When does changeover time start and stop?

It runs from the last good part of the outgoing job to the first good part of the new one. That includes pulling and hanging the mold, water hookups, heat-up, purging and first-article approval.

Should press time use the machine rate or lost margin?

Use the machine hour rate when the press has spare capacity. On a sold-out press every changeover hour is an hour of parts you cannot sell, so enter the margin those parts would have earned per hour.

How do I measure startup scrap?

Weigh it. Collect the purge and every rejected shot from restart to the first good part, weigh the bin and enter kg. Rejected shot count times shot weight, plus the purge, also works.

How much does cutting changeover time save a year?

Multiply the downtime cost per minute by the minutes you cut and by your changeovers per year. At $1.67 a minute, cutting 60 minutes from 100 changes a year saves $10,000.

Injection Molding calculator

Mold Changeover Cost Calculator

Price one mold change, per change and per part, from last good part to first good part, including purge and rejected startup shots. You need changeover time, machine and crew rates, scrap weight, resin price and run quantity.

What this calculator does

What one mold change costs in press time, crew labor and startup scrap, and what it adds to each part.

Formula used

Press time cost = changeover time × machine hour rate
Setup labor cost = changeover time × setup crew cost
Startup scrap cost = purge and startup scrap (kg) × delivered resin price
Changeover cost = press time + setup labor + startup scrap; per part = changeover cost ÷ parts in the run
Downtime cost per minute = (machine hour rate + setup crew cost) ÷ 60

Inputs explained

Changeover Time: From the setup log: last good part to first good part.
Machine Hour Rate: Press $/hr, or lost margin per hour on a sold-out press.
Setup Crew Cost: Combined burdened hourly cost of everyone working the change.
Purge and Startup Scrap: Weigh the purge and rejected shots until the first good part.
Delivered Resin Price: Resin invoice price per kg, including freight.
Parts in the Run: Good parts the job makes before the next mold change.

How to use the result

Best suited to setup charge for a short-run quote, SMED business case for quick mold change, deciding whether to split a production run.
Leaves out the carrying cost of longer runs, so it prices only the setup side of lot sizing. Purging compound and colorant count only if you add them to scrap weight at resin price.

Current U.S. benchmarks

The producer price index for plastic resins and materials stands at 280.569 (BLS, Aug 2026), up 6.6% from a year earlier. Quotes priced off last quarter's material cost miss this move.
The U.S. has 9,635 plastics product manufacturing establishments employing about 677,302 workers (Census County Business Patterns, 2023).

Common questions

When does changeover time start and stop? It runs from the last good part of the outgoing job to the first good part of the new one. That includes pulling and hanging the mold, water hookups, heat-up, purging and first-article approval.
Should press time use the machine rate or lost margin? Use the machine hour rate when the press has spare capacity. On a sold-out press every changeover hour is an hour of parts you cannot sell, so enter the margin those parts would have earned per hour.
How do I measure startup scrap? Weigh it. Collect the purge and every rejected shot from restart to the first good part, weigh the bin and enter kg. Rejected shot count times shot weight, plus the purge, also works.
How much does cutting changeover time save a year? Multiply the downtime cost per minute by the minutes you cut and by your changeovers per year. At $1.67 a minute, cutting 60 minutes from 100 changes a year saves $10,000.

Last reviewed 2026-10-01.