Error transfer route in SLS rapid investment casting process

SLS rapid investment casting generally needs three steps: SLS prototype firing, wax impregnation post-treatment and investment casting. Because there is a certain size error transfer between SLS prototype wax mold casting, in order to ensure that the final casting can meet the corresponding size accuracy requirements, the size error transfer law of the process is studied. In this chapter, aiming at the problem of SLS rapid investment casting forming accuracy, the error transfer route of forming process is proposed. It includes the rule of dimension error transfer from CAD model to SLS prototype, SLS prototype to wax mold and wax mold to casting. Through the analysis of the results of the first and second wax model experiments, the optimal process parameters were obtained. Finally, the transfer coefficient of each step is determined, which provides the basis for the subsequent firing of typical complex parts.

From the beginning of STL format conversion, the storage mode of STL format and the setting of specific parameters lead to a certain size error of parts after format conversion, Then, the dimensional accuracy of the parts imported into the rapid prototyping equipment is affected; then, in the SLS prototype manufacturing process, the influence of SLS forming materials, equipment and forming process jointly leads to the error of SLS prototype, while the dimensional error of post-processing after wax immersion is due to the infiltration of wax into SLS along the analysis line In the prototype, the size of the specimen has the corresponding error, while the error of the metal casting mainly comes from the solidification shrinkage of the metal. To sum up, the error generated by the forming software of the parts is transferred to the SLS prototype, and the error of the SLS prototype will be further transferred to the wax impregnated parts, and finally reflected in the casting. Therefore, in view of the above error transmission route, it is necessary to study the corresponding size error transmission law.