Regrinding Sandy Plastic...
I received this interesting question recently...
I have a client with ten tonnes of material awaiting regrind and re-processing. Unfortunately, the material is contaminated with sand.
I have a couple questions. First, is it unethical to regrind and re-process the material since it is contaminated? Second, what are the financial costs and ethics associated with regrinding ten tonnes of material?
In general, once a material is contaminated with a hard material such as sand, it will become highly abrasive to the grinder, screw, barrel, hot runner, and mold. To regrind that much material in such a state will most likely cause significant damage, requiring repairs and possible replacement of many components. Likewise, such an abrasive material would damage the screw and most likely require a new check ring after re-processing.
If the reground material is sold or any products are sold molded with this material without the customer's approval such an act would be unethical and most likely illegal.
Since many of the costs associated with regrinding this material depend on the material, grinder, region, as well as repair costs, it is impossible to estimate with any degree of accuracy.
This is one of the reasons it is critical to teach your employees the importance of proper handling of materials, parts, and regrind to ensure that contamination does not occur.