Great idea! The thing with recycling plastics is that when you regrind them, polymer chains are broken and you have to add at least 20% virgin pellets to ensure good quality. The more often it is regrinded the less mechanical quality it will have. For dehydration the simplest thing is to have the ground up plastic sit in sealed buckets on a bed of rice for a few weeks. A filamaker and filastruder will get you a long way for equipment. For smaller products, consider that also a paper shredder with Cross-Cut system works for grinding plastic.