JPH05220648A - Method for monitoring state of machine - Google Patents

Abstract

PURPOSE:To integrally monitor the whole of a machine tool having a plurality of movable elements and self-correct the operation abnormality of the movable elements to the life. CONSTITUTION:A plurality of movable elements such as a spindle, a spindle motor, a feed mechanism, a tool rest and the like are operated, and the operating quantity of each movable element is measured by motor current value, motor coil temperature, lost motion value, turning time or the like. On the basis of the measurement value, the remaining operating time is displayed every movable element, and an operation abnormality, if present is notified. In the feed mechanism, the back rush of a feed screw is self-corrected with the lost motion measurement value as the correction data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for monitoring the state of a machine having a plurality of movable elements, and more particularly to a state monitoring method suitable for a machine tool or the like which requires highly accurate positioning of each movable element. It is a thing.

[0002]

2. Description of the Related Art Conventionally, as a monitoring method of this type, for example, Japanese Patent Laid-Open No. 63-191553 proposes a technique of notifying the remaining operating time based on a lost motion measurement value of a feeding mechanism.

[0003]

However, according to the conventional method, since only the feed mechanism is monitored, the entire machine cannot be monitored comprehensively, and in particular, the work due to the combined movement of a plurality of movable elements is performed. In the case of a machine tool that processes a machine with high accuracy, the monitoring content was insufficient. Moreover, since no measures have been taken to eliminate the existing lost motion, there is a disadvantage that the machine is operated while the lost motion of the feeding mechanism is left unattended during the remaining operation period.

SUMMARY OF THE INVENTION An object of the present invention is to provide a state monitoring method for a machine capable of comprehensively monitoring the entire machine and self-correcting an operation abnormality of a movable element.

[0005]

In order to solve the above problems, the state monitoring method of the present invention operates a plurality of movable elements, measures the operation amount of each movable element, and based on the measured value, The remaining operating time is notified for each movable element, and the operation abnormality of the movable element is corrected by using the measured value as correction data.

[0006]

According to the method of the present invention, the entire machine is comprehensively monitored by reporting the remaining operating time for each of a plurality of movable elements. In addition, since the operation amount measurement value is used as the correction data and the operation abnormality of the movable element is self-corrected, the machine is operated in an optimum state until the end of its life.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is embodied in a lathe will be described below with reference to the drawings. First, the following table shows an outline of the state monitoring method of this embodiment.

[0008]

[Table 1]

As shown in Table 1 above, in this embodiment, as the movable elements, the spindle, the spindle motor, the feed mechanism, and the tool rest are monitored. Although there are a plurality of methods for measuring the operation amount of each movable element, the method indicated by ⊚ in Table 1 is adopted here.
Self-correction when an operation abnormality occurs is possible for each movable element, but here it is implemented in the feed mechanism. The operation amount can be measured either in the steady operation of the lathe or in the test program operation, but in the present embodiment, the latter operation mode is used.

FIG. 3 is a schematic view showing a spindle mechanism. A spindle head 1 supports a spindle 3 with a spindle bearing 2, and the spindle 3 is connected to a spindle motor 4 via a power transmission member 8. The spindle motor 4 is connected to the NC via the drive unit 5.
It is connected to the device 18. Then, the motor current value of the spindle motor 4 is measured by the current detector 6, the motor coil temperature of the spindle motor 4 is measured by the thermometer 7, and these measured values are input to the NC device 18. ..

FIG. 4 is a characteristic diagram showing the relationship between the motor current value A and the cumulative operating time T. In the figure, Anmax is the maximum motor current value, Anmin is the minimum value, Anav is the average value, and Au is the motor current. Allowable upper limit line, 0.9Au
Indicates a safety tolerance upper limit line (safety factor 10%). The motor current value A is measured by the current detector 6 for example, seven times at regular intervals during the test program operation of the lathe. Under a certain measurement condition, the variation of the measured value has a normal distribution as shown by the shaded area in FIG.
Av and maximum value Anmax are calculated by the following equation.

[0012]

[Equation 1]

Here, σ is a standard deviation value. By this processing, the probability that a value exceeding the maximum value Anmax appears will be 0.
Reduced to 15%.

