DESIGN OF A 3D INDUCTION COIL FOR LOCALIZED HEATING OF INJECTION MOLDS: THERMAL DISTRIBUTION ANALYSIS AND TEMPERATURE UNIFORMITY OPTIMIZATION

Abstract

Injection molding is widely used for manufacturing polymer components, where rapid and localized mold heating is important for improving melt flow, surface quality, dimensional accuracy, and cycle-time control. This study proposes a novel 3D induction coil for localized surface heating of injection molds, with emphasis on thermal uniformity optimization through a combined numerical-experimental approach. The experimental system integrates a 30 kW induction power supply with a water-cooled 3D coil fabricated from Ø8 mm copper tubing. Surface temperature fields were measured by infrared thermography to validate a multiphysics COMSOL model under reference conditions (I=1450 A, f=75 kHz, heating time 3-6 s). For a 100 × 20 × 3 mm plate, the predicted center-point temperatures showed relative deviations of only 0.58% and 0.43% at 3 s and 6 s, respectively, confirming high model accuracy. The model also reproduced the hot-spot morphology and thermal gradients observed experimentally. Parametric analysis revealed that increasing plate width (W) reduced peak temperature while increasing thermal non-uniformity, whereas increasing thickness (T) improved thermal balance at the expense of maximum temperature. Concave mold geometries yielded more uniform heating. In addition, coil-to-surface gap, clamping position, and power-lead orientation were identified as critical variables for improving thermal uniformity in induction-assisted injection molding.