JP2004306258A - Numerical control lathe with guide bush - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the occurrence of a serious trouble and slight damage of a tool by quickly detecting a chuck slippage of a spindle. <P>SOLUTION: In the process of machining a material 3, a spindle rotational frequency calculating part 15 calculates the rotational frequency of the spindle 1 from a signal detected by a rotation detector 4a of a spindle motor 4, and a guide bush rotational frequency calculating part 16 calculates the rotational frequency of a guide bush 2 from a signal detected by a rotation detector 5a of a guide bush motor 5. A difference between the respectively calculated spindle rotational frequency Nms and guide bush rotational frequency Ngb is calculated by a rotational frequency difference calculating part 17, and when the rotational frequency difference ΔN exceeds an allowable value of a rotational frequency difference preset on an NC device 14, a comparing part 18 generates a chuck slippage signal to thereby stop the machining operation. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention includes independent motors for rotating the main shaft and the guide bush, respectively, and controls the main shaft and the guide bush to rotate at the same rotation speed by each motor, and is chucked by the main shaft and guided and supported by the guide bush. The present invention relates to a lathe having a guide bush for processing a rod-shaped material.

In an NC lathe having such a guide bush, the main shaft and the guide bush are generally connected to each other by a single motor by a gear or a belt and are driven to rotate.
The rod-shaped material (work) chucked on the main shaft is rotated while being guided and supported by the guide bush, and a tool (such as a tool or a drill) comes into contact with the outer periphery or the end surface of the portion protruding from the guide bush, thereby cutting or drilling. And the like are performed.

  During the processing, the tool is pressed against the material, so that a large load is applied to the rotation, and slip may occur between the chuck of the spindle and the material (referred to as “chuck slip”). When this chuck slip occurs, the number of rotations of the material (work) decreases, and there is a risk of causing a serious failure such as breakage of a tool or bending of a feed slide.

Therefore, it is necessary to prevent the occurrence of chuck slip or, if it occurs, to detect it immediately and stop the machining operation.
However, in order to detect the occurrence of chuck slip, it is necessary to detect the number of rotations of the material (work) being chucked, but since it is difficult, chuck slip detection is not normally performed, and the chuck of the main spindle must be detected. It was tightened strongly to prevent chuck slippage.

  In an NC lathe having a guide bush for rotating the main shaft and the guide bush by independent motors, conventionally, both drive motors are driven to rotate by one drive control device, or both motors are driven by independent drive control devices. , The rotation speed was detected only by the spindle motor. Therefore, in this case, the chuck slip is not detected, and the chuck of the main shaft is strongly tightened as in the case described above.

  However, if the chuck is excessively tightened, the outer periphery of the material will be damaged, and it will not be possible to process a component in which a portion having the same diameter as the material remains. For this reason, it is necessary to use a material having a diameter larger than the diameter of the part and also to cut the maximum outer diameter, which results in waste of material, waste of processing time, excessive consumption of tools, and a long processing program. There was a problem.

  The present invention has been made to solve such a problem, and the chuck of the main spindle is loosely tightened so as not to damage the material, and when chuck slip occurs, it is detected promptly and seriously. It is an object of the present invention to prevent not only minor failure but also minor damage to the tool.

  In order to achieve the above object, the present invention includes independent motors for rotating the main shaft and the guide bush, respectively, and controls the main shaft and the guide bush to rotate at the same rotation speed by each motor, thereby chucking the main shaft with the chuck. An NC lathe having a guide bush for processing a bar-shaped material guided and supported by the guide bush with a tool is provided with the following means (a) to (e).

(a) during the processing of the material, a spindle rotation speed calculation means for calculating the rotation speed of the spindle from a signal detected by the spindle motor or the rotation detector of the spindle,
(b) during the processing of the material, a guide bush rotation speed calculating means for calculating the rotation speed of the guide bush from a signal detected by the guide bush motor or the rotation detector of the guide bush,
(c) a rotation speed difference calculation means for calculating a difference between the rotation speed of the main shaft calculated by the main shaft rotation speed calculation means and the rotation speed of the guide bush calculated by the guide bush rotation speed calculation means,
(d) comparing the difference between the rotation speeds calculated by the rotation speed difference calculation means with an allowable value of the difference between the rotation speeds set in advance in the NC device, and determining that the difference between the rotation speeds exceeds the allowable value; Means for generating a chuck slip signal when
(e) means for stopping the machining operation by retracting the tool and stopping the rotation of the spindle motor and the guide bush motor by the chuck slip signal,

