Method for detecting phase of tap, and method for machining internal thread of machine tool, and machine tool

Abstract

Provided are a method for detecting the phase of a tap, a method for machining an internal thread of a machine tool, and a machine tool. The phase of a tap is detected in a simple manner without using a dedicated device. While rotating the tap (4), the position of the thread (4a) of the tap (4) is measured by a sensor (laser irradiation device (7) and laser detection device (8)) from a direction intersecting the axial direction of the tap (4), the relationship between the rotation angle and the presence / absence of the thread (4a) is acquired, and the phase of the tap (4) is detected based on the acquired relationship between the rotation angle and the presence / absence of the thread (4a).

Description

Technical Field

[0001] The present invention relates to a method for detecting the phase of a tap used in internal thread machining on a machine tool, an internal thread machining method using the method, and a machine tool capable of performing the machining method. Background Technology

[0002] In machining using taps, which are tools for forming internal threads in workpieces, tap breakage is a frequent occurrence. When internal threading is performed multiple times, the cutting edge of the tap gradually wears down, thus increasing the cutting load. If the cutting load exceeds the tap's allowable load, the tap will break. Although methods are employed to monitor the cutting load and stop internal threading to prevent breakage, if internal threading is interrupted and the tap is removed, it becomes difficult to continue the internal threading process with a new tap. This is because, in internal threading, the axial feed and tap rotation must be synchronized. Therefore, in order to machine the partially machined internal thread with a new tap, the tool protrusion length and phase of the removed tap and the new tap must be aligned.

[0003] Regarding the protruding length of the tool, contact-type devices for measuring the tool length and non-contact devices using lasers are becoming increasingly common, allowing for easy correction based on the measured value. On the other hand, regarding phase, methods for determining the phase between the tap and the tool holder have been proposed. For example, Patent Document 1 discloses a tap mounting device that uses a ring gauge and a height gauge to mount the tap to the tap holder with a specified phase and protruding length. Patent Document 2 discloses a machining method that uses a distance gauge to set the relative position of the tap and the workpiece.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2015-39762

[0005] Patent Document 2: Japanese Patent Application Publication No. 2019-93478

[0006] However, the methods described in Patent Documents 1 and 2 use specialized equipment to determine the phase between the tap and the tool holder, thus presenting a problem in terms of versatility. Furthermore, the assumption that the operator must perform a series of phase determination operations presents a challenge in automation.

[0007] Therefore, the present invention was made in view of the above-mentioned problems, and its object is to provide a method for detecting the phase of a tap in a simple way without using a dedicated device.

[0008] Another object of the present invention is to provide an internal thread machining method and machine tool that can use the phase detection method of the tap to continue machining of interrupted internal thread machining. Summary of the Invention

[0009] To achieve the above objectives, the first structure of the present invention is a method for detecting the phase of a tap.

[0010] The feature is that, while the tap is rotated, the position of the thread teeth of the tap is measured by a sensor from a direction intersecting the axis of the tap, the relationship between the rotation angle and the presence or absence of the thread teeth is obtained, and the phase of the tap is detected based on the obtained relationship between the rotation angle and the presence or absence of the thread teeth.

[0011] Another aspect of the first structure of the present invention is characterized in that, in the above structure, the sensor has a laser irradiation device for irradiating the position of the threaded tooth with laser and a laser detection device for detecting the irradiated laser.

[0012] To achieve the above objectives, the second structure of the present invention is an internal thread machining method, wherein a tap is installed on the spindle of a machine tool to continue the interrupted internal thread machining, characterized in that the following steps are performed in the internal thread machining method:

[0013] The reference phase acquisition step involves installing the tap before the interruption (i.e., the reference tap) onto the spindle. While rotating the spindle, the position of the thread teeth of the reference tap is measured by a sensor from a direction intersecting the axis of the reference tap. The relationship between the rotation angle of the spindle and the presence or absence of the thread teeth is obtained in advance.

[0014] In the phase acquisition step, other taps that will continue to perform internal thread machining are installed on the spindle. While the spindle is rotating, the position of the thread teeth of the other taps is measured by the sensor to obtain the relationship between the rotation angle of the spindle and the presence or absence of the thread teeth.

