Processing device
By using multiple judgment thresholds to compare the sensor output level in NC processing and automatically set the contact threshold, the contact error monitoring problem caused by changes in the output waveform of the AE sensor is solved, ensuring processing accuracy and equipment safety.
Patent Information
- Application Number
- CN202410734508.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2023-06-13
- Filing Date
- 2024-06-07
- Publication Date
- 2024-12-13
AI Technical Summary
In NC machining, changes in output waveform level of the AE sensor lead to contact mis-monitoring, which may cause the tool to shift phase from the workpiece or trimming tool, affecting machining accuracy and potentially damage the equipment.
By comparing the output level of the sensor with multiple determination thresholds, the contact threshold is automatically set to prevent contact mis-monitoring.
Effectively prevent contact mis-monitoring, ensure high-precision monitoring of tools and tool contacts, and avoid phase offsets and equipment damage.
Smart Images
Figure CN119115727A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a processing device for performing NC (numerical control) processing. Background Art
[0002] NC machining is generally performed in a machining device that processes machine parts, etc. In NC machining, a machining tool (hereinafter referred to as a tool) or a tool contact object (a workpiece or a dressing tool) is moved using a servo motor built into the machining device.
[0003] In NC machining, it is essential to perform detection processing using sensors in its control. For example, Patent Document 1 discloses using an AE (Acoustic Emission) sensor to perform contact monitoring between a tool and a dressing cutter.
[0004] Prior art literature
[0005] Patent Literature
[0006] Patent Document 1: Japanese Patent Application Publication No. 2000-263440
[0007] Patent Document 2: Japanese Patent Application Publication No. 2020-199620 Summary of the invention
[0008] In contact monitoring using sensors, it is important to prevent false monitoring. For example, the contact monitoring of the AE sensor is to compare the output waveform of the AE sensor with a specified threshold value, and when the waveform level exceeds the threshold value, contact is detected. However, when the AE sensor is used for a long time, due to the degradation of the sensor or device mechanism over the years, or changes in the surrounding environment, it can be imagined that the waveform level during non-contact will change. When the change in the waveform level of the AE sensor becomes larger, the possibility of false contact monitoring (contact reaction when not in contact, non-contact reaction when in contact) increases. If false contact monitoring of the AE sensor occurs, a phase shift between the tool and the workpiece (or dressing tool) will occur, making high-precision processing impossible. In addition, if the phase shift is too large, the tool, device mechanism, etc. may be damaged.
[0009] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a machining device capable of preventing erroneous contact detection even when the output level of a sensor that monitors contact between a tool and a tool contact object changes.
[0010] In order to solve the above-mentioned problems, the processing device of the present invention comprises: a tool supporting unit for supporting a tool, a tool contact object supporting unit for supporting a tool contact object that can be contacted and separated relative to the tool, a sensor whose output level changes due to the contact between the tool and the tool contact object, and a control unit for monitoring the contact between the tool and the tool contact object based on the output of the sensor, characterized in that the control unit performs contact monitoring by comparing the output level of the sensor with a contact threshold, and changes the contact threshold by comparing the output level of the sensor when the tool and the tool contact object are in a non-contact state with multiple judgment thresholds.
[0011] According to the above structure, the output level of the sensor when the tool and the tool contact object are in a non-contact state is compared with a plurality of determination thresholds, and the contact threshold is changed according to the result, thereby, even if the output level of the sensor changes due to aging, etc., the contact threshold can be automatically set appropriately. Thus, false contact detection can be prevented.
[0012] [Effects of the invention]
[0013] The processing device of the present invention can achieve the following technical effects: it can automatically set a contact threshold for contact monitoring between a tool and a tool contact object, and can prevent false contact monitoring. BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Figure 1 It is a perspective view of a gear grinding device as one embodiment of the processing device of the present invention.
[0015] Figure 2 The diagram shows the meshing state between the grindstone and the workpiece when the workpiece is ground.
[0016] Figure 3 It is a figure which shows the meshing state of the grindstone and the dressing cutter when performing the dressing process of the grindstone.
[0017] Figure 4 It is a cross-sectional view including the rotation axis of the grindstone of the grindstone supporting unit.
[0018] Figure 5 This is a block diagram showing a control system for performing contact monitoring using an AE sensor and resetting a contact threshold.
