Abstract: Wire electrical discharge machining (wire-EDM) has a significant position among production technologies mainly due to its capacity of machining hard materials and intricate shapes. One of the major problems with this process is the error in cutting corners. Processing forces acting on the wire and low rigidity of the wire are responsible for wire deformation, which has a direct influence on the accuracy of the corner cutting. In this research, investigation is focused on the convex corner radii errors and alternative solutions are proposed for the case of successive cuts (one roughing and two finishings). Experiments are carried out for roughing operation by considering frequency of discharges and feed speed. The residual materials on straight and curved paths are the output parameters. Results indicate that optimization of these parameters have a better influence for control of residual material thickness on straight paths than on curved corners. One important conclusion is that roughing is the most influential stage of cutting by WEDM. Then, concave corner radii produced during successive cuts, the effect of corner angle and corner radii are investigated. Errors at radii of different corner angles are identified and related to arc length and residual material thickness in the curved corner. Finally, an effective approach is presented for improving the accuracy of the small-radius concave corner radii of finishing stage. The main conclusion is that to achieve accurate corner radii, one must increase the traversed corner arc length by wire in the small-radius concave corner radii.