Method and system for calculating correction value of position measurement sensor of machine tool

Abstract

A correction value calculation method and calculation system for a position measurement sensor of a machine tool can minimize an error generated by a correction value in a longitudinal direction of the position measurement sensor even if a peripheral temperature changes, and can enlarge a table region where a workpiece is disposed. A numerical control machine tool (M) is provided with: a table (3) capable of holding a workpiece and capable of moving at one or more degrees of freedom; a main shaft (2) on which the tool is mounted and which rotates, which has two or more translational axes, and which is capable of relative movement with two or more translational degrees of freedom with respect to the table; and a laser sensor (40) capable of measuring the position of the tool attached to the main shaft, the numerical control machine tool being capable of measuring the position of the workpiece held on the table by means of a contact probe (30) attachable to the main shaft, the laser sensor comprising: a laser beam (43) for detecting a detection object; and a reference part (45) as a position reference for the laser sensor, the reference part (45) being integrally disposed with the laser sensor in the vicinity of the laser light.

Description

Technical Field

[0001] This disclosure relates to a method and system for calculating the calibration value of a position measurement sensor for measuring the position of a workpiece in a machine tool in which a worktable holding a workpiece and a spindle holding a tool move relative to each other via a translation axis. Background Technology

[0002] In such Figure 1 In the numerically controlled machine tool M with three translation axes shown, when machining a workpiece set on the worktable 3 using a tool mounted on the spindle 2, it is necessary for the control device to pre-record the position of the workpiece as a machining reference. The position as a machining reference is obtained, for example, by measuring the position of the workpiece.

[0003] One known method for measuring the position of a workpiece is using a contact probe mounted on the spindle as a position measurement sensor. When the probe contacts the workpiece, a signal is transmitted at that instant. An NC control unit installed on the machine tool receives the signal via a connected receiver. Upon receiving the signal, the NC control unit adds a correction value in the length direction of the contact probe to the position of each axis at that instant to calculate the workpiece position.

[0004] However, the contact probe is subject to changes over time, such as thermal deformation caused by variations in room temperature. Therefore, in order to measure the position of the workpiece with high accuracy, it is necessary to appropriately re-acquire the correction value of the contact probe in the length direction.

[0005] As a method for calculating the correction value in the length direction of the contact probe, the applicant disclosed a method similar to that in Patent Document 1. In the method described in Patent Document 1, a tool sensor such as a laser sensor or a contact sensor, a reference block mounted on a base of the tool sensor, and a reference tool of known length are used. The detection position of the tool sensor, the relative position of the reference block with respect to the detection position, and the correction value in the length direction of the contact probe are obtained in advance. Then, if the detection position of the reference tool is measured using the tool sensor, and the position of the reference block is measured using the contact probe, the correction value in the length direction of the contact probe can be calculated.

[0006] Patent Document 1: Japanese Patent No. 7266511

[0007] However, if the pre-obtained relative position of the reference block with respect to the detection position of the tool sensor changes, errors may occur in the correction value of the contact probe along its length. Therefore, in Patent Document 1, the change in relative position is reduced by placing the reference block on the same base as the tool sensor. However, for example, if the linear expansion coefficients of the tool sensor and the reference block are different, even if the tool sensor and the reference block are placed on the same base, the relative position will change according to changes in the surrounding temperature. As a result, the problem of errors in the correction value of the contact probe along its length exists.

[0008] Furthermore, in most cases, as in Patent Document 1, the tool sensor and the reference block are separate components, each positioned at an arbitrary location on the worktable. Therefore, it is desirable to address the issue of the worktable area for setting the workpiece becoming smaller. Summary of the Invention

[0009] Therefore, the purpose of this disclosure is to provide a method and system for calculating the calibration value of a position measurement sensor for a machine tool, which can minimize the error caused by the calibration value in the length direction of the position measurement sensor even if the ambient temperature changes, and can expand the worktable area for setting the workpiece.