[0019] Figure 6 It is a waveform diagram showing contact monitoring using an AE sensor.
[0020] Figure 7 This is a diagram showing an example of a screen displaying an output signal of the AE sensor when contact monitoring is performed.
[0021] Figure 8 This is a diagram showing an example of switching of the screen displaying the output signal of the AE sensor when contact monitoring is performed.
[0022] Fig. 9 This is a diagram showing an example of switching of the screen displaying the output signal of the AE sensor when contact monitoring is performed.
[0023] Fig.10 This is a diagram showing an example of switching of the screen displaying the output signal of the AE sensor when contact monitoring is performed.
[0024] Fig.11 This is a diagram showing an example of switching of the screen displaying the output signal of the AE sensor when contact monitoring is performed.
[0025] Fig.12 It is a table showing the switching conditions of the determination threshold value.
[0026] [Description of Reference Numerals]
[0027] 10 Gear grinding device (processing device) 1 Base
[0028] 2 grinding stone support unit (tool support unit) 20 grinding stone (tool)
[0029] 21 Automatic balancer 210AE sensor
[0030] 3 workpiece handling units (tool contact support units) 30 spindles
[0031] 31 support column 32 tailstock
[0032] 33 Dressing device 4 Control unit
[0033] 331 Dressing tool (tool contact object) 40 Judgment unit
[0034] 41 Threshold value setting unit 42 Threshold value changing unit
[0035] W workpiece (tool contact object) S1 AE waveform signal TH1~TH4 judgment threshold THc contact threshold DETAILED DESCRIPTION
[0036] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, in this embodiment, an example is shown in which the processing device of the present invention is applied to a gear grinding device that performs grinding processing on a gear as a workpiece (work object).
[0037] Figure 1 1 is a perspective view showing the main parts of the gear grinding device 10 involved in this embodiment. In this embodiment, for the convenience of description, as shown in FIG. Figure 1The front-rear direction, the left-right direction, and the up-down direction are defined as shown. The specific structure of the mechanism of the gear grinding device 10 is disclosed in, for example, Patent Document 2, and the mechanism of the gear grinding device 10 is briefly described below.
[0038] The gear grinding device 10 grinds the workpiece W as a work object while rotating it synchronously with a grindstone 20 as a tool, and includes a base 1, a grindstone support unit (tool support unit) 2 disposed on the base 1, and a workpiece processing unit (tool contact object support unit) 3. The grindstone support unit 2 supports the grindstone 20 so that it can rotate. Figure 1 In the embodiment, the rotation axis direction of the grindstone 20 is the front-rear direction. A thread-shaped groove is formed on the outer peripheral surface of the grindstone 20.
[0039] The workpiece processing unit 3 includes a main spindle 30 and a support column 31, and a tailstock 32 and a dressing device 33 are supported integrally on the support column 31 in a rotatable manner. When grinding the workpiece W, the tailstock 32 is positioned on the main spindle 30 by rotating the support column 31, and the workpiece W is supported by the main spindle 30 and the tailstock 32 in a manner of clamping the workpiece W. The supported workpiece W can be rotated by driving the main spindle 30 to rotate with the up-and-down direction as the rotation axis direction. The gear grinding device 10 is as shown in FIG. Figure 2 As shown, the tooth surface of the workpiece W can be ground by driving the grindstone 20 and the workpiece W synchronously while the grindstone 20 is meshed with the workpiece W.
[0040] The dressing device 33 is used when performing dressing processing on the grindstone 20. Dressing processing is performed to make the thread-shaped groove of the grindstone 20 sharp again after continuously processing a predetermined number of workpieces W, such as Figure 3 As shown, the grinding stone 20 is rotated while the dressing tool 331 held by the dressing device 33 is in contact with the grinding stone 20, thereby shaping and repairing the thread-shaped groove of the grinding stone 20. If the grinding ability of the grinding stone 20 is restored, the dimensional accuracy of the grinding stone 20 is restored, and the workpiece W can be ground again.
[0041] The grinding stone support unit 2 can move in the left-right direction, and by this movement, the grinding stone 20 can be brought into contact with and separated from the workpiece W during grinding. In addition, the grinding stone 20 can be brought into contact with and separated from the dressing tool 331 during dressing. Before grinding, it is necessary to monitor the contact between the grinding stone 20 and the workpiece W as the grinding stone 20 moves. Figure 2 Before the dressing process, the contact between the grinding stone 20 and the dressing tool 331 needs to be monitored ( Figure 3That is, in this embodiment, the workpiece W or the dressing tool 331 is a tool contact object that is a contact monitoring object.
