Method for calibrating a contact tool sensor in a machine tool, storage medium and machine tool

Abstract

The present application provides a method for calibrating a contact tool sensor in a machine tool, a storage medium, and a machine tool. For the contact tool sensor, foreign matter can be detected without a special device. The following steps are performed: a tool sensor measurement step (S1) in which a reference tool is installed on a spindle, and as tool sensor measurement values, measurement position coordinates of the tip of the reference tool in a plurality of different measurement regions on the upper surface of the contact tool sensor are obtained; a difference value output step (S2) in which, based on each tool sensor measurement value, a prescribed difference value is output; an anomaly detection step (S3) in which the difference value is compared with a pre-set allowable value, and in the case where at least one difference value deviates from the allowable value, an anomaly is determined; and a tool sensor calibration step (S4) in which, in the case where no anomaly is determined in the anomaly detection step, based on each tool sensor measurement value, the positional relationship between the spindle and the contact tool sensor is calibrated.

Description

Technical Field

[0001] This disclosure relates to a method for calibrating a contact tool sensor used in a machine tool, a computer-readable storage medium for storing calibration procedures for the contact tool sensor, and a machine tool. Background Technology

[0002] In a machine tool controlled by a CNC device, during machining, the tool size and tool tip position mounted on the spindle are measured by a tool sensor.

[0003] The shape and position of cutting tools and tool sensors change due to thermal displacement of machine tools caused by changes in room temperature, thermal displacement caused by the heating of the spindle, and changes over time. Therefore, in order to maintain high-precision machining during long-term machining, tool sensor calibration is required.

[0004] Typically, the calibration of contact-type tool sensors, such as touch sensors, is performed as follows: the tool used in setting the origin of the workpiece coordinate system or a reference tool of known length is brought into contact with a contact-type tool sensor fixed to the worktable, etc., and the spindle position is recorded when a signal from the contact-type tool sensor is detected at the moment of contact.

[0005] However, in actual machine tool cutting operations, chips or cutting fluid (hereinafter referred to as foreign matter) sometimes fall onto the contact tool sensor. This foreign matter becomes a major cause of error in the calibration of the contact tool sensor, resulting in errors in the measured tool length. As a countermeasure, there is a method of cleaning the contact tool sensor with air before measurement, but it is difficult to completely remove foreign matter.

[0006] Therefore, in the past, when detecting foreign objects, operators would visually confirm the foreign objects during processing breaks.

[0007] On the other hand, as shown in Patent Document 1, detection methods using images captured by a camera are also known. Here, a method is shown for detecting the location of foreign objects from images captured of the workpiece setting area and focusing on cleaning the detected locations.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent No. 6400817 Summary of the Invention

[0011] The problem that the invention aims to solve

[0012] However, in the traditional method of visually identifying foreign objects during processing intervals, there is a problem of reduced productivity due to processing interruptions.

[0013] Furthermore, in the method of Patent Document 1, in addition to the camera that needs to take pictures of the processing area inside the machine tool, a countermeasure is also needed to prevent foreign objects from adhering to the lens of the camera, which presents a cost problem.

[0014] Therefore, the purpose of this disclosure is to provide a calibration method for a contact tool sensor in a machine tool that can detect foreign objects without special devices, as well as a computer-readable storage medium and a machine tool for storing calibration programs for the contact tool sensor.

[0015] Methods for solving problems

[0016] To achieve the above objective, the first structure of this disclosure is characterized by a method for correcting the positional relationship between the spindle and a contact-type tool sensor mounted on the worktable in a machine tool having three or more translation axes, a spindle capable of mounting a tool, a worktable, and a CNC device for controlling the translation axes and the spindle, characterized in that the method comprises the following steps:

[0017] The tool sensor measurement step involves mounting a reference tool on the spindle and using it as the tool sensor measurement value. The measurement position coordinates of the end of the reference tool in at least two different measurement areas on the upper surface of the contact tool sensor are obtained respectively.

[0018] The differential value output step outputs a specified differential value based on the measured values ​​of each of the tool sensors.

[0019] The anomaly detection step compares the difference values ​​with a preset tolerance value, and determines an anomaly if at least one of the difference values ​​deviates from the tolerance value; and

[0020] In the tool sensor calibration step, if no abnormality is determined in the abnormality detection step, the positional relationship between the spindle and the contact tool sensor is calibrated based on the measured values ​​of each tool sensor.

[0021] Another aspect of the first structure disclosed herein is characterized in that, in the above structure, when an anomaly is determined in the anomaly detection step, a cleaning step is performed to clean the upper surface of the contact tool sensor.

