Engineering tools

Injection moulding cycle time calculator — cooling time from wall thickness

Cooling dominates the injection moulding cycle, and it scales with the square of wall thickness: double the wall, quadruple the cooling. This calculator uses the classical one-dimensional cooling equation with typical material data to estimate cooling time, then adds your injection and mould-movement times for a total cycle and parts-per-hour figure — the first approximation every costing conversation starts from.

Why wall thickness rules the cycle

Plastic is a poor conductor: heat leaves a moulding through its surfaces, so the core of a thick wall stays soft long after the skin has frozen. Because cooling time grows with thickness squared, the single most effective cost reduction in part design is usually a thinner, more uniform wall — cored-out sections and ribs instead of mass. It is also why our DFM review pays so much attention to wall maps before quoting: seconds of cycle are rupees on every part, forever.

From cycle to cost

Cycle time and cavity count set your machine cost per part; part weight sets material cost. Chain this estimate into our part cost calculator, and check machine fit with the shot-size and clamping-force tools.