Why it works

Mechanism	Leftover plastic, the plastic that fed the mold, is the same plastic as the part, bought at the same price. A grinder beside the press turns it into regrind, plastic ground up and molded again in the same job while still clean. Each pound of regrind is a pound of new plastic the plant does not buy.
Math	The plant buys about 5 million pounds of plastic per year. Jobs that allow regrind use 50 percent of it, about 2.5 million pounds. We assume 1.5 percent of that is leftover plastic and rejected parts clean enough to mold again: about 37,500 pounds. At $1.50 a pound, that is about $56,300 of new plastic per year. Six grinders cost about $8,300 per year to run, in power, blades and a handler's time, which leaves about $48,000. They cost about $45,000 to buy, repaid in about 11 months.
Industry evidence	A US safety standard allows up to 25 percent regrind in new plastic of the same grade, without new tests. Customers who allow regrind often cap it at 15 to 25 percent. Trade guides advise grinding beside the press, so the plastic goes back into the same job clean. Suppliers price a grinder that stands beside a press at $3,000 to 15,000.
Limitations	It pays only on jobs whose customers allow regrind, about half of the plastic. One wrong plastic or color in a grinder can spoil a customer's batch. So each grinder keeps to one plastic and is cleaned out before another. Molds with heated channels keep that plastic melted, so they make no leftover plastic, only rejected parts. If the plant cuts its rejected parts, there is less to grind. The handler's time is a real cost, since the payroll already shows about 180 overtime hours a week.

Illustrative sample. The plant, the walk and the footage are synthetic. Figures from our analysis are estimates made with AI, not guarantees.