Page 15 - MetalForming May 2009

designs and requirements for new parts. It also, according to OCC founder Paul Teutel Sr., hopes to soon offer contract metal-fabricating services with its array of state-of-the-art machines.
“We’ve got the fenders down,” Teutel says, “and we’re close with the gas tanks. Within the next year we think we’ll be ready to offer full contract job-shop fabricating.”
Draw Quality and Repeatability Improved
In addition to timing and flexibility, quality of the outsourced deep-drawn parts also had been a concern, and Quinn quickly learned how to tune the press and tooling to improve repeata- bility—forming parts with more con- sistency than he had been receiving with the sourced stampings. Better repeatability has streamlined down- stream finishing operations.
“Our supplied deep-drawn parts came to us with undefined and irreg- ular addendum or overpress material,” says Quinn, “which made the trim- ming process in our five-axis waterjet- cutting machine very time-consuming. Every fender or fuel-tank stamping would require a unique setup in the cutting machine. Now, using the Beck- wood press, we’ve been able to define the addendum for every stamping and obtain enough repeatability to allow us move right from the press to a fixture on the waterjet machine. We stamp a few fixturing dimples in the material to locate the drawn blank in the water- jet fixture, and in about 2 min. the operator can set up the blank and start trimming out the fender. This took 10 min. out of the setup process per fender.”
Fenders are 28-in.-OD half-donut shapes, 5.5 in. wide, with a 14-in. draw. “We use only 70 percent of the drawn blank in the actual fender,” says Quinn, whose background is in fineblanking and progressive-die stamping. He described the process used to develop the fender blank profile, and the “art- to-part” development required to elim- inate the wrinkling and pinching into the upper draw ring that you might
After bringing deep drawing inhouse, OCC worked with Beckwood engineers to fine-tune the drawing process and devel- op a custom draw ring to achieve wrin- kle- and tear-free 14-in. draws on fender blanks, shown here. It also obtains a repeatable addendum shape that allows an operator to fixture, in just 2 min., each blank in the firm’s five-axis water- jet-cutting machine for final trimming.
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METALFORMING / MAY 2009 13
expect when attempting to develop a 14-in. draw.
“A lot of art and trial-and-
error development went into
the project,” he says, “as we
worked together with Beck-
wood’s technicians to finally
obtain the part quality we
were after.” Among the changes
made during trial and error
were the blank shape and the recipe for draw-ring pressure, so that by the fourth blank stamped, Quinn wound up with a usable part, and by the 12th blank the process was fine-tuned to form wrinkle-free parts.
Custom Draw Ring Flattens the Wrinkles
“The blank wound up being an elon- gated oval,” says Quinn, who started with a dog-bone-shaped blank. “Then, once we defined the optimum blank shape, one of the first process parame- ters we identified as critical was draw- ring clearance. As the fender would make its nearly-90 deg. turn up the side of the draw ring and around a 3⁄8-in. cor- ner radius, the steel would start to tear. So we added another 1⁄16 in. of clearance in the deeper ends of the draw, which eliminated the pinching that was caus- ing the tearing.
“Then,” Quinn continues, “to elim- inate the wrinkling we were getting in the middle of the part—the mounting area—I added side plates to the draw ring.” The draw ring is of 1.5-in.-thick 7075 Al; Quinn added 6 in. of flat stock to each side of the ring to smooth the
edges of the fender as it draws down. “I also machined a plate to mount to the pressure pins that hold the upper die,” he adds, “to fill the gap between the edge of the part and the pins. We use the pins to support the stamping in the outward direction as well as in the draw- ing direction. They act just as the cush- ion plate and the draw ring act togeth- er to pinch the material, so now we also get the same pinching action between the male form and the upper draw ring.
This prevents outward wrinkling.”
Dynamic Cushion Control, Four-Corner Active Leveling
After fine-tuning the tooling, Quinn then looked to use the multizone bed cushion (rated to 75 tons) of the press, which allows OCC to program and adjust draw-cushion pressure in as many as five different stages of the draw. At max, OCC uses 200 tons from the main ram and 66 percent of cushion capacity. Pressure is higher at the start of the draw, reduced in the middle of the draw and then increased again at the end. This dynamic cushion control throughout the stroke, in addition to programmable ram speed, “allowed us