Induction Mold Heating: Modelling and Hardware-in-the-Loop Simulation for Temperature Control

Mold heating is an important key factor for the mold cycle which affects the quality of the molded product. The involved molding processes regards polymers foaming, plastics injection, or resin-curing with composites. While the manufacturing cycle of plastics injection molding requires a heating/cooling system, other processes do not require the cooling phase. Polymers foaming and resin-curing require specific values of temperature to provide full chemical reactions and a good product quality on the surface. Induction heating systems are suitable for such applications; however, many industrial cases require customized solutions to support the molding cycle of different parts. A temperature control is always mandatory to reduce the energy cost and increase the heating efficiency. This paper studies a molds temperature control applied in the polyurethane foaming of footwear soles. The proposed induction heating system and its control have been studied using the Hardware-In-the-Loop simulations. Due to a high mold thermal inertia, which increases the mold temperature even if the control system turns off the thermal power, tailored controllers have been analyzed to achieve the desired temperature set-point. The thermal model of the foaming mold and the induction heating system have been modelled and developed in the MATLAB/Simulink® framework. An ATMEGA processor was used to implement and test a discrete PID controller while Simulink induction-heating system model was running, creating an Hardware-In-The-loop platform.