Mold temperature control using high-frequency proximity effect induced heating

Abstract

A rapid heating in an injection molding cycle has the advantage of improving product quality without significant increase in cycle time. In this study, high-frequency proximity effect induced heating (HFPEIH) was developed and combined with water cooling to achieve dynamic mold surface temperature control. By applying the HFPEIH system on a pair of mold plates separated with a small gap, the relevant influence of HFPEIH design was evaluated under various parameters including different mold plate material, inductor designs, and inductor channel depths beneath mold surface as well as mold separations. Simulation was also conducted and verified with experiments. Results show that all the heating rates range within 2°C/s to 4°C/s for the mold plate size of 100mm by 100mm. For the inductor design with three channels of circular cross section, the heating rate is fastest whereas one inductor design of rectangular shape exhibits the best the uniformity of temperature distribution. When the channel depth is reduced from 12mm to 4mm, the heating rate is increased significantly. The heating rate is also sensitive to mold plate surface area. When stainless steel N700 was used as the plate materials in a smaller plate of 60mm by 60mm, the heating rate can reach 7.6°C/s using one channel inductor design. The mold separation exhibits that it is less sensitive to the heating rate within 1mm to 5mm range and when it is greater than 5mm, the heating rate starts to decrease slightly. All the simulated results show good coincidence with experimental measurements.