Tool path planning is critical to fully realise the producing capabilities of multi-axis machine tools and improve the precision and efficiency in multi-axis machining. Up to now, more than 400 art...

A review on tool orientation planning in multi-axis machining

During five-axis CNC machining, the dynamic tracking error caused by imperfect servo dynamic performance is becoming the major factor affecting the accuracy during high-speed and high-precision manufacturing. The double ballbar (DBB) test is one of the commonly used dynamic performance tests, but existing DBB test methods do not have satisfactory test capability for the requirement of complex freeform surface machining. In this paper, on the basis of summarized of dynamic tracking error’s mechanism and characteristics, an improved dynamic performance test based on DBB, which is named the circle-8 test, is proposed. In this test, a provenly efficient RTCP test trajectory is used to rebuild the DBB test process, which includes complex movements of all the five motion axes. To exhibit the improvement of the circle-8 test, this test and the BK3 test of ISO standard, which is considered as a comparison, are conducted in a five-axis machine tool with a tilting rotary table. According to the simulation and experiment results, for common dynamic inaccuracy situations, the circle-8 test always has better sensitivity of dynamic performance test than BK3 test. The above-improved dynamic performance test can be applied to provide effective data for the research of modeling and error reduction of five-axis machine tools.

Dynamic performance test under complicated motion states for five-axis machine tools based on double ballbar

During five-axis CNC machining, the dynamic performance is the core factor to decide the efficiency and accuracy during high-speed and high-precision manufacturing. As a common method to detect dynamic performance of five-axis machine tools, measurement by using RTCP (Rotation Tool Centre Point) is always known as a better way than others with the advantages of high detection accuracy, variable detection trajectory and little interference. The key to effective detecting with RTCP function is the suitable trajectory, and in previous research, the 8-shape trajectory is proposed as an effective RTCP trajectory. In this paper, the 8-shape trajectory is adapted to machine tools with different rotary axes. The effects of the servo position gains, initial setup position, feed rate and on five-axis machine are shown in the simulation model, and the geometry and symmetry of the tool center point error trajectories are summarized to provide a guide to the improvement of dynamic performance.

RTCP Detection for Five-Axis CNC Machine Tool Dynamic Performance Based on 8-shape Trajectory

The improvement of ultra-precision machining technology has significantly boosted the demand for the surface quality and surface accuracy of the workpieces to be machined. However, the geometric shapes of workpiece surfaces cannot be adequately manufactured with simple plane, cylindrical, or spherical surfaces because of their different applications in various fields. In this research, a method was proposed to generate tool paths for the machining of complex spherical surfaces based on an ultra-precise five-axis turning and milling machine with a C-Y-Z-X-B structure. Through the proposed tool path generation method, ultra-precise complex spherical surface machining was achieved. First, the complex spherical surface model was modeled and calculated, and then it was combined with the designed model to generate the tool path. Then the tool paths were generated with a numerically controlled (NC) program. Based on an ultra-precision three-coordinate measuring instrument and a white light interferometer, the machining accuracy of a workpiece surface was characterized, and the effectiveness of the tool path generation method was verified. The surface roughness of the machined workpiece was less than 90 nm. Furthermore, the surface roughness within the spherical region appeared to be less than 30 nm. The presented tool path generation method in this research produced ultra-precision spherical complex surfaces. The method could be applied to complex spherical surfaces with other characteristics.

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Study of the tool path generation method for an ultra-precision spherical complex surface based on a five-axis machine tool

During five-axis CNC machining, the dynamic tracking error of the five-axis machine tool caused by imperfect servo dynamic performance is the major factor affecting the accuracy during high-speed a...

https://journals.sagepub.com/doi/pdf/10.1177/1687814020967573

An attempt to relate dynamic tracking error to occurring situation based on additional rectilinear motion for five-axis machine tools:

The five-axis machine tool has been extensively employed in complex curved surface machining area. The linkage performance of the machine tool is one of the key origins of the machining accuracy. An accuracy measurement based on RTCP (rotation tool center point) is an effective means for multi-axes motion synchronously linkage performance detection. In order to demonstrate the linkage performance more completely, an RTCP trajectory description method is presented, and some trajectories which take account of curvature and speed changes are proposed in this paper. The trajectory sensitivity analysis is applied to examine the sensitivity of RTCP measuring trajectories in mismatch parameters of the five-axis machine tool. Through comparative analysis, some RTCP measuring trajectories are more sensitive to certain error parameters than others. Therefore, the corresponding RTCP measuring trajectories are necessary for various linkage performances detection of the five-axis machine tool. For this purpose, RTCP measuring trajectory is optimized based on sensitivity analysis result. Finally, linkage performance detection experiments based on RTCP are conducted, and the tool tip errors vary for the different linkage performance and different RTCP trajectories, which is consistent with trajectory sensitivity analysis results. These results indicate that the corresponding RTCP measuring trajectories are necessary for various linkage performance detections. Therefore, the RTCP trajectory that is more favourable to detection could be put forward according to the requirements of the five-axis machine tool. Furthermore, series of RTCP trajectories can be combined to exhibit the linkage performance of five-axis machine tools more comprehensively.

Qichen Ding

Papers

Research on detection of the linkage performance for five-axis CNC machine tools based on RTCP trajectories combination