Design of an insert type induction heating and cooling system for injection moulding processes

For some injection moulding processes, the tool must be kept at high temperature when injecting plastic melt. Conventionally, this is achieved by heating the tool with hot oil or water, but heating the entire tool will cause unnecessary energy consumption. Previous studies show that using external induction in order to heat the surface of injection moulding tools is both rapid and energy efficient. However, while using a robot to put the heating coil in front of a tool cavity is very convenient, the tool must be open until heating is finished, making the injection cycle time longer. In addition, repeatedly making the tool surface exposed to too high and low temperatures may quickly damage it. The use of an insert type induction heating coil has thus been proposed to address this issue. Since the heated mass with insert type induction heating is a lot greater than with coil of external induction heating, the former has a slower heating rate on the tool surface, thus extending the life of the tool. In this approach, a coil can heat the tool during the tool opening and ejection process and a cooling channel can also be used to avoid interference with the coil inside the tool, as well as to enable cooling on the cavity surface. This study thus proposes a new tool structure, and a two-cavity tool was fabricated to verify the design concept. The results of a set of experiments show that the coil could heat the tool and achieve temperature uniformity of about 91%, while the heating rate was about 3 °C/s.