Study On Investment Casting Process And Numerical Simulation Of Rapid Prototyping Parts

Investment casting is a material net shape technology, can produce precision castings of complex structures through the technology. But the process is a manufacturing process cumbersome, long production cycle, high rejection rate and other shortcomings. With the rapid development of computer simulation technology to bring rapid tooling production technology for the investment casting new direction of development, it can shorten the testing and production of cast molding cycle, improve economic efficiency and market competitiveness. In this paper, numerical simulation and FDM rapid prototyping technology in the investment casting applications have been studied by means of numerical simulation technology to optimize the design of the impeller casting programs; by means of rapid prototyping technology to quickly generate PLA impeller mold,simplifying the process shorten the molding time, and finally validated by casting simulation accuracy and feasibility of rapid tooling.First, the three-dimensional drawing software Pro / E drawing impeller model and impeller model design a top gating schemes, then use the casting simulation software ProCAST for top injection-type program to simulate the specific process parameters set to: Pouring molten aluminum alloy temperature720 ℃, casting speed 0.15 m / s, the preheating temperature of the shell 300 ℃.The simulation results show: the presence of turbulence filling process, the central part of the blades have a greater shrinkage porosity defects and the presence of stress 221 Mpa root of the blade and the casing connections easily lead to casting defects. Improvement program using side gating system, the middle and lower parts of each setting a gate on the housing, the same simulation test parameters with the original program, the results show side gating system smooth filling process, and the inner runner gate design helps solidification, allowing castings feeding effectively reduces the shrinkage of the leaves shrinkage. The maximum shrinkage rate of 0.69 appears in the blades and the casing joints, maximum stress158 Mpa appear in the blade root. Side gating scheme shrinkage and shrinkage rateis less than the maximum effective stress top injection-type program and meet the demand.Secondly, the use of FDM rapid prototyping technology, the use of homemade kossel structure FDM 3D printer to print out the impeller solid model,to improve the printing precision aluminum impeller FDM do the relevant discussion and analysis, according to the shrinkage of PLA and aluminum to establish a correction ratio 1.013 model for the structure of each blade impeller disposed below 20 mm * 20 mm * 14 mm support, support select 30% filled,impeller body with 100% fill. Each set three single contour, a straight line is filled,the height of 0.2mm, filling speed 70 mm / s, the temperature is set to the print tray60 ℃. After 2 hours to obtain the print model impeller, the impeller solid obtained after removal of the support, and finally by flash forming two hours to produce a successful precision of 0.2mm PLA impeller entity. After bonding the impeller model wax runner, according to characteristics of the mold choices silica sol as the adhesive layer developed 4-shell technology.Finally, the process of lose-PLA. After firing off the autoclave dewaxing PLA, were pouring after cleaning inspection. During the calcination temperature is 250 ℃ one hour control, PLA impeller model is decomposed into carbon dioxide, water, acetaldehyde, carbon monoxide, PLA realized off mode. And use the process parameters were casting simulation program. Experiments show that the rapid prototyping of PLA can be applied to investment casting mold. Good to verify the accuracy of numerical simulation and Rapid PLA to replace the traditional mold in wax investment casting feasibility impeller castings complete quality.The results above show, ProCAST numerical simulation software can accurately predict the investment casting defects, product trial stage of the process parameters, design casting programs and the improvement of a reliable reference;the use of FDM prototyping of PLA impeller model can be used directly as investment casting casting mold is feasible for FDM rapid prototypingapplications and methods to explore the case in investment casting.