Quantitative and Qualitative Evaluation of Shell Casting Surfaces

The shell casting process is the most suitable casting process for producing complicated components. The development in components quality will increase its potential. The processing may be regarded as a double casting process.This lead to error propagation during processing. There-fore, sources of imperfection of the casting surface may result from one or more of the following:
1. The metalic mould used to produce the wax cast.
2. Solidefication characteristics of the wax material.
3. The procedure of shell prepartion.
4. Behaviour of the shell during pouring of metal and during solidification of melt.
5. Mode of solidiCation of the molten metal.
To investigate the process, some measurements were carried out on a three co-ordinate measuring machine for both wax mould and the cast-ting component_ The dimensions of the plate considered were about 160x130x15 mm. The study suggested two parameters to quantify the sink namely sink vol-ume and the ratio between sink volume to its surface area. A computer graphics was used to construct iso-contour mapping of the sinks in such a way to visualize the sink. The total geometry of the component is throuroghly studied through the analysis of the three dimensional measur-ements. This mean of analysis and assessment is a helpful tool towards achieving casting design of high dimensional and geometrical qualities.