[0042] Figure 4 2 is a cross-sectional view including the rotation axis of the grindstone 20 of the grindstone support unit 2. Figure 4 As shown, the grinding stone support unit 2 is provided with an automatic balancer 21, which automatically corrects the balance of the grinding stone 20 during rotation. In this embodiment, the automatic balancer 21 includes an AE sensor 210 (see FIG. 21 ) for monitoring the contact of the grinding stone 20. Figure 5 The AE sensor 210 detects the sound (elastic wave) generated when the grindstone 20 contacts the workpiece W or the dressing tool 331, and converts it into an electrical signal for output.
[0043] Figure 5 2 is a block diagram showing a control system for performing contact monitoring using the AE sensor 210 and resetting a contact threshold value THc described later. Figure 5 As shown, the gear grinding device 10 includes a control unit 4, and the control unit 4 includes: a determination unit 40, a threshold setting unit 41, and a threshold changing unit 42. The determination unit 40 compares and determines the output signal of the AE sensor 210 (the AE waveform signal S1 described later) with the threshold. The threshold setting unit 41 stores the set threshold. The threshold changing unit 42 receives the threshold determination result of the determination unit 40 and switches the threshold set in the threshold setting unit 41.
[0044] Figure 6 2 is a diagram showing an example of a screen displaying an output signal of the AE sensor 210 when performing contact monitoring. Figure 6 In the figure, S1 is a waveform signal (AE waveform signal) output by the AE sensor 210, and THc is a contact threshold value for contact monitoring by comparison with the AE waveform signal S1. Basically, when there is no contact with the grindstone 20 (contact with the tool contact object), the waveform level of the AE waveform signal S1 is lower than the contact threshold value THc. If there is contact with the grindstone 20, the waveform level of the AE waveform signal S1 rises sharply and exceeds the contact threshold value THc. When the AE waveform signal S1 exceeds the contact threshold value THc, the control unit 4 detects the contact between the grindstone 20 and the tool contact object.
[0045] In addition, the contact monitoring here is performed when the phase of the grindstone 20 and the tool contact object is aligned before the grinding process or the dressing process is performed. In the gear grinding device 10, when the grinding process or the dressing process is performed, the phase of the threaded groove of the grindstone 20 is aligned so that the workpiece W or the dressing tool 331 is appropriately aligned with the threaded groove of the grindstone 20 (such as Figure 2 or Figure 3The grinding stone 20 and the tool contact object are meshed as shown. The phase alignment is performed while repeatedly bringing the grinding stone 20 into contact with the tool contact object, and contact monitoring is performed at this time. Therefore, during the contact monitoring stage, if the grinding stone 20 and the tool contact object are detected to be in contact, control is performed to separate the grinding stone 20 and the tool contact object. As a result, the grinding stone 20 becomes non-contact again, and the waveform level of the AE waveform signal S1 also drops to the level of the non-contact state.
[0046] In order to accurately perform such contact monitoring, it is necessary to appropriately set the contact threshold THc for the AE waveform signal S1. However, sometimes the waveform level of the AE waveform signal S1 in the non-contact state may change due to the aging of the AE sensor 210 or changes in the surrounding environment. For example, if a change such as a decrease in the waveform level in the non-contact state occurs, there is a possibility of false detection of the so-called non-contact reaction in contact, that is, the AE waveform signal S1 does not exceed the contact threshold THc when the grindstone 20 is in contact. On the contrary, if a change such as an increase in the waveform level in the non-contact state occurs, there is a possibility of false detection of the so-called contact reaction in the non-contact state, that is, the AE waveform signal S1 exceeds the contact threshold THc even when the grindstone 20 is not in contact.
[0047] Such erroneous detection can be prevented by resetting the contact threshold value according to the change in the waveform level of the AE waveform signal S1. The gear grinding device 10 of the present invention can automatically reset the contact threshold value THc. The following describes a method for resetting the contact threshold value THc of the gear grinding device 10.
