Influence of Power Distribution on Surface Temperature Homogeneity in Aluminium Hot-Plate Heaters for PVC Window Welding

The surface temperature uniformity of aluminium hot‑plate heaters is a key factor affecting weld quality in PVC hot‑plate welding. Although aluminium plates are widely preferred for their high thermal conductivity, the effect of internal power distribution on surface temperature homogeneity under constant total power has not been thoroughly quantified. This study investigates the transient thermal behaviour of an aluminium heating plate using a three‑dimensional numerical heat conduction model including internal heat generation and convection–radiation losses. Two power‑distribution scenarios—symmetric (1250–1250 W) and asymmetric (1000–1500 W)—were examined with a fixed total power of 2500 W. Both reached the target temperature of 240 °C in similar times (~321 s), showing that overall heating behaviour is dictated mainly by total input power. However, spatial temperature differences were significant. The symmetric case produced global surface variations of ~30 °C, whereas the asymmetric case reduced this range to ~18 °C. In the active welding zone, temperature variation decreased from ~15 °C (symmetric) to only 4–5 °C (asymmetric). These results demonstrate that heat‑flux balance, rather than electrical symmetry, governs temperature uniformity. Therefore, internal power distribution represents an independent thermal design parameter and provides a practical basis for optimizing aluminium hot‑plate heaters used in industrial PVC welding systems.