Measurement setup
Confirm scale resolution against the expected spread, use the same conditioning interval, separate each cavity, and record consecutive cycles in production order. Tare containers and document whether the runner is included.
Balance versus repeatability
Cavity balance compares positions within a shot. Shot-weight repeatability compares cycles over time. A stable overall shot can still hide a repeatable weak cavity; a balanced single shot can still come from an unstable check ring or feed condition.
Decision criteria
Use weight as a sensitive screen, then review critical dimensions, appearance, functional requirements and the approved validation protocol. The max-to-min percentage and CV are evidence summaries, not release specifications.
Related tools
Process Validation & Stability hub · Relative Viscosity Curve Calculator · Cavity Weight Balance Calculator · Gate Seal Study Analyzer · Pressure Drop Study Calculator · Shot Weight Repeatability Calculator
Sources
PlasticsToday: Scientific Molding, Part 1 · M. Holland: Monitoring Pressure Loss · BASF: Injection-Molding Problems · NIST: Measures of Scale · NIST: Coefficient of Variation · PMC: Filling Imbalance in Multi-cavity Molds · Hingtung: Cavity Balance Study
