Keywords: graduation design of computer technology mold design
1 Introduction
Mold is a technology-intensive and capital-intensive product, and its position in China's national economy is also very important. Mould industry has been officially identified as the basic industry in China and listed as the key supporting industry in the Tenth Five-Year Plan. Due to the continuous development of new technologies, new materials and new processes, mold technology is constantly improving, and the requirements for talents' knowledge, ability and quality are also constantly improving.
According to the new requirements of social development for teaching and educating students majoring in mold, the College of Engineering and Technology of Shenzhen University has carried out great reform on the graduation design of students majoring in mold design of grade 99, and achieved good results.
2 mold students training objectives
The mold design major of Shenzhen University belongs to the mechanical manufacturing and automation major of the School of Engineering and Technology of Shenzhen University, mainly engaged in the design and manufacture of injection molds. In order to clarify the training goal of this direction, we have conducted a relatively extensive social investigation on the mold enterprises in the Pearl River Delta, especially in the surrounding areas of Shenzhen. The survey results show that employers require graduates to have high ideological quality and moral cultivation, love their jobs, have good coordination skills, require graduates to have a solid basic theory, pay attention to mastering basic skills and re-learning skills, and require graduates to be proficient in foreign languages and have certain computer software application and development capabilities.
According to the analysis of the survey results, our specification for mold professionals training is set as: training applied engineering management talents who love their jobs, have basic knowledge of machinery and various mold design and manufacturing, have strong relearning ability and creativity, and can engage in mold design and manufacturing, technology development, applied research and sales in the front line of mold production. Based on this, the basic guiding ideology of teaching in this direction is to broaden the professional caliber, set up the curriculum system reasonably, optimize the teaching content, have strong experimental research ability and wide social adaptability, and integrate mold design theory, practice and computer application.
Application of computer technology in injection mold
It is a very complicated process from design to molding production of plastic products, which includes several important aspects such as plastic product design, mold structure design, mold processing and manufacturing, and plastic parts production. It requires the joint efforts of product designer mold designer, mold processing technicians and skilled operators, and it is a process of repeated iteration, continuous optimization design, modification and redesign. Traditional manual design has become increasingly difficult to meet the needs of fierce market competition. The application of computer technology is replacing the traditional manual design method in all aspects and has achieved remarkable economic benefits. The application of computer technology in injection mold is mainly manifested in the following aspects:
(1) Design of plastic products: 3D modeling software based on features provides a convenient design platform for designers, and various physical parameters such as product quality and volume lay a good foundation for subsequent mold design and analysis.
(2) Structural analysis: Finite element analysis software can be used to analyze the strength and stress of products and improve the structural design of products.
(3) Mold structure design: According to the shape, precision, size, process requirements and production batch of plastic products, the mold design software will provide corresponding design steps, parameter selection, calculation formula and standard mold base, and finally give a complete set of mold structure design drawings.
(4) Simulation of mold opening and closing movement: CAD technology can be used to simulate the whole process of mold opening and closing and product launching, so as to check out the irrationality of mold structure design and correct it in time to reduce mold repair time.
(5) Numerical analysis of injection process: CAE method can be used to simulate the flow and pressure holding process of plastic melt in the mold cavity, and the results are of great guiding significance for improving the gating system of the mold and adjusting the injection process parameters, and can also test the rigidity and strength of the mold, the warping deformation of the product and the cooling process of the mold wall.
(6) NC machining: NC programming software can be used to simulate the real-time machining process of tools on a three-dimensional curved surface and display the shape data of the curved surface. At the same time, it can automatically generate NC wire cutting instructions for curved surfaces, three-axis and five-axis NC milling tool paths.
At present, the mainstream CAD software of injection mold in the world includes Pro/E, I-DEAS, UG Ⅱ, SolidWorks and so on. Structural Analysis software includes MSC, analysis, etc. The numerical analysis software of injection molding process includes MoldFlow, etc. CNC machining software includes MasterCAM, Cimatron, etc.
4 graduation design mode of mold specialty
Mould major students need strong comprehensive knowledge and practical ability. It is not only a comprehensive application of basic technical courses and professional courses such as mechanical drawing, engineering materials, tolerance fit and technical measurement, plastic molding technology and equipment, but also requires students to know a lot of practical experience.