[0010] To address the aforementioned issues, the first structure disclosed herein provides a method for calculating the calibration value of a position measurement sensor for a machine tool. In this method, the calibration value of the position measurement sensor in the length direction is calculated within the machine tool. The machine tool includes a worktable capable of holding a workpiece, a spindle capable of mounting and rotating a cutting tool, a translation axis capable of relative motion between the spindle and the worktable with two or more translational degrees of freedom, and a tool sensor capable of measuring the position of a cutting tool mounted on the spindle. This machine tool can measure the position of a workpiece held on the worktable using a position measurement sensor mounted on the spindle. The method for calculating the calibration value of the position measurement sensor for this machine tool is characterized in that the tool sensor includes: a detection unit that detects a detection object; and a reference unit that serves as a position reference for the tool sensor, integrally disposed near the detection unit within the tool sensor. The method for calculating the calibration value of the machine tool's position measurement sensor follows these steps: First, the tool sensor detects the position of the reference tool. A reference tool of known length is installed on the spindle, and the detection unit of the tool sensor detects the tip of the reference tool and obtains its position. The position of the detection unit of the tool sensor is then measured based on the obtained tip position and the length of the reference tool. Second, the position measurement sensor calculates its length. After obtaining the reference position using the reference tool installed on the spindle, the position measurement sensor is installed on the spindle. The position measurement sensor measures the reference position and obtains its reference position. The length of the position measurement sensor is calculated based on the obtained reference position, the length of the reference tool, and the reference position. Third, the relative position is obtained by installing the position measurement sensor on the spindle and measuring the position of the reference part. The relative position is calculated based on the measured position of the reference part and the length of the reference tool. The relative position of the reference unit with respect to the position of the detection unit is obtained by measuring the position of the detection unit in the sensor detection position measurement step and the length of the position measuring sensor calculated in the position measuring sensor length calculation step; the reference tool tip position measurement step involves mounting the reference tool on the spindle, making the tip of the reference tool contact the detection unit, and measuring the position of the tip of the reference tool; the tool sensor position measurement step involves mounting the position measuring sensor on the spindle, measuring the position of the reference unit, and thereby measuring the position of the tool sensor; and the position measuring sensor length direction correction value calculation step calculates the length direction correction value of the position measuring sensor based on the length of the reference tool, the relative position obtained in the relative position acquisition step, the position of the tip of the reference tool obtained in the reference tool tip position measurement step, and the position of the tool sensor measured in the tool sensor position measurement step.

[0011] Other aspects of the first structure disclosed herein are characterized in that, in the above structure, a tool sensor detection position measurement step is performed once to a relative position acquisition step, and multiple reference tool tip position measurement steps are performed to a position measurement sensor length direction correction value calculation step.

[0012] Another feature of the first structure disclosed herein is that, in the above structure, the detection unit and the reference unit are raw materials whose relative positions do not change within the ambient temperature range observed during machine tool processing.

[0013] To address the aforementioned issues, the second structure disclosed herein is a calibration value calculation system for a position measurement sensor of a machine tool. This system calculates the calibration value of the position measurement sensor in the length direction within the machine tool. The machine tool includes a worktable capable of holding a workpiece, a spindle capable of mounting and rotating a cutting tool, a translation axis capable of relative motion between the spindle and the worktable with two or more translational degrees of freedom, a control device for controlling the worktable, the translation axis, and the spindle, and a cutting tool sensor capable of measuring the position of the cutting tool mounted on the spindle. This machine tool can measure the position of a workpiece held on the worktable using a position measurement sensor mounted on the spindle. The calibration value calculation system for the position measurement sensor of this machine tool is characterized in that the tool sensor has: a detection unit that detects the object being detected; and a reference unit that serves as the position reference for the tool sensor, which is integrally disposed near the detection unit within the tool sensor. The calibration value calculation system for the position measurement sensor of this machine tool includes: a reference tool of known length; a tool sensor detection position measuring unit that mounts the reference tool on the spindle, moves the translation axis, and causes the detection unit of the tool sensor to detect the tip of the reference tool and acquire its tip position; and measures the position of the detection unit of the tool sensor based on the acquired tip position and the length of the reference tool; a position measurement sensor length calculation unit that mounts the reference tool on the spindle, moves the translation axis, acquires the reference position, mounts the position measurement sensor on the spindle, moves the translation axis, uses the position measurement sensor to measure the reference position and acquire its reference position; and calculates the length of the position measurement sensor based on the length of the reference tool, the reference position, and the reference position of the position measurement sensor; and relative position acquisition. The system comprises the following components: a reference tool position measuring unit, which mounts a position measuring sensor on the spindle and moves a translation axis to measure the position of a reference tool; a reference tool tip position measuring unit, which mounts a reference tool on the spindle and moves a translation axis to bring the tip of the reference tool into contact with the detection unit, and measures the position of the reference tool tip; a tool sensor position measuring unit, which mounts a position measuring sensor on the spindle and moves a translation axis to measure the position of the reference tool tip, and thus measures the position of the tool sensor; and a position measuring sensor length direction correction value calculation unit, which calculates the length direction correction value of the position measuring sensor based on the length of the reference tool, the relative position obtained by the relative position acquiring unit, the position of the reference tool tip measured by the reference tool tip position measuring unit, and the position of the tool sensor obtained by the tool sensor position measuring unit.

