Abstract: An industrial robot, designed to machine a workpiece by means of a tool supported on an extremity of a mobile arm, is controlled by a programmer whose memory is initially loaded with a preliminary program including the locations of a multiplicity of closely juxtaposed but discrete points on the workpiece surface and instructions for the guidance of that extremity establishing rectilinear or circularly arcuate paths between these points. With the tool replaced by a sensor contacting a pattern corresponding to the desired shape of the workpiece, the preliminary program is executed and deviations from the established paths are registered to modify the stored instructions, thereby converting the preliminary program into a definite program subsequently used in shaping the actual workpiece.