A super-precision machine tool B-axis milling high-precision tool setting method based on cutting straight grooves

Abstract

The present invention discloses a high-precision tool setting method for the B-axis milling of a super-precision machine tool based on cutting straight grooves. Two characteristic straight groove structures are machined on the workpiece surface by a diamond ball-end milling cutter, and the groove spacing and groove depth are measured under a high-precision probe profiler. The relationship between them and the tool setting errors ΔX and ΔZ and the B-axis swing arm is established, so as to correlate the relative transformation positions of any input coordinate points in the machine tool coordinate system, and finally complete the high-precision tool setting for the B-axis milling of the super-precision machine tool. It has the following advantages: First, the proposed method of cutting test straight grooves does not depend on the visual errors of operators and the errors of the equipment itself, and the obtained results are more objective; Second, based on the measurement of a high-precision probe profiler, the problem of limited range of traditional measurement methods can be overcome, and the measurement process is efficient and fast, and the data is intuitive and easy to process.

Description

Technical Field

[0001] The present invention relates to the field of ultra-precision machining technology, and particularly to a high-precision tool setting method for B-axis milling of an ultra-precision machine tool based on cutting straight grooves. Background Art

[0002] Ultra-precision machining can obtain high-performance optical surfaces and functional structures with sub-micron surface form accuracy, nano-scale surface texture, and nearly defect-free surface layers. At present, for high-precision and difficult-to-machine optical structure components, ultra-precision milling has become the forefront and trend of technological development due to its high surface quality, low manufacturing cost, good repeatability, etc. Among them, the B-axis of a multi-axis ultra-precision machine tool can accurately control the relative rotation angle between the tool and the workpiece. At the same time, the ultra-precision machining method based on the B-axis can realize the free rotation of the tool and the workpiece without interference, and can complete more complex curved surface optical components at one station, reducing the number of workpiece clamping times to ensure position accuracy. As an important factor affecting ultra-precision milling, the tool setting error of the B-axis will cause serious defects on the machined optical surface. For the tool setting of the B-axis in ultra-precision milling, the following steps are usually required to determine the relative position between the tool tip center and the B-axis center: First, calibrate the tool setting errors of the X-axis and Z-axis, and calculate the distance from the rotation center of the B-axis to the tool tip. Then, convert the coordinates of any point in the machining program to the machine tool coordinate system to determine the corresponding tool tip position, and finally achieve high-precision tool setting for B-axis milling of the ultra-precision machine tool. At present, the traditional methods are mainly the tool setting instrument method and the trial cutting and observation method. The tool setting instrument method uses computer vision technology to complete the detection of tool position parameters, uses a machine to replace the human eye for measurement and judgment, and processes the target information to obtain the relative position between the tool and the workpiece in the machine tool coordinate system. The trial cutting and observation method rotates the B-axis at different angles by the operator on the rotary table, and repeatedly cuts the workpiece surface in a cycle to calculate the tool offset vector until the tool setting zero point in the machine tool coordinate system is subjectively judged and calculated. For the tool setting of the B-axis in ultra-precision milling, it is very necessary to propose a high-precision tool setting method with high precision, high efficiency, and effectiveness.

[0003] The effectiveness of the traditional ultra-precision machine tool milling B-axis tool setting method has been widely verified, but there are still the following disadvantages: 1) The tool setting instrument method depends on the visual error of the operator and the error of the equipment itself, and is too dependent on the operator; 2) The tool setting instrument method is limited by the low resolution of the industrial camera and is interfered by the machine tool measurement environment and the vibration of the operating table, so it is difficult to achieve high-precision tool setting with sub-micron level position accuracy; 3) The trial cutting and observation method depends heavily on the technical level of the tool setter, the tool setting process has a long cycle, and the dynamic balance of the spindle needs to be adjusted for multiple workpiece installations, so the repeatability is low; 4) The trial cutting and observation method has a cumbersome process, and the positioning accuracy is easily reduced due to repeated clamping during the operation process, which in turn affects the machining quality of the optical surface. Summary of the Invention

