Machine tool control device

Abstract

To suppress deterioration of productivity by automatically retracting a tool without breakage when a machining abnormality or the like occurs.SOLUTION: A control device 10 of a machine tool 1 having a tool 7 attached to a main shaft 6 relatively movable to a workpiece W, and machining the workpiece W by using the tool 7, includes: parameter preparation means 13 in which parameters regarding control are preliminarily stored; retraction means 14 for performing retraction operation of the tool 7 from the workpiece W; and retraction diagnosis means 15 for diagnosing whether or not the retraction operation is normal. When the retraction diagnosis means 15 diagnoses that the retraction operation is abnormal, the control device suspends the retraction operation.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a control device in a machine tool that automatically and safely retracts a tool without breaking it when a machining abnormality or the like occurs. [Background technology]

[0002] In machine tools, when threading using a tap as a tool, if an abnormality occurs during processing, the tap must be removed from the screw hole in the middle of processing. If the removal operation is performed automatically by a machine, if cutting chips get caught between the cutting edge and the created thread surface, a large load is placed on the tap, and in the worst case, the tap breaks and the workpiece becomes defective. Therefore, currently, the removal operation is performed manually by a person while adjusting the load during the removal operation, which requires many man-hours before processing can be resumed, resulting in a decrease in productivity. Therefore, a method has been proposed to control the retraction speed during retraction based on information on the tap and information on the workpiece. For example, Patent Document 1 discloses an invention that automates the removal operation without damaging the tap or workpiece by inputting tap pitch information and workpiece material information to calculate the spindle speed for the removal operation and retracting the tool at the calculated speed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 6-59715 Summary of the Invention [Problem to be solved by the invention]

[0004] The technology of the above-mentioned Patent Document 1 proposes a technology in which the spindle speed for the extraction operation that does not cause breakage is determined in advance for each material type of the workpiece, and the tool is withdrawn at a speed calculated based on the spindle speed determined by inputting the material type information of the workpiece and the pitch information of the tap. However, depending on the state of the chips between the cutting edge and the created thread surface when the processing is interrupted, a large load is placed on the tap by simply performing a reverse operation, and breakage cannot be prevented. Figure 1 shows the operating torque when the chips are trapped in different states at the time of withdrawal in tapping. The upper figure shows a case where there is little chipping, and the lower figure shows a case where there is a lot of chipping. When there is little chipping, the tool can be withdrawn without breakage, but when there is a lot of chipping, vibration occurs in the operating torque just before the processing is interrupted, and the tool breaks after the reverse operation to withdraw. Therefore, in the worst case, in the conventional invention, breakage occurs and the workpiece becomes defective. Or, manual extraction is required, which reduces productivity.

[0005] Therefore, an object of the present disclosure is to provide a control device for a machine tool that can automatically retract a tool without breaking it when a machining abnormality or the like occurs, thereby suppressing a deterioration in productivity. [Means for solving the problem]

[0006] In order to achieve the above object, the present disclosure provides a control device for a machine tool in which a tool is attached to a spindle that is movable relative to a workpiece, and the workpiece is machined using the tool, the control device comprising: A parameter preparation means for storing predetermined parameters related to control in advance; a retracting means for retracting the tool from the workpiece; and a retraction diagnosis means for diagnosing whether the retraction operation is normal or not, the tool is a tap; the parameter preparation means stores, as the parameters, a section modulus, a tensile strength, and a safety factor of the tap; the retraction diagnosis means compares a breaking torque threshold calculated based on the section modulus, the tensile strength, and the safety factor with an operating torque of the tap to diagnose whether the retraction operation is normal or not; When the evacuation diagnosis means diagnoses the evacuation operation as abnormal, the evacuation operation is stopped. Another aspect of the present disclosure is a machining diagnostic means for diagnosing whether the machining of the workpiece is normal or not, in the above configuration, The retraction means retracts the tool from the workpiece when the machining diagnosis means diagnoses that the machining is abnormal. Another aspect of the present disclosure is a method for detecting an alarm in the above configuration, comprising: When the evacuation diagnosis means diagnoses the evacuation operation as abnormal, the evacuation operation is stopped and then an alarm is issued by the alarm issuing means. In order to achieve the above object, another aspect of the present disclosure is a control device for a machine tool in which a tool is attached to a spindle that is movable relative to a workpiece, and the workpiece is machined using the tool, A parameter preparation means for storing predetermined parameters related to control in advance; a retracting means for retracting the tool from the workpiece; an evacuation diagnosis means for diagnosing whether the evacuation operation is normal; A chip discharge means for causing the tool to discharge chips. and, Equipped with When the evacuation diagnosis means diagnoses the evacuation operation as abnormal, The retreat operation is stopped, and After the retreating operation is stopped, the chip discharge means performs a chip discharge operation. Another aspect of the present disclosure is a method for manufacturing a tapping tool according to the above configuration, The parameter preparation means stores a pitch of the chip discharge groove of the tap and a preset number of tap rotations, The chip discharge means is characterized in that, when the retraction diagnosis means diagnoses that the retraction operation is abnormal, it calculates a chip discharge operation distance from the pitch of the chip discharge groove and the number of tap rotations, and causes the tap to feed and rotate the chip discharge operation distance in the same direction as the machining direction. Another aspect of the present disclosure is characterized in that, in the above configuration, the parameter preparation means pre-identifies an operating distance at which chips can be discharged and the tap and the workpiece can be retracted without damaging them, and determines the number of tap rotations based on the identification result and the pitch. Another aspect of the present disclosure is a method for detecting an alarm in the above configuration, comprising: When the evacuation diagnosis means diagnoses the evacuation operation as abnormal, the evacuation operation is stopped and then an alarm is issued by the alarm issuing means. In another aspect of the present disclosure, in the above configuration, the parameter preparation means stores a set number threshold value that defines both the retreat operation and the chip discharge operation as one set, The alarm issuing means counts the number of sets of both the evacuation operation and the chip discharge operation, compares the counted number of sets with the set number threshold, and issues an alarm if the number of sets exceeds the set number threshold. Effect of the Invention

