JP3964413B2 - NC lathe with guide bush - Google Patents

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 rotational 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 gear or a belt and driven to rotate.
Then, the rod-shaped material (workpiece) chucked by the spindle is rotated while being guided and supported by the guide bush, and a tool (a tool, a drill, etc.) comes into contact with the outer periphery or end surface of the portion protruding from the guide bush to cut or drill. Etc. are processed.

  Since the tool is pressed against the material during the processing, a large load is applied to the rotation, and a slip (called “chuck slip”) may occur between the chuck of the spindle and the material. When this chuck slip occurs, the rotational speed of the material (workpiece) falls, and there is a risk of causing a serious failure such as breakage of the tool or bending of the feed slide.

Therefore, it is necessary to prevent the occurrence of chuck slip, or if it occurs, it is necessary to detect it quickly 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 (workpiece) being chucked. However, since this is difficult, the detection of chuck slip is not normally performed, and the spindle chuck is not Tighten tightly to prevent chuck slip.

  In NC lathes that have guide bushes that rotate the spindle and guide bush with independent motors, both motors are conventionally driven by a single drive controller, or both motors can be driven using independent drive controllers. The rotation speed was detected only by the spindle motor even when the was driven. Therefore, in this case as well, the chuck slip is not detected, and the main shaft chuck is strongly tightened as in the case described above.

  However, if the chuck is tightened too much, the outer periphery of the material will be damaged, and it will not be possible to process parts that retain the diameter of the material. For this reason, it is necessary to use a material with a diameter larger than the diameter of the part, and to cut the maximum outer diameter as well, resulting 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 problems. The spindle chuck is loosely tightened so as not to damage the material, and when a chuck slip occurs, it is detected quickly, It is an object of the present invention to not only cause minor failure but also cause minor damage to the tool.

  In order to achieve the above object, the present invention is provided with independent motors that rotate the main shaft and the guide bush, respectively, and the main shaft and the guide bush are controlled to rotate at the same number of rotations by the respective motors. An NC lathe having a guide bush for processing a rod-shaped material guided and supported by the guide bush with a tool is provided with the following means (a) to (e).

(a) Spindle speed calculation means for calculating the speed of the spindle from the signal detected by the spindle motor or the spindle rotation detector during processing of the material;
(b) 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 during processing of the material;
(c) Rotational speed difference calculating means for calculating a difference between the rotational speed of the main spindle calculated by the main spindle rotational speed calculating means and the rotational speed of the guide bush calculated by the guide bush rotational speed calculating means;
(d) The difference between the rotation speeds calculated by the rotation speed difference calculating means is compared with a permissible value of the rotation speed difference set in advance in the NC device, and the difference between the rotation speeds exceeds the permissible value. Comparison means that generates a chuck slip signal when
(e) means for stopping rotation of the spindle motor and the guide bush motor and stopping the machining operation by retracting the tool by the chuck slip signal;

The motor for rotating the guide bush may be a guide bush motor having the same or smaller rotational force as that of the spindle motor.
Further, the main shaft is a main shaft with a rotation detector, or the motor that rotates the main shaft is a main shaft motor with a rotation detector, and the guide bush is a guide bush with a rotation detector, or the motor that rotates the guide bush. Can be a guide bush motor with a rotation detector.
Furthermore, 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 rotation speed is changed, the output of the chuck slip signal is prohibited for a predetermined time preset 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 speeds of the spindle motor and the guide bush motor are set as instructed by the NC device. It is preferable to provide means for prohibiting the output of the chuck slip signal until a constant rotational state signal is output from the NC device when the rotational speed reaches the rotational speed range obtained by adding a preset allowable rotational error to the NC device. .

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

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

  With this chuck slip signal, the rotation of the spindle motor and the guide bush motor can be stopped, the tool can be retracted to stop the machining operation, 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 the rotation speed is changed, the rotation speed of the spindle and the guide bush may be different even if there is no chuck slip. Therefore, by preventing the chuck slip signal from being output for a certain period of time from the start of the operation or until it reaches a constant rotation state, it is possible to prevent erroneous detection of the chuck slip and tolerable difference in the rotation speed Is 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 failure such as breakage of a tool or bending of a feed slide.
In addition, since it is possible to avoid overdamaging the material by overtightening the chuck of the main shaft, it is possible to process a part in which the portion of the material diameter remains. For this reason, it is possible to shorten the machining time of parts, save materials, eliminate excessive wear 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 block diagram showing only a portion related to chuck slip detection of a spindle sliding 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, arranged in alignment on a common central axis L, penetrating a rod-shaped material 3, and the main shaft 1 is gripped by the chuck 1a and rotated integrally. The guide bush 2 guides and supports the vicinity of the tip of the material 3 to project the processed portion (work) 3a.

  The main shaft 1 is rotated by a main shaft motor 4 via a belt transmission mechanism 6 without slip, and the guide bush 2 is rotated by a guide bush motor 5 via a belt transmission mechanism 7 without slip. Further, the main shaft 1, the main shaft motor 4, and the belt transmission mechanism 6 slide in the arrow Z1 direction by a moving mechanism (not shown).

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

  The spindle motor 4 is provided with a rotation detector 4a for detecting the rotation thereof. The spindle motor 4 is driven by the spindle motor drive controller 12, and a signal PSM detected by the rotation detector 4a is supplied to the spindle motor drive controller. 12, and is driven and controlled to rotate the spindle 1 at a set rotational speed in accordance with a command from the NC device 14.

