JPS59169751A - Sliding table abnormality monitoring device - Google Patents

Abstract

PURPOSE:To enable safe control of operation by detecting the load or abnormality that acts on a sliding table by means of difference signals between the output of the rotation angle detector of a sliding-table driving rotary shaft and the output of a linear position detector. CONSTITUTION:A sliding table 1 is reciprocated by means of the rotation of a feed screw 3 driven by a motor 6, and its quantity of travel is detected by means of a linear position detector 12 which counts the slit of a linear scale by means of a sensor 8, while the rotary angle of the motor 6 is detected by means of a rotary angle detector 13 consisting of a pulse generator, etc., with both detected data being inputted into an abnormality monitoring device 14. This abnormality monitoring device 14 obtains the difference between a rotary angle caused by the travel of the sliding table 1 from its reference position to the existing position and the quantity of the travel and, from this quantity of deviation, it detects the reaction force and abnormal load acting on the sliding table 1 and abnormality in driving system, securely and rapidly. Thereby, the control of operation of a machine tool can be safely performed while the machining condition and maintenance can be improved by always monitoring the operating condition of the sliding table.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to sliding tables such as tables and carriages in machine tools, and monitors cutting loads or abnormal loads acting on these sliding tables and abnormalities in the sliding table drive system. This relates to a device for

Machine tools have various types of slide tables, such as the cross feed table and saddle of a lathe, and the table of a milling machine.

These slide tables are generally moved or positioned by a feed screw, and their position or amount of movement is detected by a linear position detector such as a linear scale provided on the slide table.

Figure 1 schematically shows the drive system of a conventional slide table using the cross feed table of an NC lathe as an example, where 1 is the slide table (cross feed table) and 2 is fixed to the slide table 1. 3 is a feed screw screwed into the bracket 2, 4.5 is a bearing that supports the feed screw 3 on a saddle or other member, 6 is an electric motor for driving the feed screw 3, and 7 is a sliding screw. A linear scale is mounted on the sliding table 1, 8 is a sensor for detecting the slit of the linear scale 7, 9 is a numerical control device, and 10 is a tool mounted on the sliding table 1.

The sliding table 1 reciprocates along a sliding surface or a guide body (not shown) by rotation of an electric motor 6 in the forward and reverse directions, and the amount of movement is determined by a sensor 8 counting the slits 1- of a linear scale 7. It is detected and fed back to the numerical control device 9. The numerical control device 9 compares the feedback signal from the sensor 8 with the commanded data, drives the electric motor 6, and moves the sliding table 1 to the commanded position at the commanded speed. An overcurrent detector 11 is provided in the power supply path to the electric motor 6 to stop the electric motor 6 when an abnormal load is applied to the sliding table 1.

However, this overcurrent detector 11 does not operate unless an excessive drive current flows to the motor 6.
If an abnormal load is applied while cutting the outer peripheral tapered surface of the workpiece while retracting the slide table 1, there is a problem that the abnormal load is not detected or it takes a long time to detect it. there were. In addition, in the abnormality detection means using the overcurrent detector 11, even if a fairly large fluctuation occurs in the load acting on the sliding table 1, the overcurrent detector 1 detects the fluctuation.
The abnormality is not detected at all until it reaches a size that causes the slider drive system to operate.Furthermore, it is completely impossible to detect abnormal wear of the feed screw 3 or other abnormalities in the slide table drive system.

This invention was made to solve the problems of the conventional means, and can immediately detect abnormal loads acting on various slide tables of machine tools and abnormalities in the slide table drive system. This invention was made for the purpose of obtaining a device, and further for the purpose of providing a device that can perform various types of control based on the cutting load acting on the sliding table.

Explaining using the reference numerals shown in the drawings, the sliding table abnormality monitoring device of the present invention detects the linear position of a linear scale or the like in the sliding direction of a milling machine table, lathe saddle, cross feed table, or other sliding table. In a machine tool that is provided with a detector 12 and detects the position or movement amount of the slide table 1 by the linear position detector 12, a rotating shaft (for example, the feed screw 3) that drives the slide table 1 is used. rotation angle detector 13
is provided, and a load or abnormality acting on the sliding table 1 is detected by the difference signal between the output signal of the rotation angle detector 13 and the output signal of the linear position detector 12. It is.

2 to 4 show an embodiment of the present invention. In FIG. 2, numerals 1 to 10 are the members explained in FIG. 14 is an abnormality monitoring device. The rotation angle detector 13 uses a known pulse generator or the like consisting of a slit disk and a sensor that detects the slit, and its output pulses and the output pulses of the linear position detector 12 are sent to the abnormality monitoring device 14 as input signals. It is given.

The pulse signals given from the rotation angle detector 13 and the linear position detector 12 are transmitted to the direction discriminator 1 as shown in FIG.
5.16 determines its rotation or movement direction,
It is given as a deviation amount to a deviation counter 18 via an asynchronous circuit 17. This deviation counter 18 is designed to be reset by the origin pulse a from the linear position detector 12. Therefore, the deviation counter 18 records the difference that occurs while the slide table 1 moves from the reference position to the current position. The difference between the rotation angle of the electric motor 6 and the amount of movement of the sliding table 1 is given as the positional deviation amount. On the other hand, the pulses from the rotation angle detector 13 pass through the direction discriminator 16 and are counted by the rotation angle counter 19.

