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Purging compounds.

A contract manufacturer of a variety of plastic components reduced its initial scrap rate by more than 90% and lowered its purging costs by 52% when it switched from using in-house resins to commercial purging compounds to purge its two Van Dorn 230 cold runner injection molding machines.

JC Tec Industries of Annville, KY, is a contract manufacturer of plastic components including insulators, cams, gears, end caps, rollers, ball valves, cable assemblies, latches, bearing inlets and other parts. JC Tec was running its own resins to purge when changing over from flexible PVC to acetal resin in the production of bicycle tires for training wheels. At a running rate of 200 parts-per-hour, the company was discarding an overage of 40 defective parts, a scrap rate of 20%. On a weekly basis, this translated into as many as 200 defective parts per week, with an additional cost of $175 weekly when factoring the cost of resin and machine downtime.

The two Van Dorn 230 cold runner injection molding machines (50 mm screw size), operating at a barrel temperature of 330[degrees]F to 350[degrees]F, would be purged up to five times per week. On an annualized basis, it was costing the company more than $9,000 to purge using in-house resins. After switching to Dyna-Purge, the scrap rate fell from 20% to 1.5%, a 93% reduction, and the cost to purge is only $16.82 each time, a 52% reduction. On an annualized basis, this represents a savings of approximately $5,000 with Dyna-Purge.

Resins are said to be designed for processing, not purging, according to the manufacturer of Dyna-Purge products. Commercial purging products are formulated and intended for cleaning injection molding, extrusion and blow molding machinery faster and more effectively than in-house resins and regrinds, according to the company.

Dyna-Purge V, used by JC Tec, is one of ten formulations in the Dyna-Purge line of non-chemical, non-abrasive purging compounds. Dyna-Purge V is a grade specifically designed for purging rigid and flexible resins from injection molding or extrusion equipment at 320[degrees] to 400[degrees]F (160[degrees] to 204[degrees]C).

Shuman Plastics

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Title Annotation:Case Studies
Publication:Rubber World
Date:Jun 22, 2005
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