Through graduation project, students are trained in the following basic abilities: ① the design of plastic products and the selection of molding technology; (2) the design ability of the general plastic product molding die; (3) plastic product quality analysis and process improvement ability, plastic mold structure improvement design ability; ④ Understand the common commercial software of mold design and its combination with actual design,
Strictly speaking, the previous graduation design can only be regarded as the curriculum design of mold design; Teachers designate a plastic product, and sometimes even give students a model drawing of the product. Students follow the steps of mold design in spy photos book step by step. Without practical experience, it is impossible for schools to turn students' designs into practical products. Therefore, students don't know whether these designs are reasonable. Even experienced teachers can't point out the irrationality. Students have no perceptual knowledge and can only talk on paper. When students set foot in the society and engage in actual product design, they often find that they can't start. Even if they design it, it is a piece of waste paper, and it usually takes 1 to 2 years to get started. Therefore, students often sigh: nothing has been learned at school, which is the failure of our education.
In order to change this situation, in the graduation design of Grade 99, we closely combined the content of mold design with CAD/CAM/CAE. Through advanced software simulation, students can find their own irrationalities in each step of design at any time, and find out various solutions to make the design more reasonable. At the same time, they have mastered the most advanced design, combined with analytical technology, which has improved students' interest in learning and innovation ability, and made the graduation design truly become the whole process simulation before students actually work. The design process is shown in figure 1.
In order to ensure the quality of graduation design, we set up a mold design steering group composed of four teachers, each of whom is responsible for one step in the design process. There are *** 15 students who participated in the graduation design of mold design this time. We are divided into 5 groups, each with 3 students.
First of all, when arranging graduation design topics, tell students to make a switch button without giving specific plastic products. Students can determine their own design products according to their own interests: game console handle buttons, glasses case switch buttons, light wall switch buttons, mouse buttons. Through market research and consulting a lot of literature, we can determine the shape and internal structure of our plastic parts. The internal and external structures of plastic parts are designed by using three-dimensional modeling software Pro/E, and two-dimensional drawings are drawn by AutoCAD. In the process of structural design, the structural strength, stiffness and stress of the button are analyzed by using the structural analysis software MSCPatran, and the structure is constantly revised. Students will find that the knowledge of mechanical design, industrial product design, material mechanics, theoretical mechanics and other courses is reflected at this stage, which is also a comprehensive application process of the previous courses. Fig. 2 is the assembly diagram and explosion diagram of a game machine key designed by Xue Niu, and fig. 3 is the maximum deformation and maximum stress diagram of the key when it is stressed at two diagonal points.
After the design of plastic products is completed, the mold structure is designed, and the products are classified, divided and extracted by the mold design module under Prom/E, and the core and cavity files are obtained. The standard die set parts and other accessories, such as sliders and diagonal pins, are established through expert die set system EMX(Pro/E, one of the plug-in programs of this system). In fact, this process is not over. It is closely related to the numerical analysis of the subsequent injection process. MoldFlow, an injection molding flow analysis software, was used. According to the dynamic diagram of the melt flowing in the gating system and cavity, the gating system of the mold is improved and the injection process parameters are adjusted, so as to optimize the design of each system of the mold. Fig. 4 shows the analyzed optimal pouring position and the result of injection molding with circular runner arrangement. Fig. 5 is an assembly view and an exploded view of the button die.
After the mold structure is completed, NC machining is carried out. We use MasterCAM8.0 machining software to complete the virtual machining process of the mold, and automatically compile the NC code of NC machining. The simulation module can be used to check the rationality of machining workpieces.
Finally, students should provide detailed design instructions and complete two-dimensional and three-dimensional drawings. During the thesis writing and defense, students also use ACDSee image software to capture design pictures to help introduce the whole design process. Office software is used to process words and write analysis reports.
After the whole design is completed, each student must summarize his own design process and results, and put forward the innovation and characteristics of this design. For example, in the modeling part or the runner design part, we should also consider the problems existing in the design and the corresponding solutions. Judging from the summary of most students, students are urgently aware of the lack of practical experience. Therefore, in the graduation project of the next student, we strive to invite more designers from enterprises to communicate with students, so that students can get in touch with the actual design and production process.
At this point, students have completed the whole process of a project: plastic product design-mold juice design-mold processing. Students can see the final products designed and processed by themselves on the computer and feel the feeling of success.
5 concluding remarks
Through the reform of graduation design mode, students not only summarized the four-year college courses, but also mastered the most popular design and processing methods that are closest to social reality. Therefore, this year's graduates majoring in mold have been welcomed by the society, and the mold department of a large Taiwan-funded company in Shenzhen is willing to accept five graduates from our school at one time, which has achieved good social benefits. (End)