Application of the hottest CAE in precision castin

Application of CAE in precision casting

Abstract: This paper introduces the CA precision casting process. The application of computer-aided engineering, including three-dimensional CAD and numerical simulation of solidification process, in the development of precision castings is emphasized. Ideas can easily carry out three-dimensional design or reverse engineering to obtain three-dimensional models, and then through rapid prototyping technology, can quickly get the casting prototype; ProCAST is used to simulate the pouring process of castings to optimize pouring parameters and eliminate casting defects

key words: CA precision casting computer aided engineering

1 introduction:

precision casting is a method of molding castings with a soluble (fusible) one-time model. The biggest advantages of precision casting are smooth surface and accurate size, while the disadvantages are complex process, long production cycle, many factors affecting the quality of castings, and strict requirements for materials and processes in production [1]. In the production process, mold design and manufacturing occupy a long cycle. The design and manufacture of a complex thin-walled part mold may take one year or more. With the progress of world industry and the improvement of people's living standards, the R & D cycle of products is shorter and shorter, and the response time of design requirements is shorter. Especially when the structural design needs to be modified, the early mold manufacturing cost and manufacturing period are wasted. Therefore, mold design and manufacturing become the bottleneck of new product development. The development of computer-aided engineering makes the integration of traditional industries and new technologies possible. 3D CAD can liberate the design from the drawing board, greatly simplifying the designer's design process and reducing the probability of mistakes. And with the development of rapid prototyping (RP) technology, especially laser selective sintering (SLS) [2,3,4], the three-dimensional model can be quickly transformed into the prototype required for precision casting through RP equipment, breaking the bottleneck of mold design. In addition, in the traditional casting, to develop a new casting, the process finalization needs to be tested many times and explored repeatedly. Finally, according to the casting results of various test schemes, the casting process scheme that can meet the design requirements is selected. Many times of trial casting will cost a lot of human, material and financial resources. The numerical simulation of solidification process can guide the optimization of pouring process parameters, predict the number and location of defects, and effectively improve the yield of castings. CA precision casting technology is to apply computer-aided engineering to the process of precision casting, and combine other advanced casting technologies to complete the R & D and trial production of complex products with high quality, low cost and short cycle. At present, the CA precision casting technology has been used to complete the trial production of a variety of key components such as aerospace, aviation and weapons, and achieved satisfactory results

2materials and experimental methods

CA precision casting can be applied to stainless steel, heat-resistant steel, superalloy, aluminum alloy and other alloys. The three-dimensional model can be designed by using three-dimensional design software such as ideas, UGII, PROE, etc., the process structure and model conversion are processed and repaired by magicrp, the prototype is made on the afsmz320 automatic forming system, the prototype surface is treated by melt infiltration, and the numerical simulation of solidification process is calculated by ProCAST and finite difference software

discussion on the key problems and related technologies of 3CA precision casting technology

in recent years, monomer technologies related to Ca precision casting technology, such as 3D CAD design, reverse engineering, rapid prototyping, gating system CAD, casting process numerical simulation (CPS) and special casting, have made great progress. These achievements have laid a foundation for the formation of integrated CA precision casting technology and promoted the rapid development and application of Ca precision casting technology. In order to make each monomer technology successfully used in CA precision casting, we must eliminate the interface between each other and organically combine these technologies. Thus, in product development, we can achieve real advanced design + Advanced Materials + advanced manufacturing

3.1 generation of three-dimensional model and electronic document exchange

how to get an accurate electronic data model of parts is the first step of Ca precision casting. With the development of 3D CAD software, reverse engineering and other technologies, this work has become simple and fast. This paper mainly introduces the process of entity modeling and data conversion using ideas. Ideas9 integrates 3D modeling and reverse engineering modeling modules. Through the mastermodeler module, complex models can be obtained, which can not only carry out parametric design with full geometric constraints, but also carry out free and innovative design with arbitrary geometric and engineering constraints; Surface design provides the modeling function of many kinds of free-form surfaces, including variable sweep, boundary surface and so on. Reverse engineering freeform can process the point cloud information collected by the digitizer, create curves and surfaces, and design them. After the surface is generated, it can directly generate RPM files, or send them back to the main modeling module for processing. After the entity file is generated, it needs to be converted into STL file as the input of RP equipment. During the conversion process, attention should be paid to selecting the name of the forming equipment, usually sla500, and the output accuracy of the triangle is between 0.005~0.01. When using magicrp treatment, it should be noted that multiply by 25.4 to get the actual design size