[0014] The second structure of this disclosure is characterized in that, in the above structure, the detection unit and the reference unit are raw materials in which the relative positions of the detection unit and the reference unit do not change within the ambient temperature range observed during machining on a machine tool.

[0015] According to this disclosure, by integrating the reference part into the tool sensor near the detection part, changes in relative position can be reduced even if the surrounding temperature changes. Therefore, in calculating the correction value of the position sensor in the length direction using the relative position of the reference part on the detection part and the tool sensor, the error caused by the correction value in the length direction of the position sensor can be minimized. Furthermore, since a reference block separate from the tool sensor is not required, the worktable area for setting the workpiece can be expanded.

[0016] Furthermore, by using raw materials whose relative positions to the detection unit and the reference unit do not change within the ambient temperature range observed during machine tool processing, the relative positional changes caused by temperature variations can be further reduced. Attached Figure Description

[0017] Figure 1 This is an explanatory diagram illustrating the calibration value calculation system for the position measurement sensor of this disclosure.

[0018] Figure 2 This is a block diagram showing the structure of the NC control device.

[0019] Figure 3 This is an illustrative diagram showing the laser sensor of this disclosure.

[0020] Figure 4 This is an illustrative diagram showing the contact sensor of this disclosure.

[0021] Figure 5 This is an explanatory diagram based on the reference position measurement on the upper surface of the worktable using a contact probe.

[0022] Figure 6 This is a pre-defined flowchart for calculating the length direction correction value of the contact probe disclosed herein.

[0023] Figure 7 This is an explanatory diagram based on the reference position obtained from the upper surface of the worktable of the reference tool.

[0024] Figure 8 This is an explanatory diagram of the position measurement of the reference part of the laser sensor.

[0025] Figure 9 This is an explanatory diagram of the position measurement of the reference part of a contact sensor.

[0026] Figure 10This is a flowchart of the method for calculating the length direction correction value of the contact probe disclosed herein.

[0027] Label Explanation

[0028] 2: Spindle; 3: Worktable; 8c: Z-axis position detector (translation axis position detector); 10: Reference tool; 21: NC control device (control device); 30: Contact probe (position measurement sensor); 40: Laser sensor (tool sensor); 43: Laser (detection unit); 45: Reference unit; 50: Contact sensor (tool sensor); 52: Detection unit; 54: Reference unit; M: Numerical control machine tool (machine tool). Detailed Implementation

[0029] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings.

[0030] In this embodiment, as Figure 1 The example shown is a numerically controlled machine tool M with a machining center base having three translation axes: X, Y, and Z. However, the machine tool can also be other equipment such as a multi-axis control machine tool with rotary axes in addition to translation axes, or a numerically controlled machine tool with a lathe base.

[0031] like Figure 1 and Figure 2 As shown, the numerically controlled machine tool M disclosed herein is a machine tool having a machining center base with three translation axes consisting of an X-axis, a Y-axis, and a Z-axis. The numerically controlled machine tool M has a bed 1, a spindle 2 capable of mounting a tool (not shown), a worktable 3 capable of holding a workpiece (not shown), and an NC control device 21. Furthermore, the numerically controlled machine tool M includes a tool sensor and a position measurement sensor.

[0032] The numerical control machine tool M preferably has a tool magazine that pre-stores multiple tools and a tool changing device that can automatically change the tools stored in the tool magazine and the tools mounted on the spindle 2. By pre-storing the reference tool 10 and the position measurement sensor (described later) in the tool magazine, automatic loading and unloading relative to the spindle 2 is possible, thus improving operability. Alternatively, the loading and unloading of tools relative to the spindle 2 can also be performed manually by the operator.