[0015] The phase difference calculation step, based on the relationship between the rotation angle and the presence or absence of the thread teeth obtained in the reference phase acquisition step, and the relationship between the rotation angle and the presence or absence of the thread teeth obtained in the measurement phase acquisition step, calculates the phase difference between the reference tap and the other taps; and

[0016] The machining process involves setting the starting position of the spindle rotation with the other taps installed, based on the phase difference, and continuing internal thread machining from the starting position.

[0017] Another aspect of the second structure of the present invention is characterized in that, in the above structure, in the machining step, the phase difference calculated in the phase difference calculation step is set as a phase correction amount, and the spindle is rotated from the rotation interruption angle of the spindle whose internal thread machining has been interrupted by the phase correction amount by a rotation angle offset from the rotation interruption angle of the spindle whose internal thread machining has been interrupted as the starting position.

[0018] Another aspect of the second structure of the present invention is characterized in that, in the above structure, in the machining step, a new machining start spindle phase is set in the machining program based on the machining start spindle phase in the machining program of the control device of the machine tool whose internal thread machining has been interrupted and the phase difference calculated in the phase difference calculation step, and the spindle is rotated using the new machining start spindle phase as the starting position.

[0019] Another aspect of the second structure of the present invention is characterized in that, in the above structure, the sensor has a laser irradiation device for irradiating the position of the threaded tooth with laser and a laser detection device for detecting the irradiated laser.

[0020] To achieve the above objectives, the third structure of the present invention is a machine tool capable of mounting a tap on the spindle and continuing interrupted internal thread machining, characterized in that the machine tool has:

[0021] A sensor capable of measuring the position of the thread teeth of the tap from a direction intersecting the axial direction of the tap mounted on the spindle;

[0022] The reference phase acquisition unit, while the main spindle is rotated with the tap (i.e., the reference tap) installed before the interruption, measures the position of the thread teeth of the reference tap through the sensor to obtain the relationship between the rotation angle of the main spindle and the presence or absence of the thread teeth.

[0023] The phase acquisition unit has other taps that will continue to perform internal thread machining installed on the spindle. While the spindle is rotating, the phase acquisition unit measures the position of the thread teeth of the other taps through the sensor to obtain the relationship between the rotation angle of the spindle and the presence or absence of the thread teeth.

[0024] A phase difference calculation unit calculates the phase difference between the reference tap and the other taps based on the relationship between the rotation angle and the presence or absence of the thread teeth obtained by the reference phase acquisition unit, and the relationship between the rotation angle and the presence or absence of the thread teeth obtained by the measurement phase acquisition unit; and

[0025] The machining unit, based on the phase difference, sets the starting position of the spindle rotation on which the other taps are mounted, and continues internal thread machining from the starting position.

[0026] Invention Effects

[0027] According to the first structure of the present invention, while the tap is rotated, the position of the thread teeth of the tap is measured by a sensor to obtain the relationship between the rotation angle and the presence or absence of thread teeth. Therefore, the phase of the tap can be detected in a simple way without the use of a special device.

[0028] According to the second and third structures of the present invention, by using the phase detection method of the tap of the first structure, the phase of the reference tap before the interruption can be easily made consistent with the phase of other taps after the interruption.

[0029] Therefore, internal thread machining can resume even after an interruption. Furthermore, since the phase detection and correction of the tap are performed inside the machine tool, automation can be achieved through the machining program without the need for an operator. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of one embodiment of a machining center.

[0031] Figure 2 This is an explanatory diagram showing the relationship between the tap and the laser.

[0032] Figure 3 This is an explanatory diagram showing the relationship between the phase of the reference tap and whether the laser detects thread teeth.

[0033] Figure 4 This is an explanatory diagram showing the relationship between the laser and the tap.

[0034] Figure 5 This is an explanatory diagram showing the relationship between the laser and the tap for other taps.

[0035] Figure 6 This is an explanatory diagram showing the relationship between the phase of other taps and whether the laser detected thread teeth.

[0036] Figure 7 This is a flowchart of the internal thread machining method.

[0037] Label Explanation

[0038] 1: Spindle head; 2: Spindle; 3: Tool holder; 4: Tap; 4a: Thread tooth; 5: Worktable; 6: Workpiece; 7: Laser irradiation device; 8: Laser detection device; 9: Laser; 9A: Through part; 9B: Blocking part; 10: Groove; 20: Projection view of tap outline; 21: Projection view of tap cross section; 22: Position of thread root; L: Axis of tap. Detailed Implementation

[0039] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0040] exist Figure 1 A machining center, as an example of a machine tool, is shown and described below. The machining center has a spindle head 1 capable of orthogonal 3-axis motion. The spindle head 1 has a rotatable spindle 2, and a tool holder 3 is mounted on the front end of the spindle 2. The tool holder 3 holds a tap 4. The machining center controls the rotation of the spindle 2 and the feed motion of the spindle head 1 through a control device (not shown), and uses the tap 4 to perform internal thread machining on a workpiece 6 fixed on a worktable 5.

