JPH0335030B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION ``Industrial Application Field'' The present invention relates to a focus head for a laser processing machine, and more particularly to a focus head equipped with a capacitance sensor and a damage sensor.

"Prior Art" Conventionally, it has been known to use a capacitance sensor to control the distance between a focus head and a workpiece to be constant. Usually, a focus head equipped with a capacitance sensor includes a nozzle that is installed in a housing and irradiates a laser beam from the tip toward the workpiece, and a center electrode that is insulated and provided at the tip of the nozzle. The control device is electrically connected to the center electrode, detects the capacitance between the center electrode and the workpiece, and controls the distance between the center electrode and the workpiece to be constant.

However, when the workpiece is a three-dimensional object,
When a portion of the workpiece other than the laser-processed portion approaches the center electrode, the capacitance changes accordingly, causing an error in measuring the distance between the center electrode and the laser-processed portion. For this reason, conventionally, a guard electrode is provided that surrounds the center electrode and is insulated from the center electrode, and even if a portion other than the laser-processed portion approaches the center electrode, the guard electrode blocks the influence. Efforts are being made to improve the detection accuracy (Japanese Patent Publication No. 89592/1983).

In addition, conventional damage sensors detect when a nozzle collides with a workpiece, etc., and stop further relative movement between the nozzle and the workpiece, thereby preventing the focus head from being damaged. It is intended to prevent This damage sensor is usually
The above-mentioned nozzle is provided in a housing so that it can swing, and when the nozzle collides with a workpiece and swings more than a predetermined amount with respect to the housing, the swing can be detected by a micro switch or an air switch. (Utility Model Application Publication No. 10985/1985).

"Problem to be Solved by the Invention" However, in the focus head of a conventional laser processing machine, the capacitance sensor and damage sensor are provided completely separately, which results in an increase in costs. was.

"Means for Solving the Problems" In view of such circumstances, the present invention has been developed in the focus head of a laser processing machine equipped with the above-mentioned capacitance sensor, that is, in the focus head of a laser processing machine equipped with the capacitance sensor described above, which is provided in the housing and directed from the tip toward the workpiece. A nozzle that irradiates a laser beam, a center electrode that is insulated at the tip of the nozzle, a guard electrode that surrounds this center electrode and is insulated from the center electrode, and an electrically connected center electrode that is insulated from the center electrode. In a focus head of a laser processing machine, the focus head of a laser processing machine is equipped with a control device that is connected to the center electrode and the workpiece and detects the capacitance between the center electrode and the workpiece and controls the distance between the center electrode and the workpiece to be constant. As a first configuration, the guard electrode is insulated from the nozzle or the housing, and the guard electrode and the workpiece are connected to a power circuit, respectively, so that contact between the guard electrode and the workpiece can be detected. That is.

Further, as a second configuration, in the focus head of the laser processing machine described above, the nozzle and the housing are insulated, and the nozzle is provided in the housing so as to be swingable, so that the nozzle swings relative to the housing by a predetermined amount or more. In addition, the nozzle and the guard electrode are electrically connected, and the nozzle and the housing are each connected to a power circuit, so that contact between the nozzle and the housing can be detected. It is.

"Function" According to the first configuration, the guard electrode used in the capacitance sensor can be used as a damage sensor as is, and it can be detected the moment the workpiece comes into contact with the guard electrode. Therefore, there is an advantage that there is no need to provide the nozzle in a swingable manner in the housing unlike in conventional damage sensors.

However, especially when the relative movement speed between the focus head and the workpiece is high, it is desirable to provide the nozzle in the housing in a swingable manner.
With this configuration, in addition to being able to obtain the above-mentioned effects, for example, even when processing a non-conductive workpiece, the nozzle is prevented from swinging by more than a predetermined amount. Since it is possible to detect collisions between objects and obstacles such as workpieces, it can be used as a damage sensor.

"Example" The present invention will be described below with reference to the illustrated example.
A focus head 1 of a laser processing machine includes a cylindrical metal housing 2, a condensing lens 4 attached to the housing 2 via a holder 3, and a metal nozzle 5 attached to the lower end of the housing 2. It is equipped with

The laser beam L introduced vertically downward into the shaft of the housing 2 is focused by the condenser lens 4, passes through the shaft of the nozzle 5, and is irradiated onto the workpiece 6. It's summery. Also at this time,
Assist gas is introduced into the housing 2 through the assist gas supply passage 7, and this assist gas also flows through the shaft of the nozzle 5 to emit the laser beam L.
It is designed to be supplied to the irradiation position.