[0033] The numerical control machine tool M is a so-called gantry-type machine tool. The saddle 6 is movably mounted on a track 5 extending along the X-axis, which is formed on the column 4. The spindle slide 7 is also movably mounted on the saddle 6 along the Z-axis. Furthermore, the spindle 2 is mounted at the lower end of the spindle slide 7. Therefore, the spindle 2 can move along the Z-axis and X-axis, which are two perpendicular translation axes. That is, the spindle 2 can perform two degrees of freedom of translation relative to the bed 1. The X-axis translation servo motor 11a drives the feed axis to move the saddle 6, thereby executing the X-axis movement of the spindle 2. The Z-axis translation servo motor 11c drives the feed axis to move the spindle slide 7, thereby executing the Z-axis movement of the spindle 2. Additionally, an X-axis position detector 8a is mounted on the column 4 side of the saddle 6. A Z-axis position detector 8c is mounted on the saddle 6 side of the spindle slide 7.

[0034] The worktable 3 is movably mounted on a track 9 formed in the bed 1, extending along the Y-axis, a translation axis perpendicular to the Z and X axes. That is, the worktable 3 can perform one degree of translational movement relative to the bed 1. Furthermore, the feed axis is driven by a servo motor 11b for Y-axis translation, thereby performing movement of the worktable 3 in the Y-axis direction. Additionally, a Y-axis position detector 8b is provided on the side surface of the worktable 3 on the bed 1.

[0035] like Figure 2 As shown, the NC control unit 21 functions as a recording unit 22, a display unit 23, and a servo command value generation unit 24. The NC control unit 21 includes a CPU and a memory connected to the CPU, and various processes are implemented using these.

[0036] The recording unit 22 can record information such as the machining program input through the input unit 26 (described later), the length of the reference tool 10, the detection position of the tool sensor, the relative position of the reference unit with respect to the detection position, and the correction value of the length direction of the position measurement sensor.

[0037] In addition, the recording unit 22 stores a program for the NC control device 21 to function as the tool sensor detection position measurement unit, position measurement sensor length calculation unit, relative position acquisition unit, reference tool tip position measurement unit, tool sensor position measurement unit, and position measurement sensor length direction correction value calculation unit in this disclosure.

[0038] Display unit 23 is, for example, a monitor. Display unit 23 displays information such as the machining program and the positions of the translation axes.

[0039] Furthermore, the NC control unit 21 is connected to the X-axis position detector 8a, the Y-axis position detector 8b, and the Z-axis position detector 8c, as well as the X-axis translation servo amplifiers 12a, 12b, and 12c. The servo amplifiers 12a to 12c are further connected to the X-axis translation servo motor 11a, the Y-axis translation servo motor 11b, and the Z-axis translation servo motor 11c, respectively. Therefore, based on the position information of each axis obtained from the position detectors 8a to 8c, the NC control unit 21 appropriately drives the servo motors 11a to 11c, thereby performing machining of the workpiece held on the worktable 3 by means of the tool held on the spindle 2.

[0040] Here, an example of a method for generating servo command values ​​for the translation axis executed by the servo command value generation unit 24 and an example of relative position control between the worktable 3 and the spindle 2 based on the servo command values ​​will be described.

[0041] When the machining program is input into the NC control device 21, the servo command value generation unit 24 generates the respective command values ​​for the translation axes based on the position information from the position detectors 8a to 8c of each axis and the position information of the workpiece obtained in advance.

[0042] The generated command values ​​for each translation axis are sent to the servo command value conversion unit 25 and converted into servo command values. Then, the servo command values ​​for the X-axis, Y-axis, and Z-axis are sent to the servo amplifiers 12a-12c. The servo amplifiers 12a-12c drive the servo motors 11a-11c according to the acquired servo command values ​​for the X-axis, Y-axis, and Z-axis, respectively. Therefore, by driving the servo motors 11a-11c, the relative position of the spindle 2 with respect to the worktable 3 is controlled.

[0043] The NC control device 21 is also connected to a tool sensor and a position measurement sensor. Regarding the connection to the tool sensor and position measurement sensor, it can be either by connecting a receiver to the NC control device 21 and obtaining information from the sensors wirelessly, or by a wired connection to the tool sensor and position measurement sensor. In this embodiment, it is envisioned that the NC control device 21 is wiredly connected to the tool sensor. On the other hand, it is envisioned that the NC control device 21 is wirelessly connected to the position measurement sensor. Therefore, the NC control device 21 is connected to a receiver 33 for receiving signals from the position measurement sensor.

[0044] In addition, the NC control device 21 is also connected to an input unit 26, such as a keyboard and touch panel, for the operator to perform various inputs, such as machining programs.

