JPS6231239Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to the mounting position of a sensor of a cutting tool breakage detection device in a lathe, particularly a lathe having a guide bush.

In the unmanned operation of lathes, in addition to handling chips, supplying new materials, and controlling product dimensions, it is important to accurately and sensitively detect damage to cutting tools and prevent the production of defective products. It's becoming a problem.

Devices that detect damage to cutting tools have already been considered, such as those that detect cutting power and those that detect changes in vibration.
This section describes a method for monitoring the state of the blade (hereinafter abbreviated as ) and detecting damage to the cutting tool based on changes in the state.

This method of detecting damage to cutting tools due to AE (hereinafter referred to as AE method) captures acoustic vibrations, so the sensitivity varies widely depending on the mounting position of the sensor. For milling machines, it was considered appropriate to attach it to the spindle head, and for drilling machines, it was considered appropriate to attach it to the quill of the spindle.

However, in lathes that have a large number of cutting tools, such as lathes with turret tool rests, installing a sensor for each tool would require a large number of sensors and increase costs, so it is better to install only one sensor on the tool rest. However, variations in sensitivity occur due to variations in the length and rigidity of the cutting tool, and in the case of a turret tool post, problems arise such as how to extract signals from the rotating turret. When installed, sufficient sensitivity could not be obtained because there were many bonding surfaces and oil films between the cutting point by the cutting tool and the detection point by the sensor.

The present invention aims to eliminate the above-mentioned drawbacks and has as its gist the provision of a sensor in the guide bush.

Hereinafter, an embodiment of a lathe having two turret tool rests shown in the drawings will be described in detail to explain the present invention.

In Fig. 1, a cross feed table 3 having two turret tool rests 1 and 2 slides perpendicularly to the main shaft 4.
A headstock 5 that rotatably supports the workpiece slides in the axial direction of the main spindle 4, and a guide bush housing 6 that supports the workpiece 7 that rotates through the main spindle 4 is fixed to a bed (not shown). FIG. 2 is a conceptual diagram showing the relationship between the main shaft and the turret of the numerically controlled automatic lathe.

The workpiece 7 is gripped by a collector chuck 8 provided at the tip of the spindle 4, and is moved forward and backward in the axial direction by the sliding movement of the headstock 5 while rotating together with the spindle 4. The tip of the workpiece 7 is a guide bush 9
It penetrates through and is cut at the mouth of the guide bush. The guide bush 9 is a fixed or rotating guide bush provided in the guide bush housing 6 fixed to a bed (not shown), and supports the workpiece 7 to prevent the workpiece from deflecting or vibrating due to cutting force. are doing.

An NC-controlled transverse feed table 3 in which a turret turret 1, 2, on which a cutting tool 10, a drill 11, etc. are attached, are indexably provided facing a guide bush 9.
It slides perpendicularly to the main shaft 4 to select the turret tool rests 1 and 2, and controls the cutting depth by the cutting tool.

An AE sensor 20 is fixed to the guide bush housing 6 and connected to the detection device main body 30 with a cable 40.

Here, the instrument for the AE method used in this example will be briefly explained. FIG. 2 is a block diagram of the AE method of this embodiment. The sensor 20 consists of a piezoelectric element 21 using zircon titanate and a preamplifier 22 that amplifies its output.

The output of the preamplifier 22 is input to the main amplifier 31 of the detection device main body 30 via a cable 40, and after being amplified, passes through a high-pass filter 32, passes through an envelope detector 33, and is input to a signal discriminator 34.

When a signal above the set threshold is detected,
The signal discriminator 34 is activated and outputs a signal (constant voltage signal) indicating that the cutting tool is damaged, and either stops the machine or issues a signal to contact the operator.

The operation will be explained below. The workpiece 7 is held by the chuck 8 of the main shaft 4, which rotates at a predetermined rotation speed.
Cutting feed is applied by advancing the headstock 5 under NC control, and cutting is performed with the selected cutting tool 10.

The cutting depth of the cutting tool 10 is determined by the position of the cross feed table 3 which is NC-controlled, and the desired shape and dimensions are cut by combining the position of the cross feed table 3 and the forward movement of the headstock 5. . As mentioned above, the workpiece 7
passes through the guide bush 9, and cutting is performed at its mouth. Therefore, the distance between the cutting point A of the workpiece and the sensor 20 fixed to the guide bush 9 is always approximately constant, the sound propagation path in AE is also approximately constant, and the sensitivity for detecting damage to the cutting tool is approximately constant. It becomes constant.

According to experiments, with an NC lathe with a maximum machining diameter of 12 mm,
When machining steel material (S45C), it was possible to reliably detect the breakage of a drill with a diameter of 0.6 mm. This is a practically usable result.

When the sensor 20 is fixed to the cross feed table 3, there are many joint surfaces and oil films that interfere with the propagation of sound, resulting in poor sensitivity. The distance between the point A and the sensor 20 fluctuates, and the sensitivity is not constant, and the sensitivity is also not very good, resulting in an undesirable result.

As mentioned above, according to the present invention, it is possible to sufficiently detect chips, etc. even in small diameter drills where the cutting tool is most likely to break, thereby preventing the production of defective products due to cutting tool breakage during unattended operation, and improving its practical use. The effects are huge.

In this example, an NC automatic lathe was described which has two turret tool rests, a guide bush is fixed on the bed, and a headstock slides.
Lathes with multiple cutting tools including attachments, such as Swiss-type automatic lathes, and lathes with a fixed headstock,
It is clear that the same applies to lathes in which the guide bush slides along with the tool rest in the axial direction of the spindle.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram showing the relationship between the main spindle, the turret, and the mounting position of the sensor of a lathe showing one embodiment of the present invention, and FIG. 2 is a block diagram of the detection device. 1, 2...turret turret, 3...transverse feed stand,
4... Spindle, 5... Headstock, 7... Workpiece, 9
...Guide bushing, 20...Sensor.

Claims (1)

[Scope of utility model registration request] A lathe that has a guide bush that supports a rotating workpiece and to which multiple cutting tools can be attached is characterized in that the sensor of the cutter damage detection device using AE is fixed to the guide bush housing for mounting the guide bush. A lathe equipped with a cutting tool damage detection device.