An in-situ measurement tool changing method and device based on optical microscopy and displacement sensing

Abstract

The present invention discloses an in-situ tool change method and device based on optical microscopy and displacement sensing, including the steps of: recording the machine coordinates when the initial tool is on the surface of the workpiece to be machined; driving the initial tool to leave a machining tool mark on the surface of the auxiliary workpiece, and recording the coordinate points of the machine tool and the readings of the linear displacement sensor; using the initial tool to machine the workpiece to be machined, checking the readings of the linear displacement sensor and comparing them with the initial readings, and replacing the tool when the two are not equal; recording the data of the new tool, comparing it with the data of the initial tool, compensating for the errors in the three linear axis directions respectively through the machine tool program, moving the machine tool to the initial coordinates and then using the new tool for splicing machining; repeating the above steps, infinite tool changes can be carried out with the coordinate P2 and the reading L2 of the linear displacement sensor as the unified positioning reference. The tool change method and device of the present invention have high tool change accuracy, will not damage the surface of the workpiece to be machined, and have a unified positioning reference between multiple tool changes.

Description

Technical Field

[0001] The present invention relates to the technical field of ultra-precision cutting processing, and particularly to an in-situ measurement tool change method and device based on optical microscopy and displacement sensing. Background Art

[0002] When ultra-precision machining ultra-large area or ultra-hard materials, tool wear is an inevitable problem. Tool wear will lead to a decline in the machining quality of the workpiece to be machined, and may even lead to machining failure. Tool change and splicing machining is one of the effective means to solve the problem of the decline in machining quality caused by tool wear. Tool change and splicing machining refers to replacing a new tool identical to the initial tool after the initial tool wears, and then continuing the relay machining at the place where the initial tool has worn. However, due to the installation and positioning errors of the tool, it is impossible to make the tip of the new tool completely coincide with the tip of the initial tool, making it difficult to complete the micro-structure surface splicing machining with high quality and high uniformity after tool change. Therefore, solving the technical problem that it is impossible to continue machining due to the position difference of the tool tips after tool change can meet the key technical requirements of high-quality and highly consistent ultra-precision tool change and splicing machining of the micro-structure surface of ultra-large area or ultra-hard materials. The existing technology mainly uses the trial cutting method or a specific tool change tool holder method to complete the tool change operation, and then performs tool change and splicing machining.

[0003] The principle of the trial cutting method is to perform trial cutting on the surface of the workpiece to be machined each time a tool is changed. By measuring the machining marks left by the tip of the tool on the surface of the workpiece to be machined, and then continuously adjusting the relative position between the tool and the workpiece, so as to realize the tool change and splicing machining of the new tool. However, this method will damage the surface of the workpiece to be machined during multiple tool changes, greatly affecting the machining quality of the micro-structure on the surface of the workpiece to be machined. At the same time, there is no unified positioning reference between multiple tool changes, which will affect the machining consistency of the micro-structure on the surface of the workpiece to be machined. Therefore, the trial cutting method cannot meet the key technical requirements of high-quality and highly consistent ultra-precision tool change and splicing machining of the micro-structure surface.

[0004] The specific tool change tool holder method is to install multiple tools on a specific tool holder, and replace the machining tool through the rotating pair of the specific tool holder. However, when replacing the machining tool through the rotating pair, this method ignores the inevitable and non-negligible rotating pair error, which is a random error and is difficult to measure and compensate. At the same time, it is necessary to perform tool setting operations on all the machining tools on the specific tool holder before machining, and the process is relatively cumbersome. In addition, the specific tool holder can only install a limited number of machining tools, that is, the specific tool change tool holder method can only replace a limited number of tools. If the limited number of machining tools installed on the specific tool holder cannot complete the machining task, it is impossible to continue the tool change and splicing machining. Therefore, the specific tool change tool holder method cannot meet the requirements of high-precision and infinite tool change and splicing machining in the ultra-precision machining of ultra-large area or ultra-hard materials.

