Use a transparent cost stack
Start with the complete shot mass, resin purchase price, runner/regrind policy, and yield. Add machine time from actual or validated cycle time, then add labor, energy, maintenance, inspection, packaging, logistics, and any secondary operation that applies.
Unit cost = material + conversion + tooling allocation + quality/post-process + logistics/overhead
What the current calculators cover
Material Cost Per Part allocates runner mass across cavities and applies entered unrecovered scrap. Scrap Rate reports the observed ratio of rejects. Mold Amortization spreads entered tooling and lifetime maintenance over an expected output. These are components of a cost model, not a full supplier quote.
Keep one-time and recurring costs separate
Tool design, machining, sampling, qualification, gauges, fixtures, and engineering changes are generally not the same as a recurring part cost. Record each assumption and the quantity basis. When volume changes, the tooling allocation changes even if the physical mold cost does not.
Validate the conversion side
Cycle time affects machine and labor exposure. Confirm downtime, planned uptime, cavity availability, rejection handling, and secondary operations from production records or a qualified supplier. A low material cost does not offset a complex mold, a slow cycle, insert loading, or difficult inspection.
FAQ
Does material cost equal part cost?
No. It excludes conversion, labor, energy, quality, packaging, logistics, and many one-time costs unless they are explicitly added.
When should tooling amortization change?
Whenever expected production life, maintenance scope, engineering changes, or the volume basis changes.