[0045] like Figure 3As shown, the laser sensor 40, serving as a tool sensor, includes a laser emitting section 41 that emits a laser 43 as a detection section, a laser receiving section 42 that receives the laser 43, and a base section 44. Furthermore, the laser sensor 40 has a reference section 45 integrally formed on the upper surface of the laser emitting section 41. The reference section 45 is formed from the same material as the laser emitting section 41 and the laser receiving section 42, or from a material with a similar coefficient of linear expansion. The laser sensor 40 is mounted at any position on the worktable 3.

[0046] In addition, such as Figure 4 As shown, the contact sensor 50, serving as a tool sensor, comprises a contact sensor body 51, a detection unit 52 for detecting the position of the tool tip, and a base 53. Furthermore, the contact sensor 50 has a reference portion 54 integrally formed on the upper surface of the contact sensor body 51. The reference portion 54 is formed from the same raw material as the detection unit 52 and the contact sensor body 51, or from a raw material with a similar coefficient of linear expansion. The contact sensor 50 is mounted at any position on the worktable 3.

[0047] Here, in this disclosure, a similar coefficient of linear expansion refers to a coefficient of linear expansion that, in the ambient temperature range observed during the machining of a workpiece based on a numerically controlled machine tool M, shows a similarity in the degree to which the relative position of the detection part and the reference part does not change, or even if the relative position changes, the machined product is within the permissible quality range.

[0048] In addition, the laser sensor 40 and the contact sensor 50 are arbitrarily selected based on various factors such as the structure and setting environment of the numerical control machine tool M, and are mounted on the numerical control machine tool M.

[0049] Thus, in the position measurement sensor calibration value calculation system of this disclosure, the laser sensor 40 has a reference portion 45 on the laser emitting part 41, which is formed of the same material as the laser emitting part 41 and the laser receiving part 42, or a material with a similar coefficient of linear expansion. Therefore, even if the temperature around the laser sensor 40 changes and the laser emitting part 41 undergoes thermal deformation, the relative position of the laser 43 and the reference portion 45 is not easily changed. Similarly, the contact sensor 50 has a reference portion 54 on the contact sensor body 51, which is formed of the same material as the detection part 52 and the contact sensor body 51, or a material with a similar coefficient of linear expansion. Therefore, even if the temperature around the contact sensor 50 changes and the contact sensor body 51 undergoes thermal deformation, the relative position of the detection part 52 and the reference portion 54 is not easily changed. Therefore, the error generated in the calculation of the calibration value in the length direction of the position measurement sensor described later can be minimized.

[0050] Furthermore, the reference unit 45 is integrally provided with the laser sensor 40. Similarly, the reference unit 54 is integrally provided with the contact sensor 50. Therefore, the worktable area for setting the workpiece can be expanded.

[0051] like Figure 5 As shown, the contact probe 30, as a position measurement sensor, consists of a contact probe body 31, a stylus 32 mounted at the front end, and a receiver 33 connected to the NC control device 21.

[0052] As described above, in order to use the contact probe 30 to measure the position of the workpiece or other measuring object, it is necessary to obtain the length direction correction value of the contact probe 30 in advance and have the recording unit 22 of the NC control device 21 record it in advance.

[0053] The following describes the calculation method for the length direction correction value of the contact probe 30 disclosed herein.

[0054] First, according to Figure 6 The flowchart explains how the relative positions of the detection unit and the reference unit in the tool sensor are obtained, based on a pre-set calculation of the length direction correction value of the contact probe 30 of this disclosure.

[0055] In order to perform tool measurement using a tool sensor, it is necessary to obtain the detection position of the tool sensor in advance and record it in advance by the recording unit 22 of the NC control device 21. Therefore, as S1, the detection position of the laser sensor 40 or the contact sensor 50, which serves as the tool sensor, is measured. This detection position is used to detect the position of the tool tip. S1 is the tool sensor detection position measurement step in this disclosure. Here, the measurement of the detection position in the Z-axis direction of the tool tip is described as an example.

[0056] First, a reference tool 10 of known length is mounted on the spindle 2. Then, the spindle 2 is positioned such that the tip of the reference tool 10 is directly above the laser 43. Next, as... Figure 3 As shown, the Z-axis (feed axis) moves in the negative direction. Furthermore, when the laser 43 is blocked by the tip of the reference tool 10, this is detected, and a signal is sent from the laser receiver 42 to the NC control unit 21. Upon receiving the signal from the laser sensor 40, the NC control unit 21 stops the Z-axis translation servo motor 11c. Additionally, in the NC control unit 21, the detection position Zrt', obtained by adding the length Lr of the reference tool 10 to the Z-axis position Zrt at the moment of signal reception, is measured using equation (1). This measured detection position Zrt' is the Z-axis direction detection position that should be obtained beforehand for detecting the position of the tool tip. The detection position Zrt' is recorded in the recording unit 22.