[0005] Existing technologies such as the existing trial cutting method or the specific tool changing turret method can complete the tool changing operation to a certain extent, but they all have the disadvantages of low tool changing accuracy, damaging the surface of the workpiece to be machined, and lacking a unified positioning reference between multiple tool changes. Therefore, they cannot meet the key technical requirements of high-quality and highly consistent infinite ultra-precision tool changing and splicing machining for ultra-large area or super-hard material micro-structure surfaces. Summary of the Invention

[0006] The purpose of the present invention is to provide an in-situ measurement tool changing method and device based on optical microscopy and displacement sensing to solve the problems existing in the above-mentioned existing technologies, with high tool changing accuracy, not damaging the surface of the workpiece to be machined, and having a unified positioning reference between multiple tool changes.

[0007] To achieve the above purpose, the present invention provides the following solutions:

[0008] The present invention provides an in-situ measurement tool changing method based on optical microscopy and displacement sensing. Based on the combination of a linear variable differential transformer (LVDT) and an optical microscope, it can achieve high-quality and highly consistent ultra-precision tool changing and splicing machining for ultra-large area or super-hard material micro-structure surfaces, specifically including the following steps:

[0009] Step 1: Perform initial tool alignment and record the machine tool coordinate P1 when the tip of the initial tool is on the surface of the workpiece to be machined.

[0010] Step 2: Drive the initial tool to leave a machining tool mark on the surface of the auxiliary workpiece, then move the machine tool linear axis to make the tip of the initial tool abut against the probe ball of the linear displacement sensor, and record the machine tool coordinate point P2 and the linear displacement sensor reading L2 at this time.

[0011] Step 3: Move the machine tool to coordinate P1, use the initial tool to machine the workpiece to be machined, and at the same time use a force sensor to monitor the machining state of the initial tool. When an abnormal state of the initial tool is detected, stop machining, move the machine tool to coordinate P2, check the linear displacement sensor reading at this time and compare it with L2. If the two are equal, the initial tool has not been worn, and continue to machine the workpiece to be machined; when the two are not equal, the initial tool has been worn, and perform tool replacement.

[0012] Step 4: When the initial tool is worn, disassemble the initial tool and install a new tool, and use the new tool to leave a machining tool mark on the surface of the auxiliary workpiece. Measure the parameters between the tool marks left by the initial tool and the new tool on the surface of the auxiliary workpiece using an optical microscope to obtain the relative errors δ X δ Y, after compensating for the errors in the X and Y directions through the machine tool program, move the machine tool to the coordinate P2, and record the reading L3 of the linear displacement sensor at this time; take the difference between L2 and L3 as the relative error δ in the Z direction Z ;

[0013] Step Five, compensate for the errors δ X , δ Y , δ Z in the three linear axis directions respectively through the machine tool program, move the machine tool to the coordinate P1 and then use a new tool for splicing processing;

[0014] Step Six, repeat Steps Three to Five, and infinite tool changes can be performed with the coordinate P2 and the reading L2 of the linear displacement sensor as the unified positioning reference.

[0015] Optionally, the measurement accuracy of the linear displacement sensor is 0.1 μm.

[0016] Optionally, the measurement accuracy of the optical microscope is 0.01 μm.

[0017] Optionally, the shape of the machining tool mark left by the initial tool on the surface of the auxiliary workpiece is an annular structure with horizontal linear tool marks.

[0018] Optionally, the shape of the machining tool mark left by the new tool on the surface of the auxiliary workpiece is a circular structure with horizontal linear tool marks.

[0019] Optionally, both the machining tool marks left by the initial tool and the new tool on the surface of the auxiliary workpiece include the horizontal linear tool marks, and the horizontal linear tool marks of the initial tool and the new tool are both machined when the precision rotating spindle of the machine tool is at the same angle.