[0004] To solve the problems existing in the prior art, the present invention aims to disclose a high-precision tool setting method for the B-axis milling of an ultra-precision machine tool based on cutting straight grooves, which can effectively improve the accuracy and feasibility in the tool setting process on the basis of ensuring the processing efficiency, and finally improve the surface quality of ultra-precision machining. To achieve this purpose, the present invention adopts the following technical solutions:

[0005] A high-precision tool setting method for the B-axis milling of an ultra-precision machine tool based on cutting straight grooves, comprising the following steps:

[0006] S1: Fix the workpiece on the C-axis of the ultra-precision machine tool through a chuck device and adjust the dynamic balance by relying on a dynamic balance device. Install the milling cutter and fix the milling axis on the B-axis. Realize the rough tool setting of the B-axis online through a tool setter. Rotate the B-axis based on the rough tool setting result and record the zero point as O, record the tip point as M, record the rotation center of the B-axis as N, and record the distance MN between the two, that is, the length of the B-axis swing arm as L. Record the tool setting errors along the X-axis and Z-axis as ΔX and ΔZ respectively;

[0007] S2: Finish milling the end face at a constant rotational speed w of the milling axis, find the Z-axis zero point in this state and record it as P, so as to eliminate the tool setting error ΔZ of the Z-axis. If △Z>0, the workpiece moves relative to the tool in the positive Z-axis direction by a distance △Z; if △Z<0, the workpiece moves relative to the tool in the negative Z-axis direction by a distance △Z. Record the distance OP from the rotation center O of the B-axis to the workpiece surface at this time as Zw;

[0008] S3: Maintain the constant rotational speed w of the milling axis, move the tool along the X-axis by LX with point O as the reference coordinate point, and mill the first straight groove at a cutting depth d in the positive X-axis direction at the position of the reference coordinate O point;

[0009] S4: After the first straight groove is processed, rotate the C-axis 180° clockwise, rotate the B-axis by an angle φ clockwise, and mill the second straight groove at a cutting depth d in the negative X-axis direction at this position;

[0010] S5: After the second straight groove is processed, remove the workpiece and clean it with alcohol and lint-free cloth, perform surface measurement on an ultra-precision measuring device, and process the measurement results in the relative coordinate system;

[0011] S6: Along the Z-axis direction, record the distance between the corresponding lowest points of the first straight groove and the second straight groove as D, and record the depths of the two grooves as d1 and d2 respectively. For the first straight groove, establish the relationship between the cutting depth d, the groove depth d1, the length L of the B-axis swing arm, and the distance Zw from the B-axis center to the workpiece surface, which is expressed as:

[0012] L = Zw - d + d1

[0013] For the second straight groove, record the groove depth as d2. Along the Z-axis direction, establish the relationship between the cutting depth d, the groove depth d2, the length L of the B-axis swing arm, the rotation angle φ of the B-axis, and the distance Zw from the B-axis center to the workpiece surface, which is expressed as:

[0014]

[0015] S7: Combine the formulas in S6, eliminate the distance Zw from the center of the B-axis to the workpiece surface, and solve for the length L of the B-axis swing arm, expressed as:

[0016]

[0017] S8: Along the X-axis direction, establish the relationship between the X-axis tool setting error ΔX, the tool moving distance LX, the distance D at the lowest point of the slot, the clockwise rotation angle φ of the B-axis and the B-axis swing arm length L, expressed as:

[0018]

[0019] The calculated ΔX is compensated into the machine tool system. If ΔX>0, the workpiece moves a distance ΔX relative to the tool in the positive direction of the X axis; if ΔX<0, the workpiece moves a distance ΔX relative to the tool in the negative direction of the X axis.

[0020] S9: After completing steps S1-S8, for any point of machine tool coordinates (X0, Z0), B axis swing angle α, calculate the corresponding transformation position (Xα, Zα), expressed as:

[0021]

[0022] The input coordinate points can be converted into the machine tool coordinate system in sequence to complete the high-precision tool setting for ultra-precision machine tool B-axis milling.

[0023] Furthermore, the suction cup in step S1 is a vacuum suction cup.

