It is best not to design parts with sharp corners. Sharp corners act as notches, which concentrate stress and reduce the part's impact strength. A corner radius, as shown in the Suggested Design for Corner Radius illustration, will increase the strength of the corner and improve mold filling. The radius should be in the range of 25% to 75% of wall thickness; 50% is suggested. The Stress Concentration as a Function of Wall Thickness and Corner Radius illustration shows stress concentration as a function of the ratio of corner radius to wall thickness, R/T.