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Injection Molding CAE Technology
0 Introduction
Plastic products from product design to production, including molding plastic products design, mold design, mold manufacturing and injection molding process parameters and several other main areas. The traditional injection mold design mainly rely on the designer's experience, while the injection molding process is very complex, plastic melt flow properties of different and ever-changing products and die structure, process conditions vary, forming various defects, mold design often require repeated trial-mode, maintenance mode can be put into production, with little of a successful, identify problems, not only to re-adjust the process parameters, or even to modify the plastic products and molds, not only time-consuming and laborious, but also reduces product development time . The use of injection molding CAE technology in mold manufacturing prior to simulate injection molding process (including filling, packing and cooling) and the early detection of problems, optimize mold design and process conditions set to reduce the number of test mode in order to improve production efficiency, has become a injection molding technology is an important direction of development.
1 The history of Injection Molding CAE technology
Injection Molding CAE technology is based on plastics processing rheology and heat transfer of the basic theory, the melt in the mold cavity in the flow, heat transfer physics, mathematical model, using numerical solution method of constructing the theory, the use of computer visualization technology image, visually simulate the dynamics of the actual shape of the melt filling and cooling process, an analysis techniques.
The 20th century, 60 years, the United Kingdom, the United States and Canada and other countries of the scholars, such as JRPearson (United Kingdom), JFStevenson (America), MRKamal (Canada) and KKWang (America), etc. to carry out a series of plastic melt in the mold-type cavity flow and cooling of basic research. At a reasonable simplification, based on 60 years completed a one-dimensional flow and cooling analysis programs, 70 years to complete the two-dimensional cooling analysis programs, and 80 years from the injection molding CAE technology has begun to theoretical research into the practical phase, launched a three-dimensional flow and cooling analysis and the study extended to packing, fiber orientation and warpage prediction of molecular and other fields. After 90 years carried out into the flow, packing, cooling and stress analysis, the whole process of injection molding processes are integrated research.
CAE technologies, for the injection mold design provides a reliable guarantee that its application is mold design in the history of a major change.
2 The role of Injection Molding CAE technology
Using traditional methods of design of injection mold design success will rely heavily on the experience of designers, but also for complex parts gate position is reasonable or not, the location of the exhaust slot settings, to determine the location of weld lines and so very difficult. Die in delivery will normally take before the test mode after repeated changes, until the products have been qualified, which inevitably led to the extension of the production cycle, and generally difficult to obtain an optimal design and process parameters. The use of injection molding CAE technical design, mold is not true, because of mold design concept stage, can make use of CAE technology in injection molding process simulation flow, making usually only in the mold tryout phases in order to find problems, such as short shots, weld lines or holes appear in the surface appearance of parts and other issues have been avoided. While helping the designer to complete the balance of the system, such as flow channel design, exhaust ducts, setting, rationally determine the injection molding process parameters, etc., so that usually makes the modification must be repeated tryout to determine structural parameters of the mold die design and process parameters in the conceptual stage able to determine, reduce the mold design and manufacturing cycle and improve the mold design quality.
Therefore, the role of injection molding CAE software, mainly as follows:
(1) Optimize design of plastic products
Plastic wall thickness, gate number and location of the design of flow channel system for the quality of plastic products have a significant impact. Depends on the experience of the past, designers using manual methods to achieve, time-consuming effort, but the use of CAE technology to quickly design the best products.
(2) optimize the plastic mold design
Can be cavity size, gate location and number of flow channel dimensions and cooling systems to optimize the design. On the computer simulation test mold, mold repair mold and improve quality and reduce the number of actual tryout.
(3) to optimize injection process parameters
Simulation of the injection process and found possible shape defects, to determine the best injection pressure, clamping force, mold temperature, melt temperature, injection time and cooling time.
This shows that the injection molding CAE technology in terms of improving productivity, reduce mold design and manufacture cycle and to ensure product quality, or reduce costs, reduce labor intensity and so on, have very significant technical advantages and economic significance.
3 Injection Molding CAE software types and their details
To date, a mature business are more injection molding CAE software, Moldflow Corporation Moldflow software and AC-Tech, Inc. (February 2000, was Moldflow Merger) and C-Mold software is an excellent representative; There are also foreign The TMCONCEPT, CADMold, Fidap, Stirm100, Polyflow and China's Taiwan region Moldex-peer software applications are relatively wide; and domestic in the "Eighth Five-Year" period began research in this area, and now Huazhong University of Technology HSCAE software and Zhengzhou University, Z -Mold software in China in the leading position.