Then, by calculating a straight line passing through the previous average value A (n-1) av and the current average value Anav,
The average remaining operating time Tnav is obtained from the point where the straight line intersects with the safety allowable value 0.9Au. In addition, by calculating a straight line that passes through the maximum value A (n-1) max of the previous time and the maximum value Anmax of this time, the straight line is a safety allowable value 0.9A.
Worst remaining shortest remaining operating time Tnmi from the point where u intersects
n is required. Now, the remaining operating time is Tn, and the life calculated from the empirical value or theoretical formula, that is, the maximum operating time is Tn.
Supposing lim to be Tn> Tlim, Tn <0, and Tn = ∞, all of the states are obviously abnormal. When this abnormal remaining operating time is calculated, it is regarded as Tn = 0, and the spindle 3 The life of is notified. In addition, n = 6 in FIG.
As seen in (2), the abnormality is also notified when the maximum measured value exceeds the safety allowable value (A6max> 0.9Au).

FIG. 5 is a schematic view showing the feed mechanism, in which the center table 11 on which the processing section 10 is mounted is slid on the bed 14 by the feed screw 13 via the nut 12. Lead screw 13
Is connected to a feed motor 16 via a power transmission member 15, and the feed motor 16 is provided with a detector 17. The feed position data detected by the detector 17 is NC
It is input to the device 18, and the feed motor 16 is controlled by the NC device 18 via the drive unit 19. A fixed position detector 20 is installed on the bed 14, and the NC device 18 measures the lost motion of the middle base 11 based on the outputs of the fixed position detector 20 and the detector 17. As the lost motion measuring method, the known measuring method described in Japanese Patent Laid-Open No. 63-191553 is used.

FIG. 6 is a characteristic diagram showing the relationship between the lost motion value L and the cumulative operating time T. In the diagram, Lnma
x is the maximum value of lost motion, Lnmin is the minimum value, L
nav is an average value, Lu is an allowable value upper limit line, 0.9Lu is a safety allowable value upper limit line (safety factor 10%), Tnav is an average remaining operating time, and Tnmin is a shortest remaining operating time. The lost motion value L is measured as in the case of the motor current value A, and the remaining moving time Tna is calculated based on the measured value.
v, Tnmin are obtained and an abnormality is reported. In this feed mechanism, the lost motion measurement value L is used as correction data by the NC device 18 to feed the screw 1
Backlashes such as 3 are self-corrected, and the lost motion value L after correction becomes 0, as indicated by the mark X in FIG.
As a backlash correction method, for example, the techniques disclosed in JP-A-59-59332 and JP-A-60-29259 are known.

As shown in Table 1, it is also possible to measure the operation amount of the feed mechanism based on the motor current value of the feed motor 16. In this case, the motor load increases due to seizure or insufficient lubrication, or decreases due to backlash such as wear, and the measured value of the motor current fluctuates in both directions due to the influence. For this reason, it is necessary to continue to collect the measurement data at every fixed period of the cumulative movement amount (time or distance). Then, the upper limit value and the lower limit value of the motor load that can guarantee the accuracy are set, and if the measured value is within the range, it is regarded as normal, and when it deviates from that range, an abnormality is notified. In addition, it is also possible to adopt a method of setting a normal aging curve, and when the measured value deviates greatly from this curve, obtain the remaining operating time based on the slope of the measured value curve and notify the abnormality.

Although the principle of the monitoring method in the spindle mechanism and the feed mechanism has been described above, the same principle applies to other movable elements, that is, the spindle motor 4 and the tool rest (not shown). In the spindle motor 4, the spindle motor 4 is based on the motor coil temperature measurement value measured by the thermometer 7.
Remaining operating time is calculated, and the abnormality is notified.
In the turret, the remaining operating time of the turret is obtained based on the motor current value of the turret rotation motor, and an abnormality is reported.

FIG. 7 is a block diagram showing a control circuit of the spindle mechanism. In the figure, 21 is a motor current measuring circuit and 2 is a motor current measuring circuit.
Reference numeral 2 is a measurement data storage circuit, 23 is a comparison circuit for comparing a measurement value with a safety allowance value, 24 is an operation circuit for executing the above-mentioned operation based on measurement data, 25 is a storage circuit for storing the operation result, 26 Is a remaining operating time display device, and 27 is an alarm generator. The NC device 18 has a control circuit for the main spindle mechanism, a feed mechanism having the same structure as that of the main spindle mechanism, a main spindle motor 4, and a control circuit for the tool rest built therein.