[0024] Furthermore, the workpiece material in step S1 is aluminum alloy.

[0025] Furthermore, the C-axis in the step S1 is an air spindle.

[0026] Furthermore, the dynamic balancing device in step S1 is a dynamic balancing instrument.

[0027] Furthermore, the tool setting instrument in step S1 is a CCD optical tool setting instrument.

[0028] Furthermore, the tool in step S1 is a diamond ball end milling cutter.

[0029] Furthermore, the milling spindle speed w in step S3 is 40000 rpm.

[0030] Furthermore, the cutting depth d of the milling axis in step S3 is 2 μm.

[0031] Furthermore, the ultra-precision measuring device in the step S5 is a probe-type profiler.

[0032] The beneficial effects of the present invention are as follows:

[0033] A high-precision tool setting method for B-axis milling of an ultra-precision machine tool based on cutting straight grooves disclosed by the present invention first realizes rough tool setting online and non-destructively based on an optical tool setter. Two characteristic straight groove structures are machined on the workpiece surface by a diamond ball-end milling cutter, and the groove spacing and groove depth are measured under a high-precision probe profiler, and the relationship between them and the tool setting errors ΔX and ΔZ and the B-axis swing arm is established, so as to associate the relative transformation positions of any input coordinate points in the machine tool coordinate system, and finally complete the high-precision tool setting for B-axis milling of the ultra-precision machine tool. It has the following advantages: First, the proposed method of cutting test straight grooves does not depend on the visual errors of the operator and the errors of the equipment itself, and the obtained results are more objective; Second, the measurement based on a high-precision probe profiler can break through the problem of limited range of traditional measurement methods, and the measurement process is efficient, fast and the data is intuitive and easy to process; Further, the proposed method only needs to perform a single cutting test, the tool setting process has a short cycle and avoids the problem of adjusting the dynamic balance of the main shaft required for multiple workpiece installations, so the repeatability is high. Importantly, this method can solve the problems of large errors and low repeatability of traditional methods, can realize high-precision tool setting for B-axis milling of ultra-precision machine tools, does not require multiple workpiece installations, has high efficiency and takes into account feasibility. Description of the Drawings

[0034] Figure 1 Schematic diagrams of steps 1 and 2 of a high-precision tool setting method for B-axis milling of an ultra-precision machine tool based on cutting straight grooves according to the present invention;

[0035] Figure 2 Schematic diagram of step 3 of a high-precision tool setting method for B-axis milling of an ultra-precision machine tool based on cutting straight grooves according to the present invention;

[0036] Figure 3 Schematic diagram of step 4 of a high-precision tool setting method for B-axis milling of an ultra-precision machine tool based on cutting straight grooves according to the present invention;

[0037] Figure 4 Schematic diagram of step 5 of a high-precision tool setting method for B-axis milling of an ultra-precision machine tool based on cutting straight grooves according to the present invention;

[0038] Figure 5 Schematic diagrams of steps 6 and 7 of a high-precision tool setting method for B-axis milling of an ultra-precision machine tool based on cutting straight grooves according to the present invention;

[0039] Figure 6 Schematic diagrams of steps 8 and 8 of a high-precision tool setting method for B-axis milling of an ultra-precision machine tool based on cutting straight grooves according to the present invention.

[0040] Figure 7 Schematic diagram of steps 8 and 9 of a high-precision tool setting method for the B-axis milling of an ultra-precision machine tool based on cutting straight grooves according to the present invention.

[0041] In the figure: 1, workpiece; 2, milling cutter; 3, first straight groove; 4, second straight groove; 5, probe-type profiler. Specific embodiments

[0042] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to embodiments and drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0043] Please refer to Figures 1-7 , the present invention discloses a high-precision tool setting method for the B-axis milling of an ultra-precision machine tool based on trial cutting grooves, including the following steps:

