INVESTIGATION OF FDM ADDITIVE MANUFACTURING TECHNOLOGY FOR GENERATING LOW MELTING TEMPERATURE COMPONENTS FOR INVESTMENT CASTING APPLICATION

Abstract

Additive manufacturing (AM) has proven to be an effective tool in assisting metal manufacturing industries such as Investment Casting (IC). However, due to peculiarities related to extrusion-based additive manufacturing, a challenge exists for the technology to produce wax that closely resembles the wax products used in traditional IC production. Therefore, the current study aims to explore the capabilities of the FDM-based technology to manufacture wax parts having qualities comparable to IC waxes in terms of thermal and rheological properties. In particular, the material under investigation is a wax filament having a commercial name Wax3D with a melting temperature lower than 100 °C. In addition, the melt viscosity of this polymer is considerably lower compared to popular hard plastics meant for 3D printing. Having considered the challenges related to extrusion-based manufacturing parts possessing such material features, the study starts with the material characterization where the data on material properties is collected through different analyses including mechanical, thermal, and rheological testing. By performing Taguchi’s design of experiments, the optimal FDM process parameters are identified for the successful manufacturing of wax parts. Subsequently, for improving mechanical properties and surface quality of produced parts, a few methods have been proposed. Namely, 3D printing PLA/wax multi-material is suggested to enhance the strength of the wax-based patterns which require high robustness. As for surface quality enhancement, a chemical treatment is found to be effective with the application of a white spirit dissolver. The ceramic shell cracking issue is regarded as the main downside when the 3D printed patterns are used for the investment casting application. Thus, a part of the study is dedicated to addressing this problem; a novel approach is suggested by studying the expansion forces developed during the heating of wax patterns via rheological equipment. The obtained data helped to draw a thematic comparison between the thermal expansion qualities of 3D printable wax and its traditional counterparts. In addition, dewaxing and ceramic shell burst experiments were conducted for further investigation. It was found that the 3D printed version of the wax pattern was less prone to causing shell cracking. That was due to the high porosity of the 3D printed part associated with thermal processes occurring during layered deposition. Finally, the qualities of cast metal parts were assessed after benchmarking and performing IC. For manufacturing the benchmark, the optimal 3D printing process parameters were used which were established earlier. As for ceramic shell integrity, no cracking was observed after the dewaxing/burnout stages. The study revealed that the obtained dimensional and geometrical tolerances of the cast artifact conform to the standards of IC manufacturing.