Telescopic ball bar with an indexing joint for measuring machine tool error

Self Cite

Multiaxis machine tools are widely used in manufacturing. The measurement of motion error is important to improve the machining accuracy of machine tools. A double ball bar (DBB), as a high-precision single-dimensional position reading device, is widely used to measure the motion error of the circular path of machine tools. However, the motion errors contain the cylindrical radial and axial errors with respect to the circular path plane. Therefore, the measurement results of the DBB are incomplete because they do not contain axial errors. To measure the motion error of the circular path accurately, completely and concisely, a novel measurement method based on the combined double ball bar (C-DBB) is proposed in this paper, which can directly measure the radius and axial motion error of the circular path in one measurement. First, the measuring principle of the C-DBB method is introduced, and the measurement model of the radius and axial motion error of the circular path is established. Then, a measuring device using the C-DBB method was designed based on the lever principle, and the error parameters of the designed device were analyzed. According to the error analysis results, the measurement results of the C-DBB method were compensated and corrected. Finally, the C-DBB method is used to measure the circular path on the vertical CNC milling machine, and the results are compared with the measurement results using the DBB method. It is shown that the proposed C-DBB method can obtain high-precision multidimensional motion error in a single measurement, and the designed measuring device based on the C-DBB method has high repeatability and good circular path measuring ability. The proposed method provides an effective method for machine tool multidimensional motion error measurement and compensation.

Section: Measurement Results Of Dbb-2mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A novel method for measuring radial and axial errors in a cylindrical coordinate system using a combined double ball bar

Sun

Wang

et al. 2023

Self Cite

“…The telescoping ballbar, first proposed and patented by Bryan in 1982 [3], revolutionized the measurement of radial changes in circular motion using an accurate linear scale sensor. Since their introduction, ballbars have been extensively applied in circular tests [4,5], calibration of rotary axes [6,7], assessment of the thermal or geometrical behavior of five-axis machine tools [8,9], kinematic calibration of parallel kinematic machines [10], and industrial robots [11]. As an efficient automated tool conforming to ISO 230-4 standards, the telescoping ballbar excels in error detection in machine tools and industrial robots, ensuring precise error identification [12].…”

Section: Introductionmentioning

confidence: 99%

Optimizing dynamic measurement accuracy for machine tools and industrial robots with unscented Kalman filter and particle swarm optimization methods

Xing,

Bonev,

Champliaud

et al. 2024

The telescoping ballbar is widely utilized for diagnosing accuracy and identifying faults in machine tools and industrial robots. Currently, there are no established standards for determining the optimal feeding speed for ballbar tests. This lack of clear guidelines results in time inefficiency in measurements and inconsistencies in dynamic measurements, which complicates the comparison of ballbar test results under various conditions or across different machine platforms. To mitigate dynamic variations in ballbar results, an updated ballbar data processing method that integrates the unscented Kalman filter (UKF) and particle swarm optimization (PSO) was developed and validated using real ballbar data measured at multiple feeding speeds and simulated data with varying vibration magnitudes generated through the Renishaw ballbar simulator. Experimental results revealed that the dynamic components extracted from the ballbar results were observed to increase in correlation with the vibration measured at different feeding speeds and from the simulations. Moreover, the variations in the results measured at different feeding speeds after PSO-UKF processing were significantly reduced. The findings confirm the effectiveness of the proposed method in minimizing the dynamics of the ballbar results. Ultimately, this approach enhances the efficiency and accuracy of ballbar testing and offers a general method for improved diagnostics.

“…Due to the high precision and low cost, the double-ball bar (DBB) has been widely used for the detection of the machine tool errors [7][8][9][10]. By analyzing the arc trajectory measured by DBB, the motion accuracy of the machine tool can be obtained.…”

Section: Introductionmentioning

confidence: 99%

Fast detection of geometric errors for three-axis machine tools with combined double-ball bars based on spatial circle detection

Wang,

Yue,

Yang

et al. 2023

Self Cite

The geometric accuracy of the CNC machine tools determines the quality of the sculptured mechanical parts. Measuring and compensating the geometric errors of machine tools can effectively improve the machining accuracy. However, traditional measurement methods using a double-ball bar(DBB) can only detect the error along the rod length direction and thus require multiple measurements in three orthogonal planes of the machine tool. This work proposes a fast error detection method for three-axis machine tools using combined double-ball bars (C-DBBs) based on the spatially circular detection (SCD) path. The test path of this method requires the simultaneous linkage of three linear axes of the machine tools and thus could identify 21 geometric errors of the three-axis machine tool. Firstly, the measuring principle of the SCD method is introduced, and the mathematical model for detecting 21 geometric errors of the machine tool based on the SCD method is established. Then, the detection experiment based on the SCD method is carried out, and it is shown that 21 geometric errors of the three-axis machine tool are obtained. Finally, the verification experiment using a traditional DBB is conducted to validate the effectiveness of the proposed SCD method. The radial errors in three orthogonal planes measured by traditional DBB exhibit a good agreement with those predicted using 21 geometric errors obtained by the SCD method. Compared with the traditional DBB method, the proposed SCD method could detect 21 geometric errors of three-axis machine tools in a single measurement. This work provides an effective and efficient methodology for detecting all geometric errors of the three-axis machine tool.