[0044] As Figure 1 shown, S1: Fix the workpiece 1 on the C-axis of the ultra-precision machine tool through a chuck device and adjust the dynamic balance by relying on a dynamic balance device. Install the milling cutter 2 and fix the milling axis on the B-axis. Realize rough tool setting for the B-axis online through a tool setting instrument. Rotate the B-axis based on the rough tool setting result and record the zero point as O, record the tip point as M, record the rotation center of the B-axis as N, and record the distance MN between the two, that is, the length of the B-axis swing arm, as L. Record the tool setting errors along the X-axis and Z-axis as ΔX and ΔZ respectively;

[0045] As Figure 1 shown, S2: Finish milling the end face at a constant rotational speed w of the milling axis, find the Z-axis zero point in this state and record it as P, so as to eliminate the tool setting error ΔZ of the Z-axis. If △Z>0, the workpiece 1 moves relative to the tool 2 in the positive Z-axis direction by a distance △Z; if △Z<0, the workpiece 1 moves relative to the tool 2 in the negative Z-axis direction by a distance △Z. Record the distance OP from the rotation center O of the B-axis to the workpiece surface at this time as Zw;

[0046] As Figure 2 shown, S3: Maintain the constant rotational speed w of the milling axis, move the tool along the X-axis by LX with point O as the reference coordinate point, and mill the first straight groove 3 at a cutting depth d in the positive X-axis direction at this position;

[0047] As Figure 3 shown, S4: After the first straight groove 1 is processed, rotate the C-axis clockwise by 180°, and rotate the B-axis clockwise by an angle Mill the second straight groove 4 at a cutting depth d in the negative X-axis direction at this position;

[0048] As Figure 4 shown, S5: After the second straight groove 2 is processed, remove the workpiece and clean it with alcohol and a dust-free cloth, perform surface measurement on the ultra-precision measuring device 5, and process the measurement results in the relative coordinates;

[0049] As Figure 5 shown, S6: Along the Z-axis direction, the distance at the lowest point of the first straight groove 3 and the second straight groove 4 is denoted as D, and the depths of the two grooves are denoted as d1 and d2 respectively. For the first straight groove 3, establish the relationship between the cutting depth d, the groove depth d1, the length L of the B-axis swing arm, and the distance Zw from the center of the B-axis to the workpiece surface, expressed as:

[0050] L = Zw - d + d1

[0051] For the second straight groove 4, the groove depth is denoted as d2. Along the Z-axis direction, establish the relationship between the cutting depth d, the groove depth d2, the length L of the B-axis swing arm, the rotation angle of the B-axis

[0052]

[0053] As Figure 5 shown, S7: Combine the formulas in S6, eliminate the distance Zw from the center of the B-axis to the workpiece surface, and solve for the length L of the B-axis swing arm, expressed as:

[0054]

[0055] As Figure 6 shown, S8: Along the X-axis direction, establish the relationship between the X-axis tool setting error ΔX, the tool movement distance LX, the distance D at the lowest point of the groove, the clockwise rotation angle of the B-axis

[0056]

[0057] Compensate the calculated ΔX into the machine tool system. If △X > 0, the workpiece 1 moves a distance △X in the positive X-axis direction relative to the tool 2; if △X < 0, the workpiece 1 moves a distance △X in the negative X-axis direction relative to the tool 2.

[0058] As Figure 7 shown, S9: After completing steps S1 - S8, for any machine tool coordinate (X0, Z0) and the swing angle α of the B-axis, calculate the corresponding transformed position (Xα, Zα), expressed as:

[0059]

[0060] Successively convert the input coordinate points into the machine tool coordinate system to complete the high-precision tool setting for the B-axis milling of the ultra-precision machine tool.

[0061] The suction cup selected in the present invention is a vacuum suction cup, which fixes the workpiece to be processed by vacuum adsorption and enables the workpiece to rotate with the rotating C-axis. This method is simple and convenient to operate, has stable and reliable adsorption, and has no damage to the surface of the workpiece and other advantages.