[0057] Zrt'=Zrt-Lr (1)

[0058] The tool measurement method using the contact sensor 50 is essentially the same as the tool measurement method using the laser sensor 40 described above, except for the detection method. For example... Figure 4 As shown, if it is a contact sensor 50, when the front end of the tool comes into contact with the detection part 52 of the contact sensor 50, it is determined to be a detection, and a signal is sent from the contact sensor body 51 to the NC control device 21.

[0059] After measuring the detection position Zrt' of the tool sensor, the length of the contact probe 30 is calculated as S2. S2 is the length calculation step of the position measurement sensor of this disclosure.

[0060] Similar to S1, the reference tool 10 is mounted on the spindle 2, and the spindle 2 is positioned such that the front end of the reference tool 10 is near the upper surface of the worktable 3. Then, as... Figure 7 As shown, the tip of the reference tool 10 is brought into contact with a reference block 13 of known thickness disposed on the worktable 3. The contact position between the reference tool 10 and the reference block 13 is obtained as the position Z1 of the upper surface of the worktable separated by the known thickness t of the reference block 13, by the Z-axis position detector 8c. Thus, based on the obtained position Z1, the thickness t of the reference block 13, and the length Lr of the reference tool 10, the reference position Z1' is obtained by using the calculation of equation (2).

[0061] Z1'=Z1-Lr-t (2)

[0062] Then, the contact probe 30 is mounted on the spindle 2, and the spindle 2 is positioned such that the front end of the stylus 32 is near the acquisition reference position Z1'. Then, as... Figure 5 As shown, the Z-axis (feed axis) moves in the negative direction. Furthermore, when the stylus 32 contacts the reference position Z1', a signal is sent from the contact probe body 31 to the receiver 33 connected to the NC control device 21. The contact position Z2 at this time is the reference position of the position measurement sensor disclosed herein. Based on the contact position Z2 and the reference position Z1', which serve as the reference position of the position measurement sensor, the length Lp of the contact probe is calculated using equation (3) and recorded in the recording unit 22.

[0063] Lp=Z2-Z1' (3)

[0064] After calculating the length Lp of the contact probe 30, as step S3, the relative position of the reference part 45 with respect to the detection part of the laser sensor 40, i.e., the laser 43, or the relative position of the reference part 54 with respect to the detection part 52 of the contact sensor 50 is obtained. S3 is the relative position acquisition step of this disclosure.

[0065] like Figure 8 and Figure 9 As shown, the spindle 2 is positioned such that the tip of the stylus 32 of the contact probe 30 mounted on the spindle 2 is near the reference portion 45 of the laser sensor 40 or the reference portion 54 of the contact sensor 50. Then, the Z-axis (feed axis) moves in the negative direction. Then, when the stylus 32 contacts the reference portion 45 of the laser sensor 40 or the reference portion 54 of the contact sensor 50, a signal is sent from the contact probe body 31 to the receiver 33 connected to the NC control device 21. Based on the contact position Z3, the detection position Zrt', and the length Lp of the contact probe 30 at this time, the relative position dZ3 is obtained by using the calculation of Equation (4) and recorded in the recording unit 22.

[0066] dZ3=Z3-Lp-Zrt' (4)

[0067] As described above, by executing S1 to S3, the relative positions dZ3 of the reference parts 45 and 54 in the laser sensor 40 or the contact sensor 50 with respect to the detection parts 43 and 52 are stored, thereby completing the pre-setting of the length direction correction value calculation of the contact probe 30.

[0068] Next, according to Figure 10 The flowchart explains the calculation method for the length direction correction value of the contact probe 30, which is executed after the pre-setting is completed.

[0069] As S11, the detection position of the tool sensor is remeasured. For example... Figure 3 and Figure 4 As shown, the detection position Zrt'' is measured using the same steps as S1 described above. S11 is the reference tool tip position measurement step of this disclosure.