3.2 numerical simulation of solidification process

3.2.1 numerical simulation principle of solidification process

casting is a process in which liquid metal fills the mold cavity, solidifies and cools, which contains many complex phenomena that affect the quality of castings. In actual production, experience is often used to evaluate whether a process is feasible. For a casting, the process finalization needs to be tested for many times and explored repeatedly. Finally, according to the casting results of various test schemes, a casting process scheme that can be reinstalled to meet the design requirements is selected. Many times of trial casting will cost a lot of human, material and financial resources

although the casting process is very complex and there are many accidental factors, it still follows the basic scientific theories, such as fluid mechanics, heat transfer, metal solidification, solid mechanics, etc. In this way, the casting process can be abstracted into solving the problems of liquid metal flow, solidification and temperature change, that is, to solve the Fourier heat conduction equation and elastic-plastic equation under the given initial and boundary conditions. The development of computer technology makes it possible to solve the numerical solution of physical processes. Computer numerical simulation can be used to quantitatively describe the extremely complex casting process

abstract through mathematical and physical methods, the casting process can be characterized as the coupling of several kinds of equations:

1 heat conservation equation: 2 continuity equation: 3 momentum equation: the commonly used numerical simulation methods are mainly finite difference method and finite element method. The mathematical model of finite element difference method is simple, the derivation is simple and easy to understand, and it takes up less memory. However, the calculation accuracy is general. When the casting has complex boundary shape, the error is large, and the difference lattice needs to be converted into the finite element lattice for stress analysis. The finite element method technology calculates the elements according to the variational principle, and then carries out the overall synthesis of the elements. The simulation accuracy is high, and it can solve the problem of castings with complex shapes. No matter what numerical method is used, the numerical simulation software of casting process should include three parts: pretreatment, intermediate calculation and post-processing. Pretreatment mainly provides geometric information of castings and moulds for intermediate calculation; Various physical parameters and casting process information of castings and shells. The intermediate calculation mainly provides a calculation model for numerical calculation based on the physical field of the casting process design, and predicts the casting quality according to the relationship between the casting quality or defect and the physical field. Post processing refers to the intuitive graphical expression of the calculated results

the main purpose of calculating the flow field and temperature field in the casting process is to predict the possible shrinkage cavity and porosity in the casting, optimize the process design, and control the internal quality of the casting

through the simulation of casting process on computer, the distribution of temperature field, flow field and stress field in each stage of casting can be obtained, and the occurrence and location of defects can be predicted. Comparing various process schemes and selecting the best process can greatly improve product quality and product yield

3.2.2 casting process numerical simulation software [5]

after years of research and development, there are a large number of commercialized casting process numerical simulation software in the world, indicating that this technology has become mature. Most of these software can simulate the temperature field, stress field and flow field of sand casting, metal mold casting, precision casting and pressure casting, predict the shrinkage, porosity, crack, deformation and other defects of castings and the fiber structure of various parts of castings, and have data conversion interfaces with CAD solid models, which can use solid files for finite element analysis

it can simulate most problems and physical phenomena in the casting process. In terms of the analysis of the technical filling process, it can provide the influence of gas, filtration, high pressure, rotation, etc. on the casting filling process, and can simulate the filling process of almost all casting processes such as lost foam casting, low pressure casting, centrifugal casting, and the filling process of injection molding, wax molding and pressed powder material building structure inspection technical standard gb/t50344 ⑵ 004. ProCAST can solve three kinds of heat transfer problems: heat conduction, convection and heat radiation, especially through the "gray body net radiation method" model, which makes it better at solving the problems of precision casting, especially single crystal casting. In terms of stress, the elastic-plastic and viscoplastic models are adopted, so that it has the ability to analyze the stress of castings and explore how to continue and improve the current situation of small-scale mining in the Democratic Republic of the Congo and the deformation of social and ecological effects in the future

when analyzing castings, simple model lattices can be directly generated in ProCAST. Complex models can be generated by ideas and other software, and output * UNV general exchange file, which should contain node and unit information of strength and demeanor under room temperature environment when it is below 1650 ℃. Meshcast module reads the lattice file and outputs tetrahedral cells for preprocessing. Precast defines the parameters of the model, such as material, interface heat transfer, boundary conditions, pouring speed, and finally completes the calculation by ProCAST module

using ideas and ProCAST, we simulated the solidification process of an engine component. Because the component has a thin dimension in one direction, it is easy to crack and deform during pouring. Through simulation, the structure of the pouring system is optimized to reduce stress concentration, prevent deformation and cracking, and achieve obvious results

conclusion:

1. The CA precision casting technology combined with computer-aided engineering and precision casting has strong versatility, which can shorten the development cycle and save the development cost

2. The combination of ideas and rpocast can simulate the casting process of complex parts

3. computer solidification simulation technology can be used to design and optimize the gating system of complex parts, and can accurately predict defects and their location, deformation and cracking tendency, and can be used to guide the optimization of the gating system