Machining head module, multi-axis robot, and method for controlling machining head

Abstract

The present invention stabilizes the machining operation of a drill.　A machining head (17) has a drill (37), a spindle servo motor (33) that rotationally drives the drill (37), and an actuator servo motor (26) that advances and retracts the drill (37) with respect to a workpiece (W). A control device (43) has a spindle servo amplifier (34) that detects a supplied-current value or a generated-torque value in the spindle servo motor (33), and an actuator servo amplifier (27) that detects a supplied-current value or a generated-torque value in the actuator servo motor (26). When at least one of the detection value of the spindle servo amplifier (34) and the detection value of the actuator servo amplifier (27) exceeds a threshold value, the advancing / retracting speed of the drill (37) by the actuator servo motor (26) is made lower than a desired advancing / retracting speed.

Description

Processing Head Module, Multi-Axis Robot, and Control Method for Processing Head

[0001] The present disclosure relates to a processing head module, a multi-axis robot, and a control method for a processing head.

[0002] Patent Document 1 discloses a robot having a robot arm, a drilling device attached to the tip of the robot arm, and a robot control unit that controls the robot arm. The drilling device has a drill for forming a through hole in a workpiece, a rotation mechanism for rotationally driving the drill, and a feed mechanism for advancing the rotation mechanism toward the workpiece.

[0003] Japanese Patent Application Laid-Open No. 2023-137762

[0004] In the drilling device attached to the robot arm as described above, when a servo motor is used as the feed mechanism, when the feed speed of the drill decreases due to an increase in load, by performing feedback torque control to increase the power value supplied to the servo motor and increase the output torque of the servo motor, it is possible to maintain the feed speed of the drill at the desired speed. However, in a multi-joint type robot arm in which a plurality of arms are connected, there is a clearance between the gears provided at the shaft connection part connecting the arms, so the rigidity of the entire robot arm is low. Therefore, when the feed speed decreases due to poor cutting of the drill and the power value supplied to the servo motor is increased, the cutting edge of the drill may run wild and the processing operation may not be stable, and the inner peripheral surface of the through hole may become rough or burrs may remain at the opening edge of the through hole. Furthermore, there is also a risk of shortening the life of the drill.

[0005] The present disclosure has been completed based on the above circumstances, and aims to stabilize the processing operation of the drill and extend the life of the drill.

[0006] The machining head module of the first disclosure is attached to a multi-joint arm constituting a multi-axis robot and comprises a machining head that performs drilling on a workpiece and a control device that controls the movement of the machining head, wherein the machining head has a drill that drills the workpiece while rotating, a spindle servo motor that rotationally drives the drill, and an actuator servo motor that moves the drill forward and backward relative to the workpiece, wherein the control device has a spindle servo amplifier that detects the current value supplied to the spindle servo motor or the torque value generated, and an actuator servo amplifier that detects the current value supplied to the actuator servo motor or the torque value generated, and when at least one of the detected values ​​of the spindle servo amplifier and the actuator servo amplifier exceeds a threshold, the forward and backward speed of the drill by the actuator servo motor is reduced to a predetermined forward and backward speed.

[0007] The multi-axis robot of the second disclosure comprises: an articulated arm in which a plurality of arms are connected so as to be displaceable relative to each other; a robot control unit that controls the movement of the articulated arm; a machining head attached to the articulated arm that performs drilling on a workpiece; and a control device that controls the movement of the machining head, wherein the machining head has a drill that drills the workpiece while rotating; a spindle servo motor that rotates the drill; and an actuator servo motor that moves the drill forward and backward relative to the workpiece, wherein the control device has a spindle servo amplifier that detects the current value supplied to the spindle servo motor or the torque value generated; and an actuator servo amplifier that detects the current value supplied to the actuator servo motor or the torque value generated, wherein when at least one of the detected values ​​of the spindle servo amplifier and the actuator servo amplifier exceeds a threshold, the forward and backward speed of the drill by the actuator servo motor is reduced to a predetermined forward and backward speed.