[0062] The C-axis selected in the present invention is an air spindle, which relies on a sliding bearing with air as a lubricant and has the characteristics of small viscosity compared to oil, high temperature resistance, and no pollution. Therefore, it can be used in high-speed machines, instruments, and radioactive devices. The air spindle provides extremely high radial and axial rotation accuracy. Since there is no mechanical contact, the degree of wear is minimized, thus ensuring that the accuracy always remains stable. The dynamic balancing device selected in the present invention is a dynamic balancer, which is a precise adjustment of the machine tool through dynamic balancing technology to achieve the best processing effect. It can effectively reduce the vibration interference during the machining process of the machine tool, make the machine tool run more smoothly during operation, thereby improving the machining accuracy and efficiency of the machine tool. The dynamic balancing technology of the machine tool is crucial in the field of high-precision machining.

[0063] Specifically, the material of the workpiece 1 is aluminum alloy. This material is easy to obtain and has excellent cutting performance, high toughness, no deformation after machining, and dense and defect-free material. It is a common material in the field of ultra-precision machining. The tool selected is a diamond ball-end milling cutter 2. The diamond tool has high hardness, good wear resistance, low thermal expansion coefficient, and a very long service life; the diamond ball-end milling cutter has a stable cutting state during machining and can obtain better surface quality of the straight groove.

[0064] In the present invention, optical tool setting is used for rough tool setting. This method uses CCD camera imaging and has the advantages of high efficiency and no damage to the tool. The cutting depths of the first straight groove 3 and the second straight groove 4 are the same, aiming to make the lowest point standards corresponding to these two grooves the same when measured by the measuring device, which is convenient for obtaining the measurement results and conducive to data processing.

[0065] The measuring device in the present invention is a probe profilometer 5, which is a probe contact type ultra-precision measuring instrument. The probe profilometer can achieve a vertical resolution at the sub-nanometer level, can adapt to groove profiles with obvious curvature changes and large aspect ratios, and is very suitable for the measurement of ultra-precision machined parts.

[0066] Ultra-precision fine tool setting is carried out by the above method: First, the method of the proposed diamond ball end mill 2 for trial cutting the first straight groove 3 and the second straight groove 4 on the workpiece 1 does not depend on the visual error of the operator and the error of the equipment itself, and the obtained results are more objective; Second, based on the measurement of the high-precision probe profilometer 5, the problem of limited range of traditional measurement methods can be overcome, the measurement process is efficient and fast, and the data is intuitive and easy to process; Further, the proposed method only needs to carry out single trial cutting, the tool setting process has a short cycle and avoids the problem of adjusting the dynamic balance of the spindle required for multiple workpiece installations, so the repeatability is high. Importantly, this method can solve the problems of large error and low repeatability of traditional methods, can realize high-precision tool setting for B-axis milling of ultra-precision machine tools, does not require multiple workpiece installations, has high efficiency and takes into account feasibility.

[0067] The above is the embodiment of the present invention. The above embodiments and the specific parameters in the embodiments are only for clearly expressing the invention verification process, and are not used to limit the patent protection scope of the present invention. The patent protection scope of the present invention still takes its claims as the criterion. Any equivalent structural changes made by using the content of the specification and drawings of the present invention should also be included in the protection scope of the present invention by the same token.