[0022] Another aspect of the first structure disclosed herein is characterized in that, in the above structure, during the cleaning step, at least the measurement area where the tool sensor measurement value has been obtained in relation to the difference value deviating from the allowable value is cleaned.

[0023] Another aspect of the first structure disclosed herein is characterized in that, in the above structure, after performing the cleaning step, the tool sensor measurement step, the differential value output step, and the anomaly detection step are performed again. When an anomaly is determined in the subsequent anomaly detection step, the process of re-executing the cleaning step is repeated.

[0024] When the number of times an anomaly is detected in the anomaly detection step reaches a predetermined threshold, processing is stopped and a notification step to inform the situation is executed.

[0025] Another aspect of the first structure disclosed herein is characterized in that, in the above structure, in the differential value output step, the difference between the measured values ​​of each of the tool sensors is output as the differential value.

[0026] Another aspect of the first structure of this disclosure is characterized in that, in the above structure, the following steps are performed:

[0027] The reference value recording step involves recording the measurement position coordinates of the end of the reference tool in multiple measurement areas as reference values ​​for each tool sensor, before executing the differential value output step, provided that no foreign matter adheres to the upper surface of the contact tool sensor or the reference tool.

[0028] In the displacement value output step, the difference between the reference value of each tool sensor and the measured value of each tool sensor in the same measurement area as the reference value of each tool sensor is output as the displacement value of each tool sensor.

[0029] In the differential value output step, the difference between the displacement values ​​of each of the tool sensors is used as the differential value output.

[0030] Another aspect of the first structure disclosed herein is characterized in that, in the above structure, in the differential value output step, the direction in which the spindle approaches the contact tool sensor is set as the negative direction, the minimum value among the measured values ​​of each tool sensor is set as the minimum value of the tool sensor measured value, and the difference between the tool sensor measured value other than the tool sensor measured value involved in the minimum value and the minimum value of the tool sensor measured value is used as the differential value output.

[0031] Another aspect of the first structure of this disclosure is characterized in that, in the above structure, the following steps are performed:

[0032] The reference value recording step involves recording the measurement position coordinates of the end of the reference tool in multiple measurement areas as reference values ​​for each tool sensor, before executing the differential value output step, provided that no foreign matter adheres to the upper surface of the contact tool sensor or the reference tool.

[0033] In the displacement value output step, the difference between the reference value of each tool sensor and the measured value of each tool sensor in the same measurement area as the reference value of each tool sensor is output as the displacement value of each tool sensor.

[0034] In the differential value output step, the direction in which the spindle approaches the contact tool sensor is set as the negative direction, the minimum value among the displacement values ​​of each tool sensor is set as the minimum displacement value of the tool sensor, and the difference between the displacement values ​​of the tool sensor other than the displacement values ​​of the tool sensor involved in the minimum value and the minimum displacement value of the tool sensor is used as the differential value output.

[0035] The second structure of this disclosure is a computer-readable storage medium storing a calibration program for a contact tool sensor in a machine tool. This calibration program is used to enable the CNC device to execute any one of the calibration methods for the contact tool sensor described in the first to eighth structures of this disclosure in a machine tool having three or more translation axes, a spindle capable of mounting a tool, a worktable, and a CNC device for controlling the translation axes and the spindle, with a reference tool mounted on the spindle and a contact tool sensor provided on the worktable.

[0036] The third structure disclosed herein is a machine tool having: three or more translation axes; a spindle capable of mounting cutting tools; a worktable; and a CNC device for controlling the translation axes and the spindle, characterized in that it includes:

[0037] The tool sensor measurement unit, with a reference tool mounted on the spindle and a contact tool sensor set on the worktable, obtains the measurement position coordinates of the end of the reference tool in at least two different measurement areas on the upper surface of the contact tool sensor as the measurement values ​​of each tool sensor.

[0038] A differential value output unit outputs a predetermined difference between the measured values ​​of each of the tool sensors;

[0039] An anomaly detection unit compares the difference values ​​with preset tolerance values, and determines an anomaly if at least one of the difference values ​​deviates from the tolerance value; and

[0040] The tool sensor calibration unit, when the anomaly detection unit does not determine that there is an anomaly, corrects the positional relationship between the spindle and the contact tool sensor based on the measured values ​​of each tool sensor.

[0041] Invention Effects

[0042] According to this disclosure, the adhesion of foreign objects to a contact tool sensor can be detected during machining without the need for visual inspection by the operator or special equipment. This reduces the operator's workload, minimizes idle time caused by machining interruptions, and allows verification of accurate calibration of the contact tool sensor. Furthermore, since it eliminates the need for camera-based measurement systems, it can be implemented at a relatively low cost.

