Blow Molding & Hollow Plastic Products worked example

Shot Weight with resin weight per cavity of 70 g: a worked example

What does the result look like when resin weight per cavity reaches 70 g? The full calculation is worked below with real intermediate numbers. a blow molding processor needs to estimate total resin shot weight for a bottle, preform, or hollow part mold

The inputs for this scenario

  • Resin weight per cavity: 70 g (raised for this scenario; the documented default is 28)
  • Active cavities per shot: 8 cavities (unchanged)
  • Shot allowance multiplier: 1.05 x (unchanged)
  • Unit conversion multiplier: 1 x (unchanged)

Working through the calculation

  • Applying the documented formula (Cavity resin weight per cycle = resin weight per cavity × active cavities per shot) to the inputs above produces each figure below.
  • At this operating point the engine returns 588 g or lb for total shot weight, the number this scenario is built around.
  • At this operating point the engine returns 588 g or lb for shot weight before conversion.
  • At this operating point the engine returns 1 x for unit conversion multiplier.
  • At this operating point the engine returns 560 g or lb for cavity resin weight per cycle.

How this compares with the baseline

  • Against the tool's baseline example, where resin weight per cavity sits at 28 g and the headline result is 235 g or lb, this scenario comes in 150% above the baseline at 588 g or lb.
  • A figure at this level is achievable when resin weight per cavity is genuinely sustained, not just peaked for a shift. It treats every cavity as filling equally; on imbalanced runner systems or worn tooling, real per-cavity weights vary and a single average can mask a starved cavity.

Results at a glance

  • Total shot weight: 588 g or lb (headline result)
  • Shot weight before conversion: 588 g or lb
  • Unit conversion multiplier: 1 x
  • Cavity resin weight per cycle: 560 g or lb

Run it with your numbers

  • Every input above is editable in the live Shot Weight calculator, which recalculates instantly and can be shared with the inputs intact.

Last reviewed 2026-05-12.