The housing 2 is raised and lowered by a lifting mechanism (not shown), and the housing 2 and the processing table (not shown) on which the workpiece 6 is placed are moved in mutually orthogonal directions within a horizontal plane by an appropriate drive mechanism. By relatively moving the workpiece 6
This allows the required laser processing to be performed at any location.

A center electrode 10 is attached to the lower tip of the nozzle 5 via an insulator 11 for measuring the distance between the nozzle 5 and the conductive workpiece 6, and the center electrode 10 is controlled. It is connected to an oscillation device 13 forming part of the device 12. The oscillation device 13 detects a change in capacitance due to a change in the gap between the center electrode 10 and the workpiece 6a of the workpiece 6 as a change in oscillation frequency, and the control device 12 The above-mentioned lifting mechanism is controlled based on the detected value, and the focus head 1 is moved up and down so that the distance between the center electrode 10 and the workpiece 6a is constant.

In addition, a center electrode 1 is provided at the lower tip of the nozzle 5.
A guard electrode 14 is attached to surround the center electrode 14, and this guard electrode 14 prevents the static between the center electrode 10 and the processing section 6a even if, for example, the protrusion 6a of the workpiece 6 approaches the center electrode 10. This ensures that the capacitance is not affected. Above guard electrode 1
4 is provided insulated from the center electrode 10 by the insulator 11, but is electrically connected to the nozzle 5.

An annular insulator 15 is attached to the outer periphery of the upper end of the nozzle 5, and the insulator 15 is fitted into a metal cylindrical pipe 16 constituting a part of the housing 2. It is placed on a flange portion 16a formed radially inward at the lower end of the shaped pipe 16, and a spring 17 is mounted between the housing 2 and the insulator 15, so that the nozzle is normally 5 is maintained in the illustrated state in which the axis of the housing 2 is aligned with the axis of the housing 2, and when the protrusion 6b etc. comes into contact with the nozzle 5, the spring 1
The nozzle 5 can be swung against the force 7.

Furthermore, a metal plate 18 is sandwiched between the insulator 15 and the nozzle 5, and in the illustrated state where the axis of the nozzle 5 coincides with the axis of the housing 2, the plate 18 is separated from the cylindrical pipe 16. However, when the nozzle 5 swings more than a predetermined amount with respect to the cylindrical pipe 16, the plate 18 is moved against the cylindrical pipe 1.
6 for electrical connection.

The housing 2 and the cylindrical pipe 16
is used as a ground electrode to which the workpiece is electrically connected, and the ground electrode is also connected to the power supply circuit 19 of the control device 12. On the other hand, the nozzle 5 and the guard electrode 14 are also connected to the power supply circuit 19, thereby making contact between the guard electrode 14 and the workpiece 6, and the plate 18 on the nozzle 5 side and the cylindrical pipe on the housing 2 side. 16
The control device 12 can detect that the two have come into contact with each other.

In the above configuration, when the workpiece 6 has conductivity, the workpiece 6 is first connected to the housing 2, which is a ground electrode. At this time, it goes without saying that the workpiece 6 may be directly connected to the ground electrode side of the power supply circuit 19. If laser processing is performed in this state, the control device 12 inputs the detection signal from the oscillation device 13, maintains a constant gap between the center electrode 10 and the workpiece 6, and applies the laser beam to the workpiece 6. Perform processing.

In this state, as described above, the center electrode 10 is surrounded by the guard electrode 14, so the workpiece 6
Even if the projection 6b approaches the center electrode 10, it is not affected by the capacitance between the center electrode 10 and the processed portion 6a, and therefore the gap between the center electrode 10 and the processed portion 6a is reduced. Laser processing can be performed while keeping the temperature constant.

Then, due to a teaching mistake or a mistake in setting the workpiece 6, the protrusion 6b may become attached to the guard electrode 14.
Or when it comes into contact with the nozzle 5, the nozzle 5,
Guard electrode 14, workpiece 6 and housing 2
Since a closed circuit is formed through the control device 12, the control device 12 immediately stops the relative movement between the focus head 1 and the workpiece 6, and also stops the laser oscillation.

Also, at this time, the focus head 1 and the workpiece 6
Even if the relative movement speed between the protrusion 6b and the guard electrode 14 or the nozzle 5 is high and the protrusion 6b and the guard electrode 14 or the nozzle 5 come into contact with each other and then move relative to each other, the nozzle 5 can swing relative to the housing 2. 5 and the guard electrode 14 are not damaged.

