Abstract: The software compensation technique of a multiaxis machine’s volumetric errors based on the Huazhong I type computer numerically controlled system is developed. The problem of modeling the propagation of errors of individual axes through the kinematic chain, and their effect on the position and orientation errors of the cutting tool in the machine’s work space are analyzed. A general mathematical model, which relates the error in the position of the cutting tip with respect of the machine tool structure, is established. In the volumetric error model the values of the individual error components affecting the machining accuracy are obtained by direct measurement with a laser interferometer, especially a new measurement method of the angular motion errors in roll is proposed. The error terms of the measuring points are stored in tables. Linear interpolation between points is carried out and error functions combined to obtain corrections. The CNC reads the values of the translation and rotation error terms corresponding to axis positions every 8 ms. With the aid of the full volumetric error model, including tool length and orientation, the CNC computes the resulting workpiece to tooltip errors in every motion axis. The correction for these errors is added to the nominal axis position controlled by CNC codes, and then the error compensation is obtained. Experimental results demonstrate that about 70% reduction of the machine’s volumetric errors is gained after compensation.

Key words: CNC machine tools, Error model, Geometric error, Software-based error compensation