DESIGN OF GATING-FEEDING SYSTEMS FOR LOST-WAX CASTINGS.

In the lost-wax process, the sprue and pouring cup act as a lateral feeder for the whole of the castings and they must be designed with particular reference to this function. Otherwise the shrinkage pipes will extend into the topmost ring of castings. The soundest of the known methods of calculating feeders is the one developed by R. Namur. Experiments have shown that his formula can be applied to all forms of castings and all types of feeding systems. This procedure has been used to derive simple formulae for rapidly finding the dimensions of the sprue, cup and top or lateral feeders. It is only necessary to take the drawing of the casting, add the machining allowances to the dimensions and calculate the effective ruling thickness R//e in the hot spot and the total volume of the casting.