Consumable additive FDM models in the production of aluminum alloy castings

Abstract

This article describes the results of a study aimed at improving production technology of experimental castings from aluminum alloys by investment casting using models produced by 3D printing. The consumable models were produced using fused deposition modeling (FDM). Biodegradable polylactide (PLA) was used as a material for the models. In order to decrease the surface roughness of consumable PLA  model.  chemical  post-treatment  by  dichloromethane  needs  to  be  performed.  After  immersion  of  the  model  into the solvent for 10s, its surface becomes smooth and glossy. Three-point static bending tests of PLA plates demonstrated a mechanical strength of average ~45.1 MPa. A thermomechanical analysis of polylactide demonstrated that in the course of heating of ceramic shell in excess of 150 °C, the polylactide model begins to expand intensively by exerting significant pressure on the ceramic shell. In order to decrease stress during the removal of polylactide model from ceramic mold, the heating time in the range of 150–300 °C needs to be heated to a maximum. The use of hollow consumable casting models with a cellular structure not higher than 30 % is also sensible. The stresses on the shell will not exceed its strength. Characteristic  temperature  properties  of  PLA  plastic  thermal  destruction  were detected using thermogravimetric analysis. Polylactide was established to completely burn out upon  heating  to 500  °C  leaving  no ash residue. Analysis of the results identified the burning modes of polylactide models from ceramic molds. Using a Picaso 3D Designer printer (Russia), the PLA models were printed used for production of experimental castings from aluminum alloys. It was revealed that the surface roughness (Ra) of a casting produced using a consumable model treated by dichloromethane decreases by 81.75 %: from 13.7 to 2.5 μm.