The accumulation of excess regrind must be minimized to prevent resin loss. While flash is likely to account for thirty percent or more of what is extruded, there may be unavoidable periods where one hundred percent of what is extruded is converted back to regrind.
For example, during start-ups and shutdowns or while in production, an in-process defect may require one or even all of the containers to be rejected until the correction is made.
During these periods, the proportion of regrind being added to the closed loop systems should be raised slightly to keep the regrind at a manageable level. Regrind levels must be held in check. Any regrind backlog is, in fact, valueless waste until it is converted into product. An accumulation increases resin expense and lowers profits.
Producing overweight containers is the most overlooked cause of resin loss. Each blowmoulded part normally requires that it be made with a specified amount of plastic. This amount is usually expressed in weight.
Consistent Monitoring of Product Weight
Variations in the extrusion process often make the weights drift. Weights should be monitored on a consistent basis, and any overweight condition should be adjusted so that resin isn’t needlessly wasted. If left unchecked, this too can increase resin expense and lower profitability.
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