FIG. 4 is a diagram showing the number of deaths of the rotation angle counter 19, where the vertical axis is the count value of the rotation angle counter, and the horizontal axis is the time axis. The count value of the rotation angle counter 19 is reset each time the rotation angle detector 13 generates the origin pulse b, and when the linear position detector 12 generates the origin pulse a, the microprocessor 20 is interrupted. The count value C is read by the microprocessor 20. The origin pulse b of the rotation angle detector 13 is emitted every time the electric motor 6 rotates once, and the origin pulse a of the linear position detector 12 is emitted when the slide table 1 is at the reference position. It is.

The drive system from the electric motor 6 to the slide table 1 is provided with various members such as a feed screw 3, bearings 4 and 5, a shaft coupling, and gears. The external force acting on the slide table 1 acts on these members as internal stress, and an elastic strain approximately proportional to the magnitude of the external force occurs, which causes the amount of rotation of the motor 6 and the slide table 1 to change. It appears as a deviation from the amount of movement. Furthermore, due to changes in backlash and other play between the parts of the drive system, a deviation occurs between the amount of rotation of the electric motor 6 and the amount of movement of the slide table 1. Therefore, the linear position detector 1 provided on the sliding table 1
2 and a rotation angle detector 13 provided on the electric motor 6 to monitor the magnitude of external force acting on the slide table 1 and changes in play and wear amount of the slide table drive system. will be possible. In the embodiment shown in FIG. 3, the amount of deviation from the reference position of the slide table 1 is determined by the rotation angle counter 1 at the time when the linear position detector 12 emits the origin pulse a.
9, and the deviation amount when the slide table 1 moves from the reference position to a certain position is detected by the deviation counter 18.

Such a deviation amount naturally occurs even when the slide table 1 is operating normally, so in order to detect the abnormality, it is necessary to check the pre-given basic feed amount and the actual deviation. This must be done by comparing the quantities. This standard deviation amount is obtained by performing a trial run under standard load conditions and calculating the count value of the rotation angle counter 19 at that time and the count value of the deviation counter 18 at each position of the slide table 1 in the standard data memory 21. It can be set by storing it in . Furthermore, it is also possible to input the standard deviation amount determined theoretically or empirically from the keyboard 22, and by performing checks based on such theoretical or empirical values, the operating state of the slide table 1 can be checked during trial operation. It is also possible to check in detail.

The standard deviation amount set in this way is compared with the deviation amount that appears on the rotation angle counter 19 and the deviation counter 18 during actual machine operation, and it is constantly monitored to see if the difference is within an allowable range. This makes it possible to detect abnormal loads acting on the slide table 1 and abnormalities in the drive system of the slide table 1, and detect breakages and collisions of the tool 10, abnormalities on the sliding surface, wear of the feed screw 3, and bearings. This makes it possible to reliably detect damage to the equipment. Furthermore, in the device of the present invention, the magnitude of the cutting reaction force acting on each sliding unit 1 is measured by the rotation angle counter 19.
Since the value of the deviation counter 18 can be constantly detected, the cutting reaction force can be constantly detected based on the detected value of the cutting reaction force.
By controlling the moving speed of the sliding table 1, it is also possible to control the sliding table 1 so that machining is performed under better cutting conditions.

In addition, 23 shown in FIG. 3 is a frequency-to-voltage converter, and 24 is a digital-to-analog converter, which compares the speed and acceleration of the slide table 1 from the output pulse of the linear position detector 12 via a differentiation circuit 25. By constantly monitoring changes in the count value of the deviation value counter 18 as an analog value, it is possible to detect temporal changes in the amount of movement of the slide table 1 and determine, for example, the position at the moment when the tool 10 contacts the workpiece. This shows that it can be detected.

As explained above, according to the present invention, it is possible to quickly and reliably detect cutting reaction forces and abnormal loads acting on various slide tables in a machine tool, as well as abnormalities in the slide table drive system. Not only is it possible to safely control the operation of the sliding mill, but also by using the device of the present invention, it is possible to constantly monitor the operating condition of the sliding mill, which can improve processing conditions and maintenance. It becomes possible.

[Brief explanation of drawings]

Fig. 1 is a side view schematically showing a conventional slide table drive system, Fig. 2 is a side view schematically showing a slide table drive system of the present invention, Fig. 3 is a control block diagram, and Fig. 4 FIG. 2 is a diagram showing the operation of a rotation angle counter. In the figure, 1 is a sliding table, 3 is a feed screw, 6 is an electric motor, 9 is a numerical controller, 12 is a linear position detector, 13 is a rotation angle detector, 14 is an abnormality monitoring device, a and b are home pulses It is. Agent Patent Attorney Takao Nishi 10-

Claims (1)

[Claims] (1) In a machine tool in which the position or amount of movement of the slide table is detected by a linear position detector installed in the sliding direction of the slide table, the rotation axis of the drive device of the slide table has a rotation angle. A slide in a machine tool, characterized in that a detector is provided, and a load or abnormality acting on the slide table is detected by a difference signal between an output signal of the rotation angle detector and an output signal of the linear position detector. Abnormality monitoring device for moving tables.