[0041] A laser irradiation device 7, which irradiates laser 9 along the X-axis, and a laser detection device 8, positioned opposite the laser irradiation device 7, are installed on the worktable 5. The laser detection device 8 detects the presence or absence of laser 9 irradiated by the laser irradiation device 7 and can detect whether there is an object blocking the laser 9 between the two devices. The laser irradiation device 7 and the laser detection device 8 are connected to a control device, enabling synchronized control with the machining center. Figure 1 This is a schematic diagram showing the overall view, and therefore does not depict the position where the tap 4 is measured by the laser 9. However, during the phase detection of the tap 4, the spindle head 1 is moved to a position where the laser 9 irradiates the thread teeth of the tap 4. Furthermore, the control device has the function of calculating the phase of the tap 4 based on the relationship between the phase of the spindle 2 and the detection by the laser 9, enabling the execution of the reference phase acquisition unit, the phase measurement acquisition unit, the phase difference calculation unit, and the machining unit of this invention.

[0042] Figure 2 This is a magnified perspective view of tap 4 and laser 9 during phase detection of tap 4. To facilitate chip removal, tap 4 is cut with grooves 10 in the axial direction; in this embodiment, it has four equally spaced grooves 10, 10… In this figure, laser 9 is blocked because it irradiates the thread 4a of tap 4, thus remaining undetected in the laser detection device 8. Later, as the spindle 2 gradually rotates, causing tap 4 to rotate, laser 9 is positioned at the root of the thread 4 and is no longer blocked, thus being detected by the laser detection device 8. Furthermore, laser 9 is also detected when it is positioned within the groove 10 of tap 4.

[0043] Figure 3 This example illustrates the phase of the tap 4 based on this method and the measurement waveform obtained by laser detection using the laser detection device 8. The measurement waveform is uniquely determined by the phase when the tap 4 is mounted on the tool holder 3 and the spindle 2. The phase difference between the tap being measured and the reference tap is expressed as the left-right offset of the measurement waveform. Therefore, the phase difference of the tap can be corrected based on the offset from the reference waveform. Furthermore, the phase can also be determined from characteristic points of the measurement waveform. For example, in... Figure 3In this context, the value at the center of phases a and b is the phase of the vertex of the thread tooth, so the phase difference of the tap can also be calculated based on the phase of the vertex of the thread tooth.

[0044] Next, the relationship between the phase of tap 4 and the measured waveform will be described in detail. Furthermore, for convenience, for tap 4 and laser 9, it will be explained in reverse order, assuming tap 4 is fixed and laser 9 rotates on tap 4.

[0045] Figure 4 It is a projection of the cross section of the tap 4 obtained by cutting the surface irradiated by the laser 9 onto a plane orthogonal to the axis L of the tap 4. The projection 20 of the shape of the tap 4 is a circle centered on the axis L of the tap 4. In contrast, the thread 4a of the tap 4 is helical, so the projection 21 of its cross section is not rotationally symmetric.

[0046] Here, by setting the distance between the straight line of laser 9 and the straight line formed by the axis L of tap 4 to between half the outer diameter of tap 4 and half the root diameter of the thread, when tap 4 rotates, laser 9 will pass through the root of the thread or be blocked by the thread tooth 4a. Figure 4 In the diagram, between the projection of the outer diameter of the tap 4 (20) and the position 22 of the tooth root, the circle formed by the laser 9 is shown. The shape through which the laser 9 can pass without irradiating the thread tooth 4a is shown as the passing part 9A (solid line), and the shape through which the laser 9 irradiates the thread tooth 4a and is blocked is shown as the blocking part 9B (dashed line).

[0047] exist Figure 3 In this diagram, the state of the laser 9 is shown as a measured waveform detected by the laser detection device 8. Here, a pair of blocking portions 9B, 9B are detected with a phase angle of 90° as the center.