  The guide bush motor 5 is also provided with a rotation detector 5a for detecting the rotation thereof. The guide bush motor 5 is driven by the guide bush motor drive control unit 13, and the signal PGM detected by the rotation detector 5a is supplied to the guide bush motor. Feedback is sent to the drive control unit 13, and the drive is controlled so that the guide bush 2 is rotated at the same set rotational speed as that of the main shaft 1 in accordance with a command from the NC device 14.

  Further, from the signal PSM detected by the rotation detector 4 a of the spindle motor 4 during the processing of the material 3, the spindle rotation speed calculation unit 15 calculates the spindle rotation speed Nms 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 the difference between the spindle rotation speed Nms and the guide bush rotation speed Ngb. As described above, the rotation of the spindle motor 4 and the guide bush motor 5 is controlled by the NC device 14, the spindle motor drive control unit 12 and the guide bush motor drive control unit 13 so that Ngb = Nms = set rotation speed. Therefore, usually there should be almost no difference in rotational speed.

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

  This chuck slip signal is given to the NC device 14, the spindle motor drive controller 12 and the guide bush motor drive controller 13 to stop the rotation of the spindle motor 4 and the guide bush motor 5, and the spindle 1 feed mechanism (not shown). Then, the moving mechanism of the tool post 8 and the back spindle stock 10 is also retracted to stop the machining operation. Further, an alarm operation can be performed by operating the buzzer 19 by the NC device 14.

  However, when the spindle motor 4 and the guide bush motor 5 are started, braked, or when the rotational speed is changed, a rotational speed difference exceeding an allowable value may occur even if chuck slip does not occur. The output prohibition signal is given to the comparison unit 18 for a predetermined time set in advance, and the output of the chuck slip signal is prohibited. As a result, it is possible to prevent erroneous detection of chuck slip when the spindle motor 4 and the guide bush motor 5 are started, braked, or when the rotation speed is changed.

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

  By the way, in the embodiment shown in FIG. 1, each part for detecting a chuck slip from the rotational speed of the spindle motor 4 and the rotational speed of the guide bush motor 5 is shown separately from the NC device 14. Although it seems that a dedicated arithmetic circuit and a comparator are provided, these functions can be performed by software processing by a microcomputer in the NC device 14.

FIG. 2 is a flowchart of the chuck slip detection process in that case.
When the machining operation is started, this process is started. First, it is checked whether the spindle motor 4 and the guide bush motor 5 are activated, braked, or the rotation speed is changed. If so, a predetermined time is set. Wait until it has passed, 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 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. Furthermore, the rotational speed difference between the calculated spindle rotational speed and guide bush rotational 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, return to the first step and repeat the above process.

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

Even in this case, when a chuck slip occurs, it can be immediately detected, and appropriate measures such as a machining operation stop or an alarm can be taken.
In addition, when the spindle motor 4 and the guide bush motor 5 are started, braked, or the rotational speed is changed, a chuck slip is not erroneously detected.

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

  In addition, since it is possible to avoid overdamaging the material by overtightening the chuck of the main shaft, it is possible to process a part in which the portion of the material diameter remains. Therefore, it is possible to shorten the machining time of such parts, save materials, eliminate excessive tool consumption, shorten the machining program, and the like.

It is a block diagram which shows only the part relevant to the chuck slip detection of the spindle sliding NC lathe which is one Example of this invention. 2 is a flowchart of processing when chuck slip detection is performed in the NC apparatus of FIG. 1. 6 is a flowchart of another chuck slip detection process performed in the NC apparatus of FIG. 1.

Explanation of symbols

1: Main shaft 1a: Main shaft chuck 2: Guide bush 3: Rod-shaped material 3a: Processing part (work) 4: Main shaft motor 4a: Rotation detector 5: Guide bush motor 5a: Rotation detector 6, 7: Belt transmission mechanism 8: Tool post 9: Tool (byte)
10: Back headstock 11: Tool (drill)
12: Spindle motor drive controller 13: Guide bush motor drive controller 14: NC device 15: Spindle speed calculator 16: Guide bush speed calculator 17: Speed difference calculator 18: Comparison section 19: Buzzer

Claims (4)

An independent motor for rotating the main shaft and the guide bush is provided, and the motor and the guide bush are controlled to rotate at the same rotational speed by each motor, and are chucked by the main shaft and guided and supported by the guide bush. NC lathes with guide bushes that machine rod-shaped materials with tools
A spindle rotation speed calculating means for calculating the rotation speed of the spindle from a signal detected by a rotation detector of the spindle or spindle motor during 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 a rotation detector of the guide bush or the guide bush motor during processing of the material;
A rotational speed difference calculating means for calculating a difference between the rotational speed of the main spindle calculated by the main spindle rotational speed calculating means and the rotational speed of the guide bush calculated by the guide bush rotational speed calculating means;
When the rotation speed difference calculated by the rotation speed difference calculating means is compared with an allowable value of the rotation speed difference preset in the NC device, and the rotation speed difference exceeds the allowable value A comparison means for generating a chuck slip signal;
An NC lathe having a guide bush, comprising: means for stopping rotation of the spindle motor and the guide bush motor and stopping the machining operation by retracting the tool by the chuck slip signal. An NC lathe having a guide bush according to claim 1,
An NC lathe having a guide bush, characterized in that means for performing an alarm operation in response to the chuck slip signal is provided. An NC lathe having a guide bush according to claim 1 or 2,
A means is provided for prohibiting the output of the chuck slip signal for a predetermined time preset in the NC device when the spindle motor and the guide bush motor are started, braked, and when the rotation speed is changed. NC lathe with guide bush. An NC lathe having a 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 NC apparatus and the set rotation speed commanded by the NC apparatus. And a guide bush for disabling the output of the chuck slip signal until a constant rotation state signal is output from the NC device when a rotation speed range to which an allowable rotation error is added is reached. NC lathe with.

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