[0007] According to the present disclosure, the retraction operation of the tool is diagnosed, and if the retraction operation is abnormal, the retraction operation is stopped, so that when a machining abnormality or the like occurs, the tool can be automatically retracted without breakage, and deterioration of productivity can be suppressed. [Brief description of the drawings]

[0008] [Figure 1] FIG. 11 is an explanatory diagram showing a change in operating torque of a spindle when retracting in tapping. [Diagram 2] FIG. 2 is a block diagram of a control device for a machine tool. [Diagram 3] 4 is a flowchart showing a control performed by the control device. [Figure 4] FIG. 11 is an explanatory diagram showing a change in operating torque of a spindle when control is applied. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. 2 is a block diagram showing an example of a control device of the present disclosure. A control device 10 is provided in addition to the machine tool 1. The control device 10 may be included in a position control device (not shown) of the machine tool 1. First, machine tool 1 includes a table 3 supported on bed 2 so as to be movable in the left-right direction (Y-axis direction) on the page, a column 4 fixed on bed 2, and a spindle head 5 supported on column 4 so as to be movable in the direction perpendicular to the page (X-axis direction) and in the up-down direction (Z-axis direction). A downward-facing spindle 6 is rotatably supported on spindle head 5, and a tool 7 can be attached to it.

[0010] The control device 10 is provided with a machining information acquisition means 11, a machining diagnosis means 12, a parameter preparation means 13, an evacuation means 14, an evacuation diagnosis means 15, an evacuation continuation determination means 16, a chip discharge means 17, and an alarm issuing means 18. The machining information acquiring means 11 acquires control information of the machine tool 1 and measurement signals of various sensors (not shown) as machining information. The processing diagnosis means 12 diagnoses whether the processing is normal or abnormal based on the processing information acquired by the processing information acquisition means 11. In the parameter preparation means 13, parameters used for the control of the present disclosure are input or calculated, and the values ​​are stored. The retraction means 14 instructs the machine tool 1 to perform a retraction operation to retract the tool 7 from the workpiece W when an abnormality is detected by the machining diagnosis means 12 . The evacuation diagnosis means 15 compares the breaking torque threshold calculated based on the setting value of the parameter preparation means 13 with the processing information, diagnoses whether the evacuation operation is normal or abnormal, and outputs the diagnosis result to the evacuation continuation determination means 16.

[0011] If the diagnosis result of the evacuation diagnosis means 15 is normal, the evacuation continuation determination means 16 instructs the evacuation means 14 to continue the evacuation operation, and if the diagnosis result is abnormal, it instructs the evacuation means 14 to stop the evacuation operation and instructs the chip discharge means 17 to perform a chip discharge operation to discharge the chips. The chip discharge means 17 commands the machine tool 1 to perform a chip discharge operation in which the tool 7 is fed and rotated by a discharge operation distance calculated using the set value of the parameter preparation means 13 . The alarm issuing means 18 counts both the evacuation operation and the chip discharge operation as one set, compares the counted number of sets with the set number threshold, which is the setting value of the parameter preparation means 13, and determines whether to stop the operation and issue an alarm, or to continue the evacuation operation.

