Case history (January 01, 2001)

New United Motor Manufacturing Inc. (Fremont, CA) has increased the productivity of three 2,800 ton UBE injection molding machines to free up machine time for mold trials and solve an inventory management problem.

The automotive molder, more commonly known as NUMMI, achieved a cycle time reduction from 70 seconds to as little as 49 seconds for car bumpers, and from 65 seconds to approximately 51 seconds for truck bumpers.

Jim Forgash of UBE Machinery, Inc. worked with NUMMI on making the cycle time improvements. “We’ve optimized the delay time for hydraulics, trimmed down the lag times and worked with a supplier for a quick mold change system,” says Forgash.

One of the reduction techniques UBE and NUMMI pursued was what UBE calls the replastification mode. “Part of their problem was that they were always waiting for a lag time in screw recovery or getting the next shot charged,” Forgash explains. “Their cooling time was less than their charging time, so what we did is allow a break in the screw recovery period. The screw would recover until the clamp would open. Then, when the clamp reached the full open position, the screw would complete the shot recovery as the part was being ejected and removed by the robot. So while the robot was removing the part and taking up unnecessary time, we would finish the plastification mode. In other words, we overlapped some cycles between the robot and the screw recovery. It’s not typically done that way. This involved some software changes and some retrofitting of the machine.”

By reducing the cycle times, NUMMI will be able to get the molding lines and painting processes in sync, alleviating an inventory management problem and eliminating a third shift for the molding machines.

The cycle time reduction also helped create machine time for trials on new molds arriving from Japan.

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