[0048] In this embodiment, at the time of starting the contact monitoring of the grindstone 20, as shown in FIG. Figure 7 to Figure 11 As shown in the left figure of FIG. 1 , four determination thresholds TH1 to TH4 (collectively referred to as determination thresholds TH) are set in order from low to high levels. Among them, the determination threshold TH3 is equivalent to the above-mentioned contact threshold THc.
[0049] Figure 7 to Figure 11 The left figure is a waveform diagram of the AE waveform signal S1 measured for a predetermined period of time immediately after the contact monitoring starts. During the predetermined period, although the grinding stone 20 moves in a direction close to the tool contact object, it maintains a non-contact state during the predetermined period. That is, Figure 7 to Figure 11 The AE waveform signal S1 in the left figure is a waveform (non-contact waveform) in a state where the grindstone 20 is not in contact with the tool contact object.
[0050] The non-contact waveform of the AE waveform signal S1 is compared with the determination threshold TH, and the determination threshold TH is switched according to the comparison result. That is, when the level of the non-contact waveform is low, the determination threshold TH is switched to a low level, and when the level of the non-contact waveform is high, the determination threshold TH is switched to a high level. In addition, the switching of the determination threshold TH must include the switching of the determination threshold TH3 (i.e., the contact threshold THc).
[0051] Fig.12 is a table showing the switching conditions of the determination threshold TH. Fig.12 In the table, the level ratios with respect to the respective values of the determination threshold values TH1 to TH4 are shown, assuming that the maximum level value of the AE waveform signal S1 is 100% and the minimum level value is 0%.
[0052] Taking the contact monitoring when the grinding stone 20 and the workpiece W are aligned in phase as an example, the judgment threshold TH at the beginning of the detection is set to Fig.12 That is, the values of the judgment thresholds TH1 to TH4 are set to 3%, 20%, 40%, and 60%, respectively. This setting is equivalent to Figure 7 to Figure 11 Left picture.
[0053] When the non-contact waveform of the AE waveform signal S1 is between the determination threshold TH1 and the determination threshold TH2, it is determined that the level of the non-contact waveform is low, and the determination threshold TH is switched to Fig.12 That is, the values of the judgment thresholds TH1 to TH4 are switched to 0%, 35%, 40%, and 99%, respectively. This switching is equivalent to changing from Figure 7 The left figure switches to the right figure. The determination result at this time is output from the determination unit 40 to the threshold value changing unit 42 as a threshold value determination result. In addition, the threshold value changing unit 42 receives the threshold value determination result and changes the determination threshold value TH set in the threshold value setting unit 41.
[0054] When the non-contact waveform of the AE waveform signal S1 is between the determination threshold TH2 and the determination threshold TH3, the level of the non-contact waveform is determined to be in the intermediate state, and the determination threshold TH is switched to Fig.12 That is, the values of the judgment thresholds TH1 to TH4 are switched to 0%, 50%, 55%, and 99%, respectively. This switching is equivalent to changing from Figure 8 Switch from the left image to the right image.
[0055] When the non-contact waveform of the AE waveform signal S1 is between the determination threshold TH3 and the determination threshold TH4, the level of the non-contact waveform is determined to be high, and the determination threshold TH is switched to Fig.12That is, the values of the judgment thresholds TH1 to TH4 are switched to 0%, 70%, 75%, and 99%, respectively. This switching is equivalent to changing from Fig. 9 Switch from the left image to the right image.
[0056] The contact monitoring during the phase alignment between the grindstone 20 and the dressing cutter 331 is basically performed in the same manner as the contact monitoring during the grinding phase alignment. However, the values of the determination thresholds TH for the contact monitoring during the dressing phase alignment and the contact monitoring during the grinding phase alignment may be the same or different. Fig.12 In the example, the value of the determination threshold TH3 is different when comparing "workpiece threshold (low)" to "workpiece threshold (high)" and "dressing threshold (low)" to "dressing threshold (high)". This is because the tool contact object in contact with the grindstone 20 for contact monitoring during dressing phase alignment and contact monitoring during grinding phase alignment is different, so the increase in the AE waveform signal S1 during contact may be different. That is, the value of the determination threshold TH3 after the determination threshold TH is switched is preferably set according to the increase in the AE waveform signal S1 during contact.
