Page 16 - MetalForming September 2009

Ag Stamper
and into a compound die installed on either a 500-ton Minster mechanical press or a recently overhauled Bliss press, designed for very tight bed deflec- tion. Plates are flat stampings that might look simple, but can prove quite chal- lenging. Part flatness is critical, specified to a tolerance of 0.004 in. per 6 in., with surface finish specified to 32 RMS minimum. To meet these requirements, GMP runs parts through a series of secondary processes.
“In most cases, we use compound dies for this product line to gain opti- mum control over flatness,” says Mall- mann, “since the die cuts all of the sur- faces in one stroke. But we still have to run the stampings through secondary processes. The tangs on the outside edge of the separator plates are specified with critical edge conditions, requir- ing a secondary shaving operation to straighten the edges. Then we feed the parts through a rotary deburring oper- ation and into a series of levelers (straighteners from Bruderer) to attain the required flatness in two directions.”
The compound die employs an upper punch that cuts the plate OD and also acts as the die to knock out the center hole of the blank. A punch below the stamping works the ID. GMP stocks 40 different dies for the plates in various styles and sizes, and changes dies an average of two times per shift; the press runs at 20 to 25 strokes/min.
QDC,ThroughTraining
Within the last two years, the firm has focused on implementing quick- die-change processes, including stan- dardizing on die sets, employing self- locating plates, and staging dies closer to the presses. Die changes that once aver- aged 4 hr. now occur in 30 min. or less.
“The key to making such a signifi- cant improvement was implementing the die-set training course produced by the Precision Metalforming Associ- ation (PMA),” shares Mallmann. “We trained all of our press operators using that course a couple of years ago, and it proved to be a real eye-opener. We are an old company that historically used a lot of old and accepted methods, and
GMP specializes in stamping transmis- sion separator plates (shown here), of a modified Type 1035 steel (Rc 20-28 hardness), 0.068-in. thick and typically 10- to 20-in. dia. Part flatness is critical, specified to a tolerance of 0.004 in. per 6 in., with surface finish specified to 32 RMS minimum. To meet these require- ments, GMP runs parts through a series of secondary processes.
a mechanical slide conveyor,” says Mall- man. “If we lose suction at the wrong time, the part can remain in the die set and cause a crash. Adding the vacuum sensor to the press so that it can connect to each die set, and tying it to the OmniLink II controller, allows us to protect every die that runs on that press with one sensor. When the die picks up the part, the sensor looks for a vac- uum generated, and communicates to the controller to indicate whether or not the part is present.
“The vacuum sensor has solved most of the problems we had experienced with most of our dies,” Mallman con- tinues, noting that the firm had to retro- fit some of its dies with an additional part-ejection sensor. Results: Die crash- es have been reduced by 80 percent, the firm spends significantly less time
GMP converted a fabricated door assembly
components that now are robotically welded
cell acts as a material handler, holding and manipulating the parts—including the heavy, 173-lb. drawn shell, of 6-mm-thick cold-rolled steel—while a second robot, mounted overhead, performs the welding operation, adding 16 parts to the door.
the PMA system did a great job of get- ting everyone to think of ways to improve the processes, and to do it together, uniformly throughout the plant.”
Also yielding a significant improve- ment in productivity has been the plant’s recent addition of a new die- protection system (with a Link Systems’ OmniLink II control) on its 500-ton Minster press. Installed early in 2008, the system features a vacuum sensor that detects a stamped part being gripped by the top tool.
“With a lot of the compound dies, the challenge is getting the part out, and we use suction to hold the part up until just the right moment when it can be dropped out of the die and onto
14 METALFORMING / SEPTEMBER 2009
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for a skid steer into a set of stamped in this production cell. One robot in the