[0020] The in-situ measurement tool change device based on optical microscopy and displacement sensing includes a linear displacement sensor, an optical microscope, and a force sensor. The linear displacement sensor is arranged on the outer shell of the precision rotating spindle of the machine tool, and the axis of the linear displacement sensor is parallel to the axis of the precision rotating spindle; the optical microscope is arranged on one side of the tool holder, and the measurement optical axis of the optical microscope and the axis of the initial tool are both parallel to the axis of the precision rotating spindle; the force sensor is installed on the tool holder and is used to monitor the working state of the initial tool or the new tool.

[0021] Optionally, the precision rotating spindle is arranged on the X slide of the machine tool, and the tool holder and the optical microscope are arranged on the Z slide; the workpiece to be machined is installed on the precision rotating spindle, and an auxiliary workpiece is arranged around the outside of the workpiece to be machined.

[0022] Optionally, the linear displacement sensor is installed on one side of the outer shell of the precision rotating spindle through a linear displacement sensor bracket; the linear displacement sensor includes a probe ball.

[0023] The present invention has achieved the following technical effects compared with the prior art:

[0024] The present invention provides an in-situ measurement tool change method and device based on optical microscopy and displacement sensing. This tool change method is applicable to all types of machine tools with a four-axis topological structure. Its tool change positioning accuracy can reach 0.01 μm in the X and Y axis directions, 0.1 μm in the Z axis direction, and the overall tool change positioning accuracy can reach 101 nm. It can online monitor the tool processing status and in-situ judge whether the tool is worn, avoiding replacing unworn tools and wasting resources. It can in-situ detect the degree of tool wear to select whether to continue processing or change the tool for processing, reducing unnecessary tool change operations and saving time and cost. It can in-situ locate the position of machining defects on the workpiece surface and perform reprocessing and repair, improving the machining quality of the workpiece. It can in-situ detect the machining quality of the workpiece and adjust the machine tool processing program accordingly in a timely manner, improving the machining accuracy of the workpiece. The operation method is simple and does not require a large amount of calculation, featuring simplicity and high efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0026] Figure 1 Schematic diagram of the layout of the optical microscope and linear displacement sensor of the present invention;

[0027] Figure 2 Schematic diagram of the shape of the specific machining tool marks left by the initial tool on the auxiliary workpiece surface;

[0028] Figure 3 Schematic diagram of the shape of the machining tool marks left by the new tool on the auxiliary workpiece surface;

[0029] Figure 4 Schematic diagram of measuring the position difference δ X 、δ Y between the initial tool and the new tool based on the optical microscope;

[0030] Figure 5 Schematic diagram of calculating the position difference δ Z between the initial tool and the new tool based on the readings of the linear displacement sensor;

[0031] Description of reference numerals: 1 - optical microscope, 2 - linear displacement sensor, 201 - probe ball, 3 - linear displacement sensor bracket, 4 - precision rotating spindle, 5 - X slide, 6 - tool holder, 7 - Z slide, 8 - initial tool, 9 - workpiece to be machined, 10 - auxiliary workpiece, 11 - new tool, 12 - circular machining tool mark, 13 - horizontal tool mark, 14 - circular machining tool mark. Detailed implementation manners

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0033] The purpose of the present invention is to provide an in-situ measurement tool change method and device based on optical microscopy and displacement sensing to solve the problems existing in the above-mentioned prior art, with high tool change accuracy, no damage to the surface of the workpiece to be machined, and a unified positioning reference between multiple tool changes.

[0034] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific implementation manners.

[0035] For the high-quality and highly consistent ultra-precision tool change and stitching machining of the micro-structure surface of ultra-large area or ultra-hard materials, the key technical problem is how to ensure that the tip of the new tool after tool change has the same coordinate position as the tip of the initial tool in the machine tool coordinate system. The relative position difference between the tip of the new tool and the tip of the initial tool in the machine tool coordinate system can be represented by the body diagonal of a cube, and the position differences in the three linear axes X, Y, and Z directions are δ X 、δ Y 、δ Z . Therefore, after compensating for δ X 、δ Y 、δ Z in sequence, it is possible to ensure that the tip of the new tool after tool change has the same coordinate position as the tip of the initial tool in the machine tool coordinate system.

