JPS62136342A - Trouble prediction device for feeding device - Google Patents

Abstract

PURPOSE:To make it possible to predict troubles in a feeding device of a machine tool such as a machining center (MC) by providing the feeding device with a feed command means, a vibration detection means, a comparison means, a calculation means and a display means, thereby detecting abnormality in the feeding device at an early stage. CONSTITUTION:After finishing a machine assembly, values of vibration and current are measured with a vibration detector 17 fixed on an attachment block 13 of a ball nut 14 and with a current detector 23 arranged between a feeding servomotor 16 and a numerically controlled device 20 while moving a feeding table 11 without load, and the measurements are stored via an analog-digital (AD) converters 26a and 26b into a computer 30. After using the machine for a specified period of time, when a trouble predicting operation is commanded with a button 29a on a console 29, the feeding table 11 repeats back-and-forth movements according to a monitor program to measure the values of vibration at the time of actual use, compare the measurements with those when the feeding table is in normal condition, and displays compared results on a cathode-ray tube screen. This makes it possible to know easily the increase in the vibration compared with that immediately after the machine is assembled and the predict troubles.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a failure detection device used to predict failure of a feeder in a machine tool.

<Prior art> In machine tools such as machining centers, a movable body such as a feed table is slidably supported by a sliding surface, and this movable body is connected to the output shaft of a feed servo motor via a ball screw mechanism. The movable body is connected to the robot and moves at the commanded speed.

In such a feeding device, if the pole screw becomes abnormally worn due to long-term use or galling occurs on the sliding surface due to poor lubrication, the movable body cannot be fed smoothly and abnormal vibrations occur. If this vibration exceeds a permissible range, the necessary machining accuracy cannot be obtained, but conventionally, no device has been provided that can predict such failures of the feeding device.

<Problems to be solved by the invention> As described above, in conventional machines, failure of the feeding device cannot be predicted, and vibrations exceeding the allowable range occur during operating hours, making normal machining impossible and disrupting the machining line. There were problems that had a significant impact on the production schedule, such as the suspension of production.

Means for Solving the Problems> In view of the problems of the conventional art, the present invention provides a feed command means for rotating a servo motor to move a movable body under no load, and a feed command means based on the commands of the feed command means. Vibration detection means for detecting vibrations generated while the movable body is moving, and comparison means for comparing the magnitude of the vibration detected by the vibration detection means with the magnitude of vibration during normal no-load conditions. The present invention is characterized in that a failure of the feeding device is predicted based on the comparison results obtained by the comparison means.

Function> The feed command means is operated at regular intervals to move the movable body under no load. Then, the magnitude of vibration generated when the movable body is moving based on the command from the feed command means is detected by the vibration detection means. The magnitude of the vibration detected by the vibration detection means is compared with the magnitude of vibration under normal no-load conditions by the comparison means, and failure of the feeding device is predicted based on the result of this comparison.

<Embodiment> In FIG. 1, reference numeral 10 denotes a feeding device of a machine tool, in which a feeding table 11 is slidably supported as a movable body via a sliding surface 12a formed on the upper surface of a bed 12. A ball nut 14 holding a large number of balls in a circulating manner is attached to the lower surface of the feed table 11 via a mounting block 13.
A feed screw 15 connected to the output shaft of a feed servo motor 16 is screwed into the feed screw 4 .

Further, a vibration detector 17 consisting of an accelerometer, an AE sensor, etc. is attached to the side surface of the mounting block 13 that holds the ball nut 14.

On the other hand, 20 is a numerical control device, and 21 is a sequence control device. In addition to the numerical control program for machining, the numerical control program for failure detection shown in FIG. 4 is stored in the memory of the numerical control device 20. has been done. The numerical control device 20 selectively executes a numerical control program for machining or a numerical control program for fault detection in response to commands from the sequence control device 21.

The numerical control device 20 also includes a feeding servo motor 16.
A servo motor drive circuit 22 that controls the rotation of the servo motor drive circuit 22 is connected, and when a command pulse is distributed from the numerical control device 20 to the servo motor drive circuit 22 based on a movement command included in the numerical control program, the servo motor drive circuit 22
The drive current is controlled to rotate the feed servo motor 16 at a speed corresponding to the frequency of the distributed command pulse. Further, between the numerical control device 20 and the feed servo motor 16, a feed servo motor 16 is provided.
A current detector 23 is provided for detecting the magnitude of the current flowing to.

