Page 85 - MetalForming October 2011

Tooling Tech
G&S recently overcame these hur- dles with a takeover tool used to pro- duce five different styles of muffin pans. Among the problems experienced with this die: material feed. A mechanical feed working off of press-ram motion made feed adjustment difficult, and proved unreliable for achieving accu- rate feed lengths. Says G&S Metal automation engineer Steve Kerg:
“We improved feed accuracy by replacing the mechanical feed with an air feed and installing hall-effect sen- sors on the pistons. We also redesigned the top of the die to reduce changeover time to 20 min., and replaced all of the coil springs with nitrogen.” Previously, changeovers could take as long as a full shift. With movable rails in the die, changeovers for five parts with different widths and material thickness can be performed with little effort.
“The presence of the feed bars also is monitored,” adds Kerg, “so they can’t be smashed in the press. In the past, we might smash as many as one part per 20 due to a misfeed. We haven’t smashed a part in more than 40 shifts.”
With feed problems solved, Kerg then tackled another issue: in-die assembly of the 12 muffin cups into the frame. Some of the cups would shift during transfer, or frames them- selves could be transferred incorrectly. As did KLS Controls, G&S found its solution by installing a vision camera, which detects the presence and orien- tation of the frame. Flags on the upstroke and downstroke of the ram trigger the camera. If the camera fails to detect the part and its proper orienta- tion, the press stops and the operator clears the error on the PLC to stroke the press. If any part sticks to the upper die section, an optical part-out sensor stops the press at the top of the stroke. A custom-programmed PLC is used for sensor logic and for signaling emer- gency stops or top-stops.
Bottom line: An inherited tool that previously ran under less-than-ideal conditions now continuously produces good parts without risk of damage to the die. MF
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MetalForming/October 2011 83
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