Injection Mold
Meaning ~ Capital asset comprising machined steel plates used to shape resin under pressure, governing production speed, part precision, and lifecycle per-unit cost.
Runner Scrap Rate
Meaning
Material efficiency metrics measured during plastic injection molding quantify the proportion of resin consumed in feed channels relative to finished parts. Process engineers calculate the runner scrap rate to evaluate cold-runner tooling waste against hot-runner efficiency baselines. The metric tracks material losses during molding operations, terminating when regrind re-processing or part production halts.
Accurate measurement optimizes resin consumption across high-volume molding operations.
Efficiency Metric
Cold-runner molds generate solidified plastic channels that must be trimmed from finished parts. High runner scrap rate percentages indicate inefficient mold design or excessive feed channel volume. Comparing runner weight to total shot weight identifies opportunities for tooling modifications or conversion to hot-runner systems.
Financial Consequence
High material waste directly increases part production costs when processing expensive engineering resins. If a runner scrap rate exceeds target estimates, suppliers incur higher raw material bills that erode manufacturing margins. Regrinding scrap offers partial material recovery, but re-melted plastic can degrade mechanical properties if regrind ratios are uncontrolled.
Process Optimization
Tooling redesigns and valve-gate conversions reduce material consumption per injection cycle. Modifying runner diameters or transitioning to insulated hot-runner manifolds minimizes scrap generation. Lowering scrap rates improves sustainable manufacturing performance and reduces unit piece costs.