[0043] In particular, by employing a structure that cleans the contact tool sensor when an anomaly is detected, the contact tool sensor can be accurately calibrated while eliminating the influence of foreign matter adhesion. This allows for accurate measurement of the tool length used in machining, maintaining machining accuracy during processing. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of a machining center.

[0045] Figure 2 This is a schematic diagram of an example of the apparatus used for measurement in Method 1.

[0046] Figure 3 This is an example of the measurement area observed from a direction perpendicular to the reaction surface of the contact tool sensor in Method 1.

[0047] Figure 4 This is a functional block diagram of the CNC device in Method 1.

[0048] Figure 5 This is a flowchart of the calibration method for the contact tool sensor in Method 1.

[0049] Figure 6 This is a functional block diagram of the CNC device in Method 2.

[0050] Figure 7 This is a flowchart of the calibration method for the contact tool sensor in Method 2.

[0051] Figure 8 This is a schematic diagram of an example of the apparatus used for the measurement in Method 3.

[0052] Figure 9 This is another example of the measurement area observed from a direction perpendicular to the reaction surface of the contact tool sensor in Method 3.

[0053] Figure 10 This is a functional block diagram of the CNC device in method 3.

[0054] Figure 11 This is a functional block diagram of the CNC device in method 4.

[0055] Figure 12 This is an example of an area that is judged to contain foreign matter by being observed from a direction perpendicular to the reaction surface of a contact tool sensor.

[0056] Figure 13 This is another example of an area that is judged to contain foreign matter by being viewed from a direction perpendicular to the reaction surface of a contact tool sensor.

[0057] Figure 14 This is a flowchart illustrating a modified calibration method for a contact tool sensor.

[0058] Symbol Explanation

[0059] 1. Bed, 2. Spindle head, 3. Worktable, 6. Reference tool, 20. Contact tool sensor, 7. Reaction surface, 9-12. Tool sensor measurement unit, 21-24. Displacement output unit, 13. Differential output unit, 14. Anomaly detection unit, 15. Tool sensor calibration unit, 16. Measurement and recording unit, 18. Foreign object position detection unit, 19. Cleaning unit, 30. CNC device, M. Machining center. Detailed Implementation

[0060] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings.

[0061] [Method 1]

[0062] Figure 1 This is a schematic diagram of a machining center M with three mutually orthogonal translation axes, representing one type of machine tool. The spindle head 2 (spindle) can move with 2 degrees of freedom of translation relative to the bed 1 via the X and Z axes, which are mutually orthogonal to each other. The worktable 3 can move with 1 degree of freedom of translation relative to the bed 1 via the Y axis, which is orthogonal to the X and Z axes. Therefore, the spindle head 2 can move with 3 degrees of freedom of translation relative to the worktable 3. The movements of the X, Y, and Z axes are executed by servo motors controlled by a CNC device 30 (described later). The workpiece is fixed to the worktable 3, the cutting tool is mounted on the spindle head 2 and rotated, and the relative position and posture of the workpiece and the cutting tool are controlled to perform workpiece machining.

[0063] Furthermore, the machine tool involved in this disclosure is not limited to 3 axes, but may also have 4 or 5 axes. Alternatively, it may be a mechanism that enables the worktable 3 and the spindle head 2 to have more than 1 degree of rotational freedom through a rotary axis.

[0064] Figure 2 This is a schematic diagram of a device that uses a contact-type tool sensor (hereinafter referred to as "tool sensor") 7 installed on the worktable 3 for measurement. The CNC device 30 controls the relative position of the spindle head 2 and the XYZ axes of the worktable 3, thereby changing the relative position relationship between the reference tool 6 mounted on the spindle head 2 and the tool sensor 7. A signal is emitted from the tool sensor 7 by bringing the end of the reference tool 6 into contact with the reaction surface 8 of the tool sensor 7. Based on the relative position coordinates of the spindle head 2 and the XYZ axes of the worktable 3 at the moment the signal is emitted and the length of the reference tool 6, the relative position coordinates of the reaction surface 8 perpendicular to the reaction surface 8 and the worktable 3 can be detected. This reaction surface 8 serves as a reference surface for measuring the tool length. The tool sensor 7, the reference tool 6, and the CNC device 30 function as the tool sensor measurement unit of this disclosure. Hereinafter, the direction in which the spindle head 2 approaches the tool sensor 7 will be considered the negative direction.

[0065] If the reference tool 6 mounted on the spindle head 2 is not deformed, even if mechanical deformation occurs and the positional relationship between the spindle head 2 and the reaction surface 8 of the tool sensor 7 changes, the reference surface can still be corrected in the tool length measurement by bringing the end of the reference tool 6 to the reaction surface 8 and measuring the relative position of the reaction surface 8 in the axial direction perpendicular to the reaction surface 8 again.

