Research On Key Technologies Of Automatic Parting Design In Injection Mold

With the rapid development of science and technology,the product life cycle is becoming shorter and shorter.For injection mold enterprises,shorten lead-time to respond the customized demands faster becomes the key to win market competition.In order to improve the rapid response ability,automatic design,network design and concurrent design become the tendency of injection mold.Especially in the aspect of automatic design,with the continuous development and in-depth application of CAD technology,the tedious and repetitive design work such as the design of standard parts and mold base have been eliminated,and the design efficiency and quality have been greatly improved.However,the current injection mold parting design system is still dominated by tools which involve a great deal of human-computer interaction.The key problems such as automatic recognition of mold piece regions and automatic generation of mold parts have not made a breakthrough,which seriously restrict the implementation and application of the automatic injection mold parting design.Parting design is the important process of injection mold design,breaking through the above bottleneck problem is vital for the realization of automatic and intelligent injection mold design.Therefore,this dissertation focus on the automatic parting design,wherein the key technologies such as parting information solution,mold piece region recognition and molding parts generation are throughly studied.The 3D CAD model of injection product is the main model of data transmission in the process of injection mold design.In this dissertation,the parting design process of injection mold is analyzed concretely,and the information transmission and transformation of 3D CAD model of injection product in the process is then discussed.A non-discretized flowchart and method of automatic parting design is proposed.The architecture of the non-discretized parting design system is constructed,and the key technology for realizing the system is discussed in detail.Parting information,which includes parting direction,surface visibility and so on,is the data infrastructure of automatic parting design process.In this dissertation,a rotational iterative method is proposed for the oriented bounding box of 3D CAD model,which can effectively improve the efficiency of the parting direction calculation.A silhouette-curve-based method is developed for visibility evaluation of the free-form surface,which can accurately solve the surface visibility of 3D CAD model of injection product,and avoid the ambiguity of traditional UV method.Fusing the results of surface visibility,an extend attributed face-edge graph model is constructed,and the effective organization and expression of injection mold parting information is realizedMold piece recognition is the key step to transform product parting information into injection mold parting scheme.In order to recognize undercut features effectively,a new hierarchical mechanism of mold piece region is proposed.Based on this mechanism,a heuristic algorithm for searching mold piece region is developed,which can effectively construct the set of candidate mold piece regions.Considering the complexity of parting curve,the number of cavity surface,the position of undercut features and the demoulding distance,a fuzzy comprehensive evaluation mathematical model of parting curve is established.Based on this model,the mold piece region is optimized and the boundary of mold piece region is extracted automatically to realize the automatic generation of injection mold parting scheme.The driving components of core pulling mechanism are complex and changeable,and are heavily dependent on design experience.In this paper,a variant design method of core-pulling mechanism for different motion environments is proposed,and the assembly model of core-pulling mechanism supporting variant design is constructed.The type of core-pulling mechanism,core-pulling force and distance,and the shape of undercut region are adopted as feature information to form case index.The case similarity of core-pulling mechanism is evaluated based on nearest neighbor algorithm.The variant design of geometry and assembly tree of the retrieved core-pulling mechanism assembly model are carried out,which effectively improved the efficiency and quality of core-pulling mechanism design.Based on the research results,by using Siemens NX 11.0 as the CAD platform,this dissertation develops the prototype of the automatic parting design system of injection mold,and verifies the validity and feasibility of the system through application example.The system can significantly improve the efficiency and quality of the parting design.