[0008] The third disclosure provides a method for controlling a machining head, comprising: a multi-joint arm in which a plurality of arms are connected so as to be relatively displaceable; a robot control unit for controlling the movement of the multi-joint arm; a machining head attached to the multi-joint arm for drilling a workpiece; and a control device for controlling the movement of the machining head, wherein the machining head includes: a drill for drilling the workpiece while rotating; a spindle servo motor for rotationally driving the drill; and an actuator servo motor for moving the drill forward and backward relative to the workpiece, and wherein the control device includes: a spindle servo amplifier for detecting a current value supplied to the spindle servo motor or a torque value generated; and an actuator servo amplifier for detecting a current value supplied to the actuator servo motor or a torque value generated, and wherein when at least one of the detected values ​​of the spindle servo amplifier and the actuator servo amplifier exceeds a threshold, the control device reduces the forward and backward speed of the drill by the actuator servo motor to a predetermined forward and backward speed.

[0009] According to the first to third disclosures, the machining operation of the drill can be stabilized, and the lifespan of the drill can be extended.

[0010] This is a perspective view of the multi-axis robot of Embodiment 1. This is a perspective view of the machining head viewed from diagonally below. This is a side cross-sectional view showing the state in which the rotation axis of the machining head is perpendicular to the surface to be drilled and the foot is in contact with the surface to be drilled. This is a side cross-sectional view showing the state in which the workpiece has been drilled by the drill. This is a plan cross-sectional view of the machining head. This is a block diagram showing the configuration for controlling the machining head.

[0011] Herein, we present examples of preferred embodiments of this disclosure. Any combination of the following examples of embodiments, provided they do not contradict each other, is also included as an embodiment for carrying out the invention.

[0012] The machining head module of the first disclosure comprises (1) a machining head attached to a multi-joint arm constituting a multi-axis robot and performing drilling on a workpiece, and a control device for controlling the movement of the machining head. The machining head has a drill that drills the workpiece while rotating, a spindle servo motor that rotationally drives the drill, and an actuator servo motor that moves the drill forward and backward relative to the workpiece. The control device has a spindle servo amplifier that detects the current value supplied to the spindle servo motor or the torque value generated, and an actuator servo amplifier that detects the current value supplied to the actuator servo motor or the torque value generated, and when at least one of the detected values ​​of the spindle servo amplifier and the actuator servo amplifier exceeds a threshold, the control device reduces the forward and backward speed of the drill by the actuator servo motor to a predetermined forward and backward speed.

[0013] If the decrease in rotational speed of the actuator servo motor or spindle servo motor is due to a decrease in cutting edge quality caused by aging or temperature rise of the drill, increasing the power supplied to the servo motor will not prevent excessive frictional resistance between the drill and the workpiece. Therefore, excessively increasing the supplied power may cause the drill's cutting edge to become unstable, leading to rough inner surfaces of through-holes or burrs remaining on the opening edges of through-holes. Furthermore, it may shorten the lifespan of the drill. As a countermeasure, the first disclosure reduces the forward and backward movement speed of the drill by the actuator servo motor to below the intended forward and backward movement speed when at least one of the detected values ​​(supplied current value or generated torque value) of the spindle servo amplifier and the actuator servo amplifier exceeds a threshold. This control reduces frictional resistance between the drill and the workpiece, thereby stabilizing the drill's machining operation and extending the lifespan of the drill.

[0014] Furthermore, when the drill's forward and backward speed is reduced, and the detected value (hereinafter referred to as the target detected value) from at least one of the servo amplifiers (the spindle servo amplifier and the actuator servo amplifier) ​​falls below a threshold, it is preferable to increase the drill's forward and backward speed to control it so that the target detected value remains within the threshold range. By performing such control, the drill's machining operation can be efficiently stabilized. The target of detection is preferably the current value in the actuator servo motor or the spindle servo motor. Note that the fact that the target detected value has fallen outside the threshold can be accurately determined by comparison with the command value, etc.