The motor for rotating the guide bush may be a guide bush motor having a rotation force equal to or smaller than that of the spindle motor.
Also, the spindle is a spindle with a rotation detector, or a motor for rotating the spindle is a spindle motor with a rotation detector, and the guide bush is a guide bush with a rotation detector, or a motor for rotating the guide bush. Can be a guide bush motor with a rotation detector.
Further, it is desirable to provide means for performing an alarm operation by the chuck slip signal.
In the NC lathe having the guide bush, when the spindle motor and the guide bush motor are started, braked, and when the number of revolutions is changed, the output of the chuck slide signal is prohibited for a predetermined time set in the NC device. Means may be provided.

  Alternatively, in the NC lathe having the guide bush, when the spindle motor and the guide bush motor are started, braked, and when the rotation speed is changed, the rotation speed of the spindle motor and the guide bush motor is set by an instruction from the NC device. When the rotation speed reaches the rotation speed range obtained by adding the rotation speed and the allowable rotation error set in advance to the NC device, a means for inhibiting the output of the chuck slide signal until the constant rotation state signal is output from the NC device may be provided. .

  In the NC lathe having the guide bush according to the present invention, when chuck slip occurs, the rotation speed of the material is lower than the rotation speed of the main shaft, but since the material is pressed against the guide bush by the pressing torque of the tool, the rotation of the guide bush is reduced. Reduce the number of revolutions equally. For this reason, there is a difference between the rotation speeds of the main shaft and the guide bush. By detecting the difference, the chuck slip can be detected.

That is, during processing of the material, the rotation speed of the spindle is calculated from the signal detected by the spindle motor or the rotation detector of the spindle, and the rotation of the guide bush is determined from the signal detected by the rotation sensor of the guide bush motor or the guide bush. Calculate the number.
Then, a difference between the calculated rotation speed of the main shaft and the rotation speed of the guide bush is calculated, and a chuck slip signal is generated when the difference exceeds a permissible value of the rotation speed difference preset in the NC device. .

  By the chuck slip signal, the rotation of the spindle motor and the guide bush motor is stopped, the tool is retracted, the machining operation is stopped, and an alarm operation by a buzzer or the like can be performed.

Further, in the NC lathe having the guide bush, when the spindle motor and the guide bush motor are started, braked, and when the rotation speed is changed, there may be a difference in the rotation speed between the main shaft and the guide bush even without chuck slip. Therefore, by not outputting the chuck slip signal only for a certain period of time from the start of the operation or until the state of the constant rotation is reached, erroneous detection of the chuck slip can be prevented, and the allowable value of the difference in the number of rotations can be prevented. Can be set to a small value, and even a slight chuck slip can be detected.
Therefore, according to the present invention, there is no danger of causing a serious trouble such as breakage of the tool or bending of the feed slide.
In addition, since it is not necessary to damage the material by overtightening the chuck of the main shaft, it is possible to process a part in which a part having the same diameter as the material remains. Therefore, it is possible to shorten the machining time of parts, save materials, eliminate unnecessary consumption of tools, shorten the machining program, and the like.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a configuration diagram showing only a portion related to chuck slip detection of a spindle-sliding type NC lathe which is an embodiment of an NC lathe having a guide bush according to the present invention.

  In FIG. 1, 1 is a main shaft, 2 is a guide bush, which is aligned and arranged on a common central axis L, penetrates a bar-shaped material 3, and the main shaft 1 grasps the material 3 by a chuck 1a and rotates it integrally. The guide bush 2 guides and supports the vicinity of the front end of the material 3 so that a processed portion (work) 3a is projected.

  The main shaft 1 is rotated by a main shaft motor 4 via a belt transmission mechanism 6 having no slip, and the guide bush 2 is rotated by a guide bush motor 5 via a belt transmission mechanism 7 having no slip. The main shaft 1, main shaft motor 4 and belt transmission mechanism 6 slide in the direction of arrow Z1 by a moving mechanism (not shown).

  A tool rest 8 movable in the direction of arrow X1 is provided on the upper side on the front side of the guide bush 2, and the outer diameter of the processed portion 3a of the material 3 is processed by a tool 9 such as a tool attached thereto. Can be. Further, a rear headstock 10 is provided so as to be movable in the Z2 direction and the X2 direction as indicated by the arrow, facing the guide bush 2, and a tool 11 such as a drill attached thereto is used to form a hole or the like on an end face of the processing portion 3a. Can be processed.

