Influencing factors of rotary table geometric error measurement using four-station laser tracers

The laser tracer multi-station measurement method has outstanding performance in computerized numerical control (CNC) rotary table geometric error measurement and separation. However, external factors, such as layout, selected distance between the target mirror and measurement coordinate system, uncertainty of the length measurement, selection of measuring radii for the rotary table, and installation deviation from the target mirror center to the rotary table surface, have negative effects on the results. In this research, the position dilution of precision in the global positioning system measurement process is introduced to evaluate the influence of the laser tracers’ positions on measurement errors. The optimal measurement layout of the laser tracer is used to select the distance between the target mirror and XY plane of the laser tracer measurement coordinate system for the simulation. Then, the influence of the length measurement uncertainty on the laser tracer self-calibration and point measurement results used for calibration is examined based on the Monte Carlo simulation method. Different measurement radii in the rotary table are selected, and four-station laser tracers are used to perform the virtual measurement and evaluate the maximum uncertainty in the X, Y, and Z directions to further determine the best measurement radii of the CNC rotary table. Finally, the effects of the deviation of the target mirror installation center on the geometric error items of the CNC rotary table are quantitatively examined through a simulation. The analysis of the influencing factors in the geometric error measurement and separation process of the CNC rotary table can help further understand how the final results are formed, so as to control the influencing factors during the measurement process and finally optimize them in practice.

Multistage Asymmetric Rotors Coaxial Measurement Stacking Method Based on Minimization of Exciting Force

The unbalanced exciting force of high-speed rotary asymmetric rotor equipment is the main factor causing rotor vibration. In order to effectively suppress the vibration of the asymmetric rotor equipment, the paper establishes a multistage asymmetric rotor coaxial measurement stacking method that minimizes the exciting force. By analyzing the propagation process of the centroid of the multistage asymmetric rotor assembly and analyzing the relationship between the geometric center and the centroid of a single asymmetric rotor, a multistage asymmetric unbalanced rotor propagation model based on geometric center stacking is established. The genetic algorithm is used to optimize the unbalance of the multistage asymmetric rotors. Combined with the vibration principle under the exciting force, the vibration amplitude of the left bearing at different rotation speeds under the minimization of the exciting force and the random assembly phase is analyzed. Finally, the experimental asymmetric rotors are dynamically measured, combined with the asymmetric rotors’ geometric error measurement experiment. The experimental results confirm that the vibration amplitude of the assembly phase with the minimum exciting force is smaller than the vibration amplitude under the random assembly phase at three-speed modes, and the optimization rate reached 73.2% at 9000 rpm, which proves the effectiveness of the assembly method in minimizing the exciting force.

The Geometric Error Measurement and Compensation for a Five-Axis Machining Center’s Tilting Rotary Table

The geometric error measurement and compensation for a five-axis machining center’s tilting rotary table is a difficult problem in the machine tool industry. Aiming at this problem, and based on a thorough study of the geometric error of a vertical five-axis machining center’s tilting rotary table, a method has been suggested in this paper to measure the geometric error of the tilting rotary table using the ball bar performing a three-axis circular interpolation. Eight center bias values in the X and Y directions were obtained by the use of four specific three-axis circular interpolation tests. According to the geometric relations of these four specific forms of circular tests, a geometric error separation model of the tilting rotary table was established. The process of circle test of A-axis and C-axis for vertical five-axis machining center is given in detail. The contrast tests, before and after compensation, were carried out in a vertical five-axis machining center. The experimental results showed that the positional errors and angular errors after compensation were much smaller than those before compensation. The positional error decreased from the maximum value of - 0.089 mm before compensation to the maximum value of - 0.004 mm, and the angle error decreased from the maximum value of - 0.012° before compensation to the maximum value of 0.002°. This method has provided an important reference for the geometric error measurement and compensation for a vertical five-axis machining center’s tilting rotary table.

Geometric Error Identification and Analysis of Rotary Axes on Five-Axis Machine Tool Based on Precision Balls

This paper presents the design of a precise “ball-column” device to efficiently and accurately measure the geometric error terms of both rotary axes of the five-axis machine tool. A geometric error measurement method of spherical contact was proposed based on the influence of the geometric error term from a five-axis machine tool rotating axis on the integrated geometric error of the machine tool. A multiple degree of freedom, step-by-step contact method based on on-machine measure for measuring the spherical center point is proposed, and the solution formula of each geometric error term of the rotating axis is established, respectively. This method can identify 12 geometric errors based on the influence of one rotating axis on another rotating axis after long term operation. The spatial error field of the five-axis machine tool was constructed by analyzing the error law of the two rotating axes of machine tools based on various positions and postures. Finally, after the comparison of the experiment, the results showed that the accuracy of the developed error measurement device reached 91.8% and the detection time was as short as 30–40 min.