[0012] The control by the control device 10 will be described in detail below with reference to the flowchart of FIG. Step 1 shown in FIG. 3 (hereinafter simply referred to as "S") is executed by the parameter preparation means 13, S2 to S3 by the machining diagnosis means 12, S4, S15, and S17 by the evacuation means 14, S5 to S6, and S8 by the evacuation diagnosis means 15, S7 by the machining information acquisition means 11, S9 by the evacuation continuation determination means 16, S10 to S11 by the cutting chip discharge means 17 and the evacuation means 14, and S12 to S14 and S16 by the alarm issuance means 18. First, in S1, the section modulus Z of the tap that will be the tool 7, the tensile strength H, the safety factor S, the pitch P of the chip discharge groove, and the set number threshold Ns are input and stored. The number of tap rotations Nr is calculated by identifying the operating distance at which it has been confirmed that the chips can be discharged and the tap and workpiece W can be retracted without damaging them, and dividing the identified result by the pitch P of the chip discharge groove, and then storing it. A machining diagnosis is performed in S2, and if no machining abnormality is detected in the judgment in S3, the machining diagnosis is continued in S2, and if a machining abnormality is detected, a retraction operation is performed in S4 to remove the tool 7 from the workpiece W. In S5, it is determined whether or not to continue the control, and if not, the evacuation operation is continued in S15, and in S17, it is determined whether or not the evacuation operation is completed, and if completed, the operation is terminated, and if not, the operation returns to S5. If the control is to be continued in S5, the operation proceeds to S6.

[0013] In S6, the breaking torque threshold Tb is calculated from the section modulus Z, tensile strength H, and safety factor S of the tap by the following formula (1). Tb = 2ZH / S (1) In S7, the operating torque Tc of the spindle 6 during the retraction operation is measured, and in S8, the operating torque Tc is compared with the breaking torque threshold Tb. If the operating torque Tc is smaller than the breaking torque threshold Tb, the retraction operation is determined to be normal, and if it is greater, it is determined to be abnormal and output to S9. In S9, if the retraction operation is normal, it is determined to continue the retraction operation, and the retraction operation is continued in S15. If the retraction operation is abnormal, it is determined to stop the retraction, the retraction operation is stopped in S10, and the discharge operation distance L is calculated using the following formula (2). L = P Nr (2)

[0014] In S11, a chip discharge operation is performed in which the tap is fed and rotated by a discharge operation distance L. The spindle rotation speed and feed speed of the chip discharge operation are not limited in any way, and in this embodiment, the conditions are the same as those of the machining operation. In S12, the number of sets N is counted, with both the retreat operation and the chip discharge operation as one set. In S13, the number of sets N is compared with a set number threshold Ns. The set number threshold Ns is determined by checking in advance the number of sets that does not cause damage to the machine's operating axis, with both the retreat operation and the chip discharge operation as one set, and using that value. If the determination in S13 is that the number of sets N is smaller than the set number threshold Ns (No in S13), the evacuation operation continues in S4, and if it is greater (Yes in S13), the operation is stopped in S14, an alarm is issued, and the number of sets N is reset in S16 and the process ends.

[0015] Figure 4 shows the change in operating torque of the spindle 6 when the control in this embodiment is applied. After diagnosing a machining abnormality, the operating torque during the retraction operation is monitored with the breaking torque threshold, and when the breaking torque threshold is exceeded, the chip discharge operation is performed, and when the operating torque does not exceed the breaking torque threshold, the retraction operation is performed again, which shows that the tap can be retracted from the workpiece without breakage.

[0016] In this manner, the control device 10 of the machine tool 1 in the above-described form comprises a parameter preparation means 13 in which control-related parameters are pre-stored, a retraction means 14 which retracts the tool 7 from the workpiece W, and a retraction diagnosis means 15 which diagnoses whether the retraction operation is normal or not, and if the retraction diagnosis means 15 diagnoses the retraction operation as abnormal, the retraction operation is stopped. Therefore, when a machining abnormality occurs, the tool 7 can be automatically retracted without being broken, and deterioration of productivity can be suppressed.