[0066] Figure 3 This is an example of the measurement area when viewed from a direction perpendicular to the reaction surface 8. In this method, the reference tool 6 only abuts against a portion of the reaction surface 8, and the relative positions of the reaction surfaces 8 are measured in two or more areas without overlapping measurement areas. Here, measurements in four different measurement areas are listed as an example, as shown by the dashed circles. The measurement units in each measurement area are designated as tool sensor measurement unit 9, tool sensor measurement unit 10, tool sensor measurement unit 11, and tool sensor measurement unit 12.

[0067] Figure 4 This is a functional block diagram of the parts involved in the calibration of the tool sensor 7 in the CNC device 30. The CNC device 30 includes a differential value output unit 14, an anomaly detection unit 15, a tool sensor calibration unit 16, a measurement and recording unit 17, a foreign object position detection unit 18, and a cleaning unit 19 as calibration function units.

[0068] The differential value output unit 14 serves as the differential value output unit of this disclosure, and outputs a specified differential value based on the tool sensor measurement values ​​A to D output from each tool sensor measurement unit 9 to 12.

[0069] The anomaly detection unit 15, as the anomaly detection unit of this disclosure, determines whether there is an anomaly based on the output difference value.

[0070] The tool sensor calibration unit 16, as the tool sensor calibration unit of this disclosure, performs calibration of the reference surface when the anomaly detection unit 15 determines that there is no anomaly.

[0071] The measurement and recording unit 17 records the measured values ​​A to D of the tool sensor.

[0072] The foreign object location detection unit 18 detects the location of the foreign object in the measurement area when the anomaly detection unit 15 determines that there is an anomaly.

[0073] The cleaning unit 19 cleans the measurement area where foreign objects are detected by the foreign object location detection unit 18.

[0074] The CNC device 30 executes a computer-readable storage medium storing a calibration program for the contact tool sensor stored in the storage unit. Figure 5 The flowchart shows the calibration method for the tool sensor 7.

[0075] First, in step S1, the end of the reference tool 6 is brought into contact with four measurement areas of the reaction surface 8 of the tool sensor 7, and the relative positions of the reaction surface 8 along the axial direction perpendicular to the reaction surface 8 are measured (tool sensor measurement step). The measurement results of the relative positions of the reaction surfaces 8 in the tool sensor measurement units 9 to 12 are set as tool sensor measurement value A, tool sensor measurement value B, tool sensor measurement value C, and tool sensor measurement value D, respectively. Each tool sensor measurement value A to D is input to the differential value output unit 14.

[0076] In S2, the differential value output unit 14 calculates the absolute values ​​of the differences AB between tool sensor measured values ​​A and B, BC between tool sensor measured values ​​B and C, CD between tool sensor measured values ​​C and D, and DA between tool sensor measured values ​​D and A (differential value output step). Each differential value output from the differential value output unit 14 is then input to the anomaly detection unit 15.

[0077] In S3, the anomaly detection unit 15 determines whether each difference value is below a preset allowable value (anomaly detection step).

[0078] Here, if all differential values ​​are below the allowable value, it is determined that there is no abnormality, and the tool sensor measurement values ​​A to D are output to the tool sensor calibration unit 16 and recorded in the measurement record unit 17. In S4, the tool sensor calibration unit 16 updates the calibration value of the reference plane in the measurement of tool length based on the tool sensor measurement values ​​A to D (tool sensor calibration step).

[0079] On the other hand, in the judgment of S3, if any difference value exceeds the allowable value, it is determined that there is an abnormality, and the judgment result is output to the foreign object position detection unit 18.

[0080] In S5, the foreign object location detection unit 18 determines that a foreign object exists in the measurement area of ​​the tool sensor measurement unit that determines the differential value to be abnormal (exceeding the allowable value), and outputs the determination result to the cleaning unit 19.

[0081] In S6, the cleaning unit 19 cleans the measurement area where foreign objects are detected by the foreign object location detection unit 18 by means of fluid jetting or the like (cleaning step).

[0082] Thus, based on the calibration method of tool sensor 7 according to Method 1 described above, and the computer-readable storage medium storing the calibration program of the contact tool sensor, the machining center M outputs a specified difference value based on the measured values ​​A to D of the tool sensor and compares the difference value with the allowable value. If at least one difference value deviates from the allowable value, it is determined to be abnormal. On the other hand, if it is not determined to be abnormal, the positional relationship between the spindle head 2 and the tool sensor 7 is corrected based on the measured values ​​of each tool sensor. Therefore, during machining, the attachment of foreign objects on the tool sensor 7 can be detected without the need for visual confirmation by the operator or special devices. As a result, the burden on the operator can be reduced, the idle time caused by machining interruption can be reduced, and it can be confirmed whether the calibration of the tool sensor 7 has been performed accurately.

