Research on non-contact measurement method of ball screw nut based on spectral confocal principle

The ball screw nut is the key component in the ball screw pair. Because of its complex inner structure and small hole size, it is difficult to measure machined accuracy of the ball screw nut. A non-contact measurement method of the ball screw nut based on spectral confocal principle is presented. The measurement space of the cylindrical coordinate of the nut is established according to its structure features. The inner cavity is scanned by dividing the section layer by layer to obtain the three-dimensional point-cloud data of the inner surface. Through transferring measurement space of the cylindrical coordinate into the calculation space of the rectangular coordinate the structure parameters of the inner groove of the ball screw nut are calculated, including pitch, inner diameter, pitch diameter, median runout and lead angle. The chord height difference method is used to denoise and filter the measurement data to get the more actual measured data. The three-dimensional reconstruction of the nut cavity structure is carried out using reverse technology to display the processed textures. The feasibility and effectiveness of the method is verified by the measurement experiment of ball screw nut. The experimental results show that the measurement method proposed in this paper can effectively check the ball screw nut with the high measurement accuracy, and has the ability of wide measurement range, and good expansion.