JPH0655360B2 - Laser processing head adjustment device - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a laser processing apparatus for irradiating a workpiece with a laser beam together with an assist gas to perform necessary processing, and particularly to a distance between a nozzle of a processing head and the workpiece. The present invention relates to a processing head adjusting device for always keeping constant.

2. Description of the Related Art In the laser processing apparatus, the distance between the processing head and the workpiece directly affects the processing accuracy. Therefore, in high precision machining,
Focusing control for focusing the laser beam on the processing position of the workpiece is required by keeping the distance between the tip of the processing head and the workpiece constant.

Conventionally, a contact type sensor having a contactor, an electromagnetic or capacitance type non-contact sensor, a sensor utilizing back pressure of air, and the like have been used as the distance measuring means.

In the above contact type sensor, a large amount of friction is generated between the sensor and the contact portion of the workpiece, and smooth processing cannot be performed. In addition, when trying to measure a distance with an electromagnetic or capacitance sensor, such a sensor cannot be used when the workpiece is a non-conductive material such as wood, ceramics, or plastic. In addition, since the sensor that uses the back pressure of air uses air, the detection signal is unstable, and the condensing point of the laser beam, that is, the processing point and the detection point of the back pressure sensor are separated. In addition to not being able to perform highly accurate focus control, the back pressure type sensor uses the back pressure of air, which requires an air source for the sensor, which increases the cost and the size of the entire device. It becomes a thing.

Therefore, the object of the present invention does not require a dedicated air source, enables processing even if the work piece is a non-conductor, and can detect the non-work piece in a non-contact state. Thus, good laser processing can be performed without being affected by the surface condition of the workpiece.

Therefore, in order to achieve the above object, the present invention focuses on an assist gas that is indispensable for laser processing, and measures the pressure of the assist gas at two positions so that the processing head can be calculated from the pressure difference. The tip of the nozzle, that is, the distance between the nozzle and the workpiece is indirectly measured.

That is, according to the present invention, fine pressure detection holes are formed inside the tip of the nozzle hole for irradiating the laser beam as well as on the tip surface of the nozzle facing the workpiece, while ejecting the assist gas. Has been done. When the assist gas is jetted from the nozzle holes to the workpiece, negative pressure appears in the respective hole portions, and the pressure values differ due to the difference in the opening portions. Therefore, the pressure sensor detects the difference between the two pressures and converts it into an electrical signal. Then, the control device receives the pressure signal as an input, determines the magnitude of the signal level and the sign thereof, and controls the rotation direction and the rotation amount of the servo motor based on the result of the determination, and thereby the laser It moves the condenser lens of the light beam so that the distance between the tip of the nozzle and the workpiece is always in focus and works to keep it constant.

Further, according to the preferred embodiment, two or more pressure detecting holes are provided at each position, and the pressure is detected while being averaged. Further, the control device includes therein a damper circuit having an appropriate time constant and a proportional discriminating circuit for setting a range of proportional operation. Therefore, the pressure signal is stabilized by the time constant of the damper circuit, and becomes control information in a state where noise and other unstable elements are removed. Further, the comparison / discrimination circuit acts to interrupt unnecessary control by suspending servo control when the pressure signal deviates from a predetermined processing range by locking the servo when the pressure signal suddenly changes.

First Embodiment FIG. 1 shows a laser processing apparatus 1 of the present invention. The laser beam 2 is generated by the laser oscillator 3,
The light is guided to the inside of the processing head 5 by the mirror 4, converged by the condenser lens 6, and irradiated from the nozzle hole 9 of the nozzle 8 to the processing position of the workpiece.

The upper portion of the processing head 5 is fixed to the pedestal 11 by the saddle 10, and the expandable sleeve 12 and the nozzle 8 in the lower portion of the processing head 5 are both fixed to the slider 14 on the feed nut 13 side. .

The feed nut 13 is different from the feed screw 15 in the adjustment direction.
It fits under the screw pair. And this lead screw 1
The bearing 5 is rotatably supported by the bearing 16 at the same position with respect to the saddle 10, and is driven by the servomotor 17. These feed nuts 1
3, the feed screw 15, the servomotor 17, etc. constitute a position adjusting means for the machining head 5.

On the other hand, the assist gas 18 is housed inside a gas cylinder 19 as shown in FIG.
After passing through a, it is guided from the port of the nozzle 8 into the inside of the nozzle 8 and is jetted from the tip of the nozzle hole 9 onto the workpiece 7.

The laser processing head adjusting device 20 of the present invention is the second
As shown in the figure. The nozzle 8 is opened on the surface facing the workpiece 7 near the nozzle hole 9 and one or two or more fine first detection holes 21 which are opened on the inner surface on the tip side of the nozzle hole 9. It is provided with one or more fine second detection holes 22. The first detection hole 21 and the second detection hole 22 are both converted into an electric signal proportional to their pressure difference by a fine differential pressure sensor 24 as a pressure-electricity conversion means inside the pressure sensor 23. The differential transformer preamplifier 25 inputs the electric pressure signal A to the control device 26.

The control device 26 includes a damper circuit 27 connected to the pressure sensor 23, a comparison / determination circuit 28 connected to the damper circuit 27, and a lock circuit 29 to which an output of the comparison / determination circuit 28 is input.
The comparison / determination circuit 28 and the lock circuit 29 are both connected to the servo controller 30 of the servo motor 17. An encoder 31 connected to a servo controller 30 is connected to the servo motor 17.