[0083] Hereinafter, other embodiments of this disclosure will be described. However, structural parts such as the machining center that are the same as those in Embodiment 1 will be labeled with the same reference numerals, and repeated descriptions will be omitted.

[0084] [Method 2]

[0085] Figure 6 This is a functional block diagram illustrating another example of the part involved in the calibration of the tool sensor 7 in the CNC device 30. Here, the difference from Method 1 is that a displacement value output unit 13 is provided, which calculates the difference between the measured value of each tool sensor and the reference value of each tool sensor as the displacement value.

[0086] In this method 2, such as Figure 7 As shown in the flowchart, firstly, in S11, with the tool sensor measuring units 9 to 12 and the reference tool 6 free of foreign matter, the measuring position coordinates of the end of the reference tool 6 in each measuring area are measured and recorded in the measuring record unit 17 as tool sensor reference value A, tool sensor reference value B, tool sensor reference value C, and tool sensor reference value D (reference value recording step).

[0087] Next, in S12, the measurement values ​​A to D of the tool sensor 7 are obtained by measuring each measurement area.

[0088] Next, in S13, the displacement value output unit 13 calculates the differences between the tool sensor measured value A and the tool sensor reference value A, the tool sensor measured value B and the tool sensor reference value B, the tool sensor measured value C and the tool sensor reference value C, and the tool sensor measured value D and the tool sensor reference value D, respectively (displacement value output step). These differences are then set as displacement value A, displacement value B, displacement value C, and displacement value D, respectively.

[0089] Next, in S14, the differential value output unit 14 calculates the difference AB between displacement value A and displacement value B, the difference BC between displacement value B and displacement value C, the difference CD between displacement value C and displacement value D, and the difference DA between displacement value D and displacement value A.

[0090] Next, in S15, the anomaly detection unit 15 determines whether each difference value is below the allowable value. If there is no difference value exceeding the allowable value, the correction value is updated (S16). If there is a difference value exceeding the allowable value, it is determined to be abnormal, the location of the foreign object is detected (S17), and the measurement area is cleaned (S18).

[0091] Thus, in the tool sensor 7 calibration method of Method 2 described above, and in the computer-readable storage medium storing the calibration program of the contact tool sensor, the attachment of foreign objects on the tool sensor 7 can be detected without the need for visual confirmation by the operator during machining, and with the aid of a special device. This reduces the operator's workload, minimizes idle time caused by machining interruptions, and allows confirmation that the tool sensor 7 has been accurately calibrated.

[0092] In particular, by calculating the difference value based on the displacement value of the same measurement location, the influence of the flatness and parallelism of the end of the tool sensor 7 and the reference tool 6 can be eliminated. Therefore, compared with the method in Method 1, the adhesion of foreign objects can be detected with high precision.

[0093] [Method 3]

[0094] Figure 8 This is a schematic diagram of another example of the measuring apparatus in this disclosure. A reference tool 20, which is as thick as the area that can form an overlapping measuring area when it abuts against the upper surface of the tool sensor 7 at multiple locations, is mounted on the spindle head 2.

[0095] Figure 9 This is another example of the measurement area viewed from a direction perpendicular to the reaction surface 8 of the tool sensor 7. Figure 10 This is another example of a functional block diagram showing the part involved in the calibration of the tool sensor 7 in the CNC device 30. Here, a displacement value output unit is not provided, resulting in the same structure as in mode 1.

[0096] In this method 3, the reference tool 20 only contacts a portion of the reaction surface 8 of the tool sensor 7. In cases of overlapping measurement areas, the relative positions of the reaction surfaces 8 of the tool sensor 7 are measured in two or more areas. Here, measurements in four different measurement areas are given as an example. Figure 9 As shown by the arc-shaped dashed lines in (A) to (D), the measuring units in each measuring area are designated as tool sensor measuring unit 21, tool sensor measuring unit 22, tool sensor measuring unit 23, and tool sensor measuring unit 24.

[0097] The process of the correction method in Method 3 is the same as Figure 5 The same applies. First, in S1, the relative positions of the reaction surfaces 8 of the tool sensors 7 in the tool sensor measuring units 21-24 are measured. The measurement results are set as tool sensor measured values ​​A', B', C', and D', respectively. Then, the value that is the minimum among the tool sensor measured values ​​A' to D' (the value where the position of the spindle head 2 is closest to the tool sensor 7 when it reacts) is set as the minimum tool sensor measured value. Figure 10 The diagram shows the case where the tool sensor reading C' becomes the minimum value of the tool sensor reading.