Claims

1. A high-precision tool setting method for the B-axis milling of a ultra-precision machine tool based on cutting straight grooves, characterized in that: It includes the following steps: S1: Fix the workpiece on the C-axis of the ultra-precision machine tool through the suction cup device and adjust the dynamic balance by relying on the dynamic balance device. Install the milling cutter and fix the milling shaft on the B-axis. Realize the rough alignment of the B-axis online through the tool setter. Based on the rough alignment result, rotate the B-axis and record the zero point as O, record the tip point as M, record the rotation center of the B-axis as N, and record the distance MN between the two, that is, the length of the B-axis swing arm as L. Record the alignment errors along the X-axis and Z-axis as ΔX and ΔZ respectively; S2: Milling the end face with a constant rotational speed w of the milling shaft, find the Z-axis zero point in this state and record it as P to eliminate the Z-axis alignment error ΔZ. If △Z>0, the workpiece moves a distance △Z relative to the tool in the positive direction of the Z-axis; if △Z<0, the workpiece moves a distance △Z relative to the tool in the negative direction of the Z-axis. Record the distance OP from the rotation center O of the B-axis to the workpiece surface at this time as Zw; S3: Maintain the constant rotational speed w of the milling shaft, move the tool along the X-axis by LX with point O as the reference coordinate point, and mill the first straight groove along the positive direction of the X-axis at the reference coordinate point O with a cutting depth d; S4: After the first straight groove is processed, rotate the C-axis 180° clockwise, rotate the B-axis by an angle φ clockwise, and mill the second straight groove along the negative direction of the X-axis at this position with a cutting depth d; S5: After the second straight groove is processed, remove the workpiece and clean it with alcohol and lint-free cloth, perform surface measurement on the ultra-precision measurement equipment, and process the measurement results in the relative coordinates; S6: Along the Z-axis direction, record the distance between the lowest points of the corresponding grooves of the first straight groove and the second straight groove as D, and record the depths of the two grooves as d1 and d2 respectively. For the first straight groove, establish the relationship between the cutting depth d, the groove depth d1, the length L of the B-axis swing arm, and the distance Zw from the B-axis center to the workpiece surface, which is expressed as: L = Zw - d + d1 For the second straight groove, record the groove depth as d2. Along the Z-axis direction, establish the relationship between the cutting depth d, the groove depth d2, the length L of the B-axis swing arm, the rotation angle φ of the B-axis, and the distance Zw from the B-axis center to the workpiece surface, which is expressed as: S7: Combine the formulas in S6, eliminate the distance Zw from the B-axis center to the workpiece surface, and solve for the length L of the B-axis swing arm, which is expressed as: S8: Along the X-axis direction, establish the relationship between the X-axis alignment error ΔX, the tool movement distance LX, the distance D at the lowest point of the groove, the rotation angle φ of the B-axis clockwise, and the length L of the B-axis swing arm, which is expressed as: Compensate the calculated ΔX into the machine tool system. If △X>0, the workpiece moves a distance △X relative to the tool in the positive direction of the X-axis; if △X<0, the workpiece moves a distance △X relative to the tool in the negative direction of the X-axis. S9: After completing steps S1 - S8, for any machine tool coordinate (X0, Z0) and the swing angle α of the B-axis, calculate the corresponding transformation position (Xα, Zα), which is expressed as: Convert the input coordinate points to the machine tool coordinate system in sequence to complete the high-precision alignment of the B-axis milling of the ultra-precision machine tool.

2. A high-precision alignment method for B-axis milling of an ultra-precision machine tool based on cutting straight grooves according to claim 1, characterized in that: The suction cup in step S1 is a vacuum suction cup.

3. A high-precision tool setting method for B-axis milling of an ultra-precision machine tool based on cutting straight grooves according to claim 1, characterized in that: The workpiece material in the step S1 is aluminum alloy.

4. A high-precision tool setting method for B-axis milling of an ultra-precision machine tool based on cutting straight grooves according to claim 1, characterized in that: The C-axis in the step S1 is an air spindle.

5. A high-precision tool setting method for B-axis milling of an ultra-precision machine tool based on cutting straight grooves according to claim 1, characterized in that: The dynamic balancing device in the step S1 is a dynamic balancer.

6. A high-precision tool setting method for B-axis milling of an ultra-precision machine tool based on cutting straight grooves according to claim 1, characterized in that: The tool setting instrument in the step S1 is a CCD optical tool setting instrument.

7. A high-precision tool setting method for B-axis milling of an ultra-precision machine tool based on cutting straight grooves according to claim 1, characterized in that: The cutting tool in the step S1 is a diamond ball-end milling cutter.

8. A high-precision tool setting method for B-axis milling of an ultra-precision machine tool based on cutting straight grooves according to claim 1, characterized in that: The rotational speed w of the milling axis in the step S3 is 40000 rpm.

9. A high-precision tool setting method for B-axis milling of an ultra-precision machine tool based on cutting straight grooves according to claim 1, characterized in that: The cutting depth d of the milling axis in the step S3 is 2 μm.

10. A high-precision tool setting method for B-axis milling of an ultra-precision machine tool based on cutting straight grooves according to claim 1, characterized in that: The ultra-precision measuring device in the step S5 is a probe-type profilometer.

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