[0036] To solve the above problems, the present invention innovatively measures δ X 、δ Y 、δ Z in-situ through a combination of a linear displacement sensor and an optical microscope. Refer to FIGS. Figure 1 、FIGS. Figure 2 、FIGS. Figure 3 、FIGS. Figure 4 and FIGS. Figure 5As shown in the figure, the device adopted by the in-situ measurement tool change method based on the combination of an optical microscope and a displacement sensor in the present invention includes an optical microscope 1 and a linear displacement sensor 2. The linear displacement sensor 2 includes a probe ball 201. The linear displacement sensor 2 is arranged on the outer shell of the precision rotating spindle 4 of the machine tool through a linear displacement sensor bracket 3, and the axis of the linear displacement sensor 2 is parallel to the axis of the precision rotating spindle 4. The precision rotating spindle 4 is arranged on the X slide 5 of the machine tool. The tool holder 6 and the optical microscope 1 are arranged on the Z slide 7. The measuring optical axis of the optical microscope 1 and the axis of the initial tool 8 are respectively parallel to the axis of the precision rotating spindle 4. A mechanical sensor is arranged on the tool holder 6 to monitor the working state of the initial tool 8 or the new tool 11 on the tool holder 6. The workpiece to be machined 9 is installed on the precision rotating spindle 4, and an auxiliary workpiece 10 is arranged around the outside of the workpiece to be machined 9; Figure 2 、 Figure 3 and Figure 4 In Figure 2 , Figure 3 , and Figure 4 , the dotted box area is the measurement area of the optical microscope 1. By measuring the circular machining tool marks 14, circular-ring machining tool marks 12, and the horizontal tool marks 13 between the new tool 11 and the initial tool 8 on the surface of the auxiliary workpiece 10 in-situ with the optical microscope 1, the position differences δ X 、δ Y in the X and Y directions of the linear axes of the tips of the new tool 11 and the initial tool 8 can be directly measured. Among them, the position difference δ X in the X direction of the linear axis is obtained by measuring the distance between the circular-ring machining tool marks 12 and the circular machining tool marks 14, and the position difference δ Y in the Y direction of the linear axis is obtained by measuring the distance between the two horizontal tool marks 13. The measurement accuracy of both is 0.01 μm. According to the measurement results, by modifying the machine tool program to compensate for the position differences δ X 、δ Y in the X and Y directions of the linear axes, in the same machine tool coordinate system, there is only a position difference δ Z in the Z direction of the linear axis between the tips of the new tool 11 and the initial tool 8. This position difference δ Z can be directly calculated by the indicated value of the linear displacement sensor 2 in the in-situ measurement method as δ Z = L3 - L2, where L3 and L2 are the indicated values when the linear displacement sensor 2 measures the tips of the new tool 11 and the initial tool 8 in the same machine tool coordinate system respectively, and the measurement accuracy is 0.1 μm. According to the maximum value of the measurement error, the overall tool change positioning accuracy is calculated according to the Pythagorean theorem. It can be known that the tool change positioning accuracy of the tip of the new tool 11 and the tip of the initial tool 8 in the machine tool coordinate system is 101 nm.

[0037] In addition, the tool rest 6 integrated with a force sensor can online detect the machining state of the tool by detecting force. When the machining state of the tool is detected to be abnormal, the machining is stopped. The linear displacement sensor 2 is used to measure the tip of the tool, and the measured value shown by the linear displacement sensor 2 is compared with the value shown before machining, so as to determine whether the tool is worn and the degree of wear. According to the wear condition of the tool, it is possible to choose to continue machining or to machine after changing the tool, which can avoid replacing the tool that is not worn or the wear degree of which does not affect the machining quality, avoid waste of resources, and save time and cost.

