Why do we need rounded corners at the corners of castings，and How big should the rounded corners be?

1. In order to get a smooth transition of different parts of castings, prevent sharp transition of different wall thicknesses, and reduce slag, iron beans and bubbles formed by eddy current at sharp corners, especially to prevent defects such as cracks in castings caused by shell overheating. We need to set a R at the intersection of parallel or intersecting walls

2. We need to set a proper R because too big or too small also cause defects on parts of  casting. Generally the R is according to the two walls thickness. If we Suppose two wall thickness are A and B, the R should be 1/3 -1/5 （A+B）.