Injection Molding: Custom Dual Degating Station Yields Zero-Vestige Auto Parts

Automotive molder needed a custom degating station beside the injection press to trim pairs of two different parts on one machine.

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FIPA Inc., Cary, N.C., a supplier of robot gripper systems, air nippers, and end-of-arm tooling, recently developed a custom solution for Proper Polymers, part of Proper Group, a custom injection molder and moldmaker in Anderson, S.C. Proper needed a degating station that could provide a perfect flush cut with zero vestige on two different parts, front and rear automotive wheel arches—and it needed it quickly.

Among the challenges of the project were the ability to handle two different-sized parts in the same cutting station, the precise cut required, and the very limited work space. While it is common in the auto industry to mold two parts in adjacent machines, in this case only one machine was available for the project, so the two parts are molded alternately in the same press. Likewise, there was no room for two cutting stations to cut the different parts side by side.

The solution was a rotating-mount, dual cutting station that handles two front or two rear wheel arches in parallel. When changing production from the front to rear arch, the injection mold is changed and the cutting station indexed 180°.

A robot picks up two wheel arches from the injection press and inserts them into the cutting station. FIPA air nippers remove the gates with zero millimeters of remaining gate vestige. The robot then removes the two arches and runners and places them on a conveyor.

The actual gate cutting presented challenges. The gate geometry was difficult, and the standard air-nipper blade opening was smaller than the gate. FIPA then inserted stiffer springs in the blades and substituted a custom drive that allowed for a wider blade opening. In addition, the parallel grippers with rubber pads that hold the wheel arch in position without marring it required greater opening tolerance to accommodate minor variations in presentation of the parts to the grippers, while maintaining precise final positioning of the part prior to degating.

FIPA delivered the system on an expedited schedule, with 20 hr of design and 20 hr of assembly and testing. The system degated a pair of wheel arches within the allowed cycle time of the injection machine, according to Mark Foster, engineering manager at Proper Polymers.