Numerical simulation of two-dimensional wick debinding in MIM by body fitted finite element method

Abstract

Thermal debinding in metal powder injection moulding (MIM) is an intricate phenomenon. An alternative description of wick debinding in the 2D compact–wick material combination is developed here by numerical simulation. To simplify the problem and to qualitatively investigate the wick debinding process, the assumptions of a single component binder and fully saturated compact with molten binder are adopted. As the flow of molten binder is a moving boundary phenomenon, which is similar to a fluid flowing through porous media, a new numerical technique, body fitted FEM, is used to generate grids inside the physical domain and to calculate the distributions of pressure and other relative properties. Results show that the predictions of debinding time versus compact thickness squared and the debinding rate agree well with those issued by German and Vetter et al., respectively; this identifies the reliability and accuracy of the present numerical analysis. Low Reynolds number Re and low capillary number Ca indicate that capillarity is more dominant than effects such as inertial force, viscous force, etc. Though high permeability of the wick can increase the artery of the draining compact, the capillary pressure will decrease with the larger pores. The shape of the flow front of the molten binder and the outer geometry of compact are found to be closely matched in the final step of wick debinding.