Multi-point RTCP detection method for spatial precision recession of large-scale gantry five-axis machine tool

Abstract

The invention discloses a multi-point RTCP detection method for spatial precision decline of a large-scale gantry five-axis machine tool. The method comprises the following steps: S1, determining timing detection time and a preset rotation analyzer ball head fixing position; assuming that the space precision of the machine tool is detected for N times in the whole machining process, equally dividing the complete machining cycle T to obtain timing detection time T / N; according to the machine tool workbench range occupied by the machined workpiece and the preset machining path, rotating analyzer balls are evenly fixed to the non-machining area of a workbench; s2, determining an RTCP detection track; and S3, the ball head is detected according to the machining path, whether the space precision meets the machining requirement or not is judged, if yes, compensation is not carried out, otherwise, compensation is carried out, and then machining and detection are continued till machining is finished. According to the multi-point RTCP detection method for the spatial precision decline of the large gantry five-axis machine tool, the preset ball heads are fixed at multiple points on the workbench, the wireless measurement probe is added into the machine tool magazine, machining is stopped at regular time, and RTCP detection is carried out.

Description

Technical Field

[0001] The invention belongs to the technical field of RTCP detection of five-axis CNC machine tools, and in particular relates to a multi-point RTCP detection method for spatial precision decay of large gantry five-axis machine tools. Background Art

[0002] The spatial accuracy of a five-axis machine tool refers to the ability of the machine tool to accurately control the position and posture of the tool relative to the workpiece in three-dimensional space, which is affected by the machine tool structure, transmission system, control system, and tool system. During processing, thermal deformation, force deformation, component wear and aging, and vibration will cause the spatial accuracy of the AC double-swing head five-axis gantry machine tool to decline, so it is necessary to continuously measure during the processing process to determine whether the spatial accuracy meets the processing requirements.

[0003] The RTCP (Rotation Tool Center Point) function of a five-axis machine tool is a programming technique commonly used in five-axis linkage machining. This function changes the process of interpolation calculations so that the tool center point can perform precise rotational motion around the workpiece, allowing programmers to use the tool center point as a programming reference point to set the tool path without considering the actual swing angle of the tool and the specific motion model of the machine tool. Based on this function, an RTCP detection method for detecting the spatial accuracy of machine tools has been developed, that is, the tool tip point position is fixed through the written detection driver, and the tool axis center is allowed to perform five-axis linkage on a predetermined trajectory, an "8"-shaped RTCP detection trajectory, and then various detection equipment are used to detect the offset of the tool tip point to achieve the measurement of the five-axis linkage spatial error.

[0004] Taking the AC double-swing head five-axis machine tool as an example, after turning on the RTCP function, the coordinate conversion relationship between the tool tip point and the tool axis point is:

[0005]

[0006] Where L is the distance from the tool tip to the tool axis, (X, Y, Z) is the coordinate of the tool tip, (X axis , Y axis , Z axis ) is the coordinate of the tool axis point.

[0007] The wireless rotation analyzer is mainly composed of a ball head on the machine tool workbench and a wireless measuring probe inserted into the spindle. Users can customize the device to carry out multi-axis testing. Its measurement principle is the same as that of the rotation detector. During measurement, the ball head representing the workpiece is used as a reference to measure the probe path representing the tool center point (TCP). In this way, the error in the cutting path can be directly measured and intuitively presented in three dimensions: x, y, and z. The ball head can be placed with the help of a magnetic base, and the probe can be placed in the tool chain for call and measurement operations when needed.

[0008] The existing measurement methods all stop processing at intervals during the processing and use non-cutting instruments to measure the spatial error. These detection methods require repeated disassembly and assembly of the detection equipment, which is troublesome to measure. At the same time, the detection process has the problems of low detection efficiency and high detection cost. Summary of the invention

[0009] The purpose of the present invention is to solve the above problems and provide a multi-point RTCP detection method for spatial precision degradation of large gantry five-axis machine tools with high detection efficiency and convenient inspection.

