Injection Molding worked example

Defect Rate by Cavity with rejected parts from this cavity of 6 parts: a worked example

Here is what the math looks like when conditions slip. We hold every other input steady and drop rejected parts from this cavity to 6 parts, then walk the calculation through step by step. Calculate the defect rate for a specific mold cavity to identify problem cavities that need maintenance or correction.

The inputs for this scenario

  • Rejected parts from this cavity: 6 parts (the input this scenario stresses; the baseline uses 12)
  • Total parts produced from this cavity: 500 parts (held at the documented default)

Working through the calculation

  • The calculation starts from the formula this tool documents: Cavity defect rate = (Rejected parts / Total parts from cavity) x 100.
  • Rate works out to 1.2 % at these inputs, and this is the headline figure for the scenario.
  • Gap to target works out to -1.2 points at these inputs.
  • Affected count works out to 6 count at these inputs.
  • Total count works out to 500 count at these inputs.

How this compares with the baseline

  • Against the tool's baseline example, where rejected parts from this cavity sits at 12 parts and the headline result is 2.4 %, this scenario comes in 50% below the baseline at 1.2 %.
  • The practical read: the gap between this scenario and the baseline is entirely attributable to rejected parts from this cavity, so recovering it is worth quantifying in dollars before considering equipment or staffing changes. It only flags which cavity is bad, not why — you still need to inspect the cavity for the root cause (gate wear, venting, cooling imbalance), and small sample sizes make a single reject swing the rate.

Results at a glance

  • Rate: 1.2 % (headline result)
  • Gap to target: -1.2 points
  • Affected count: 6 count
  • Total count: 500 count

Run it with your numbers

  • To rerun this with your own numbers, open the live Defect Rate by Cavity calculator, set rejected parts from this cavity to your actual value, and adjust the remaining inputs to match your operation.

Last reviewed 2026-05-12.