[0015] The multi-axis robot of the second disclosure includes (2) a multi-joint arm in which a plurality of arms are connected so as to be displaceable relative to each other, a robot control unit that controls the movement of the multi-joint arm, a machining head attached to the multi-joint arm that performs drilling on a workpiece, and a control device that controls the movement of the machining head. The machining head has a drill that drills the workpiece while rotating, a spindle servo motor that rotates the drill, and an actuator servo motor that moves the drill forward and backward relative to the workpiece. The control device has a spindle servo amplifier that detects the current value supplied to the spindle servo motor or the torque value generated, and an actuator servo amplifier that detects the current value supplied to the actuator servo motor or the torque value generated, and when at least one of the detected values ​​of the spindle servo amplifier and the actuator servo amplifier exceeds a threshold, the control device reduces the forward and backward speed of the drill by the actuator servo motor to a predetermined forward and backward speed. According to the second disclosure, similar to the first disclosure, the frictional resistance between the drill and the workpiece is reduced, which stabilizes the drill's machining operation and extends the drill's lifespan.

[0016] (3) In (2), it is preferable that the control device is equipped with a notification device that notifies when the drill needs to be replaced, and during the process in which the drill is drilling the workpiece, when the advance speed of the drill by the servo motor for the actuator falls below a threshold, the control device stops the servo motor for the actuator and activates the notification device. With this configuration, the notification device can notify the user at an appropriate time that it is time to replace the drill.

[0017] The third disclosure's method for controlling a machining head includes: (4) an articulated arm in which a plurality of arms are connected so as to be displaceable relative to each other; a robot control unit for controlling the movement of the articulated arm; a machining head attached to the articulated arm for drilling a workpiece; and a control device for controlling the movement of the machining head. The machining head includes a drill that drills the workpiece while rotating; a spindle servo motor for rotationally driving the drill; and an actuator servo motor for moving the drill forward and backward relative to the workpiece. The control device includes a spindle servo amplifier for detecting a current value supplied to the spindle servo motor or a torque value generated; and an actuator servo amplifier for detecting a current value supplied to the actuator servo motor or a torque value generated. With the above configuration, the control device reduces the forward and backward speed of the drill by the actuator servo motor to a predetermined forward and backward speed when at least one of the detected values ​​of the spindle servo amplifier and the actuator servo amplifier exceeds a threshold. According to the third disclosure, similar to the first and second disclosures, the frictional resistance between the drill and the workpiece is reduced, which stabilizes the drill's machining operation and extends the drill's lifespan.

[0018] <Embodiment 1> Embodiment 1, which embodies the present disclosure, will be described with reference to Figures 1 to 6. However, the present invention is not limited to these examples, and is intended to be shown by the claims, with all modifications in the meaning and scope of equivalence to the claims being included. In Embodiment 1, the front-to-back direction is defined as the direction F in Figures 1 to 5. The up-and-down direction is defined as the direction H in Figures 1 to 4. The left-to-right direction is defined as the direction R in Figures 1, 2, and 5.

[0019] The multi-axis robot 10 of this embodiment 1 comprises a base 11, a multi-joint arm 12, a machining head module 16, a robot control unit 47, and a notification device 45. The base 11 is fixed to the floor surface. The multi-joint arm 12 is constructed by connecting a plurality of arms 13 in series via joints 14. The connected arms 13 can be displaced (rotated) relative to each other by arm servo motors 15. The base end of the multi-joint arm 12 is supported on the upper surface of the base 11 so as to be driven to rotate horizontally. The position, movement speed, and orientation of the tip 12A of the multi-joint arm 12 in three dimensions are controlled by the operation of at least one arm servo motor 15.

