Meaning
High frequency dielectric heating inside a steel tool cavity applies alternating electromagnetic fields to polar polymer molecules during compression or transfer cycles. Mold frame RF propagation governs internal thermal buildup within thick thermoset blocks before final cure, preventing voids caused by uneven thermal gradients. This specific electromagnetic behavior ceases to influence material consolidation once the resin reaches crosslinking vitrification.
Process engineers adjust generator output to match the dielectric loss factor of glass filled phenolic compounds.
Resin Absorption Rate
Polar additives absorb electromagnetic energy at varying efficiencies determined by moisture content and molecular dipole moments. Undried polyester moulding compounds trap steam when dielectric fields heat internal moisture above boiling points before the polymer chains crosslink. Material specifications define allowable volatile limits whereas part specifications dictate final structural density.
Virgin compounds maintain predictable dielectric properties whereas regrind batches exhibit higher electrical conductivity due to thermal history degradation.
Tooling Geometry Factor
Metallic cavity walls reflect high frequency waves and create standing wave patterns across complex parting lines. Tool designers compensate for edge effects by recessing copper electrodes away from thin sections to prevent localized overheating. A datasheet value for dielectric strength applies to flat laboratory plaques rather than three dimensional geometries encountered in production.
Moulders hold tighter dimensional tolerances on cavity pressure when electromagnetic preheating replaces conventional conduction heating plates.
Thermal Defect Control
Excessive generator dwell time degrades polymer backbones and releases volatile gases that create internal blistering within thick sections. Insufficient energy application leaves uncured cores that warp upon demolding due to differential shrinkage across the cross section. Production lines incur scrap costs when dielectric tuning drifts outside validated frequency windows during continuous multi cavity runs.
Final mechanical performance depends entirely upon uniform energy distribution throughout the entire mass of the moulded component.
