We've long established that regrind isn't an acceptable substitute for purging compounds and that it leads to layering and eventual contamination. But you have regrind, so what should you do with it? Ground up runners and process-related rejects have a place.
Some folks have just in time loaders at the side of the machine. These loaders pull from the bottom of grinders and transfer the regrind back into the molding process. This is okay, if the part print allows for regrinds to be used in production. Regrind quality is always an issue and can add to poor processing issues. Powder in regrinds melt quicker than the chips and can cause black specks, short shots, and contribute to an inconsistent overall process.
If you are getting large amounts of powder from your grinder, you may want to follow these tips to improve the chip quality:
- Make sure the blades are sharp and are not missing any edges
- The speed of the blades will affect chip quality as well--faster is better
- It is always better to grind up hot or warm runners and parts for better chip quality. If you are grinding cold runners and parts, this is the number one source for powder in the regrinds.
If you are not reusing regrinds but are storing them to be recycled, it is always a good idea to keep the storage package covered and away from other contamination sources.
Again, regrinds are not a good source for purging materials as they are not designed to clean and can add to the contamination issues.
Ready to reduce your production downtime to protect your profits? Learn more about how purging compounds and process efficiency work in tandem.