Machine tools realize tool movements with high accuracy mainly due to highly developed computerized numerical controls (CNCs). As articulated industrial robots are used more and more for machining, robot controllers (RC) have to be equipped with additional path planning capabilities, similar to machine tools. A RC is very similar to a CNC from a software and hardware point of view, but with one major difference, the RC has an additional transformation stage, the transformation from Cartesian space to joint space. Machining with robots is a field intensely researched in the last years. CNC systems for robots are commercially available, furthermore, more and more CAM systems have extensions for machining with robots. Most of these offer a simulation of the machining process using a robot model, in order to solve the inverse kinematic problem and, additionally, to take into consideration axis motion limits (maximum angular amplitudes) and singularities. Moreover, path planning for machining robots is done in exactly the same way as for machine tools, with the mentioned additional transformation stage. This paper describes the advantages and challenges which result from the integration of the kinematic transformation in the path planning stage.