Efficient Method for Identifying Key Errors Based on 21-Geometric-Error Measurement of Three Linear Axes of Machine Tools  
[PERSON] Key errors of machine tools have a significant impact on their accuracy, however accurately and quickly measuring the geometric errors of machine tools is essential for key error identification. Fortunately, a quick and direct laser measurement method and system for 21 geometric errors of three linear axes of machine tools were proposed previously, which enables the measurement of all 21 geometric errors via a one-step installation and a three-step automated measurement process. Based on this, to efficiently identify the key error factors, this paper first utilizes the 21 geometric errors obtained from the proposed measurement system to evaluate the contribution of each error to the volumetric errors of machine tools, leading to the building of a 21-geometric-error sensitivity analysis model. Then, experiments are carried out on the vertical machining tool TH5656, and all 21 geometric errors are obtained in 5 min. After this, the volumetric error distribution in the machining workspace is mapped according to the relationship between the geometric errors and the machining errors, and the key error factors affecting the manufacturing and machining accuracy of the TH5656 are ultimately determined. Thus, this new method provides a way to quickly identify key errors of the three linear axes of machine tools, and offers guidance for the machine tool configuration design, machining technology determination, and geometric error compensation. 21 geometrical errors; volumetric error; laser measurement; key geometric errors; sensitivity analysis; machine tools +
Footnote †: journal:  
Table 1 illustrates a total of 21 geometric errors that require measurement for the three linear axes of machine tools [5]. Presently, the laser interferometer is widely employed as it offers high measurement accuracy at a relatively low cost. However, it is a single-parameter measurement instrument, requiring the replacement of different optical attachments and readjustment of the optical path for each error measurement. This process is time-consuming and labor-intensive, leading to low measurement efficiency. Moreover, it falls short of achieving a full-parameter measurement. Thus, to reduce the economic and time costs required for error compensation and to improve the efficiency of error compensation in machine tools, researchers have conducted studies from two aspects. On the one hand, various measurement methods with multiple parameters have been proposed to improve the measurement efficiency. Indirect measurement methods have been explored, such as utilizing a ball bar [7], a planar orthogonal grating [8], a workpiece testing method [9], or a laser tracking interferometer [10]. While indirect measurement methods offer higher measurement efficiency, it is important to note that they may provide relatively lower accuracy compared to the laser interferometers. Direct measurement methods primarily focus on assessing the geometric errors of a single linear axis. For example, [PERSON] [11] used a one-dimensional grating to simultaneously measure the six-degrees-of-freedom geometric errors of a linear axis. [PERSON] [12] proposed the use of a semiconductor laser as a light source to measure position error by laser interferometry, and other geometric errors are obtained by laser collimation. Similar measurement methods were proposed by [PERSON] [13]. [PERSON] [14] utilized a reflection grating encoder to achieve simultaneous measurement of dual-channel six-degree-of-freedom errors. [PERSON] [15] employed a dual optical frequency comb to measure multiple geometric errors. These direct methods have not yet been developed into commercial instruments, while the main commercial instruments available are the laser 5D/6D measuring instruments by API and the XM-60 measuring instrument by Renishaw.