[0010] In order to solve the above technical problems, the technical solution of the present invention is: a multi-point RTCP detection method for spatial precision decay of a large gantry five-axis machine tool, comprising the following steps:

[0011] S1, determine the timing detection time and preset the fixed position of the rotating analyzer ball head;

[0012] Assuming that the spatial accuracy of the machine tool is tested N times during the entire machining process, the complete machining cycle T is evenly divided to obtain the timing detection time T / N; according to the range of the machine tool worktable occupied by the workpiece to be machined and the predetermined machining path, the rotating analyzer ball head is evenly fixed in the non-machining area of ​​the worktable;

[0013] S2, determine the RTCP detection trajectory;

[0014] S3. Detect the ball head according to the processing path to determine whether the spatial accuracy meets the processing requirements. If it does, no compensation is made. Otherwise, compensation is made. Then continue processing and detection until the processing is completed.

[0015] Furthermore, the preset position of the ball head of the rotary analyzer in S1 needs to leave space for performing the RTCP test with the contour of the workpiece to avoid collision between the tool movement and the workpiece during detection.

[0016] Furthermore, the preset number of the rotating analyzer ball heads in S1 is N.

[0017] Furthermore, the step S2 is specifically as follows: selecting a detection trajectory with good detection performance as the RTCP detection trajectory of all ball heads, the detection trajectory is composed of a finite number of points, and a short stop is made at each point to ensure that the wireless rotation analyzer can collect stable error data.

[0018] Furthermore, the detection trajectory in step S2 is an "8"-shaped detection trajectory. The "8"-shaped detection trajectory is selected as the RTCP detection trajectory of all ball heads in consideration of the influence of the detection trajectory on the accuracy of the detection error; the 8-shaped trajectory is composed of the A-axis and C-axis angles of the machine tool at a finite number of points, and a short stop is made at each point to ensure that the wireless rotation analyzer can collect stable error data. The 8-shaped trajectory function expression used is:

[0019]

[0020] Among them, ρ1, ρ2 are the swing amplitudes of A and C, ω is the frequency of the trigonometric function, is the initial phase of A and C. When selecting these values, avoid making A and C exceed the machine tool limit.

[0021] Furthermore, step S3 is specifically as follows: according to the processing path and the timed detection time plan, the processing is stopped at a fixed time, the tool is replaced with a wireless measuring probe in the tool magazine, and the tool tip is moved to the top of the corresponding ball head to carry out low-speed RTCP detection. At this time, it can be considered that the tool tip deviation is mainly caused by the spatial error; the measurement result of the wireless rotation analyzer in the detection trajectory is the deviation Δx in the three directions of the machine tool coordinate system X, Y, and Z i , Δy i , Δz i (i=1,...,n), and the conversion relationship between the spatial errors of each axis:

[0022]

[0023] Where K x ,K y ,K z ,K A ,K C is the error coefficient matrix of each axis, R x ,R y ,R z ,R A ,R C is the error matrix composed of the error terms related to the 6 positions of each axis; for the detection trajectory of each ball head position, there are N point deviations (Δx i , Δy i , Δz i ). The comprehensive deviation of each point is defined as:

[0024]

[0025] The spatial error of the ball head position is defined as:

[0026]

[0027] Define the spatial error threshold of the machining process as ε r , ε r The size needs to be adjusted according to actual processing requirements.

[0028] Get spatial error After that, it is determined whether it meets the processing requirements; if not, compensation is required; then the processing continues, and the inspection is repeated according to the predetermined inspection time plan until the entire processing cycle is completed.

[0029] The beneficial effects of the present invention are:

[0030] 1. The multi-point RTCP detection method for the spatial precision degradation of large gantry five-axis machine tools provided by the present invention uses a wireless rotation analyzer to carry out RTCP detection, fixes a preset ball head at multiple points on the workbench, adds a wireless measurement probe to the machine tool magazine, stops processing at a fixed time, and carries out RTCP detection. A multi-point RTCP detection method for the spatial precision degradation of large gantry five-axis machine tools is proposed.

[0031] 2. The present invention solves the problems of low detection efficiency and high detection cost in the detection process of the prior art.

[0032] 3. Compared with the detection method of the prior art, the detection method of the present invention only needs to fix the preset rotating analyzer ball head at multiple points before processing, and add the wireless probe to the tool magazine to realize multi-point error detection in the entire processing cycle. This method does not need to install the detection instrument before each detection, thereby greatly improving the detection efficiency, simplifying the detection process, and reducing the detection cost.

[0033] 4. The present invention effectively avoids the detection uncertainty that may be introduced due to repeated installation of the detection instrument, and further improves the accuracy and reliability of the detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a flow chart of a multi-point RTCP detection method for spatial precision decay of a large gantry five-axis machine tool according to the present invention.

