JPS60123254A - Tool abrasion monitoring method - Google Patents

Abstract

PURPOSE:To discriminate the condition of abrasion of a tool, by comparing the output of a pressure sensor during cutting, which is disposed between a holder for a cutting tool and a tool main body or between the tool main body and the tip of the tool, with the output of the pressure sensor which is previously st as a value upon normal cutting. CONSTITUTION:A cutting tool 10 is secured to a piezo sensor 1 laid on a bed for the tool 10. A force from a workpiece is exerted to the tip of the tool due to the resistance of cutting, and is also applied to a pressure sensor 1, and an electric charge in proportional to the force is generated. This electric charge is compared with an electric charge which has been obtained beforehand upon normal cutting. Accordingly, if the electric charge abruptly increases, it is indicated that any fault takes places in the tip, and further, the more the frequency of increases in the electrical charge, the more the abrasion of the tool progresses.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for monitoring the wear condition of a cutting tool during cutting.

BACKGROUND ART In automatic processing devices such as NC lathes and machining centers, it is necessary to determine the degree of wear on cutting tools during processing, and to quickly replace the cutting tools when the wear exceeds a predetermined level.

As this type of wear monitoring method, a method has been proposed in which the current consumption of a drive motor in a processing device is detected and whether or not it exceeds a predetermined value is monitored. That is, this method takes advantage of the phenomenon that when a cutting tool wears out, the coefficient of friction between the two increases, cutting resistance increases accordingly, and the current consumption of the motor increases accordingly. However, the current consumption of a motor naturally depends on load fluctuations in the power transmission system, such as a gear train, that is interposed between the workpiece and the motor, and this type of load fluctuation changes significantly from moment to moment. Therefore, it is difficult to judge the state of wear from momentary changes in current consumption. Therefore, it is necessary to monitor the magnitude of the average value of the current consumption at each predetermined time, but due to fluctuations in the load of the power transmission system, etc., the wear condition that can be distinguished from the normal consumption current is significantly reduced. At the point when the wear has progressed,
In the end, this method inevitably reduces responsiveness. Mainly, this method is not applicable to processing equipment in which the motor is controlled with constant torque.

Although research has begun on monitoring methods using afousti-isolation, it is currently difficult to separate the signal from the signal generated by the motor or transmission system, and it is difficult to separate the signal from the signal generated by the motor or transmission system. Reliability to withstand use has not been tested.

Now, as mentioned above, a noticeable phenomenon caused by the wear of cutting tools is an increase in cutting resistance, which also increases the current consumption of the motor, but in addition to this, of course, the cutting tool receives a corresponding force. That's why there is. Then, if we directly extract and monitor the force exerted by the tool itself, which is the object to be monitored,
Accordingly, it is possible to perform reliable I'll cutting of the worn state with a good S/N ratio.

The present invention is based on the foregoing, and provides a method for reliably and easily monitoring the wear state of a cutting tool without adding any processing to the cutting tool. For example, between the tool body and the thousand knobs,
A piezoelectric sensor consisting of a barium titanate piece and an electrode is used to extract the piezoelectric sensor output during cutting, and the wear state of the cutting tool is determined by comparing the piezoelectric sensor output with the piezoelectric sensor output during normal cutting. It is designed to be separated by t'll.

In the present invention, it is necessary to extract the force that the cutting tool receives during cutting without applying any processing to the cutting tool. Therefore, a piezoelectric sensor that can be interposed between the r and il of the cutting tool holder and the tool body, or between the tool body and the number is used as a force detection element. In other words, when used as a cutting tool on a lathe, it is an indexable insert.

For those using cutting tool 1, as shown in Figure il1,
A piezoelectric sensor is installed at the tip of the main body 11 of the chip 2, and the chip 12 is placed on top of the piezoelectric sensor.
I) The body is integrally fastened to the body with a bolt (not shown) through the body. In addition, in generating cutting tools,
As shown in Figure ff12, the piezoelectric sensor 1 is installed on the pedestal 21'' of the holder 20, the cutting tool 10' is placed on it, and the tool 10' is integrally attached to the holder 20 through the fixing pole) 22.231. conclude.

Turning is performed by bringing the tip of the cutting tool into contact with the rotating workpiece, and due to the cutting resistance, force is applied from the workpiece to the tip of the cutting tool, and as a result, force is also applied to the piezoelectric sensor 1. A charge proportional to the force is generated in the piezoelectric sensor 1. Therefore, if the tip is worn out and becomes stiff or chipped, the cutting resistance increases (i), and the generated charge increases accordingly.

Next, this charge is compared with a predetermined charge during normal cutting.

The easiest way to make a comparison is to compare the magnitude of the electric charge.If the electric charge suddenly ignites compared to the electric charge generated during normal cutting, it is clear that chip failure has occurred! lI
Also, if the frequency at which the electric charge is applied increases, it becomes clear that the wear has progressed accordingly. - According to an experimental example, it was confirmed that when the tip tip was slightly chipped, the effective value of the output change reached 1.5 times that of the normal value. A more detailed comparison method is to compare the charge patterns on the time axis, and by this, (r), the state of wear from a more minor stage can be determined.

The above is a case where the component force in one direction (vertical direction) of the piezoelectric sensor 1 is compared with the normal state.
It is sensitive to direction, and by converting component forces in the front-rear direction and left-right direction into electrical charges, and comparing them with each other, it is possible to monitor the wear state in more detail. Become.

As described above, the present invention directly detects the force applied to the cutting tool to be monitored without machining the cutting tool u-, and compares it with the force during normal cutting. Since the wear state is determined based on the wear condition, the S/N ratio is high, and the response can be determined in detail and response <f11, which is simple.

[Brief explanation of drawings]

1 and 2 are perspective views showing a piezoelectric sensor installed in a cutting tool (=1 state) for carrying out the present invention. 10: Cutting tool 11: Tool body 12: Chip 20
: Horg applicant

Claims (1)

[Claims] 1. During cutting, a piezoelectric sensor is interposed between the holder of the cutting tool and the tool body, or between the tool body and the tip.
A tool wear monitoring method that extracts the piezoelectric sensor output and compares the piezoelectric sensor output with the piezoelectric sensor output during normal cutting in advance to determine the state of wear of the cutting tool.