JPH0583340B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for diagnosing the condition of industrial machines, particularly machine tools that perform accurate position control of driven bodies, such as machine tools.

Prior Art When the table of a machine tool is driven by a feed screw on a sliding surface and is positioned by sliding, there is a loss that has a size unique to the machine due to the sliding surface, sliding resistance, rigidity of the feeding mechanism, etc. Motion appears. The value of this lost motion is determined by the lubricating oil supply condition.
Increased due to foreign matter contamination of the guide surface, deterioration of the sliding surface and increase in sliding resistance with the cumulative operating time of the machine, or a decrease in rigidity of the feeding mechanism such as wear of bearings and hole screws, loosening of the drive belt, etc. It is known. This impairs the positioning accuracy of the driven member, and as a result, the machining accuracy deteriorates. In the worst case, an uncontrollable burn-in phenomenon occurs. For example, Japanese Patent Application Laid-open No. 59332/1983 is known as a method that takes into consideration the backlash that is a part of such problems. This device measures the amount of backlash by counting the pulses generated by a pulse generator connected to the feed motor until the first movement of the driven part is detected. Further, in Japanese Patent Application Laid-Open No. 60-29259, errors due to backlash and distortion are set in n positioning operations after the positioning direction is reversed, and the set amounts are corrected.

Problems to be Solved by the Invention The above-mentioned known methods are aimed at correcting the amount of lost motion, and do not take into consideration the field of diagnosing the state of the machine. There was a problem that it was not possible to predict in advance whether the system would become unusable.

Measures to solve the problem Measure the lost motion value of the driven member every time the machine starts based on the measurement cycle program built into the control device every time the machine starts, and store this measured value in memory. When the warning value approaches the predetermined lost motion tolerance value,
The operation time required to reach the lost motion tolerance is estimated from several previously stored values, and a warning is given in advance as to how many hours it will take to reach the lost motion tolerance.

Embodiments Hereinafter, embodiments of the present invention will be described based on the drawings. A table 3 is slidably placed on two sliding guide surfaces 2 provided parallel to the upper surface of the bed 1. A nut 4 is attached to the lower surface of the table 3, and a feed screw 6 which is rotatably supported on the bed 1 by a bearing 5 is screwed into the table 3. Also, a feed motor 7 is attached to the side of the bed 1, with a gear 8 on its output shaft and a gear 9 on the end of the feed screw 6.
Rotation is transmitted without slippage between the timing belt 10 and the timing belt 10. A detector 11 for detecting the current position of the table 3 based on the rotation of the feed screw 6 is attached to the feed motor 7. The feed motor 7 is controlled and rotated by a drive device 13 based on commands from a control device 12 managed by an NC device or a computer, and the output of the detector 11 is input to the NC device 12. The table 3 is supplied with lubricating oil from a management 15 by a lubricating oil supply device 14 to, for example, a hydrostatic bearing portion 6 on a lower sliding surface to enable smooth sliding. On this table 3, there is a workpiece required for processing or a jig 17 on which a workpiece is attached.
is installed. Furthermore, a detector 18 is installed at a predetermined position on the upper surface of the bed 1, and detects a certain position of, for example, a nut 4 on the table 3, and its detection output is NC.
input to device 12; Detector 18 is on table 3
A non-contact displacement meter such as a magnetic scale that detects a specific position such as the front end face of the nut 4, an electric microphone meter, etc. that detects the distance or position difference between the front end face and the detector, or a proximity switch, for example. , a touch sensor, a limit switch, etc., which output a detection output when a certain position such as the front end face of the nut of the table 3 comes in front of the detection can be used. The former detector 18 has an NC table.
The position difference is detected when the device is positioned at a fixed position in the forward and reverse directions. The latter detector 18 has a table fed from the forward and reverse directions.
A method of use is adopted in which the position of the table when the detection output No. 8 is received is read by the detector 11 and the position difference is detected.

Function Now assume that the displacement meter is installed to detect the former position difference. It is assumed that the NC device 12 has a built-in program that executes a lost motion measurement cycle every time the machine is started up, and a lost motion tolerance value determined by experiment, experience, etc. is input. When the machine is started, the NC device issues a command based on the program, and the drive device 13 drives the feed motor 7 to feed the table 3 in the + direction to a certain position.
It is stopped when the detected position matches the command value.
Specific measurement position of table 3 and detector 1 at this time
8 is stored in a memory which is sent to the NC device 12. Next, the NC device sends a command to send the table 3 further in the + direction a predetermined distance and then send it from one direction to the same position as before, and is stopped when the detected position of the detector 11 matches the command value. The positional difference between the specific measurement position of the table 3 and the detector 18 at this time is sent to the NC device 12 and stored in the memory, and the positional difference between the two, that is, the lost motion value, is calculated by the calculation circuit and stored in the memory. be remembered.

Each time the machine is started, a lost motion value is calculated by an arithmetic circuit and stored in a memory, and at the same time, the operating time of the machine at the time of this detection is accumulated. Then, a curve of change in lost motion value with respect to cumulative time as shown in FIG. 2 is obtained as a graph. As the operating time of the machine increases, this change curve approaches a preset tolerance value, and the cumulative operating time of the machine that reaches the tolerance value can be calculated accurately. That is, the point where the tangent to the curve passing through the last three memorized points intersects the tolerance line is defined as the critical operating time. Therefore, when the lost motion value reaches a predetermined value, for example 90% of the allowable value, the NC device issues a warning by calculating the tangent to the curve passing through the three points above and telling you how many hours it will take to reach the limit operating time. will be displayed on the display.

Effects As described above, this application measures the lost motion value every time the device is started, and when the lost motion value reaches a predetermined value compared to the allowable value, a warning is given as to how many hours remain until the limit operating time is reached. Therefore, it is possible to accurately judge the condition of the sliding surface, the feeding mechanism, etc., and to take measures against failures in advance, which has the effect of making it possible to operate the mechanism efficiently.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the configuration of the present invention, and FIG. 2 is a diagram showing a change curve of lost motion values. 1...Bed, 3...Table, 4...Nut, 6...Feed screw, 7...Feed motor, 12...
...NC device, 11,18...detector.

Claims (1)

[Claims] 1. In an industrial machine in which a driven member is controlled by a feed mechanism, the lost motion value of the driven member is measured each time the machine is started based on a measurement cycle program built into the control device for each time the machine is started, This measured value is stored in memory, and when a warning value approaching a predetermined lost motion tolerance value is reached, the operating time to reach the lost motion tolerance value is estimated from the previously stored several points of that value. A method for diagnosing the condition of a machine, characterized in that it warns in advance how many hours later a lost motion tolerance will be reached.