[0020] The machining head module 16 comprises a machining head 17 and a control device 43 (see Figure 6). The machining head 17 is attached to the tip 12A of the articulated arm 12. The machining head 17 comprises a frame 18 fixed to the tip 12A of the articulated arm 12, an actuator 23 attached to the frame 18, a spindle 32 attached to the actuator 23, a drill replacement mechanism 44 located inside the spindle 32, and a drill 37 for drilling that is rotationally driven by the spindle 32.

[0021] The structure of the machining head 17 will now be described assuming the rotation axis of the drill 37 is facing vertically. The frame 18 has a horizontal bottom plate portion 19 that forms a rectangle in a plan view when the machining head 17 is viewed from above, four vertical plate portions 20 rising from the outer edge of the bottom plate portion 19 on the front, back, left, and right sides, and a top plate portion 21 that is rectangular in plan view and connected to the upper edges of the four vertical plate portions 20.

[0022] The actuator 23 is attached to the rear plate portion 20R of the four vertical plate portions 20. The actuator 23 comprises a male threaded rod 24 whose axis is oriented parallel to the rotation axis of the drill 37, a guide groove 25 extending parallel to the male threaded rod 24, an actuator servo motor 26 that rotates the male threaded rod 24 in both forward and reverse directions, and a lifting member 29 having a female threaded hole 30. The lifting member 29 is fitted into the guide groove 25 in a non-rotatable state with the female threaded hole 30 fitted into the male threaded rod 24. When the actuator servo motor 26 is driven to rotate the male threaded rod 24, the lifting member 29 slides in a direction parallel to the rotation axis of the drill 37 (up and down direction) while sliding against the guide groove 25.

[0023] The operating status of the actuator servo motor 26 is detected by a detection unit such as an encoder built into the actuator servo motor 26, and is returned as a feedback signal to the actuator servo amplifier 27 in the control device 43. Based on this feedback signal, the current value supplied to the actuator servo motor 26, the torque value generated, and the lifting speed of the lifting member 29 are detected.

[0024] A spindle 32 is attached to the lifting member 29. The spindle 32 is driven to move up and down by an actuator servo motor 26. The spindle 32 has a spindle servo motor 33 and a drill 37. The spindle servo motor 33 is fixed to the lifting member 29 and moves up and down together with the lifting member 29. A chuck 36, which is rotationally driven by the spindle servo motor 33, is provided at the lower end of the spindle servo motor 33. The drill 37 is detachably attached to the chuck 36. The drill 37 is an elongated member with its rotation axis oriented vertically and protrudes downward from the chuck 36.

[0025] The operating status of the spindle servo motor 33 is detected by a detection unit such as an encoder built into the spindle servo motor 33, and the signal is returned as a feedback signal to the spindle servo amplifier 34 in the control device 43. Based on this feedback signal, the current value supplied to the spindle servo motor 33, the torque value generated, and the rotational speed of the drill 37 are detected.

[0026] A communication hole 38 is formed in the bottom plate portion 19 of the frame 18. A duct member 39 is fixed to the lower surface of the bottom plate portion 19. The duct member 39 has a cylindrical portion 40 with its axis oriented vertically and a discharge portion 41 extending diagonally upward and forward from the outer circumferential surface of the cylindrical portion 40. The upper end of the cylindrical portion 40 communicates with the communication hole 38. The chuck 36 of the spindle 32 is positioned at a height that penetrates the communication hole 38. When the spindle 32 is at its uppermost position in its vertical stroke, the lower end of the drill 37 is positioned above the lower end of the cylindrical portion 40 (duct member 39). When the spindle 32 is at its lowermost position in its vertical stroke, the lower end of the drill 37 is positioned below the lower end of the cylindrical portion 40.

