Numerical simulation and experimental validation of low-pressure powder injection molding process using Moldflow

Abstract

Low-pressure powder injection molding (LPIM) is a manufacturing technique used to produce parts exhibiting a high geometric complexity and high mechanical properties at lower manufacturing costs as compared to the conventional techniques such as machining or forging. This technique involves four main steps including feedstock formulation, the injection, the debinding, and sintering. Although all these stages are important to be controlled, this project focuses on the injection stage to better understand the flow behavior and pressure profiles of the feedstock within the mold cavity. In this respect, there are only few studies focusing on the development on the injection stage using low-viscosity mixtures and to the best of the author's knowledge, experimental validation of simulated pressures values has been performed only once using two simple shape mold cavities. The objective of this work is thus to evaluate the capability of the commercial numerical simulation package to capture the influence of process parameters on injection pressure. The numerical simulation was performed by Autodesk Moldflow Synergy 2019, while experimental validation was done using real-scale injections within five (5) different mold cavities with different shape complexity. Four different feedstocks formulated from two different powders (water and gas atomized) and from two solids loading (60 and 65 vol. %) were fully characterized to obtain properties such as viscosity, specific heat, density, and thermal conductivity that were finally implemented in the numerical model. These feedstocks were then injected into different mold cavities and the pressure were experimentally recorded in the gate. The numerical results of the flow pattern were in good agreement with the experimental data for different mold filling stage. Since the injections were performed using a constant volumetric flow, the results confirmed that the feedstock properties, feedstock temperature, and mold temperature have no influence on the flow pattern behavior. The simulated pressure results were in good agreement with experimental results over the majority of the mold filling stage with maximum relative differences varying from 30 to 64% depending on particular feedstocks and process parameters, including the capability to predict the filling stage associated with the changes in pressure values.

Date	15 Apr 2022
Original language	American English
Awarding Institution	École de technologie supérieure
Supervisor	Vincent Demers (Supervisor)