[0098] In S2, the differential output unit 14 calculates the difference A'C' between the minimum value measured by the tool sensor and the tool sensor measured value A', the difference B'C' between the minimum value measured by the tool sensor and the tool sensor measured value B', and the difference D'C' between the minimum value measured by the tool sensor and the tool sensor measured value D'.

[0099] Then, in S3, in the anomaly detection unit 15, it is determined whether each difference value is below the allowable value. If there is no difference value exceeding the allowable value, the correction value is updated (S4). If there is a difference value exceeding the allowable value, it is determined to be abnormal, the location of the foreign object is detected (S5), and the measurement area is cleaned (S6).

[0100] Thus, in the tool sensor 7 calibration method of Method 3 described above, and in the computer-readable storage medium storing the calibration program of the contact tool sensor, the attachment of foreign objects on the tool sensor 7 can be detected without the need for visual confirmation by the operator during machining, or with a special device. This reduces the operator's workload, minimizes idle time caused by machining interruptions, and allows confirmation that the tool sensor 7 has been accurately calibrated.

[0101] [Method 4]

[0102] Figure 11 This is a functional block diagram illustrating another example of the part involved in the calibration of the tool sensor 7 in the CNC device 30. Here, a displacement value output unit 13 is included, similar to that in mode 2.

[0103] The process of the correction method in Method 4 is the same as Figure 7 Same. First, in S11, with no foreign matter attached to the tool sensor measuring units 21 to 24 and the reference tool 20, the measuring position coordinates of the end of the reference tool 20 in each measuring area are measured and recorded in the measuring record unit 17 as normal tool sensor reference values ​​A', B', C', and D'.

[0104] Next, in S12, the measurement values ​​A' to D' of each measurement area of ​​the tool sensor 7 are obtained.

[0105] Next, in S13, the displacement value output unit 13 calculates the differences between the tool sensor measured value A' and the tool sensor reference value A', the differences between the tool sensor measured value B' and the tool sensor reference value B', the differences between the tool sensor measured value C' and the tool sensor reference value C', and the differences between the tool sensor measured value D' and the tool sensor reference value D', respectively, for the same measurement area. These differences are set as displacement values ​​A', B', C', and D', respectively. The minimum value among these displacement values ​​is taken as the minimum displacement value. Figure 11 The figure shows the case where the displacement value C' is at its minimum.

[0106] Next, in S14, the differential value output unit 14 calculates the difference A'C' between the minimum displacement value and the displacement value A', the difference B'C' between the minimum displacement value and the displacement value B', and the difference D'C' between the minimum displacement value and the displacement value D'.

[0107] Next, in S15, the anomaly detection unit 15 determines whether each difference value is below the allowable value. If there is no difference value exceeding the allowable value, the correction value is updated (S16). If there is a difference value exceeding the allowable value, it is determined to be abnormal, the location of the foreign object is detected (S17), and the measurement area is cleaned (S18).

[0108] Thus, in the tool sensor 7 calibration method of Method 4 described above, and in the computer-readable storage medium storing the calibration program of the contact tool sensor, the attachment of foreign objects on the tool sensor 7 can be detected without the need for visual confirmation by the operator during machining, and with the aid of a special device. This reduces the operator's workload, minimizes idle time caused by machining interruptions, and allows confirmation that the tool sensor 7 has been accurately calibrated.

[0109] In particular, since the differential value is calculated based on the displacement value of the same measurement location, the influence of the flatness and parallelism of the end of the tool sensor 7 and the reference tool 20 can be eliminated. Therefore, the adhesion of foreign objects can be detected with higher accuracy compared with the method of method 3.

[0110] Furthermore, in the methods shown in methods 1 and 2, when obtaining the difference between the tool sensor measurement values ​​in the measurement areas that include the overlapping measurement areas, if there are foreign objects attached in the overlapping measurement areas, the anomaly detection unit 15 may sometimes fail to detect the anomaly. However, in method 4, such failure to detect anomalies can be avoided.

[0111] Next, the cleaning process of the cleaning section 19 will be explained in detail.

