Page 83 - MetalForming October 2011

Pronic) using rollformed taps to elimi- nate any debris inside the die. Tapping a hole in relatively thin material with an extruded sidewall allows the tap to float within 0.003 to 0.006 in. without affect- ing thread quality or hole location.
For Exact Tool & Die, the challenge came from tapping four 3⁄8-in.-dia. holes in material thicker than 0.210 in. This left little room for misfeeds or broken taps. Monitoring the feed with a proprietary plunger and sensor sys- tem eliminated the chance of a mishit due to a short or long feed, but broken taps were another story. Should a tap break and move into the next station, the damage could be pretty excessive.
To avoid such a scenario, the firm installed four sensors (from Sick Automation, Fig. 1) in the die. The sen- sors detect the presence of a broken tap in the strip, uninhibited by any coolant mist or smoke from the stamping oper- ation. Because the sensors use back- ground suppression, only the tap will be detected. This eliminates the chance
of nuisance faults caused by any other die components.
Since installing and calibrating the sensors, the die has been running con- tinuously without fault. “The die is running at 40 strokes/min., as fast as it can possibly run,” says Ron Gunter, Exact Tool & Die’s director of manu- facturing. “We haven’t had any damage from broken taps since the sensors have been added.”
Case II: Eliminating Human Error in the Pressroom
One of the greatest roadblocks to metalforming success can be human discretion. A minor defect in a part unacceptable during a normal pro- duction run, yet passes inspection at the 11th hour before an emergency shipment, can be confusing to the operator and wreak havoc on process management. Even the use of a go/no- go gauge is susceptible to interpreta- tion. Use of the terms slip-fit or inter- ference-fit often can bring different
results in a quality check performed by different people.
When an operation is performed manually, quality can be compro- mised by poor judgment, a lack of understanding of necessary features (fit, form and function) or even fatigue. For these reasons and others, intro- ducing an automated solution to a manual task can eliminate scrap and excessive downtime. Case in point: KLS Controls, Menomonee Falls, WI. KLS president Scott Shaw describes a recent application from a customer that manufactures heavy equipment.
“We were tasked with stamping heavy-gauge steel plate with several holes pierced from another press oper- ation. When the operator loads the part into the press for forming, he must be sure to orient it properly or the part becomes scrap—it is possible to orient the part four different ways.”
This is a common problem—a man- ually loaded secondary operation that can be nested incorrectly while the
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