[0048] This Figure 3 The measured waveform is used as the reference waveform, and when the second and subsequent taps are used, for example, as shown in Figure 4... Figure 5 That is relative to Figure 4 When rotated 90°, in the detected measurement waveform, such as Figure 6 A pair of obstructed portions 9B, 9B were detected centered at a phase angle of 180°. The measured waveform is... Figure 3 The diagram is obtained by shifting the phase of the reference waveform to the right, so the phase difference between the first tap 4 and the second and subsequent taps 4 can be calculated based on this shift.

[0049] Next, in Figure 7 The flowchart illustrates a specific internal thread machining method based on a machining center.

[0050] First, the first tap is used as the reference tap before the internal thread machining is interrupted, and the protrusion length (S1) is set.

[0051] Next, when the spindle head 1 is moved a predetermined length along the Z-axis and the spindle 2 is rotated, the spindle head 1 is moved along the X and Y axes so that the laser 9 is alternately positioned at the position of the thread tooth 4a and the root of the first tap 4, and the reference position for phase measurement is set (S2).

[0052] Next, the spindle 2 is rotated to obtain the phase of the first tap 4 and the measured waveform of the laser detection as described above, which serves as the phase reference (S3: reference phase acquisition step).

[0053] Then, internal thread machining is performed using a reference tap. If machining is interrupted due to damage to the reference tap, other taps are used. In this case, for the second and subsequent taps 4, first, after correction in a manner that makes the protrusion length consistent with the reference tap (S4), the spindle head 1 is moved in the X, Y, Z axis directions to the reference position determined by the phase set by the reference tap (S5).

[0054] Then, the phase of other taps 4 and the measured waveform of laser detection are obtained here, and the phase difference with the reference waveform obtained in S3 is calculated (S6: Phase measurement acquisition step and phase difference calculation step).

[0055] Based on the phase difference obtained in this way, a starting position is set for the spindle 2, on which other taps 4 are mounted, to rotate, and internal thread machining continues from this starting position (S7: machining step).

[0056] In this machining step, specifically, the phase difference calculated in S6 is set in the control device as the phase correction amount for the other taps 4. The control device sets the rotation angle (starting position) of the spindle 2 to the rotation angle offset from the rotation angle at which the internal thread machining was interrupted, i.e., the rotation interruption angle, by the phase correction amount. Therefore, internal thread machining can continue with the same phase as the reference tap.

[0057] Alternatively, as another example of a machining step, the following method can be used: instead of inputting a phase correction amount, the phase after the spindle phase shifted from the start of machining when the internal thread machining was interrupted is set as the new start spindle phase in the machining program that instructs the machine tool's machining actions. In this case, if the control device reads the new start spindle phase from the machining program, it uses this new start spindle phase as the starting position and rotates the spindle 2, thus enabling the internal thread to be machined at the same phase as the reference tap.

[0058] Thus, in the above-described method for detecting the phase of a tap, while rotating the tap 4, the position of the thread tooth 4a of the tap 4 is determined by the laser irradiation device 7 and the laser detection device 8 from the direction intersecting the axis of the tap 4, and the relationship between the rotation angle and the presence or absence of the thread tooth 4a is obtained. The phase of the tap 4 is detected based on the obtained relationship between the rotation angle and the presence or absence of the thread tooth 4a.

[0059] Based on this structure, the phase of the tap can be detected in a simple way without the use of a special device.

[0060] In particular, since the sensor has a laser irradiation device 7 that irradiates the laser 9 at the position of the thread tooth 4a and a laser detection device 8 that detects the irradiated laser 9, even if the thread tooth 4a is measured, the tap 4 and the sensor will not be damaged.

[0061] Furthermore, in the internal thread machining method and machining center described above, the relationship between the rotation angle of the spindle 2 and the presence or absence of thread teeth corresponding to the reference tap before the interruption is obtained in advance by the sensor. After the interruption, the relationship between the rotation angle of the spindle 2 and the presence or absence of thread teeth corresponding to other taps is obtained, the phase difference between the reference tap and other taps is calculated, and the starting position of internal thread machining is set based on the phase difference and internal thread machining continues.

[0062] This structure allows for easy alignment of the phase of the reference tap before the interruption with that of other taps after the interruption. Therefore, internal thread machining can resume after an interruption. Furthermore, since the phase detection and correction of the tap are performed within the machining center, automation can be achieved through the machining program without the need for an operator.

[0063] Furthermore, the sensor only needs to be able to measure the threads of the tap; it can be any type of non-contact sensor or a contact sensor. The shape of the tap is also not limited to the methods described above. For example, the number of grooves can be more or less than those described above.

