Injection Molding worked example

Resin Cost Per Part with shot weight per part including runner share of 80 g: a worked example in injection molding

Push shot weight per part including runner share up to 80 g and the picture changes. This example computes every intermediate figure at that operating point. Use this when building part cost breakdowns, comparing resin grades, or estimating material savings from weight reduction or hot runner conversion.

The inputs for this scenario

  • Shot weight per part including runner share: 80 g (raised for this scenario; the documented default is 32)
  • Resin purchase price: 2.85 $/kg (unchanged)
  • Scrap/overage allowance factor: 1.05 x (unchanged)

Working through the calculation

  • Applying the documented formula (Resin cost per part = (Material per part / 1000) x Resin price x Waste factor) to the inputs above produces each figure below.
  • At this operating point the engine returns 239 $ for result, the number this scenario is built around.
  • At this operating point the engine returns 239 value for base material cost (before waste factor).
  • At this operating point the engine returns 1 x for multiplier.
  • At this operating point the engine returns 228 value for factor a x b.

How this compares with the baseline

  • Against the tool's baseline example, where shot weight per part including runner share sits at 32 g and the headline result is 95.76 $, this scenario comes in 150% above the baseline at 239 $.
  • It computes the per-part resin dollar cost by converting shot weight to kilograms, multiplying by resin price, and applying a waste factor. The value of this scenario is the size of the gap it exposes: that gap, priced out over a year, is the budget you can justify spending to close it.

Results at a glance

  • Result: 239 $ (headline result)
  • Base material cost (before waste factor): 239 value
  • Multiplier: 1 x
  • Factor A x B: 228 value

Run it with your numbers

  • Every input above is editable in the live Resin Cost Per Part calculator, which recalculates instantly and can be shared with the inputs intact.

Last reviewed 2026-05-12.