Moldflow software is specialized in injection molding CAE software and consulting for Moldflow's range of products, the company issued since 1976, the world's first set of injection molding CAE software, has been a leading injection molding CAE software market. To 2004, Moldflow Injection Molding CAE software in the global market share of over 75%.
MoldFlow software includes three parts: MoldFlow Plastics Advisers (product optimization consultant, MPA), MoldFlow Plastics Insisht (injection molding simulation analysis, MPI), and MoldFlow Plastics Xpert (injection molding process control specialists, MPX).
Under normal circumstances, the most commonly used MPI, is mainly used for injection molding process simulation to get the best number and location of the gate, reasonable flow channel system and cooling system, and cavity size, gate size, runner size and cooling systems to optimize the size and the injection molding process parameters may also be optimized.
Moldflow Software Moldflow analysis techniques can be divided into three kinds, namely, Midplane, Fusion and 3D .
4 Moldflow analysis of Midplane
Midplane (in the surface flow) applications began in the 20th century, the 80s. The grid is a three-node triangular element, its principle is the 3D geometric model of simplified geometric model of the neutral surface (to be created in the model grid the middle of the wall thickness), using established simulation analysis of the neutral surface, ie to flow in plane to simulate three-dimensional solid flow. The analysis of technological development has been very mature and stable, and the advantages for the analysis of speed and high efficiency.
Based on the flow of surface flow simulation of injection molding technology, software applications, the longest, widest range. But the practice shows that, based on the surface flow simulation software in the application of technology that has significant limitations, specifically as follows:
(1) The user must construct a mid-surface model. Using manual directly from the physical model structure in the surface model is very difficult and often takes a lot of time and can not be converted from other CAD models.
(2) can not be described in a number of three-dimensional features. If they can not describe the inertia effect, gravitational effects on melt flow, which fail to predict jet phenomenon, melt the forefront of Quan phenomena.
(3) The use of CAD phase of the product model and stages of the use of CAE analysis model is not unified, so that the inevitable second modeling, CAD and CAE systems integration can not be achieved.
5 Moldflow's Fusion analysis
Fusion (double flow) analysis technique is based on Moldflow's patented Dual Domain of analysis techniques. Fusion launched in 2000, analysis techniques, enabling users do not need to extract the neutral surface can be analyzed, to overcome the reconstruction of the geometric model, thus greatly reducing the burden on the user modeling. Grid is also a triangular element, and its principle is to mold cavity or the products in the thickness direction is divided into two parts, finite element mesh on the surface of the cavity or the products. In the flow process, the upper and lower surface of the plastic melt at the same time two and to coordinate movement of the simulation shown .
Clearly, Fusion technology, the surface of the grid is based on the neutral surface is still not solve the fundamental problem the neutral surface, so double-sided application of the principle of streaming technologies and methods applied in the surface flow with no difference in the nature, the The difference is two-sided flow using a series of related algorithms, will flow along the surface of the single-stranded melts evolved along the upper and lower surface of the coordination of the flow of dual-stream.
Double-sided flow of technology's biggest advantage is that the model greatly shorten the preparation time, thus greatly reducing the burden on the user modeling, will take several hours or even days of the original modeling work reduced to a few minutes. Therefore, based on double-sided flow simulation software technology, although the advent of time, only a few years, but in the world but has a huge user base, get the majority of customers for their support and praise.
But the double-sided flow of technology has the following deficiencies:
(1) The two-sided flow of technology does not fundamentally resolve the issue of a neutral face, they still can not describe some three-dimensional features, such as the inertial effect can not describe gravity effect on the melt flow, which fail to predict jet phenomenon, melt cutting-edge Quanyong phenomena.
(2) the upper and lower surfaces corresponding to the melt flow front there are differences. As the upper and lower surface of the grid can not be one correspondence, but the grid shape, orientation and size can not be completely symmetrical, so how the upper and lower surfaces corresponding to the difference between the melt flow front control is within the scope permitted by Difficulties in the implementation of double-sided streaming technology.