[0035] Figure 2 It is a structural schematic diagram of the rotary analyzer of the present invention;

[0036] Figure 3 It is a schematic diagram of the layout of the ball head of the multi-point fixed rotating analyzer in the non-processing area of ​​the workbench of the present invention;

[0037] Figure 4 It is a schematic diagram of the "8"-shaped detection trajectory adopted by the present invention. DETAILED DESCRIPTION

[0038] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments:

[0039] like Figures 1 to 4 As shown, the present invention provides a multi-point RTCP detection method for spatial precision decay of a large gantry five-axis machine tool, comprising the following steps:

[0040] S1. Determine the timing detection time and preset the fixed position of the rotating analyzer ball head.

[0041] Assuming that the spatial accuracy of the machine tool is tested N times during the entire machining process, the complete machining cycle T is evenly divided to obtain the timing detection time T / N. The preset number of the rotating analyzer ball heads in S1 is N. According to the range of the machine tool worktable occupied by the workpiece and the predetermined machining path, the rotating analyzer ball heads are evenly fixed in the non-machining area of ​​the worktable.

[0042] The structure of the rotating analyzer in S1 is as follows Figure 2 An example of a multi-point fixed rotating analyzer ball head layout is shown in Figure 3 As shown in the figure, the spatial accuracy of the machine tool is determined by detecting the deviation between the actual position of the ball head and the RTCP programmed position. The preset position of the ball head needs to leave space for RTCP testing with the workpiece contour to avoid collision between the tool movement and the workpiece during detection.

[0043] S2. Determine the RTCP detection trajectory.

[0044] S2 is specifically: select a detection trajectory with good detection performance as the RTCP detection trajectory of all ball heads. The detection trajectory consists of a finite number of points, and it will stay at each point for a short time to ensure that the wireless rotation analyzer can collect stable error data.

[0045] The detection trajectory in step S2 is an "8"-shaped detection trajectory, such as Figure 4 As shown in the figure, the "8"-shaped detection trajectory is selected as the RTCP detection trajectory of all ball heads in consideration of the influence of the detection trajectory on the accuracy of the detection error; the 8-shaped trajectory is composed of the machine tool A-axis and C-axis angles at a limited number of points, and it stays briefly at each point to ensure that the wireless rotation analyzer can collect stable error data. The 8-shaped trajectory function expression used is:

[0046]

[0047] Among them, ρ1, ρ2 are the swing amplitudes of A and C, ω is the frequency of the trigonometric function, is the initial phase of A and C. When selecting these values, avoid making A and C exceed the machine tool limit.

[0048] S3. Detect the ball head according to the processing path to determine whether the spatial accuracy meets the processing requirements. If it does, no compensation is made. Otherwise, compensation is made. Then continue processing and detection until the processing is completed.

[0049] Step S3 is as follows: according to the machining path and the timed detection time plan, the machining is stopped at a fixed time, the tool is replaced with a wireless measuring probe in the tool magazine, and the tool tip is moved to the top of the corresponding ball head to carry out low-speed RTCP detection. At this time, it can be considered that the tool tip deviation is mainly caused by the spatial error; the measurement result of the wireless rotation analyzer in the detection trajectory is the deviation Δx in the three directions of the machine tool coordinate system X, Y, and Z. i , Δy i , Δz i (i=1,...,b), and the conversion relationship between the spatial errors of each axis:

[0050]

[0051] Where K x ,K y ,K z ,K A ,K C is the error coefficient matrix of each axis, R x ,R y ,R z ,R A ,R C is the error matrix composed of the error terms related to the 6 positions of each axis; for the detection trajectory of each ball head position, there are N point deviations (Δx i , Δy i , Δz i ). The comprehensive deviation of each point is defined as:

[0052]

[0053] The spatial error of the ball head position is defined as:

[0054]

[0055] Define the spatial error threshold of the machining process as ε r , ε r The size needs to be adjusted according to actual processing requirements.

[0056] Get spatial error After that, with the threshold ε r Compare and determine whether it meets the processing requirements; if not, compensation is required; then continue processing and repeatedly inspect according to the predetermined inspection time plan until the entire processing cycle is completed.

