Rotational Molding Cycle Time Calculator
Plastics manufacturing & hollow products: Calculate oven cook time, forced cooling duration, wall thickness scaling law, and Peak Internal Air Temperature (PIAT).
Part Thickness & Oven Conditions
Cycle Timing & Production Throughput
Recommended Tools & Equipment
Tested hardware and components for high reliability
Frequently Asked Questions
What is Peak Internal Air Temperature (PIAT) in rotational molding?
PIAT is the single most critical quality control metric in rotomolding. It measures the temperature of the air pocket trapped inside the hollow cavity during the oven cycle. Reaching the resin-specific PIAT (typically 195–205°C for LLDPE) guarantees that all polymer powder grains have sintered together and all microscopic air bubbles have diffused out of the melt without thermally oxidizing the plastic.
Why does cook time scale with wall thickness to the power of ~1.5?
Unlike metals, thermoplastics are poor thermal conductors. Heat from the hot oven air must conduct through the metallic mold shell and then through the growing insulating layer of coalescing plastic melt. As wall thickness increases, the conduction path resistance grows non-linearly according to transient thermal diffusion laws.
How does the cooling rate affect rotomolded part mechanical properties?
Rapid cooling (e.g. direct cold water spray) suppresses polymer spherulite crystallization, resulting in a more amorphous structure with lower stiffness, higher impact ductility, and reduced mold shrinkage, but often triggers severe warpage. Controlled air and mist cooling promotes uniform crystallization, minimizing residual stress.