Small part, big solution

An Ontario injection molder recently came this close to having an unnecessary, time-wasting manual operation in an auto part production line.

The molder – who wishes to remain anonymous – had just landed a contract to produce a small linkage component for a car door handle, and was considering molding in a standard horizontal machine and then manually inserting the part into another for the overmolding.

But then cooler heads prevailed.

“We were brought in to provide a turnkey injection molding cell for the company during the tool design process, before the initial kick-off,” said Brad Lemieux, En-Plas Inc. “We helped them find a better way to integrate the eight-cavity, two-shot multi-material application without running up extra costs by over-engineering the cell.” 

The finished cell, installed early in 2011, includes a 120 ton Nissei two-shot injection molding machine and a Yushin RC 150SLL servo robot with extended traverse stroke. Each part has a combination of nylon and Santoprene. “The robot takes the first shot from the left or ‘A’ side of the mold, and then shuttles over to the right or ‘B’ side to pick the finished part; it then loads the initial part extracted from side A onto side B so the second material can be over-molded,” Lemieux said. “The good finished parts are then taken over to a precise scale where each part is individually weighed to a tolerance of .01 grams.”

It might sound simple, but it wasn’t; probably nothing that relates to a part approximately 7/8^th an inch long by 3/8^th of an inch wide ever is. “This was a complex cell with a complex EOAT requirement,” Lemieux said. “The main challenges we faced in the design were associated with tiny part size and tight configuration of the cavities within the mold.”

With a cycle time of 38 seconds, the customer was well pleased with the cell, Lemieux continued, and ordered a second that was sent to a satellite operation outside Canada.

“We helped them find a better way to integrate the eight-cavity, two-shot multi-material application without running up extra costs by over-engineering the cell,” Lemieux said.