[0057] The present invention aims at the problem that the spatial accuracy of large gantry five-axis machine tools declines and the detection efficiency of the prior art detection process is low. The present invention fixes preset ball heads at multiple points on the workbench, adds wireless measuring probes to the machine tool magazine, stops processing at regular intervals and conducts detection to determine whether the spatial accuracy meets the processing requirements, thereby achieving the purpose of rapid detection without repeatedly disassembling and assembling the detection equipment during the processing, simplifying the detection process and improving the detection efficiency. The present invention fixes preset ball heads at multiple points on the non-processing path before processing, without the need for repeated disassembly and assembly during the processing, and can achieve rapid detection of spatial accuracy during the processing. During the entire processing cycle, the detection efficiency of spatial accuracy can be improved by targeted selection of the number of preset ball heads and the spatial positions of the ball heads.

[0058] Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the principles of the present invention, and should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific variations and combinations that do not deviate from the essence of the present invention based on the technical revelations disclosed by the present invention, and these variations and combinations are still within the protection scope of the present invention.

Claims

1. A multi-point RTCP detection method for spatial precision decay of large gantry five-axis machine tools, characterized in that: The following steps are involved: S1, determine the timing detection time and preset the fixed position of the rotating analyzer ball head; Assuming that the spatial accuracy of the machine tool is tested N times during the entire machining process, the complete machining cycle T is evenly divided to obtain the timing detection time T / N; according to the range of the machine tool worktable occupied by the workpiece to be machined and the predetermined machining path, the rotating analyzer ball head is evenly fixed in the non-machining area of ​​the worktable; S2, determine the RTCP detection trajectory; S3. Detect the ball head according to the processing path to determine whether the spatial accuracy meets the processing requirements. If it does, no compensation is made. Otherwise, compensation is made. Then continue processing and detection until the processing is completed.

2. The multi-point RTCP detection method for spatial precision decay of a large gantry five-axis machine tool according to claim 1, characterized in that: The preset position of the ball head of the rotary analyzer in S1 needs to leave space for conducting the RTCP test with the workpiece contour to avoid collision between the tool movement and the workpiece during detection.

3. The multi-point RTCP detection method for spatial precision decay of a large gantry five-axis machine tool according to claim 1, characterized in that: The preset number of the rotating analyzer ball heads in S1 is N.

4. The multi-point RTCP detection method for spatial precision decay of a large gantry five-axis machine tool according to claim 1, characterized in that: The step S2 specifically includes: selecting a detection trajectory with good detection performance as the RTCP detection trajectory of all ball heads, the detection trajectory is composed of a finite number of points, and a short stop is made at each point to ensure that the wireless rotation analyzer can collect stable error data.

5. The multi-point RTCP detection method for spatial precision decay of a large gantry five-axis machine tool according to claim 1, characterized in that: The detection trajectory in step S2 is an "8"-shaped detection trajectory. The "8"-shaped detection trajectory is selected as the RTCP detection trajectory of all ball heads in consideration of the influence of the detection trajectory on the accuracy of the detection error; the 8-shaped trajectory is composed of the A-axis and C-axis angles of the machine tool at a finite number of points, and a short stop is made at each point to ensure that the wireless rotation analyzer can collect stable error data.

6. The multi-point RTCP detection method for spatial precision decay of a large gantry five-axis machine tool according to claim 1, characterized in that: The step S3 is specifically as follows: according to the processing path and the timed detection time plan, the processing is stopped at a fixed time, the tool is replaced with a wireless measuring probe in the tool magazine, and the tool tip is moved to the top of the corresponding ball head, and a low-speed RTCP detection is performed. At this time, it can be considered that the tool tip deviation is mainly caused by the spatial error; the measurement result of the wireless rotation analyzer in the detection trajectory is the deviation Δx in the three directions of the machine tool coordinate system X, Y, and Z i , Δy i , Δz i (i=1,...,n), and the conversion relationship between the spatial errors of each axis: Where K x ,K y ,K z ,K A ,K C is the error coefficient matrix of each axis, R x ,R y ,R z ,R A ,R C is the error matrix composed of the error terms related to the 6 positions of each axis; for the detection trajectory of each ball head position, there are N point deviations (Δx i , Δy i , Δz i ); define the comprehensive deviation of each point as: The spatial error of the ball head position is defined as: Define the spatial error threshold of the machining process as ε r , ε r The size needs to be adjusted according to actual processing requirements; Get spatial error After that, it is determined whether it meets the processing requirements; if not, compensation is required; then the processing continues, and the inspection is repeated according to the predetermined inspection time plan until the entire processing cycle is completed.

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