Abstract
In order to simulate more accurately the powder injection moulding process, the explicit finite element method solver is extended with the surface tension effect. The evaluation of surface tension takes the notion of pressure boundary method, while a simple and systematic scheme is proposed to fit the finite element method solver for the Laplacian operator. Because of the difference in dimension for filling function and velocity function, the integration of filling function in second derivative is not suitable to be transformed into the boundary integration and the integration of function in lower order derivative. To evaluate conveniently the curvature of filling front, hence the force of surface tension, a simple and systematic scheme is suggested and implemented into the finite element method solver. This specific scheme includes only the vectorial operations in low cost, and is completely systematic without piecemeal operations. Fitness of the proposed method is proved by the numerical examples of filling flow in a small-scaled channel. It shows the considerable effect of surface tension for the problems in micro-scale of sub-millimeter sizes, in which the boundary conditions at front surface are not negligible in powder injection moulding process. The surface tension effect becomes the dominating role for governing the trace and shape of filling front, which can no longer be neglected.
Highlights
Injection moulding process is an effective manufacturing method for mass production of the components with very small size and complicated shape [1]
In the continuum surface force (CSF) model, surface tension effect is treated as a body force Fb in a thin layer of the elements that locate on the filling front
It provides an effective way to evaluate the complex effect of surface tension in injection moulding of small powder injection components
Summary
Injection moulding process is an effective manufacturing method for mass production of the components with very small size and complicated shape [1]. Thermoplastic polymer is injected into the die cavity mould air inside is squeezed out. W. Cao et al developed a model to take into account the dynamic contact angle between fluid and micro die cavity to simulate the surface tension effect in the filling of micro-channel. Kim et al investigated the transient filling flow in micro channel by experiments and simulations. Their conclusion indicated that the surface tension affect significantly the filling flow of small thickness from 20 to 40 μm in micro-channel injected components. For the investigation of powder injection moulding process, some simulations are made for the example of filling flow in sub-millimeter sizes of high loaded polymer in a straight channel of features heaving
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