Process of designing and manufacturing plastic products is extremely complex, encompassing several key aspects such as plastic product design, mold structure design, mold processing and manufacturing, and molding production. It requires collaborative efforts of product designers, mold designers, mold processing engineers, and skilled operators, and is a process of iterative design, modification, and redesign, constantly optimizing process. Traditional manual design and manufacturing are increasingly unable to meet demands of fierce market competition. Application of computer technology is replacing traditional manual design methods in various aspects and has achieved significant economic benefits. Application of computer technology in injection molds is mainly reflected in following aspects:
1. Plastic Product and Mold Structure Design
Commercial 3D CAD modeling software such as Pro/Engineer, UG, and CATIA provide designers with a convenient design platform. Their powerful surface modeling and editing functions, as well as realistic display effects, allow designers to freely express their design intentions, truly achieving "what you think is what you get." Furthermore, various physical parameters such as product's mass and volume are calculated and saved simultaneously, laying a solid foundation for subsequent mold design and analysis. Meanwhile, these software programs all have dedicated injection mold design modules, providing convenient tools for defining mold parting surfaces. This allows for automatic generation of complex molded parts. Furthermore, they offer comprehensive libraries of standard mold bases, typical structures, and standard parts, which are easy to access and add, significantly reducing mold design time. They also provide mold opening and closing motion simulation functions, ensuring rationality of mold structure design.
2. Numerical Analysis of Injection Molding Process
Using CAE software such as MoldFlow to simulate flow, pressure holding, and cooling processes of molten plastic in mold cavity, and to predict potential warping of product, results provide important guidance for optimizing mold structure and injection molding process parameters, improving success rate of first-time trial molding. This will be discussed in detail in following sections.
3. CNC Machining
CNC programming software can simulate real-time machining process of tools on three-dimensional curved surfaces and display relevant surface shape data to ensure reliability of machining process. It can also automatically generate CNC wire cutting commands, three-axis and five-axis CNC milling tool trajectories for curved surfaces, etc.

MoldFlow software is a product of MOLDFLOW Corporation, an American company that has dominated plastic molding CAE software market since releasing world's first plastic injection molding flow analysis software in 1976. In April 2000, it acquired another world-renowned plastic molding analysis software, C-MOLD.
MoldFlow software consists of three parts:
MoldFlow Plastics Advisers (MPA): After completing their product designs, plastic product designers use MPA software for simulation and analysis. In a short time, they can obtain optimized product design solutions and confirm product surface quality.
MoldFlow Plastics Insight (MPI): A software package for in-depth analysis of plastic products and molds. It can simulate and analyze the entire injection molding process on a computer, including filling, holding pressure, cooling, warpage, fiber orientation, structural stress and shrinkage, as well as gas-assisted molding analysis. This allows mold designers to identify potential defects in future products during design phase, improving success rate of first-time molding trials. In late 2001, MOLDFLOW released MPI 3.0, integrating functions of MPI 2.0 and C-Mold 2000.7. It has now been upgraded to version 3.1. Compared to MPI 2.0, MPI 3.1 simplifies operation by providing a unified interface for model preparation and analysis, resulting in more accurate analysis results. This software package is widely used in mainland China, and subsequent lectures will focus on MPI 3.1.
MoldFlow Plastics Xpert (MPX): An integrated hardware and software injection molding quality control expert. It can directly connect to injection molding machine controller for process optimization and quality monitoring, automatically optimizing injection cycles, reducing scrap rates, and monitoring the entire production process.
Role of MoldFlow software in injection mold design is mainly reflected in following aspects:
1. Optimizing Plastic Products. Using MoldFlow software, actual minimum wall thickness of product can be obtained, optimizing product structure, reducing material costs, shortening production cycle, and ensuring that product is fully filled.
2. Optimize Mold Structure. Using MoldFlow software, optimal number and location of gates, a reasonable runner system and cooling system can be obtained. Cavity dimensions, gate dimensions, runner dimensions, and cooling system dimensions can be optimized. Trial molding and mold repair can be performed on computer, greatly improving mold quality and reducing number of repairs.
3. Optimize Injection Molding Process Parameters. Using MoldFlow software, optimal injection pressure, holding pressure, clamping force, mold temperature, melt temperature, injection time, holding time, and cooling time can be determined to produce the best plastic products.

 

1. Model Input and Repair. MPI3.1 offers three analysis methods: center-plane-based analysis, surface-based analysis, and 3D analysis. Center-plane analysis can be completed using MPI software's modeling functions or extracted from other CAD models and then edited. Surface analysis models and 3D analysis models can directly read other CAD models, such as Rapid Prototyping Format (STL), IGES, STEP, Pro/E models, UG models, etc. After model is input, software provides various repair tools to generate meshes that yield accurate results while reducing analysis time.
2. Plastic Material and Injection Molding Machine Database. Material database contains detailed data on over 4000 plastic materials, and injection molding machine database contains operating parameters for 290 commercial injection molding machines. Both databases are fully accessible to users.
3. Flow Analysis. Analyzes flow of plastic in mold and optimizes cavity layout, material selection, filling, and holding pressure process parameters.
4. Cooling Analysis. Analyzes impact of cooling system on flow process, optimizes layout and operating conditions of cooling channels, and, combined with flow analysis, achieves a perfect dynamic injection molding process.
5. Warpage Analysis. Analyzes warpage deformation of the entire plastic part, including linear, linear bending, and non-linear warpage, while identifying main causes of warpage and corresponding improvement measures.
6. Fiber Infill Orientation Analysis. Fiber orientation of plastic part has a significant impact on properties (such as tensile strength) of parts made from fibrous plastics. MPI software uses a series of integrated analysis tools to optimize and predict fiber orientation throughout injection molding process, ensuring a reasonable distribution and effectively improving performance of plastic parts.
7. Optimize Injection Molding Process Parameters. Based on given mold, injection molding machine, and plastic part material parameters, as well as flow analysis results, it automatically generates filling and holding pressure curves to control injection molding machine, eliminating need for repeated adjustments to injection molding machine parameters during trial molding.
8. Structural Stress Analysis. Analyzes mechanical properties of plastic part under external loads, optimizing strength and stiffness of part while considering injection molding process.
9. Determine a Reasonable Plastic Shrinkage Rate. MPI 3.1 determines a reasonable plastic shrinkage rate based on flow analysis results, ensuring that mold cavity dimensions are within allowable tolerances, thereby reducing scrap rate and improving product quality.
10. Gas-Assisted Molding Analysis. Simulates gas-assisted injection molding process to optimize the entire molding process.
11. Analysis of Special Injection Molding Processes. MPI 3.1 can simulate and optimize special injection molding processes such as co-injection, reaction injection, and microchip encapsulation.