[0112] Figure 12 This is an example where the area where a foreign object is determined to exist is covered when viewed from a direction perpendicular to the reaction surface 8 of the tool sensor 7. In the foreign object location detection unit 18, for example... Figure 9 When measurements are taken in the four measurement areas shown, if the anomaly detection unit 15 determines that only the tool sensor measurement value A of the tool sensor measurement unit 21 is abnormal, the area detected as having foreign matter attached is coated. If there is an anomaly only in the difference containing the tool sensor measurement value A, and other differences are not determined to be abnormal, it is determined that foreign matter is attached to the portion remaining after removing the areas where tool sensor measurement values ​​B, C, and D were measured from the area where tool sensor measurement value A was measured. In this case, the cleaning unit 19 can clean the area... Figure 12 The areas covered by the coating are then cleaned using methods such as fluid jetting.

[0113] Figure 13 This is another example of an area that is judged to contain foreign matter by being viewed from a direction perpendicular to the reaction surface 8 of the tool sensor 7.

[0114] In the foreign object location detection unit 18 of methods 3 and 4, for example, if the anomaly detection unit 15 determines that the tool sensor measurement values ​​A and B of the tool sensor measurement units 21 and 22 are abnormal, the area where foreign objects are detected is completely coated. When the tool sensor measurement value C is at its minimum, there are anomalies in the difference between the tool sensor measurement value A and the minimum tool sensor measurement value, and in the difference between the tool sensor measurement value B and the minimum tool sensor measurement value. If the tool sensor measurement value D is not determined to be abnormal, it is determined that foreign objects are attached to the portion remaining after removing the area where the tool sensor measurement values ​​C and D are measured from the area where the tool sensor measurement values ​​A and B are measured. In this case, even if foreign objects are attached to the area where the measurement areas of the tool sensor measurement values ​​A and B overlap, it is possible to determine the attachment of foreign objects. Therefore, the cleaning unit 19 can clean the area where the tool sensor measurement values ​​A and B overlap. Figure 13 The areas covered by the coating are cleaned using methods such as fluid jetting.

[0115] However, in each method, the cleaning unit 19 can clean the tool sensor 7 not only in the measurement area where foreign matter is determined to be attached, but also on the entire upper surface of the tool sensor 7.

[0116] On the other hand, in each method, the following process can be repeated: after cleaning is performed as if there is an abnormality, the cleaning measurement area is measured again, and based on the obtained tool sensor measurement value, the differential value output unit 14 calculates a new differential value, and the abnormality detection unit 15 determines again whether there is an abnormality.

[0117] Figure 14 This is a flowchart illustrating an example of repeatedly checking for abnormalities. S21 to S24 are related to... Figure 5 The same process applies: when an exception is determined in S23, the number of times n is determined in S25 is counted.

[0118] Next, in S26, it is determined whether the number of counts, n, exceeds a predetermined threshold. If n does not exceed the threshold, the location of the foreign object is detected in S27, the measurement area is cleaned in S28, and the tool sensor is measured again in S21, repeating the subsequent processing. On the other hand, if n exceeds the threshold in the determination in S26, an alarm or other notification is issued in S29 (notification step), and the process ends.

[0119] In addition, execution in methods 3 and 4 Figure 14In the case of the flowchart, the process of recording the tool sensor reference value before the tool sensor measurement and the process of calculating the displacement value after the tool sensor measurement are added. Therefore, in the difference value output step of S22, the difference between the minimum value of the tool sensor measurement or the minimum value of the displacement value recorded in the measurement recording unit 17 is obtained.

[0120] Furthermore, in each method, the locations of the tool sensor for measurement are not limited to four. If there are two or more locations, differential values ​​can be calculated, and therefore the number can be increased or decreased as appropriate.

[0121] The shape of the tool sensor is not limited to the above-described manner. For example, the reaction surface can also be a shape other than a circle when viewed from above.

[0122] This disclosure can also be applied to machine tools other than machining centers.

Claims

1. A calibration method for a contact-type tool sensor in a machine tool, the machine tool having three or more translation axes, a spindle capable of mounting a tool for machining a workpiece, a worktable, a CNC device for controlling the translation axes and the spindle, and a contact-type tool sensor for measuring a reference surface of the tool mounted on the spindle, the reference surface being a flat plane, the calibration method being a method for calibrating the positional relationship between the spindle and the contact-type tool sensor mounted on the worktable in the machine tool, characterized in that... The following steps are performed in this method: The tool sensor measurement step involves mounting a reference tool on the spindle and using it as the tool sensor measurement value. The measurement position coordinates of the end of the reference tool in at least two different measurement areas on the reference surface of the contact tool sensor are obtained. The differential value output step outputs a differential value based on the difference between the measured values ​​of each of the tool sensors. The anomaly detection step compares the difference value with a preset tolerance value. If at least one of the difference values ​​deviates from the tolerance value, it is determined to be an anomaly. Otherwise, it is not determined to be an anomaly. as well as In the tool sensor calibration step, if no abnormality is determined in the abnormality detection step, the positional relationship between the spindle and the contact tool sensor is calibrated based on the measured values ​​of each tool sensor.