[0070] As in S12, the contact probe 30 is mounted on the spindle 2, and the spindle 2 is positioned such that the tip of the stylus 32 is near the position of the reference portion 45 of the laser sensor 40 or the reference portion 54 of the contact sensor 50 as measured in S3. Then, as... Figure 8 and Figure 9As shown, the Z-axis (feed axis) moves in the negative direction. Then, the stylus 32 is brought into contact with the reference portion 45 of the laser sensor 40 or the reference portion 54 of the contact sensor 50, and the contact position Z3' is measured. The contact position Z3' is the sensor position of this disclosure, and S12 is the tool sensor position measurement step.

[0071] Then, as in S13, based on the detection position Zrt'' measured in S11, the contact position Z3' obtained in S12, and the relative position dZ3 obtained and recorded in the recording unit 22 in S3, the correction value Lp' of the length direction of the contact probe 30 is calculated using the operation of Equation (5), and recorded in the recording unit 22. S13 is the step for calculating the correction value of the length direction of the position measurement sensor of this disclosure.

[0072] Furthermore, in the position measurement sensor calibration value calculation method disclosed herein, S1 to S3, which are pre-set for calculating the length direction calibration value of the contact probe 30, can be executed multiple times.

[0073] Lp'=Z3'-Zrt''-dZ3 (5)

[0074] The correction value Lp' in the length direction of the contact probe 30, calculated as described above, is used to correct the measurement position when measuring the position of the workpiece.

[0075] In the position measurement sensor calibration value calculation method disclosed herein, a laser sensor 40 with a reference portion 45 on the laser emitting unit 41 is used as a tool sensor. This reference portion 45 is formed from the same raw material as the laser emitting unit 41 and the laser receiving unit 42, or from a raw material with a similar coefficient of linear expansion. Therefore, even if the temperature around the laser sensor 40 changes and the laser emitting unit 41 undergoes thermal deformation, the relative position of the laser 43 and the reference portion 45 is less likely to change. The same applies when a contact sensor 50 is used as a tool sensor. The contact sensor 50 has a reference portion 54 on the contact sensor body 51, which is formed from the same raw material as the detection unit 52 and the contact sensor body 51, or from a raw material with a similar coefficient of linear expansion. Therefore, even if the temperature around the contact sensor 50 changes and the contact sensor body 51 undergoes thermal deformation, the relative position of the detection unit 52 and the reference portion 54 is less likely to change. Therefore, errors in the calculation of the calibration value in the length direction of the position measurement sensor can be minimized.

[0076] The method for calculating the calibration value of the machine tool position measurement sensor and the structure of the system disclosed herein are not limited in any way to the manner described in the above embodiments, and can be appropriately modified as needed without departing from the spirit of the invention.

[0077] For example, regarding the location of the reference part, as long as it is integrated with the tool sensor near the detection part, it may not need to be located on the upper surface of the tool sensor. Furthermore, while the reference part has been emphasized in the above embodiments and figures, other than the detection part, certain parts of the tool sensor may also be considered as the reference part.

[0078] The tool sensor and position measurement sensor were explained using laser sensor, contact sensor and contact probe as examples, but other sensors can also be used.

Claims

1. A method for calculating the calibration value of a position measurement sensor for a machine tool, wherein the calibration value of the position measurement sensor in the length direction is calculated in the machine tool, the machine tool having a worktable capable of holding a workpiece, a spindle capable of mounting and rotating a cutting tool, a translation axis capable of relative motion between the spindle and the worktable with two or more translational degrees of freedom, and a cutting tool sensor capable of measuring the position of the cutting tool mounted on the spindle, the machine tool being able to measure the position of a workpiece held on the worktable using a position measurement sensor mounted on the spindle, characterized in that... The tool sensor has: The testing department, which conducts testing on the objects to be tested; and The reference portion, which serves as the position reference for the tool sensor, is integrally disposed on the tool sensor near the detection portion. The method for calculating the calibration value of the position measurement sensor of this machine tool involves the following steps: The tool sensor detection position measurement step involves installing a reference tool of known length on the spindle, causing the detection unit of the tool sensor to detect the front end of the reference tool and obtain the position of the front end of the reference tool, and measuring the position of the detection unit of the tool sensor based on the obtained position of the front end of the reference tool and the length of the reference tool. The steps for calculating the length of the position measurement sensor are as follows: After obtaining the reference position using the reference tool mounted on the spindle, the position measurement sensor is mounted on the spindle. The reference position is measured using the position measurement sensor to obtain the reference position of the position measurement sensor. The length of the position measurement sensor is calculated based on the obtained reference position of the position measurement sensor, the length of the reference tool, and the reference position. In the relative position acquisition step, the position measuring sensor is installed on the spindle, the position of the reference part is measured, and the relative position of the reference part with respect to the position of the detection part is obtained based on the measured position of the reference part, the position of the detection part measured in the tool sensor detection position measurement step, and the length of the position measuring sensor calculated in the position measuring sensor length calculation step. The reference tool tip position measurement step involves mounting the reference tool on the spindle, making the tip of the reference tool contact the detection unit, and measuring the position of the tip of the reference tool. The tool sensor position measurement step involves installing the position measurement sensor on the spindle, measuring the position of the reference part, and thereby measuring the position of the tool sensor. as well as The length direction correction value calculation step of the position measurement sensor involves calculating the length direction correction value of the position measurement sensor based on the length of the reference tool, the relative position obtained in the relative position acquisition step, the position of the front end of the reference tool measured in the reference tool front end position measurement step, and the position of the tool sensor measured in the tool sensor position measurement step.