On the other hand, if the workpiece 6 is made of a non-conductive material, the gap between the workpiece 6 and the center electrode 8 cannot be detected, but the focus head 1
It is possible to perform laser processing while keeping the height constant.

In this case, when the guard electrode 14 or the nozzle 5 comes into contact with the protrusion 6b of the workpiece 6, unlike the case described above, the contact cannot be immediately detected, but the contact causes the nozzle to 5 is swung by a predetermined amount or more with respect to the cylindrical pipe 16, the plate 18 on the nozzle 5 side moves against the cylindrical pipe 1.
6, a closed circuit is formed through the nozzle 5, plate 18, cylindrical pipe 16, and housing 2.

Therefore, in this case as well, the control device 12 immediately stops the relative movement between the focus head 1 and the workpiece 6, and also stops the laser oscillation.

Detection of a collision due to the rocking of the nozzle 5 is performed when the nozzle 5 encounters an obstacle made of a non-conductive material other than the workpiece 6 while processing the workpiece 6 made of a conductive material. It is also effective in the event of a collision.

In the above embodiment, the nozzle 5 is swingable with respect to the housing 2, but when processing a non-workpiece 6 made of a conductive material, it is easier to use a nozzle electrically connected to the guard electrode 14. 5 is fixed to the housing 2 via an insulator, or a guard electrode 14 is fixed to the nozzle 5 fixed to the housing 2 via an insulator, and the guard electrode 14 and the workpiece 6 are respectively connected to a power supply circuit 19. The guard electrode may be connected to detect contact between the guard electrode and the workpiece.

"Effects of the Invention" As described above, the guard electrode is insulated from the nozzle or the housing, and the guard electrode and the workpiece are connected to a power supply circuit to prevent contact between the guard electrode and the workpiece. According to the present invention, which enables detection, the guard electrode used in a capacitance sensor can be used as a damage sensor as is, and moreover, it can be detected the moment the workpiece contacts the guard electrode. Therefore, unlike conventional damage sensors, there is no need to provide the nozzle in a swingable manner in the housing.

In addition to insulating the nozzle and the housing, the nozzle is swingably provided in the housing so that they can come into contact when the nozzle swings relative to the housing by more than a predetermined amount, and furthermore, the nozzle and the guard electrode are connected to each other. electrically connecting the nozzle and the housing, respectively connecting the nozzle and the housing to a power supply circuit,
In the case where the contact between the nozzle and the housing can be detected, if the workpiece is made of a conductive material, substantially the same effect as above can be obtained by connecting it to a power source. In addition, even if the workpiece is made of a non-conductive material, it is possible to detect a collision with an obstacle including the workpiece by swinging the nozzle by a predetermined amount or more. can get.

[Brief explanation of drawings]

The figure is a partially sectional system diagram showing one embodiment of the present invention. 1...Focus head, 2...Housing,
5... Nozzle, 6... Workpiece, 10... Center electrode, 11, 15... Insulator, 12... Control device,
13...Oscillating device, 14...Guard electrode, 16...
...Cylindrical pipe, 18...Plate, 19...Power circuit, L...Laser beam.

Claims (1)

[Claims] 1. A nozzle provided in a housing and irradiating a laser beam from its tip toward a workpiece, a center electrode provided insulated at the tip of the nozzle, and surrounding this center electrode, and a guard electrode provided insulated from the center electrode, which is electrically connected to the center electrode, detects the capacitance between the center electrode and the workpiece, and detects the capacitance between the center electrode and the workpiece. In a focus head of a laser processing machine, the guard electrode is insulated from the nozzle or the housing, and the guard electrode and the workpiece are each connected to a power supply circuit. A focus head for a laser processing machine, characterized in that contact between the guard electrode and a workpiece can be detected. 2. A focus head for a laser processing machine according to claim 1, wherein the nozzle is swingably provided in a housing. 3. A nozzle provided in the housing that irradiates a laser beam from the tip toward the workpiece, a center electrode provided insulated at the tip of the nozzle, and a nozzle that surrounds this center electrode and is connected to the center electrode. A guard electrode provided insulated from the center electrode is electrically connected to the center electrode, and the gap between the center electrode and the workpiece is kept constant by detecting the capacitance between the center electrode and the workpiece. In a focus head of a laser processing machine equipped with a control device, the nozzle and the housing are insulated, and the nozzle is provided in the housing so that it can swing, so that when the nozzle swings relative to the housing by a predetermined amount or more, The nozzle and the guard electrode are electrically connected to each other, and the nozzle and the housing are connected to a power supply circuit, respectively.
A focus head for a laser processing machine, characterized in that contact between the nozzle and the housing can be detected.