  The spindle motor 4 is provided with a rotation detector 4a for detecting the rotation of the spindle motor 4. The rotation detector 4a is driven by the spindle motor drive controller 12, and outputs a signal PSM detected by the rotation detector 4a to the spindle motor drive controller. The drive is controlled so as to rotate the spindle 1 at the set number of revolutions in response to a command from the NC device 14.

  The guide bush motor 5 is also provided with a rotation detector 5a for detecting its rotation. The guide bush motor 5 is driven by the guide bush motor drive control unit 13 and outputs a signal PGM detected by the rotation detector 5a. The drive is controlled so as to rotate the guide bush 2 at the same set rotation speed as the main shaft 1 by feedback to the drive control unit 13 and by a command from the NC device 14.

  Further, during processing of the material 3, the spindle rotation speed calculation unit 15 calculates the spindle rotation speed Nms from the signal PSM detected by the rotation detector 4 a of the spindle motor 4, and the rotation detector 5 a of the guide bush motor 5 From the detected signal PGM, the guide bush rotation speed calculation unit 16 calculates the guide bush rotation speed Ngb.

  Then, the rotation speed difference calculation unit 17 calculates a difference between the main shaft rotation speed Nms and the guide bush rotation speed Ngb. As described above, the rotations of the spindle motor 4 and the guide bush motor 5 are controlled by the NC device 14, the spindle motor drive control unit 12, and the guide bush motor drive control unit 13 such that Ngb = Nms = set rotation speed. In general, there should be almost no difference in the number of rotations.

However, if chuck slip occurs, the rotation speed of the guide bush 2 also decreases due to the reduction in the rotation speed of the material 3 as described above, and thereby the rotation speed of the guide bush motor 5 also decreases. Therefore, Ngb <Nms, and a rotation speed difference ΔN occurs.
The rotational speed difference ΔN is input to the comparing unit 18 and compared with an allowable value of the rotational speed difference set (stored) in a memory in the NC device 14 in advance. Generates a chuck slip signal when exceeding.

  The chuck slip signal is supplied to the NC device 14, the spindle motor drive control unit 12 and the guide bush motor drive control unit 13 to stop the rotation of the spindle motor 4 and the guide bush motor 5, and to feed the spindle 1 not shown. Then, the moving mechanisms of the tool rest 8 and the rear headstock 10 are also in the retracted state, and the machining operation is stopped. Also, the buzzer 19 can be operated by the NC device 14 to perform an alarm operation.

  However, when the spindle motor 4 and the guide bush motor 5 are started, braked, and the number of revolutions is changed, a difference in the number of revolutions exceeding an allowable value may occur even if chuck slip does not occur. , An output prohibition signal is given to the comparison unit 18 for a predetermined time period, and the output of the chuck slip signal is prohibited. This can prevent erroneous detection of chuck slip when the spindle motor 4 and the guide bush motor 5 are started, braked, and when the number of revolutions is changed.

  It should be noted that it is not possible to detect the occurrence of chuck slip (which may be due to other causes) also due to an overload, an overcurrent of the guide bush motor 5, or an excessive rotation number error between the command rotation number and the actual rotation number. Although it is possible, these are detection functions for the purpose of protecting the motor, and it is difficult to accurately detect chuck slip only by this. Therefore, even if a serious failure does not occur, there is a high possibility that minor damage to the tool or the like will occur.

  By the way, in the embodiment shown in FIG. 1, each part for detecting the chuck slip from the rotation speed of the spindle motor 4 and the rotation speed of the guide bush motor 5 is illustrated as being provided separately from the NC device 14. Although it seems that dedicated arithmetic circuits and comparators are provided, it is also possible to perform these functions by software processing by a microcomputer in the NC unit 14.

FIG. 2 is a flowchart of the chuck slip detection process in that case.
When the machining operation is started, this processing is started. First, it is checked whether any one of the starting, braking, and rotation speed changes of the spindle motor 4 and the guide bush motor 5 is performed. Wait until it has elapsed, otherwise proceed immediately to the next step.

Then, a signal from the spindle motor 4 detected by the rotation detector 4a is read to calculate the spindle rotation speed. Next, a signal from the guide bush motor 5 detected by the rotation detector 5a is read to calculate the guide bush rotation speed. Further, a difference between the calculated spindle speed and the guide bush speed is calculated.
Next, the rotational speed difference is compared with a preset allowable value of the rotational speed difference, and if the calculated rotational speed difference exceeds the allowable value, a chuck slip signal is generated. If not, the process returns to the first step and repeats the above processing.

