Injection Molding worked example
Shot Size with part weight plus runner weight per shot of 70 g: a worked example
What does the result look like when part weight plus runner weight per shot reaches 70 g? The full calculation is worked below with real intermediate numbers. Use this when sizing a barrel or screw, verifying that the machine shot capacity covers the mold, or comparing actual vs. theoretical shot weight.
The inputs for this scenario
- Part weight plus runner weight per shot: 70 g (raised for this scenario; the documented default is 28)
- Number of cavities: 4 cavities (unchanged)
- Overfill/cushion factor: 1.08 x (unchanged)
Working through the calculation
- Applying the documented formula (Total shot size = (Part + runner weight) x Cavities x Overfill factor) to the inputs above produces each figure below.
- At this operating point the engine returns 302 g for result, the number this scenario is built around.
- At this operating point the engine returns 302 value for net shot weight (before overfill).
- At this operating point the engine returns 1 x for multiplier.
- At this operating point the engine returns 280 value for factor a x b.
How this compares with the baseline
- Against the tool's baseline example, where part weight plus runner weight per shot sits at 28 g and the headline result is 121 g, this scenario comes in 150% above the baseline at 302 g.
- A figure at this level is achievable when part weight plus runner weight per shot is genuinely sustained, not just peaked for a shift. It assumes one resin density across all cavities and a balanced runner; family molds with mixed part weights or hot-runner systems need a per-cavity breakdown.
Results at a glance
- Result: 302 g (headline result)
- Net shot weight (before overfill): 302 value
- Multiplier: 1 x
- Factor A x B: 280 value
Run it with your numbers
- Every input above is editable in the live Shot Size calculator, which recalculates instantly and can be shared with the inputs intact.
Last reviewed 2026-05-12.