| Plaster molding for investment casting has the characteristics of high precision and low roughness of molded castings,and it is more and more widely used in aerospace,military and other fields.Traditional Plaster molding for investment casting is to form investment molds through molds.However,with the increasing complexity of the internal cavities,curved surfaces and thin walls of the parts,resulting the mold structure is more complicated and a series of problems such as long design and manufacturing cycle and high manufacturing cost have appeared.This article combines 3D printing preparation of investment molds with plaster precision casting,the main research contents and results are as follows:(1)A comparative study on the preparation of investment molds from three 3D printing technologies of SLA,FDM and SLS was carried out,and the research on printing materials,printing process and use performance was carried out:a)The influence of the content of each component in the photosensitive resin of SLA on the viscosity and curing depth of the photosensitive resin is studied: when the system components are EA/HDDA=1:1,the TPO content is 1 wt%,the photoinitiator has good fluidity and high curing depth.b)The printing process and wax immersion process of polystyrene(PS)samples prepared by SLS are studied: when the stress surface of the PS samples prepared by SLS is the printing layer,the bending strength and impact strength of the samples are the largest;PS There are many internal holes in the sample,and the surface quality and mechanical properties are poor,which can be significantly improved by the wax immersion process;the wax immersion can reduce the roughness of the sample by nearly 80%,and the mechanical properties are significantly improved.c)The performance of the samples prepared by three 3D printing technologies was compared and studied.The study showed that the PS samples prepared by SLS after paraffin immersion have higher surface quality,better linear shrinkage rate,thermal stability,residual ash content and cost than SLA and FDM samples,and the other properties meet the investment requirements;SLS is suitable for investment plaster casting to prepare patterns.(2)Applied research on ZL105 A impeller castings for an aero-engine,using Pro CAST software to assist in process design,preparing investment plaster casting patterns through SLS,and conducting trial production of parts:a)The plaster casting process of the impeller was studied,and the program was simulated and optimized using Pro CAST software.The PS pattern of the impeller was prepared by using the optimal SLS.The obtained pattern has high precision,and the small structure of the cavity and the complex guide vane are completely formed;and then the gypsum is used to prepare the PS pattern of the impeller.The mold was poured under vacuum and pressure,and a complete casting was successfully produced.b)The properties of the castings were tested,and the microstructure was analyzed through OM,SEM,etc.: The mechanical properties of the castings met the requirements,and no casting defects were found by X-ray inspection;the mechanical properties of the T5 heat treatment were significantly improved,mainly due to the solution treatment The flake eutectic silicon fuse and passivation,reducing its aggregation in the ? phase.(3)The PS pattern prepared by SLS is suitable for investment plaster casting after being immersed in wax.It can produce thin-walled castings with complex structures and has a broad application prospect. |
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