[0064] As a machine tool, it is sufficient as long as it can perform internal thread machining based on taps, and is not limited to machining centers.

Claims

1. A method for phase detection of a tap, wherein, The phase detection of a tap is characterized by, While the tap is rotated, a sensor detects the presence or absence of the thread teeth and the position traversed by the thread root at a location intersecting the tap's axial direction, thus obtaining the relationship between the rotation angle and the presence or absence of the thread teeth. The phase of the tap is detected based on the relationship between the obtained rotation angle and the presence or absence of the thread teeth.

2. The phase detection method for a tap according to claim 1, characterized in that, The sensor has a laser irradiation device for irradiating laser light at the location through which the thread tooth and the root of the tooth pass, and a laser detection device for detecting the irradiated laser light.

3. A method for machining internal threads on a machine tool, wherein, A tap is installed on the spindle of a machine tool to continue the interrupted internal thread machining, characterized in that... The following steps are performed in the internal thread machining method of this machine tool: In the reference phase acquisition step, the tap before the interruption, i.e. the reference tap, is installed on the spindle. While the spindle is rotated, the presence or absence of the thread teeth and the root of the reference tap is detected by a sensor from the direction intersecting the axis of the reference tap. The relationship between the rotation angle of the spindle and the presence or absence of the thread teeth is obtained in advance. In the phase acquisition step, other taps that will continue internal thread machining are installed on the spindle. While the spindle is rotating, the sensor detects the presence or absence of the thread teeth and the position through which the thread teeth of the other taps pass, and obtains the relationship between the rotation angle of the spindle and the presence or absence of the thread teeth. The phase difference calculation step, based on the relationship between the rotation angle and the presence or absence of the thread teeth obtained in the reference phase acquisition step, and the relationship between the rotation angle and the presence or absence of the thread teeth obtained in the measurement phase acquisition step, calculates the phase difference between the reference tap and the other taps; and The machining process involves setting the starting position of the spindle rotation with the other taps installed, based on the phase difference, and continuing internal thread machining from the starting position.

4. The method for machining internal threads on a machine tool according to claim 3, characterized in that, In the machining step, the phase difference calculated in the phase difference calculation step is set as the phase correction amount, and the spindle is rotated from the rotation interruption angle of the spindle whose internal thread machining was interrupted by the phase correction amount by the rotation angle offset from the phase correction amount as the starting position.

5. The method for machining internal threads on a machine tool according to claim 3, characterized in that, In the machining step, based on the machining start spindle phase in the machining program of the machine tool control device where the internal thread machining has been interrupted and the phase difference calculated in the phase difference calculation step, a new machining start spindle phase is set in the machining program, and the spindle is rotated using the new machining start spindle phase as the starting position.

6. The method for machining internal threads on a machine tool according to any one of claims 3 to 5, characterized in that, The sensor has a laser irradiation device for irradiating laser light at the location through which the thread tooth and the root of the tooth pass, and a laser detection device for detecting the irradiated laser light.

7. A machine tool, wherein, This machine tool is capable of mounting a tap on the spindle and continuing interrupted internal thread machining, characterized in that the machine tool has: A sensor capable of measuring the position of the thread teeth of the tap from a direction intersecting the axial direction of the tap mounted on the spindle; The reference phase acquisition unit, while the main spindle is rotated with the tap (i.e., the reference tap) installed before the interruption, detects the presence or absence of the thread teeth at the position passed by the thread root of the reference tap through the sensor, and obtains the relationship between the rotation angle of the main spindle and the presence or absence of the thread teeth. The phase acquisition unit is used to install other taps that will continue internal thread machining on the spindle. While the spindle is rotating, the phase acquisition unit uses the sensor to detect the presence or absence of the thread teeth and the position through which the thread roots of the other taps pass, and obtains the relationship between the rotation angle of the spindle and the presence or absence of the thread teeth. A phase difference calculation unit calculates the phase difference between the reference tap and the other taps based on the relationship between the rotation angle and the presence or absence of the thread teeth obtained by the reference phase acquisition unit, and the relationship between the rotation angle and the presence or absence of the thread teeth obtained by the measurement phase acquisition unit; and The machining unit, based on the phase difference, sets the starting position of the spindle rotation on which the other taps are mounted, and continues internal thread machining from the starting position.

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