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Parison control improves blow molding

By: Bill Bregar

November 16, 2012

PITTSBURGH (Nov. 16, 11:50 a.m. ET) — A variable-speed drive and parison control for extrusion blow molding can greatly improve quality and reduce power consumption, Kim Shipway, technical sales manager for Invensys Eurotherm USA, said at the Society of Plastics Engineers’ Blow Molding Conference.

Closed-loop parison control is important because the weight of the parison hanging down will elongate the parison, resulting in a thinner top portion and thicker bottom, he said. Also, cooling time is reduced if the thickness is uniform.

Parison control can be used on major types of blow molding machines, including time-based continuous extrusion machines, accumulator-head machines and wheels. It gives real-time results and links the machine with downstream equipment such as weighing, vision and leak detection.

The machine also provides an alert when it needs maintenance, he said at the Oct. 9-10 conference in Pittsburgh.

Shipway said variable-speed drive of the clamping unit can pay for itself. It scales down when power is not needed.

Invensys Eurotherm USA is based in Ashburn, Va.