[0017] Modifications of the present disclosure will be described below. In the above embodiment, an evacuation operation is performed when a processing abnormality occurs, but the evacuation operation is not limited to when a processing abnormality occurs, and the present disclosure can also be applied to cases where an evacuation operation is performed during normal processing to prevent collisions, etc. In the above embodiment, the evacuation diagnosis means and the evacuation continuation determination means for determining whether or not to continue the evacuation operation are provided, but the evacuation continuation determination means may be omitted and the evacuation operation may be stopped based on an abnormality diagnosis of the evacuation operation by the evacuation diagnosis means. The evacuation diagnosis means may include a process for determining whether to continue the evacuation. In the above embodiment, when the retraction operation is diagnosed as abnormal, the retraction operation is stopped and the chips are discharged, but an alarm may be issued without discharging the chips. In this case, too, the breakage of the tool can be prevented by stopping the retraction operation.

[0018] There is no problem with the processing diagnosis means using a method of comparing the processing information with a preset threshold value to diagnose whether it is normal or abnormal, or a method of using a mathematical model that has learned the processing information using machine learning to diagnose whether it is normal or abnormal. The machine tool is not limited to the above-mentioned form, and the tool is not limited to a tap. [Explanation of symbols]

[0019] 1...machine tool, 2...bed, 3...table, 4...column, 5...spindle head, 6...spindle, 7...tool, 10...control device, 11...machining information acquisition means, 12...machining diagnosis means, 13...parameter preparation means, 14...evacuation means, 15...evacuation diagnosis means, 16...evacuation continuation determination means, 17...chip discharge means, 18...alarm issuance means, W...workpiece.

Claims

1. A control device for a machine tool in which a tool is attached to a spindle that is movable relative to a workpiece and the workpiece is machined using the tool, A parameter preparation means for storing predetermined parameters related to control in advance; a retracting means for retracting the tool from the workpiece; and a retraction diagnosis means for diagnosing whether the retraction operation is normal or not, the tool is a tap; the parameter preparation means stores, as the parameters, a section modulus, a tensile strength, and a safety factor of the tap; the retraction diagnosis means compares a breaking torque threshold calculated based on the section modulus, the tensile strength, and the safety factor with an operating torque of the tap to diagnose whether the retraction operation is normal or not; 4. A control device for a machine tool, comprising: a control unit for controlling a machine tool, the control unit causing a machine tool to stop the retraction operation when the retraction diagnosis means diagnoses the retraction operation as being abnormal.

2. A machining diagnostic means is provided for diagnosing whether machining of the workpiece is normal or not, 2. The control device for a machine tool according to claim 1, wherein the retraction means retracts the tool from the workpiece when the machining diagnosis means diagnoses that the machining is abnormal.

3. An alarm issuing means for issuing an alarm, 3. The control device for a machine tool according to claim 1, wherein when the evacuation diagnosis means diagnoses the evacuation operation as abnormal, the alarm issuing means issues an alarm after the evacuation operation is stopped.

4. A control device for a machine tool in which a tool is attached to a spindle that is movable relative to a workpiece and the workpiece is machined using the tool, A parameter preparation means for storing predetermined parameters related to control in advance; a retracting means for retracting the tool from the workpiece; an evacuation diagnosis means for diagnosing whether the evacuation operation is normal; and a chip discharge means for causing the tool to discharge chips, A control device for a machine tool, characterized in that if the evacuation diagnosis means diagnoses the evacuation operation as abnormal, the evacuation operation is stopped and, after the evacuation operation is stopped, the chip discharge means performs a chip discharge operation.

5. the tool is a tap; The parameter preparation means stores a pitch of the chip discharge groove of the tap and a preset number of tap rotations, 5. The control device for a machine tool according to claim 4, characterized in that, when the retraction diagnosis means diagnoses that the retraction operation is abnormal, the chip discharge means calculates a chip discharge operation distance from the pitch of the chip discharge groove and the number of tap rotations, and causes the tap to feed and rotate in the same direction as the machining direction by the chip discharge operation distance.

6. 6. The control device for a machine tool according to claim 5, wherein the parameter preparation means identifies in advance an operating distance at which chips can be discharged and at which the tap and the workpiece can be retracted without damaging them, and determines the number of rotations of the tap based on the identification result and the pitch.

7. An alarm issuing means for issuing an alarm, 7. A control device for a machine tool according to claim 4, wherein when said evacuation diagnosis means diagnoses said evacuation operation as abnormal, said alarm issuing means issues an alarm after said evacuation operation is stopped.

8. The parameter preparation means stores a set number threshold value that defines both the retreat operation and the chip discharge operation as one set, The control device for a machine tool according to claim 7, characterized in that the alarm issuing means counts the number of sets of both the evacuation operation and the chip discharge operation, compares the counted number of sets with the set number threshold, and issues an alarm if the number of sets exceeds the set number threshold.

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