2. The calibration method for a contact-type tool sensor in a machine tool according to claim 1, characterized in that, When an anomaly is detected in the anomaly detection step, a cleaning step is performed to clean the reference surface of the contact tool sensor.

3. The calibration method for a contact-type tool sensor in a machine tool according to claim 2, characterized in that, In the cleaning step, at least the measurement area where the tool sensor measurement value was obtained related to the difference value deviating from the allowable value is cleaned.

4. The calibration method for a contact-type tool sensor in a machine tool according to claim 2, characterized in that, After performing the cleaning step, the tool sensor measurement step, the differential value output step, and the anomaly detection step are performed again. If an anomaly is detected in the subsequent anomaly detection step, the cleaning step is repeatedly executed. When the number of times an anomaly is detected in the anomaly detection step reaches a predetermined threshold, processing is stopped and a notification step to inform the situation is executed.

5. The calibration method for a contact-type tool sensor in a machine tool according to claim 1, characterized in that, Perform the following steps: The reference value recording step involves recording the measurement position coordinates of the end of the reference tool in multiple measurement areas as reference values ​​for each tool sensor before executing the differential value output step, under the condition that no foreign matter is attached to the reference surface of the contact tool sensor and the reference tool. as well as In the displacement value output step, the difference between the reference value of each tool sensor and the measured value of each tool sensor in the same measurement area as the reference value of each tool sensor is output as the displacement value of each tool sensor. In the differential value output step, the difference between the displacement values ​​of each of the tool sensors is used as the differential value output.

6. The calibration method for a contact-type tool sensor in a machine tool according to claim 1, characterized in that, In the differential value output step, the direction in which the spindle approaches the contact tool sensor is set as the negative direction, the minimum value among the measured values ​​of each tool sensor is set as the minimum value of the tool sensor measurement, and the difference between the tool sensor measurement values ​​other than the tool sensor measurement values ​​involved in the minimum value and the minimum value of the tool sensor measurement is used as the differential value output.

7. The calibration method for a contact-type tool sensor in a machine tool according to claim 1, characterized in that, Perform the following steps: The reference value recording step involves recording the measurement position coordinates of the end of the reference tool in multiple measurement areas as reference values ​​for each tool sensor before executing the differential value output step, under the condition that no foreign matter is attached to the reference surface of the contact tool sensor and the reference tool. as well as In the displacement value output step, the difference between the reference value of each tool sensor and the measured value of each tool sensor in the same measurement area as the reference value of each tool sensor is output as the displacement value of each tool sensor. In the differential value output step, the direction in which the spindle approaches the contact tool sensor is set as the negative direction, the minimum value among the displacement values ​​of each tool sensor is set as the minimum displacement value of the tool sensor, and the difference between the displacement values ​​of the tool sensor other than the displacement values ​​of the tool sensor involved in the minimum value and the minimum displacement value of the tool sensor is used as the differential value output.

8. A computer-readable storage medium storing a calibration program for a contact tool sensor in a machine tool, the calibration program being used to cause the CNC device to execute the calibration method for the contact tool sensor according to any one of claims 1 to 7 in a machine tool having three or more translation axes, a spindle capable of mounting a tool, a worktable, and a CNC device for controlling the translation axes and the spindle, wherein a reference tool is mounted on the spindle and a contact tool sensor is provided on the worktable.

9. A machine tool comprising: three or more translation axes; a spindle capable of mounting a tool for machining a workpiece; a worktable; a CNC device for controlling the translation axes and the spindle; and a contact-type tool sensor for measuring a reference surface of the tool mounted on the spindle, the reference surface being a flat plane, characterized in that, include: The tool sensor measurement unit, with a reference tool mounted on the spindle and the contact tool sensor set on the worktable, obtains the measurement position coordinates of the end of the reference tool in at least two different measurement areas of the reference surface of the contact tool sensor as the measurement values ​​of each tool sensor. The differential value output unit outputs a differential value based on the difference between the measured values ​​of each of the tool sensors; An anomaly detection unit compares the difference value with a preset tolerance value, and determines that an anomaly occurs if at least one of the difference values ​​deviates from the tolerance value; otherwise, it does not determine that an anomaly occurs. as well as The tool sensor calibration unit, when the anomaly detection unit does not determine that there is an anomaly, corrects the positional relationship between the spindle and the contact tool sensor based on the measured values ​​of each tool sensor.

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