent of the avail- able press-feed window.