Compensation of electrode orbiting in electrical discharge machining based on non-uniform offsetting

In orbiting EDM, the orbital motion of electrode makes the cavity dimension in the workpiece deviate from the design objective. This paper presents a compensation method for electrode orbiting. The presented techniques are used to modify the geometric shape of free-form electrode, so as to eliminate the effects to the cavity dimension that arise from the electrode orbiting. The basic approach consists of three steps: (1) NURBS parameters extraction of electrode surfaces and surface adaptive sampling; (2) non-uniform offsetting of the sampled points according to the orbiting patterns; (3) approximation of non-uniform offset surface under error control. And the method to handle trimmed surface in compensation is also discussed. Quite a few implemented examples and machining results show that the developed techniques can compensate the orbital motion and improve the machining precision effectively.