I. Development overview and application background
The plastics industry has developed rapidly in the past 20 years. As early as 7 years ago, the annual output of plastics has exceeded the total annual output of steel and non-ferrous metals by volume. Plastic products are in the pillar industries of the automobile, electromechanical, instrument, aerospace and other countries and the people. It has been widely used in various fields related to daily life. Although there are many methods for forming plastic products, the most important method is injection molding. About half of the world's plastic forming molds are injection molds.
With the improvement of the complexity and precision requirements of plastic products and the shortening of the production cycle, the traditional mold design methods relying mainly on experience can not meet the requirements of the market. In large-scale complex and small precision injection molds, China also needs to import molds from abroad.
Second, key technologies and practical functions
1 . Replace the center layer model with a 3D solid model
Traditional injection molding simulation software is based on the center layer model of the product. The user first abstracts the thin-walled plastic product into approximate planes and surfaces, which are called the center layer. A two-dimensional planar triangular mesh is generated on these central layers, and the two-dimensional planar triangular mesh is used for finite element calculation, and the final analysis result is displayed on the middle surface. The injection molding product model mostly adopts the 3D solid model. Due to the inconsistency between the two models, the secondary modeling is inevitable. However, because the shape of injection molding products is complex and varied, it is very difficult to abstract the center level from the three-dimensional entity. The extraction process is very cumbersome and time-consuming, so the designer has a fear of the simulation software, which has become the injection molding simulation software. Promote the bottleneck of the application. China hot mold network
HSCaE 3D is primarily an STL file format that accepts 3D solid/surface models. Current mainstream CaD/CaM systems, such as UG, Pro/ENGINEER, CaTIa, and SolidWorks, can output higher quality STL format files. This means that the user can generate an STL format file of the 3D geometric model of the desired product with any commercial CaD/CaE system. HSCaE 3D can automatically convert the STL file into a finite element mesh model, through surface matching and introducing new The boundary conditions ensure the coordinated flow of the corresponding surface, realize the analysis based on the 3D solid model, and display the 3D analysis results, eliminating the complicated steps of abstracting the center layer and then generating the mesh in the central layer simulation technology, breaking the simulation. The bottleneck of system promotion and application greatly reduces the burden of user modeling, reduces the technical requirements for users, and shortens the training time for users from several weeks to several hours.
2 . Comprehensive application of finite element, finite difference and control volume methods
The injection molded products are thin-walled products. The thickness of the product is much smaller than the other two directions. The physical quantity such as temperature changes very much in the thickness direction. If the finite element method or the finite difference method is used, the analysis time will be too long. Can not meet the actual needs of mold design and manufacturing. We use the finite element method in the flow plane and the finite difference method in the thickness direction to establish the meshes corresponding to the flow plane and thickness direction respectively and perform the coupling solution. Under the premise of ensuring the calculation accuracy, the calculation speed meets the needs of the project. The control volume method is used to solve the moving boundary problem in forming. For products with different internal and external corresponding surfaces, it can be divided into two parts of volume, and each form a control equation, and the coordination of the two parts is ensured by interpolation at the intersection.
3 . The combination of numerical calculation and artificial intelligence technology
It is preferred that the injection molding process parameters have always been the concern of the majority of mold designers. Although the traditional CaE software can simulate the injection molding under the specified process conditions on the computer, it cannot automatically optimize the process parameters. CaE software users must set different process conditions for multiple CaE analysis, and compare them with actual experience to obtain a satisfactory process plan. At the same time, after CaE analysis of the parts, the system will generate a lot of information about the program (products, process conditions, analysis results, etc.), and the analysis results often appear in the form of various data fields, requiring users to have analysis and understanding. CaE's ability to analyze results, so the traditional CaE software is a passive computing tool that does not provide users with intuitive and effective engineering conclusions. The requirements for software users are too high, affecting the CaE system to a greater extent. Application and popularity.
In view of the above deficiencies, HSCaE 3D software introduces knowledge engineering technology into the development of the system based on the accurate calculation function of the original CaE system, and utilizes the thinking and reasoning ability of artificial intelligence to replace the user to complete the analysis and processing of a large amount of information. Directly provide instructive process conclusions and recommendations, effectively resolve the contradiction between the complexity of the CaE system and the simplicity of user requirements, shorten the distance between the CaE system and the user, and use the traditional "passive" simulation software. "The calculation tool is promoted to the "active" optimization system. The HSCaE 3D system mainly applies artificial intelligence technology to the initial process design, the interpretation and evaluation of CaE analysis results, and the improvement and optimization of the analysis scheme.
The main optimization method used in knowledge-based simulation systems:
(1) Optimization based on case-based reasoning. It is mainly applied to the initial design of forming process with discrete value space. The shape of the product and the structure of the gating system are encoded, and the dimensional information is described by characteristic parameters. Based on the collection and abstraction of previous successful process design, an instance library index and retrieval mechanism described in the form of a framework is established.
(2) Optimization based on artificial neural network. The parameters with continuous value space such as injection time and injection temperature in the process design are optimized by artificial neural network. Using the optimization objective function and under certain optimization strategies, the optimal parameters confirmed by the optimization system are obtained.
(3) Optimization based on rule-based reasoning. Mainly used for interpretation and evaluation of analysis results. The expert system rule base established by the system is based on expert knowledge in the field of injection molding, covering short shots, flow balance, melt degradation, temperature difference control, dwell time, allowable shear stress, shear rate, On the basis of the analysis and refinement of the calculation results, the knowledge of the clamping force is driven to drive the expert system for reasoning, analyze and evaluate the forming scheme, and give specific optimization and improvement suggestions.
4 . Integrated analysis of three-dimensional flow pressure retention of products and runner systems
The flow channel system generally adopts a cylindrical unit, and the product adopts a triangular unit. The HSCaE 3D system uses a semi-analytical method to solve the integrated solution problem of the hybrid unit, so that the HSCaE 3D system can not only analyze large and complex products of one cavity and one cavity, but also The ability to analyze a multi-cavity small precision product greatly expands the range of use of the system. The current HSCaE 3D system is the world's leading 3D simulation software that analyzes the problem of multi-cavity flow balance.
5 . Efficient algorithm for prediction of weld lines in plastic products
The fusion pattern has an important influence on the strength and appearance of the product. Accurately predicting the position of the fusion line is a difficult problem in the simulation software. The HSCaE 3D system greatly improves the accuracy and efficiency of fusion fab prediction through the node feature model method, and its accuracy reaches the advanced level of international similar products. The neural network method is used to qualitatively evaluate the influence degree of the fusion pattern, which provides a direct judgment for the user to evaluate the forming quality.