2. The method for calculating the calibration value of the position measurement sensor of a machine tool according to claim 1, characterized in that, Perform the tool sensor detection position measurement step once until the relative position acquisition step. Perform the reference tool tip position measurement step multiple times until the position measurement sensor length direction correction value calculation step.

3. The method for calculating the calibration value of the position measurement sensor of a machine tool according to claim 1 or 2, characterized in that, The detection unit and the reference unit are materials in which the relative positions of the detection unit and the reference unit do not change during the ambient temperature range observed in the machining process based on the machine tool.

4. A calibration value calculation system for a position measurement sensor in a machine tool, which calculates the calibration value of the position measurement sensor in the length direction in the machine tool, the machine tool having a worktable capable of holding a workpiece, a spindle capable of mounting a cutting tool and rotating, a translation axis capable of relative motion between the spindle and the worktable with two or more translational degrees of freedom, a control device for controlling the worktable, the translation axis and the spindle, and a cutting tool sensor capable of measuring the position of the cutting tool mounted on the spindle, the machine tool being able to measure the position of a workpiece held on the worktable using a position measurement sensor mounted on the spindle, characterized in that... The tool sensor has: The testing department, which conducts testing on the objects to be tested; and The reference portion, which serves as the position reference for the tool sensor, is integrally disposed on the tool sensor near the detection portion. The calibration value calculation system for the position measurement sensor of this machine tool has the following features: A reference tool of known length; The tool sensor detection position measurement unit mounts the reference tool on the spindle, causes the translation axis to move, and causes the detection unit of the tool sensor to detect the front end of the reference tool and obtain the front end position of the reference tool. The position of the detection unit of the tool sensor is measured based on the obtained front end position of the reference tool and the length of the reference tool. The position measurement sensor length calculation unit mounts the reference tool on the spindle, moves the translation axis, and after obtaining the reference position, mounts the position measurement sensor on the spindle, moves the translation axis, uses the position measurement sensor to measure the reference position and obtain the position measurement sensor reference position, and calculates the length of the position measurement sensor based on the length of the reference tool, the reference position, and the position measurement sensor reference position. The relative position acquisition unit mounts the position measurement sensor on the spindle, causes the translation axis to move, measures the position of the reference unit, and obtains the relative position of the reference unit with respect to the position of the detection unit based on the measured position of the reference unit, the position of the detection unit measured by the tool sensor detection position measurement unit, and the length of the position measurement sensor calculated by the position measurement sensor length calculation unit. The reference tool tip position measuring unit mounts the reference tool on the spindle, causes the translation axis to move, and causes the tip of the reference tool to contact the detection unit to measure the position of the tip of the reference tool. The tool sensor position measuring unit mounts the position measuring sensor on the spindle, causes the translation axis to move, measures the position of the reference unit, and thereby measures the position of the tool sensor. as well as The length direction correction value calculation unit of the position measurement sensor calculates the correction value of the length direction of the position measurement sensor based on the length of the reference tool, the relative position obtained by the relative position acquisition unit, the position of the front end of the reference tool measured by the reference tool front end position measurement unit, and the position of the tool sensor measured by the tool sensor position measurement unit.

5. The calibration value calculation system for the machine tool position measurement sensor according to claim 4, characterized in that, The detection unit and the reference unit are materials in which the relative positions of the detection unit and the reference unit do not change during the ambient temperature range observed in the machining process based on the machine tool.

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