Next, a method of monitoring the states of the spindle mechanism and the feed mechanism will be described with reference to the flowcharts of FIGS.
In the spindle mechanism, as shown in FIG. 1, first, when a predetermined measurement interval has elapsed (step S1), the test program operation of the lathe is started (step S).
2). Then, the spindle motor 4 rotates the spindle 3 at the maximum rotation speed (step S3), and the motor current value is measured a plurality of times when the rotation speed of the spindle 3 is stable (step S4). Next, the measured value is compared with the safety allowable value (step S5), and if the measured value exceeds the safety allowable value, an alarm is generated (step S14).

If the measured value is less than the safety tolerance,
After the average value and the maximum value of the motor current are calculated based on the measurement data by using the equation (1) (step S6), the previous measurement data is read (step S7). Then, a straight line passing through the previous measured value and the current measured value is calculated (step S8), and the average value and the shortest value of the remaining operating time are calculated based on the straight line (step S9). Subsequently, it is determined whether there is an abnormality in the remaining operating time by using the above inequality (step S10), and if there is no abnormality, the current measurement data is stored instead of the previous measurement data (step S10). S11), the remaining operating time is displayed (step S12). If the remaining operating time is abnormal, the remaining operating time is set to 0 (step S1
3), an alarm is immediately issued (step S1)
4).

In the feeding mechanism, as shown in FIG.
After the measurement interval has passed (step S21),
When the test program operation is started (step S2
2) First, the feed motor 16 is rotated at the maximum speed with the backlash correction function stopped (step S2).
3), the lost motion value is measured multiple times (step S24). Then, based on this lost motion measurement value, the remaining operating time is calculated and displayed through the same steps as in the case of the spindle mechanism, and after an alarm is generated in the event of an abnormality (steps S25 to 34), the measurement value is corrected. Backlash of the feed screw 13 and the like is self-corrected as data (step S35). Therefore, the feed mechanism can be operated in an optimal state until the end of its life. For the spindle motor and the tool rest, the same program as for the spindle mechanism is applied.

In the above embodiment, the state of the lathe is monitored during the test program operation, but it can also be carried out in the steady operation mode. In this case, after the measurement interval has elapsed, the cutting operation is stopped, the spindle is rotated, and the feed mechanism is operated in the rapid feed stroke. It suffices to perform the measurement once. In addition, the present invention is not limited to the above embodiment, a machine tool other than a lathe, or
It is also possible to embody the present invention by appropriately changing the shape and configuration of each part without departing from the spirit of the present invention, such as application to various industrial machines.

[0024]

As described above in detail, according to the present invention, the remaining operating time is informed for each of a plurality of movable elements, the entire machine can be comprehensively monitored, and the operation amount measurement value is used as the correction data. As a result, it is possible to self-correct the operation abnormality of the movable element, and as a result, it is possible to operate the machine in an optimal state until the end of its life.

[Brief description of drawings]

FIG. 1 is a flowchart showing a spindle mechanism monitoring program according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a feed mechanism monitoring program according to an embodiment of the present invention.

FIG. 3 is a schematic view of a spindle mechanism.

FIG. 4 is a characteristic diagram illustrating the principle of spindle mechanism monitoring.

FIG. 5 is a schematic view of a feeding mechanism.

FIG. 6 is a characteristic diagram illustrating a feed mechanism monitoring principle.

FIG. 7 is a block diagram showing a control circuit of a spindle mechanism.

[Explanation of symbols]

1 ... Main spindle head, 2 ... Main spindle bearing, 3 Main spindle, 4 Main spindle motor, 5 Drive unit, 6 Current detector, 7 Thermometer, 8 Power transmission member, 10・ Processing part, 11 ・ ・ Middle stand, 12 ・ ・ Nut, 13 ・ ・ Feed screw, 14 ・ ・ Bed, 15 ・ ・ Power transmission member, 16 ・ ・
Feed motor, 17 ... Detector, 18 ... NC lathe, 19
..Drive units, 20 .. Fixed position detectors, 21 ..
.Motor current measuring circuit, 22..Measurement data storage circuit,
23..Comparison circuit, 24..arithmetic circuit, 25..memory circuit, 26..remaining operating time display device, 27..alarm generation device.

Claims (1)

[Claims] 1. A plurality of movable elements are driven, the operation amount of each movable element is measured, the remaining operating time is informed for each movable element based on the measured value, and the measured value is used as correction data for the movable element. A method for monitoring the state of a machine, which is characterized by correcting an abnormal operation of the machine.