Process Window

Parameter Interdependence

Temperature adjustments alter melt viscosity, shifting the required injection pressure and hold time parameters. Operating within a defined process window prevents thermal degradation while ensuring full cavity packing before gate freeze off occurs. Design of experiments methodology identifies parameter interactions that govern key part dimensions.

Viscosity changes between material lots shrink usable operating windows, requiring process trimming.

Quality Boundaries

Boundary conditions are established by systematically varying fill speed and packing pressure until defects emerge. Sink marks define the lower hold pressure boundary, whereas part flash sets the upper pressure limit. Melt temperature limits are bounded by resin degradation at the high end and incomplete filling at the low end.

Material Sensitivity

Unfilled commodity polymers exhibit wider operating boundaries than highly filled engineering resins. Moisture variations in hygroscopic materials narrow the process envelope by causing hydrolysis and surface splay defects. Regrind content alters viscosity profiles, forcing operators to recalculate holding pressure limits.

Continuous monitoring of cavity pressure profiles verifies that moulding conditions remain within target boundaries.