Grinders at the heaviest bins

A grinder beside each of the six jobs with the heaviest bins: one first, the others once it has shown its pounds.

Cost	About $45,000
Payback	About 11 months
Limitation	Each grinder keeps to one plastic and one color. A grinder at a job with a light bin does not pay back, so each job is weighed first.

What changes

Among jobs that allow regrind, the six with the heaviest bins each get a small grinder on a cart.

The operator drops each runner and rejected part into it, and it cuts them into small flakes.

The flakes go back into the same job at a set share by weight, within what the customer allows.

The first grinder goes to the heaviest bin after the first check, and the others follow once it has shown its pounds.

What it costs and could save

Six grinders cost about $45,000, about $7,500 each.
By our estimate, they could save about $48,000 per year, a payback of about 11 months.

Why it works

Mechanism	A runner is the same plastic as the part it fed, bought at the same price. Ground into flakes beside the press, it goes back into the same job before it can pick up dirt, moisture or another plastic. Each pound molded again is a pound of new resin that is not bought.
Math	The plant buys about 5 million pounds of resin per year, about $7.5 million. Jobs that allow regrind take 50 percent of it, about 2.5 million pounds. We count 1.5 percent of those pounds as runners and rejected parts that are ground and molded again, about 37,500 pounds. At $1.50 per pound that is about $56,300 of new resin 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, a payback of about 11 months. Each grinder is worth about $8,000 per year, by an even split.
Industry evidence	A US safety standard for molded plastic parts lets a molder blend up to 25 percent regrind into new resin 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 flakes return to the same job clean and unmixed. Suppliers price a grinder that stands beside a press at $3,000 to 15,000. No bin was weighed on our visit, so the pounds are our estimate.
Limitations	It pays only on jobs whose customers allow regrind, about half of the resin by the plant's records. One wrong plastic or color in a grinder can spoil a customer's lot, so each grinder keeps to one plastic and is cleaned out before another. A mold with heated feed channels makes no runner, so its bin holds rejected parts only. If scrap falls on the molds that make the most of it, there are fewer rejected parts to grind. The handler's time is a cost in full only if it adds overtime. The payroll shows about 180 overtime hours per week, so we count it in full.

Implementation plan	3 steps
Risks	3