[0027] The control device 43 is located separately from the multi-axis robot 10. The control device 43 includes a PLC (Programmable Logic Controller) 46, an actuator servo amplifier 27, and a spindle servo amplifier 34. The actuator servo amplifier 27 receives commands from the PLC 46 and supplies the necessary power to the actuator servo motor 26 to perform the task. The spindle servo amplifier 34 supplies the necessary power to the spindle servo motor 33 to perform the task of the command received from the PLC 46. Based on the feedback signals returned to the actuator servo amplifier 27 and the spindle servo amplifier 34, the control device 43 controls the actuator servo motor 26 of the actuator 23 and the spindle servo motor 33 to perform a suitable drilling with the drill 37. The control device 43 also sends commands to the robot control unit 47 based on the feedback signals input via the robot control unit 47.

[0028] The robot control unit 47 is located in a separate component or device (position) from the multi-axis robot 10 and the control device 43. The robot control unit 47 has a servo amplifier (not shown) that receives commands from the control device 43 and supplies the necessary power to the arm servo motor 15 to execute the task.

[0029] Next, the process of forming a through hole H perpendicular to the drilling target surface S in a workpiece W, which is made of metal or synthetic resin and has a plate-like shape, with its drilling target surface S (plane) facing horizontally upward, will be described. First, the actuator servo motor 26 is started to move the drill 37 upward, and the lower end (tip) of the drill 37 is moved to a position above the lower edge 39L of the duct member 39. Next, the arm servo motor 15 is driven to bring the lower edge 39L of the duct member 39 into contact with the drilling target surface S from above in a pressing state. After this, the actuator servo motor 26 and the spindle servo motor 33 are started to rotate the drill 37 at a predetermined rotational speed, and the actuator 23 is lowered to advance the drill 37 toward the workpiece W at a predetermined speed. As a result, the drill 37 forms a through hole H in the workpiece W with its rotation axis perpendicular to the drilling target surface S.

[0030] The control device 43 determines the actual rotational speed of the drill 37 and the current required for its operation by performing calculations based on the feedback signal returned to the spindle servo amplifier 34. Then, it supplies power to the spindle servo motor 33 so that the drill 37 maintains the predetermined rotational speed set as the optimal rotational speed for drilling.

[0031] During the machining of the workpiece W, the cutting edge of the drill 37 may deteriorate over time or its temperature may rise, and the load may increase as the frictional resistance between the drill 37 and the workpiece W becomes excessive. In such cases, more power is required to maintain the desired rotational speed of the drill 37. At this time, a feedback signal detects an increase in the torque value and an increase in the current value supplied to the spindle servo motor 33. Therefore, when the current value supplied to the spindle servo motor 33 exceeds a preset threshold for the spindle, the control device 43 sends a command to the actuator servo motor 26 to reduce the drill 37's advance speed to a speed lower than the desired advance speed.

[0032] Furthermore, the control device 43 determines the actual advancement speed of the drill 37 (spindle 32) by performing calculations based on the feedback signal returned to the actuator servo amplifier 27. Then, it supplies power to the actuator servo motor 26 so that the drill 37 maintains the predetermined advancement speed, which is set as the optimal advancement speed for drilling.

[0033] During the machining of the workpiece W, if the cutting edge of the drill 37 deteriorates due to aging or temperature rise, or if the load increases as the frictional resistance between the drill 37 and the workpiece W becomes excessive for other reasons, more power supply is required to maintain the desired advancement speed of the drill 37. At this time, the feedback signal detects an increase in torque value and an increase in current value. Therefore, when the current value supplied to the actuator servo motor 26 exceeds a preset threshold for the actuator, the control device 43 sends a command to the actuator servo motor 26 to reduce the advancement speed of the drill 37 to a speed lower than the desired advancement speed.