Reference numeral 30 denotes a personal computer programmed to display the linear movement value detected by the linear movement detector 17 and the current value detected by the current detector 23; The output of the current detector 23 is the amplifier 2
5a, 25b and AD converters 26a, 26b. In the memory of this personal computer 30, a program for inputting setting values shown in FIG. 2 and a program for monitoring shown in FIG. 3 are stored. Using the keyboard 30a of the personal computer 30, enter the command “vS” to input the vibration setting value.
” is keyed in, “V
40), and the command "IS" to input the current setting value.
When is keyed in, “Is
The value input after "" is stored as the set current value Si (41).

On the other hand, when an M code M40 instructing the start of monitoring is supplied from the numerical control device 20 via the sequence control device 21, the personal computer 30 executes the process shown in FIG. Process of displaying only fixed parts such as the frame and title of the monitor screen shown in the figure (50)
Then, the process (51) of clearing the maximum value DVO,])io in the buffer to zero is performed. Thereafter, the monitor routine of steps (52) to (61) is repeatedly executed until the code MO2 indicating the end of the program is output from the numerical control device 20 via the sequence control device 21.

In this monitor routine, the AD converter 26a.

26b, the signal V representing the magnitude of vibration and the current value i are read (52), and it is determined whether the read values are larger than the maximum values Dvo and Dio (53), (56) ), if v, i
Set as the maximum value I) vo, D io (
55), (57). And the maximum value Dvo, Dio
are divided by the set values Sv and Si, respectively, to obtain the set values Sv and Si
The relative size DDV of the maximum value Dvo and Dto for
, DDt is calculated (58), and after this, DD
In order to display a bar graph according to the size of v, DDi on the CRT screen, the length of the bar graph on the screen is calculated (60), and the bar graphs 31a and 31b of this calculated length are displayed on the CRT screen. Processing for displaying on the screen is performed (62).

Next, the operation of predicting a failure in the above device will be explained.

First, when the assembly of the machine is completed, the feed table 11 is moved at a set speed in an unloaded state, and the output values of the AD converters 26a and 26b at this time are determined by the above-mentioned "VS" and "IS".
” input using the command.

As a result, the personal computer 30 operates as shown in FIG.
l, (by the processing in bl, the magnitude of vibration in the no-load state and the magnitude of the current value at the time of completion of machine assembly are registered in the non-volatile storage area as set values Sv, Si.

Thereafter, after the machine is installed at the customer's factory, the fault detection operation button 29a on the operation panel 29 is pressed periodically to issue a command for fault detection operation.

When the fault detection operation button 29a is pressed, a program selection command is supplied from the sequence control device 21 to the numerical control device 20, and the start of the numerical control program for fault detection shown in FIG. 4 is instructed.

As a result, the numerical control device 20 starts executing the numerical control program for fault detection, and first, the first block N0
Read M2O programmed in IO. M2O
When this data is output one after another, this data is output to the sequence control device 21 and
1 to the personal computer 30, and in response, the personal computer 30 starts executing the monitor program shown in FIG. As a result, the screen shown in FIG. 5 is displayed on the CRT screen of the personal computer 30.

At this time, since the feed table 11 is not moving and the outputs of the AD converters 26a and 26b are zero, no bar graph is displayed on the CRT screen, and only the fixed portion is displayed.

Following this, GOI Floo xlooooo programmed in block NO2O is sent to the numerical controller 20.
When read by Floo, the pulse distribution speed is set to a value according to Floo, and a positive command pulse is output to the servo motor drive circuit 22, and the servo motor drive circuit 22 operates at a speed according to the frequency of the command pulse. The feed servo motor 16 is rotated in the normal direction, and thereby the feed table 11
is advanced. Furthermore, following this, block N030
X-100000, X1° o o of block N040
o o o, when X-100000 of block N030 is read out sequentially, the numerical control device 20 sequentially supplies a negative command pulse, a positive command pulse, and a negative command pulse to the servo motor drive circuit 22 in response to this. As a result, the feed table 11 sequentially moves backward, forward, and backward.

Note that the speed corresponding to Floo is the feed speed when the vibration value and current value are measured during assembly.