[0038] The surface of the workpiece 9 to be machined can be detected in situ by the optical microscope 1 to locate the position where tool wear occurs. Then, after changing the tool, the machining defects at this position can be reprocessed and repaired to improve the machining quality. The machining quality of the workpiece 9 to be machined can also be detected in situ by the optical microscope 1, and the machining accuracy of the workpiece 9 to be machined can be improved by timely adjusting the machine tool machining program.

[0039] Specifically, the in-situ measurement tool change method based on optical microscopy and displacement sensing of the present invention includes the following steps:

[0040] Step 1, after the initial tool 8 is aligned, record the coordinates P1(X1, Y1, Z1) of the tip of the initial tool 8 on the surface of the workpiece 9 to be machined at this time;

[0041] Step 2, first use the initial tool 8 to leave a specific circular ring machining tool mark 12 on the surface of the auxiliary workpiece 10, then move the machine tool linear axis so that the tip of the initial tool 8 presses on the probe ball 201 of the linear displacement sensor 2, and record the coordinate point P2(X2, Y2, Z2) of the machine tool and the value L2 shown by the linear displacement sensor 2 at this time; The coordinate P2 is the unified positioning reference for measuring the Z-direction installation positioning error during subsequent tool change, and L2 is the unified reference for solving δ Z of the unified reference.

[0042] Step 3, move the machine tool to the coordinates P1(X1, Y1, Z1), use the initial tool 8 to machine the workpiece 9 to be machined, use the force sensor on the tool rest 6 integrated with a force sensor to monitor the machining state of the tool. When the tool state is detected to be abnormal, stop the machining, and move the machine tool to the coordinates P2(X2, Y2, Z2), check the value shown by the linear displacement sensor 2 at this time and compare it with L2. If the two are equal, the initial tool 8 is not worn; when the two are not equal, it means that the initial tool 8 is worn and the tool needs to be changed;

[0043] Step 4: Dismantle the initial tool 8 and install the new tool 11, and use the new tool 11 to leave a circular machining tool mark 14 on the surface of the auxiliary workpiece 10. Measure the parameters between the tool marks left by the initial tool 8 and the new tool 11 on the surface of the auxiliary workpiece 10 by using the optical microscope 1, and obtain the relative errors δ X 、δ Y in the X and Y directions between the initial tool 8 and the new tool 11. After compensating for the errors in the X and Y directions through the machine tool program, run the machine tool to the coordinate P2(X2, Y2, Z2), and record the reading L3 of the linear displacement sensor 2 at this time; the difference between L2 and L3 is the relative error δ Z in the Z direction;

[0044] Step 5: Compensate for the errors δ X 、δ Y 、δ Z in the three linear axis directions respectively through the machine tool program, and then the machine tool can be moved to the coordinate P1(X1, Y1, Z1) and the new tool 11 can be used for splicing machining.

[0045] Step 6: Repeat the processes of Step 3 to Step 5, and then the tool can be changed infinitely with the coordinate P2(X2, Y2, Z2) and the reading L2 of the linear displacement sensor 2 as the unified positioning reference.

[0046] By the above method, the present invention can simply and efficiently achieve high-quality and highly consistent infinitely precise tool change and splicing machining on the surface of microstructures of ultra-large area or ultra-hard materials.

[0047] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "top", "bottom", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, so it cannot be understood as a limitation to the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0048] Specific examples are applied in the present invention to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be understood as a limitation to the present invention.