[0034] The timing for reducing the advance speed of the drill 37 to a speed lower than the intended advance speed may be when the detected value of either the spindle servo amplifier 34 or the actuator servo amplifier 27 exceeds a threshold, or when both the detected value of the spindle servo amplifier 34 and the actuator servo amplifier 27 exceed a threshold. Reducing the advance speed of the drill 37 reduces the frictional resistance between the drill 37 and the workpiece W, so that the workpiece W can be processed while the rotation speed of the spindle servo motor 33 is maintained at the rated rotation speed, that is, while the rotation speed of the drill 37 is maintained at the intended rotation speed, and good drilling is performed. When drilling by the drill 37 is complete, the actuator servo motor 26 moves the spindle 32 in the opposite direction to when drilling, and withdraws the drill 37 from the through hole H.

[0035] While the drill 37 is drilling the workpiece W, if the advance speed of the drill 37 by the actuator servo motor 26 falls below a threshold, the control device 43 stops the spindle servo motor 33 and the actuator servo motor 26. Furthermore, the control device 43 activates the notification device 45 to notify that the drill 37 needs to be replaced. The notification device 45 is a device that flashes a lamp, lights up a lamp, outputs a notification sound, and outputs a voice. Furthermore, the control device 43 sends a command to the drill replacement mechanism 44, which automatically replaces the drill 37.

[0036] The multi-axis robot 10 of this embodiment 1 includes a multi-joint arm 12 in which a plurality of arms 13 are connected so as to be displaceable relative to each other, a robot control unit 47 that controls the movement of the multi-joint arm 12, and a machining head module 16 attached to the tip 12A of the multi-joint arm 12. The machining head module 16 includes a machining head 17 attached to the multi-joint arm 12 that performs drilling on a workpiece W, and a control device 43 that controls the movement of the machining head 17. The machining head 17 has a drill 37 that drills into the workpiece W while rotating, a spindle servo motor 33 that rotates the drill 37, and an actuator servo motor 26 that moves the drill 37 forward and backward relative to the workpiece W. The control device 43 has a spindle servo amplifier 34 and an actuator servo amplifier 27. The spindle servo amplifier 34 detects the current value supplied to the spindle servo motor 33 or the torque value generated in the spindle servo motor 33. The actuator servo amplifier 27 detects the current value supplied to the actuator servo motor 26, or the torque value generated in the actuator servo motor 26.

[0037] If the decrease in rotational speed of the actuator servo motor 26 and the spindle servo motor 33 is due to a decrease in cutting performance caused by aging or temperature rise of the drill 37, then even if the amount of power supplied to the servo motor is increased, the frictional resistance between the drill 37 and the workpiece W will remain excessive. Therefore, if the power supply is increased excessively, the cutting edge of the drill 37 may become unstable, causing the machining operation to become unstable, which may result in a rough inner surface of the through hole H or burrs remaining on the opening edge of the through hole H. Furthermore, it may shorten the lifespan of the drill 37.

[0038] As a countermeasure, the control method for the control device 43 and machining head 17 of the multi-axis robot 10 in this embodiment 1 is configured such that when at least one of the detected values ​​of the spindle servo amplifier 34 and the actuator servo amplifier 27 exceeds a threshold, the forward and backward speed of the drill 37 by the actuator servo motor 26 is reduced to a lower speed than the intended forward and backward speed. This control reduces the frictional resistance between the drill 37 and the workpiece W, thereby stabilizing the machining operation of the drill 37 and extending the life of the drill.

[0039] The multi-axis robot 10 is equipped with a notification device 45 that notifies the user when the drill 37 needs to be replaced. While the drill 37 is drilling the workpiece W, the control device 43 stops the actuator servo motor 26 and activates the notification device 45 when the drill 37's advancement speed by the actuator servo motor 26 falls below a threshold. With this configuration, the notification device 45 can notify the user at an appropriate time when it is time to replace the drill 37.

[0040] Furthermore, by setting threshold levels, the servo motor 26 for the actuator may be kept running while the notification device 45 is activated during the first activation stage. With this configuration, the notification device 45 can alert the user at an appropriate time that the drill 37 is nearing the time for replacement without stopping the device.

