Élaboration et caractérisation des nouveaux mélanges poudre-liant à basse viscosité pour l'impression 3D

Abstract

Material extrusion additive manufacturing is a recent technology for the construction of polymeric, ceramic, metallic and even composite parts. After the success of the use of this technology in the production of based-polymer parts, it was introduced for other materials in several forms, among them the 3D printing plunger-based MEX. This technique promotes, as the majority of AM techniques, the production of parts with complex geometry at a practically low cost compared to traditional manufacturing methods and especially parts with low production density, on the other hand, it favors the prototyping of parts obtained by metal or ceramic injection molding with similar properties. The first step in this manufacturing technology is the formulation of a suitable mixture for printing and that provides the best properties after the debinding and sintering phase. Therefore, the study of the rheological behavior of a feedstock in 3D printing is crucial to obtain parts with exact shapes and dimensions, as well as to optimize the whole process in terms of temperature and printing parameters. The choice of binders’ proportions and the quantity of powders have an impact on the properties of the final product, and on the debinding and sintering phase. In this context, the objective of the project is to study the impact of binders and their proportions on the rheological behavior of stainless-steel based mixtures dedicated to 3D printing by material extrusion. To achieve these objectives, the stability and repeatability of viscosity measurements were performed, then the influence of EVA, solid loading and temperature were measured. Finally, printing at three (3) temperatures (75°C, 85°C, 95°C) of a mixture with 65 vol. % solid powder loading, 23 vol.% paraffine wax (PW), 10 vol.% ethylene vinyl acetate (EVA) and 2 vol.% stearic acid (SA) were performed to determine the best shaping results. The analysis of the experiments carried out showed the effect of the composition of the binder and the temperature on the flow behavior of the evaluated feedstocks, these analyses helped to define that for each mixture there is a critical solid loading to be respected, the volume percentage of EVA must be well selected so that the dimensions and shape of the product to be printed will be reliable to the designed models. For the printed parts, the results confirmed the influence of the temperature on the quality of the product, more precisely on the coalescence and the adhesion of the layers. A temperature of 85°C was mentioned as the best printing temperature for the printed mixture after validation by numerical simulations of the shear rate in combination with the printer parameters.

Date	25 Nov 2022
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	Vincent Demers (Supervisor)