(3) melt is only along the upper and lower surface flows, in the thickness direction is not to make any treatment, lack of realism.
6 Moldflow's 3D analysis techniques
These two techniques have overlooked the thickness direction of the physical quantity, only two-dimensional simulation, and therefore results are not very precise. Moldflow Corporation's 3D (3D) analysis technology uses a true three-dimensional solid model flow analysis techniques, through rigorous theoretical derivation and repeated verification, the inertial effect, non-isothermal flow, taking into account factors such as finite element analysis, the melt thickness direction of the physical quantity changes will no longer be ignored, can be a more comprehensive description of the process of filling flow phenomena, so that results of the analysis more realistic conditions, applicable to all plastic products. Its three-dimensional grid is from the four-node tetrahedron unit. And using the new 3D stereoscopic display technology, can quickly model clearly shows that internal and external flow field, temperature field, stress field and velocity field such as analysis results. For the above-mentioned results of the analysis can also be used such as bit lines or equipotential surface display, so that physical models and external changes in the variables show more clearly the case, Moldfiow also offers animation capabilities, through 3D animation display plastic melt in the changes in the flow cavity, allowing users to more intuitively see the design and manufacturing process may encounter problems.
But the 3D technology, meshing demanding, more complex equations to calculate the amount of large, long duration and the computational efficiency is low, not suitable for short development cycle and need to be repeatedly revised by CAE verification injection mold design. Therefore, the current penetration rate of the technology is not very high, but it will eventually replace the surface flow of technology and double-sided streaming technology.
7 Development Trend of Injection Molding
Injection Molding CAE technology, whether in theory or in the application have made great strides, but in the following still needs further improvement and development :
(1) mathematical models, numerical algorithms to gradually improve the
Injection Molding CAE technology, practicality, depending on the accuracy of the mathematical model and numerical algorithm accuracy. The current commercial simulation software models do not fully consider the physical quantities in the thickness direction of the impact of the software in order to further improve the analysis accuracy and scope to further improve the existing mathematical models and algorithms.
(2) the whole process of injection molding simulation
At present, the injection molding simulation software are mainly filling, flow, packing, cooling, stress and strain and warpage analysis modules, each module was developed based on independent mathematical models, these models has been simplified to a large extent, ignored of the mutual effects. However, in view of injection molding process, plastic melt filling, flow, packing and cooling are intertwined and affect each other and, therefore, filling, flow, packing and cooling analysis module must be organically combined to carry out coupling analysis, in order to comprehensively reflect the real situation of injection molding.
(3) optimization theory and algorithms, so that CAE technology "active" to optimize the design
Artificial intelligence technologies, such as expert systems and neural networks on the design calculations, so that simulation can "wisdom" to choose the injection molding process parameters, product size and cooling to fix the piping layout programs to reduce manual intervention in the program.
(4) a new method of injection molding simulation analysis of the current
In the conventional injection molding technology, based on and the development of a number of new injection molding methods, such as gas-assisted injection, thin wall injection molding, reaction injection and co-injection . However, no specific methods for these molding simulation software, so untapped.
(5) injection mold CAD / CAE / CAM integrated and network-based
The current commercial injection molding CAE software and CAD, CAM software, data transfer between the mainly rely on the file conversion, which easily lead to data loss and errors. Therefore, in design and manufacturing process to take a single model, the establishment of injection mold CAD / CAE / CAM system, a unified database to strengthen the linkages between the three directions of future development. In order to meet the development requirements of e-commerce, this integrated system will achieve different places of the "Collaborative Design" and "virtual manufacturing."
8 Conclusion
Despite the adoption of a large number of practice has proved, in the plastic mold industry, the introduction of CAE technology, greatly reducing the mold design and manufacturing cycle and improve the life of the mold and manufacturing precision. At the same time, CAE technologies has also made from the traditional injection mold design experience and skills onto the road of scientific, to a certain extent, changed the injection mold of traditional production methods, but there is no substitute for CAE technology and people's creative work, only can serve as a complementary tool to help engineers understand the problems in the program, but also difficult to provide a clear improvement program, still need to through repeated interactions (analysis - changes - re-analysis) in order to reflect the experience of the designer's right to die design go, the program is designed to determine to a large extent continue to rely on the designer's experience and level.
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