Claims

1. An in-situ tool change measurement method based on optical microscopy and displacement sensing, characterized in that: It includes the following steps: Step 1: Perform tool setting for the initial tool, and record the machine coordinates P1 when the tip of the initial tool is on the surface of the workpiece to be machined. Step 2: Drive the initial tool to leave a machining mark on the surface of the auxiliary workpiece, then move the linear axis of the machine tool so that the tip of the initial tool abuts against the probe ball of the linear displacement sensor, and record the machine coordinate point P2 and the reading L2 of the linear displacement sensor at this time. Step 3: Move the machine tool to the coordinate P1, use the initial tool to machine the workpiece to be machined, and at the same time use the force sensor to monitor the machining state of the initial tool. When it is detected that the state of the initial tool is abnormal, stop machining, move the machine tool to the coordinate P2, check the reading of the linear displacement sensor at this time and compare it with L2. If the two are equal, the initial tool has not worn, and continue to machine the workpiece to be machined; when the two are not equal, the initial tool has worn, and replace the tool. Step 4, when the initial tool wears out, disassemble the initial tool and install a new tool, and use the new tool to leave a machining tool mark on the surface of the auxiliary workpiece. Measure the parameters between the tool marks left by the initial tool and the new tool on the surface of the auxiliary workpiece using an optical microscope to obtain the relative errors δ X and δ Y in the X and Y directions between the initial tool and the new tool. After compensating for the errors in the X and Y directions through the machine tool program, run the machine tool to coordinate P2 and record the reading L3 of the linear displacement sensor at this time; take the difference between L2 and L3 as the relative error δ Z in the Z direction; Step 5: Compensate for the errors δ X , δ Y , δ Z in the three linear axis directions respectively, move the machine tool to coordinate P1 and then use a new tool for splicing machining; Step 6: Repeat Steps 3 to 5, and infinite tool changes can be carried out with the coordinate P2 and the reading L2 of the linear displacement sensor as the unified positioning reference.

2. The in-situ measurement tool changing method based on optical microscopy and displacement sensing according to claim 1, wherein: The measurement accuracy of the linear displacement sensor is 0.1 μm.

3. The in-situ measurement tool change method based on optical microscopy and displacement sensing according to claim 1, characterized in that: The measurement accuracy of the optical microscope is 0.01 μm.

4. The in-situ measurement tool change method based on optical microscopy and displacement sensing according to claim 1, characterized in that: The shape of the machining mark left by the initial tool on the surface of the auxiliary workpiece is an annular structure with horizontal line-shaped marks.

5. The in-situ measurement tool change method based on optical microscopy and displacement sensing according to claim 1, wherein: The shape of the machining mark left by the new tool on the surface of the auxiliary workpiece is a circular structure with horizontal line-shaped marks.

6. The in-situ measurement tool change method based on optical microscopy and displacement sensing according to claim 1, characterized in that: Both the machining marks left by the initial tool and the new tool on the surface of the auxiliary workpiece include horizontal line-shaped marks, and the horizontal line-shaped marks of the initial tool and the new tool are machined when the precision rotating spindle of the machine tool is at the same angle.

7. An in-situ measurement tool changing device for the in-situ measurement tool changing method based on optical microscopy and displacement sensing according to any one of claims 1 to 6, characterized in that: It includes a linear displacement sensor, an optical microscope and a force sensor. The linear displacement sensor is arranged on the housing of the precision rotating spindle of the machine tool, and the axis of the linear displacement sensor is parallel to the axis of the precision rotating spindle; the optical microscope is arranged on one side of the tool post, and the measurement optical axis of the optical microscope and the axis of the initial tool are respectively parallel to the axis of the precision rotating spindle; the force sensor is installed on the tool post for monitoring the working state of the initial tool or the new tool.

8. The in-situ measurement tool changing device based on optical microscopy and displacement sensing according to claim 7, characterized in that: The precision rotating spindle is arranged on the X slide of the machine tool, and the tool post and the optical microscope are arranged on the Z slide; the workpiece to be machined is installed on the precision rotating spindle, and an auxiliary workpiece is arranged around the outside of the workpiece to be machined.

9. The in-situ measurement tool changing device based on optical microscopy and displacement sensing according to claim 7, characterized in that: The linear displacement sensor is installed on one side of the housing of the precision rotating spindle through a linear displacement sensor bracket; the linear displacement sensor includes a probe ball.

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