Modeling And Analysis Of Three-dimensional Transient Heat Transfer For Injection Mold

Plastic injection molding is one of the most efficient processing methods for plasticproducts. The temperature regulation system has an important influence on the productioncycle and the product quality. The accurate simulation of the temperature field is of greatimportance for cooling system optimization and the subsequent thermal stress and warpinganalysis. The traditional steady cooling analysis is not suitable for injection process in whichthe temperature oscillates in a big range. This paper researches on modeling and analysis ofthree-dimensional transient heat transfer for injection mold.The paper analyzes the heat balance and heat flow of the heat transfer system forinjection mold, and discusses the thermal boundary conditions of different injection processstages at first. The model of the contact thermal resistance (TCR) between cavity wall andplastic parts of the contact thermal resistance is established, the treatment of the boundaryconditions for the cooling stage, ejection stage and heating stage is presented. Then themodel of the3D transient heat transfer analysis is proposed, which is based on the finiteelement method and suitable for more plastic process.The analysis of3D transient heat transfer for injection molding is realized with ANSYS.Compared with the transient temperature field of a regular mold calculated by Moldflow, theanalysis model is proved to be correct. What’s more, the analysis model of the rapid heatingcycled mold (RHCM) is established. The simulation results show that the temperaturedifference between the edge and the middle area of the cavity wall is about20℃because ofthe relative large thermal conductivity coefficient of the mold. Complicated and precisemold should be analyzed with3D model as the predicted heating time is about10%shorterusing2D model. TCR reduces the efficiency of heat transfer a lot and the cooling time rises12.8%as a result. So it’s recommend that minimizing TCR by changing process parametersis a good way to improve efficiency.The module of the3D transient heat transfer simulation for injection mold ispreliminarily developed. Matrix assembly, dispersion of the time and treatment of the mixedboundaries are realized. As the temperature of the mold and the plastic part changed with the time, we have to map the part temperature to the mold on the contact area at every sub step.Compared with the result calculated with ANSYS, the heat transfer process analyzed by themodule is accurate.