FIG. 3 is a flowchart of another chuck slip detection process.
When the machining operation is started, this process is started. First, it is checked whether the motor is in a constant rotation state, and if so, the process proceeds to the next step. If not, the process waits while performing a check. Proceed to step.
From the next step onward, chuck slip detection is performed by the same processing as in FIG.

Even in this case, when the chuck slip occurs, it can be immediately detected, and accordingly, an appropriate action such as a stop of the processing operation or an alarm can be taken.
In addition, there is no possibility of erroneous detection of chuck slip when starting, braking, or changing the rotation speed of the spindle motor 4 and the guide bush motor 5.

  As described above, the present invention can be applied to a lathe having a guide bush that processes a bar-shaped material that is chucked to the main shaft and guided and supported by the guide bush, and when a chuck slip exceeding an allowable value occurs, Since it can be detected immediately and a chuck slip signal is generated, whereby the machining operation can be stopped immediately, there is no danger of causing a serious failure such as breakage of the tool or bending of the feed slide.

  In addition, since it is not necessary to damage the material by overtightening the chuck of the main shaft, it is possible to process a part in which a part having the same diameter as the material remains. Therefore, it is possible to shorten the machining time of such parts, save materials, eliminate unnecessary consumption of tools, shorten the machining program, and the like.

FIG. 1 is a configuration diagram showing only a portion related to chuck slip detection of a spindle sliding NC lathe according to an embodiment of the present invention. 2 is a flowchart of a process when chuck slip detection is performed in the NC device of FIG. 1. 6 is a flowchart of another chuck slip detection process performed in the NC device of FIG. 1.

Explanation of reference numerals

1: Spindle 1a: Spindle chuck 2: Guide bush 3: Bar-shaped material 3a: Processing part (work) 4: Spindle motor 4a: Rotation detector 5: Guide bush motor 5a: Rotation detector 6, 7: Belt transmission mechanism 8: Tool post 9: Tool (byte)
10: Rear headstock 11: Tool (drill)
12: Spindle motor drive control unit 13: Guide bush motor drive control unit 14: NC device 15: Spindle rotation speed calculation unit 16: Guide bush rotation speed calculation unit 17: Rotation speed difference calculation unit 18: Comparison unit 19: Buzzer

Claims (4)

An independent motor for rotating the main shaft and the guide bush is provided, and the respective motors are controlled to rotate the main shaft and the guide bush at the same rotation speed, chucked by the main shaft and guided and supported by the guide bush. NC lathe with a guide bush that processes a bar-shaped material with a tool,
During the processing of the material, a spindle rotation speed calculation unit that calculates the rotation speed of the spindle from a signal detected by a rotation detector of the spindle or the spindle motor,
During the processing of the material, a guide bush rotation number calculating unit that calculates the rotation number of the guide bush from a signal detected by a rotation detector of the guide bush or the guide bush motor,
Rotation speed difference calculation means for calculating a difference between the rotation speed of the main shaft calculated by the main shaft rotation speed calculation means and the rotation speed of the guide bush calculated by the guide bush rotation speed calculation means,
The difference between the rotation speeds calculated by the rotation speed difference calculation means is compared with an allowable value of the difference between the rotation speeds set in advance in the NC device, and when the difference between the rotation speeds exceeds the allowable value. Comparing means for generating a chuck slip signal;
Means for stopping the rotation of the spindle motor and the guide bush motor in accordance with the chuck slip signal and for retreating the tool to stop the machining operation, the NC lathe having a guide bush. An NC lathe having the guide bush according to claim 1,
An NC lathe having a guide bush, wherein a means for performing an alarm operation by the chuck slip signal is provided. An NC lathe having the guide bush according to claim 1 or 2,
When the spindle motor and the guide bush motor are started, braked, and the number of revolutions is changed, a means is provided for inhibiting the output of the chuck slide signal for a predetermined time set in the NC device. NC lathe with guide bush. An NC lathe having the guide bush according to claim 1 or 2,
When the spindle motor and the guide bush motor are started, braked, and when the rotation speed is changed, the rotation speeds of the spindle motor and the guide bush motor are preset in the set rotation speed commanded by the NC device and the NC device. A guide bush, wherein when the number of rotations reaches a certain number of rotations to which a permissible rotation error has been added, means for inhibiting the output of the chuck slip signal until a constant rotation state signal is output from the NC device is provided. NC lathe with.

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