When the feed table 11 is moved forward and backward in this manner, a predetermined current flows through the feed servo motor 16 and vibrations are generated in the feed table 11.

As a result, the outputs of the vibration detector 17 and the current detector 23 increase from zero, and the AD converters 26a and 26b output the vibration value 2 and the current value i during the movement of the feed table 11.

During this time, the personal computer 30 repeatedly executes the processes of steps (52) to (61) in FIG. The ratio of the size to the values Sv and Si is calculated and displayed on the screen as shown in FIG.

As a result, by looking at the CRT screen, the operator can check the magnitude of vibration during no-load movement of the feed table 11 and the magnitude of the current supplied to the feed servo motor 16 in the normal state immediately after assembly. This allows you to easily and reliably detect increases in vibration due to wear of the balls in the ball nut 14 or stiffening of the slide surface, or increases in the load on the feed servo motor 16. can be discovered.

As a result, it is possible to predict failures before they occur, such as large pole wear or galling that would make it impossible to perform normal machining. This eliminates problems such as equipment failure and production stoppages.

In the above embodiment, the movable body was moved in an unloaded state by a numerical control program for failure prediction, but the servo motor drive circuit 22 was activated by a command from the sequence control device 2 to drive the feed servo motor 16. While rotating at a constant speed, the personal computer 3
It is also possible to supply a monitor command to 0.

FIG. 6 shows a modification of the present invention, in which the maximum value D
Compare vo and Dio with the set values Sv and Si65),
(66), maximum value 1) vo, Dio are set values 3v,
If the tolerance value Lv, Li is larger than 3i, an abnormality signal is sent out (67). With this device, failure of the feeding device can be predicted by sending out an abnormal signal by appropriately setting the allowable values Lv and Li.

<Effects of the Invention> As described above, in the present invention, a movable body such as a feed table is moved under no load by the rotation of the feed servo motor, and vibrations of the movable body that occur during the movement of the feed table are suppressed. The detected vibration magnitude can be compared with the vibration magnitude in the normal state immediately after assembly, making it easy to see how much the vibration magnitude has increased while the movable body is moving. can be grasped. Therefore, abnormalities that may lead to failure of the feeding device, such as wear of the balls of the ball screw mechanism, can be discovered at an early stage, and there is an advantage that failure of the feeding device can be predicted.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 shows the overall configuration of a feeding device equipped with a failure prediction device, and FIGS. 2 and 3 show the operation of the personal computer 30 in FIG. 1. 4 is a program sheet showing a numerical control program for failure prediction, FIG. 5 is a diagram showing the display screen of the personal computer 30 in FIG. 1, and FIG. 6 is a flow chart showing a modification of the present invention. 11...Feeding table, 14...Pole nut, 1
5...Feeding screw, 16...Feeding servo motor, 1
7... Vibration detector, 20... Numerical control device, 21.
...Sequence control device, 22...Servo motor drive circuit, 23...Current detector, 26a, 26b...A
D converter, 30...Personal computer.

Claims (3)

[Claims] (1) In a feeding device in which a movable body is guided and supported by a sliding surface and the movable body is connected to an output shaft of a feed servo motor via a feed screw mechanism, the movable body is moved in an unloaded state. A feed command means for rotating a servo motor, a vibration detection means for detecting vibrations generated while the movable body is moving based on commands from the feed command means, and vibration detection means for detecting vibrations detected by the vibration detection means. A failure detection device for a feeding device, characterized in that a comparison means is provided for comparing the magnitude of vibration with the magnitude of vibration under normal no-load conditions, and a failure of the feeding device is predicted based on the comparison result by the comparison device. Device. (2) The comparison means includes a calculation means for calculating a ratio of the magnitude of the vibration detected by the vibration detection means to the magnitude of vibration during normal no-load conditions, and displays the ratio calculated by the calculation means. A failure prediction device for a feeding device according to claim (1), characterized in that it is constituted by a display means. (3) The comparing means compares the magnitude of the vibration detected by the vibration detecting means with the magnitude of vibration during normal no-load conditions, and determines that the magnitude of the vibration detected by the vibration detecting means is normal under no load. Failure prediction of a feeding device according to claim (1), characterized in that it is constituted by an abnormality determining means that generates an abnormal signal when the magnitude of vibration increases by a predetermined amount or more. Device.