Investigation On Design And Forming Process Of Lattice-structure Conformal Cooling Channels In Plastic Injection Mould

Mold technology plays a pivotal role in manufacturing, and becomes one of the most important indicators of the manufacturing level of a country. Up to now, mould used for the fabrication of plastic products is generally plastic injection mould. Conventional cooling channels of plastic injection mould manufactured by drilling technique, however, cannot meet the increasing requirements of higher cooling efficiency and uniformity during the forming process of plastic products. Therefore,a novel cooling channel structure and the corresponding processing technique are needed to be explored.Lattice structure, as a new multifunctional material, has the advantages of high strength, low relative density, self-supporting characteristics and so on, is a good candidate filling material for conformal cooling channels, which can improve cooling efficiency and uniformity significantly. Selective laser melting technology(SLM) is a recently developed metal additive manufacturing technology. Compared with traditional processing methods, SLM has the feature of design flexibility and capability of manufacturing complex inner structures. As a consequence, SLM is capable of manufacturing lattice-structures conformal cooling channels.This dissertation investigates the possibility and effectiveness of applying lattice structures into designing conformal cooling channels for plastic injection mould using the SLM processing technique.Firstly, a lattice structure that can be used to design conformal cooling channels and manufactured by selective laser melting was designed. And compared with finite element simulation and compressive tests, a mathematical model of the elastic modulus of the lattice structure was established.Secondly, a design method of lattice-structure conformal cooling channels was carried out. By using Moldflow software to implement analog simulation analysis, it revealed that the mould with lattice-structure conformal cooling channels had shorter ejector time and less overall deformation.Finally, in heating experiment, when samples reached thermal equilibrium, the sample with lattice-structure conformal cooling channels inside bad shorter heating up time and less rising temperatures.To meet the requirement of designing lattice-structure conformal cooling channels, the optimal design of the lattice structure was done. A new structure having characteristics of self-supporting and high porosity was developed. Experimental results showed that the new conformal cooling channels could be successfully manufactured by the SLM process. Moreover, compared with conformal cooling channels with circular cross section, computational fluid dynamics analysis and experimental results revealed that the lattice-structure cooling channels were more efficient and uniform. In addition, it also proved the possibility of manufacturing the new conformal cooling channels, providing an approach to design more efficient cooling channels in plastic injection mould.