[0041] <Other Embodiments> The present invention is not limited to the embodiments described above and drawn, and the following embodiments, for example, are also included in the technical scope of the present invention. A notification device may not be provided. The drill may be replaced manually.

[0042] 10... Multi-axis robot 11... Base 12... Multi-joint arm 12A... Tip of the multi-joint arm 13... Arm 14... Joint 15... Servo motor for arm 16... Machining head module 17... Machining head 18... Frame 19... Bottom plate 20... Upright plate 20R... Rear plate 21... Top plate 23... Actuator 24... Male threaded rod 25... Guide groove 26... Servo motor for actuator 27... Servo amplifier for actuator 29... Lifting member 30... Female threaded hole 32... Spindle 33... Servo motor for spindle 34... Servo amplifier for spindle 36... Chuck 37... Drill 38... Communication hole 39... Duct member 39L... Lower edge of duct member 40... Cylindrical part 41... Discharge part 43... Control device 44... Drill replacement mechanism 45... Notification device 46... PLC 47...Robot control unit H...Through hole S...Surface to be drilled W...Workpiece

Claims

1. A machining head module comprising: a machining head attached to a multi-joint arm constituting a multi-axis robot for drilling a workpiece; and a control device for controlling the movement of the machining head, wherein the machining head includes: a drill that drills the workpiece while rotating; a spindle servo motor that rotationally drives the drill; and an actuator servo motor that moves the drill forward and backward relative to the workpiece, wherein the control device includes: a spindle servo amplifier that detects the current value supplied to the spindle servo motor or the torque value generated; and an actuator servo amplifier that detects the current value supplied to the actuator servo motor or the torque value generated, wherein when at least one of the detected values ​​of the spindle servo amplifier and the actuator servo amplifier exceeds a threshold, the machining head module reduces the forward and backward speed of the drill by the actuator servo motor to a predetermined forward and backward speed.

2. A multi-axis robot comprising: a multi-joint arm having multiple arms connected so as to be relatively displaceable; a robot control unit for controlling the movement of the multi-joint arm; a processing head attached to the multi-joint arm for drilling a workpiece; and a control device for controlling the movement of the processing head, wherein the processing head has a drill for drilling the workpiece while rotating; a spindle servo motor for rotationally driving the drill; and an actuator servo motor for moving the drill forward and backward relative to the workpiece, wherein the control device has a spindle servo amplifier for detecting the current value supplied to the spindle servo motor or the torque value generated; and an actuator servo amplifier for detecting the current value supplied to the actuator servo motor or the torque value generated, and when at least one of the detected values ​​of the spindle servo amplifier and the actuator servo amplifier exceeds a threshold, the robot reduces the forward and backward speed of the drill by the actuator servo motor to a predetermined forward and backward speed.

3. The multi-axis robot according to claim 2, further comprising a notification device for notifying that the drill needs to be replaced, wherein, in the process of the drill drilling the workpiece, the control device stops the actuator servo motor and activates the notification device when the advance speed of the drill by the actuator servo motor falls below a threshold.

4. A method for controlling a machining head comprising: a multi-joint arm in which a plurality of arms are connected so as to be relatively displaceable; a robot control unit for controlling the movement of the multi-joint arm; a machining head attached to the multi-joint arm for drilling a workpiece; and a control device for controlling the movement of the machining head, wherein the machining head includes a drill that drills the workpiece while rotating; a spindle servo motor for rotationally driving the drill; and an actuator servo motor for moving the drill forward and backward relative to the workpiece, and the control device includes a spindle servo amplifier for detecting a current value supplied to the spindle servo motor or a torque value generated, and an actuator servo amplifier for detecting a current value supplied to the actuator servo motor or a torque value generated, wherein the control device reduces the forward and backward speed of the drill by the actuator servo motor to a predetermined forward and backward speed when at least one of the detected values ​​of the spindle servo amplifier and the actuator servo amplifier exceeds a threshold value.

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