[0057] After the judgment threshold TH is switched, contact monitoring continues. Figure 7 to Figure 9 In the right figure of FIG. 1 , the AE waveform signal S1 whose waveform level rises sharply due to the contact of the grindstone 20 exceeds the determination threshold TH3 (contact threshold THc) after switching. That is, based on the determination threshold TH3 after switching, appropriate contact determination of the grindstone 20 is achieved. The determination result at this time is output from the determination unit 40 as a contact determination result.
[0058] In this way, in the contact monitoring of the gear grinding device 10 of the present invention, the level of the non-contact waveform is judged by comparing the non-contact waveform of the AE waveform signal S1 with multiple judgment thresholds TH, and the contact threshold THc is appropriately set according to the level of the non-contact waveform, thereby preventing erroneous monitoring of contact.
[0059] In addition, the non-contact waveform of the AE waveform signal S1 also exists: when it exceeds the determination threshold TH4 ( Fig.10 left figure), and when it is lower than the judgment threshold TH1 ( Fig.11 In these cases, there may be an abnormality other than contact error monitoring (such as wire breakage, AE sensor 210 failure), so the contact monitoring process is terminated. In addition, when the contact monitoring process is terminated, control is performed to separate the grinding stone 20 from the tool contact object.
[0060] In addition, after the determination threshold TH is switched, contact monitoring is performed by comparing the AE waveform signal S1 with the determination threshold TH3. Therefore, the change caused by the switching of the determination threshold TH may be only the determination threshold TH3. Fig.12 In the example, not only the judgment threshold TH3 but also the judgment threshold TH2 is changed. This is because: when performing contact monitoring, if the waveform level of the AE waveform signal S1 exceeds the judgment threshold TH2 but does not exceed the judgment threshold TH3 for a specified period of time (for example, about 2 seconds), it is assumed that incomplete contact has occurred, so that the contact monitoring process can be terminated. For example, when the dressing tool deteriorates during the dressing phase alignment, even if the grinding stone 20 and the dressing tool come into contact, the AE waveform signal S1 will not change as shown in the figure. Figure 6 The sharp rise shown may cause a situation in which the waveform level of the so-called AE waveform signal S1 exceeds the determination threshold value TH2 but does not exceed the determination threshold value TH3.
[0061] The embodiments disclosed this time are examples in all points and are not to be interpreted as limiting. Therefore, the technical scope of the present invention is not to be interpreted only by the above-mentioned embodiments but is to be determined by the description of the claims.
[0062] For example, in the above-mentioned embodiment, an example of a gear grinding device is shown as the processing device of the present invention, but in the present invention, the type of processing performed by the processing device or the shape of the workpiece is not particularly limited. That is, for NC machine tools, in order to determine the quasi-position of the workpiece during processing, it is necessary to monitor the contact starting point between the tool and the tool contact object, and the contact monitoring used for this purpose can also be applied to the present invention. In addition, the type of sensor used for contact monitoring is not particularly limited, and sensors other than AE sensors can also be used (appropriate sensors can be selected according to the type of processing).
[0063] In the above embodiment, the contact and separation between the tool and the tool contact object is caused by the movement of the tool, but it can also be caused by the movement of the tool contact object. That is, the contact and separation between the tool and the tool contact object can be caused by the relative movement of the tool relative to the tool contact object.
Claims
1. A processing device comprising: A tool support unit, which supports the tool; a tool contact object supporting unit that supports a tool contact object capable of being brought into contact with and separated from the tool; a sensor whose output level changes in response to contact between the tool and the tool-contact object; as well as a control unit for monitoring contact between the tool and the tool contact object based on the output of the sensor, It is characterized in that The control unit performs contact monitoring by comparing the output level of the sensor with a contact threshold, and changes the contact threshold by comparing the output level of the sensor when the tool and the tool contact object are in a non-contact state with multiple determination thresholds.
2. The processing device according to claim 1, It is characterized in that The tool contact object is a workpiece to be machined using the tool.
3. The processing device according to claim 2, It is characterized in that The workpiece is a gear, The tool is a grindstone for grinding the tooth surface of the gear.
4. The processing device according to claim 1, It is characterized in that The tool is a grinding stone for grinding. The tool contact object is a dressing tool for performing a dressing process on the grindstone.
5. The processing device according to claim 1, It is characterized in that The tool is a grinding stone for grinding. The sensor is an AE sensor.