Operation of Embodiment The processing head 5 performs necessary processing on the workpiece 7 by converging the laser beam 2 by the condenser lens 6 and matching the convergence point with the processing point of the workpiece 7. Of course, the laser beam 2 continuously forms a machining locus required for the work 7 by the relative movement with the work 7.

On the other hand, during such processing, the assist gas 18 is converted into an optimum pressure by the regulator 20, is sent into the inside of the nozzle 8, and is injected from the nozzle hole 9 in the irradiation direction of the laser beam 2.

During this process, the pressure sensor 23, the pressure P ₁ of the first detection hole _21, and detects the pressure P ₂ of the second detection holes 22, detects their pressure differential by low differential pressure sensor 24, further , By the differential transformer preamplifier 25,
The pressure difference P ₀ is converted into an electrical signal, and the pressure signal is converted to A
Then, it is sent to the control device 26.

The pressure difference P _{0 at} this time is detected with the pressure difference at the optimum focus of the focused laser beam 2 being 0. As shown in FIG. 4, the distance h between the tip of the nozzle 8 and the workpiece 7 is
Pressures P ₁ and P ₂ at the ideal optimum distance h ₀ during cutting
The difference between the two is P ₀ . If the distance h ₀ becomes long, the value of the pressure P ₂ becomes high and the pressure difference P ₀ between them increases. Conversely, when the distance h ₀ becomes smaller, the pressure P ₂ becomes lower, so that the pressure difference P ₂ changes in the decreasing direction. In this way, if the optimum distance h ₀ for cutting is set in advance, the signal level of the pressure signal A and its sign will change depending on whether the optimum distance h ₀ is excessive or insufficient.

Therefore, the control device 26 first integrates the pressure signal A by the integration function of the damper circuit 27, removes unstable elements due to noise and other causes in the generation process thereof, and converts it into an integrated pressure signal B. From the comparison and determination circuit 2
Send to 8. Therefore, the comparison / discrimination circuit 28 discriminates whether or not it is within a predetermined adjustment range, that is, other than the diagonal line in FIG. 4, and when it is within the adjustment range, generates a control signal C proportional to the pressure signal A. , And sends this to the servo controller 30. Therefore, the servo controller 30 controls the control signal C
The direction of rotation of the servo motor 17 is set according to the sign of, and the servo motor 17 is proportional to the signal level.
Control the amount of rotation of. This rotation amount is calculated by the encoder 3
1 is detected and fed back as a feedback signal of the servo controller 30. The rotation of the servomotor 17 causes the feed screw 15 to rotate, and the vertical movement of the feed nut 13 also vertically moves the condenser lens 6 inside the processing head 5, so that the laser beam 2 is focused on the workpiece 7. Set the position. When such focus control is performed, the distance h between the nozzle 8 and the workpiece 7 is automatically adjusted to the predetermined optimum distance h ₀ , so the controller 26 stops the rotation of the servo motor 17. , To prepare for the subsequent operation.

When the laser beam 2 deviates from the cutting range of the workpiece 7, or when the cut portion is irradiated with the laser beam 2 again, the pressure signal A changes abruptly. At this time, the comparison / determination circuit 28 determines that the integrated pressure signal B
Is outside the adjustment range, and the lock circuit 29 is operated. Therefore, the lock circuit 29 generates a lock signal D, which causes the servo controller 30 to stop operating. In this way, focus control is continuously performed only within a predetermined range. In addition, such a servo motor 1
The control speed range of 7 can be set from the outside.

EFFECTS OF THE INVENTION In the present invention, an assist gas that is not affected from the outside is used to measure the distance between the nozzle and the workpiece, and the distance is indirectly measured by the pressure difference between two different points at the ejection portion. Unlike the conventional back pressure type sensor, a precise pressure source and a dedicated injection nozzle are not required, and effective distance measurement is possible even in a corner portion where the processing range is narrow.

Further, if two or more first and second detection holes are uniformly provided in the nozzle portion, the pressure values of the respective measurement portions are averaged, so that an average measurement operation is possible. .

In addition, if a damper circuit with an appropriate time constant is provided inside the control device, fluctuations in the pressure signal and noise are reduced, so control instability disappears and stable control is continuously possible. Becomes

Furthermore, a comparison / discrimination circuit is provided inside the control device, and since the servo lock is applied within the adjustment range, when the workpiece is out of the large opening of the workpiece or the predetermined machining range, The focus control is automatically stopped during the period, and the servo motor does not follow at a high speed, so that collision due to unnecessary control or abnormal control can be prevented in advance.

[Brief description of drawings]

FIG. 1 is a side view of a mechanical portion of a laser processing device, and FIG.
FIG. 4 is a block diagram of the laser processing head adjusting apparatus of the present invention, FIG. 3 is an enlarged cross-sectional view of the nozzle tip portion, and FIG. 1 ... Laser processing device, 2 ... Laser beam, 5 ... Processing head, 6 ... Focusing lens, 7 ... Workpiece, 8 ...
Nozzle, 9 ... Nozzle hole, 13 ... Feed nut, 15 ...
... Feed screw, 17 ... Servomotor, 18 ... Assist gas, 20 ... Laser processing head adjusting device, 21 ... First detection hole, 22 ... Second detection hole, 23 ... Pressure sensor, 24 ...... Small differential pressure sensor, 25 ...... Differential transformer / preamplifier, 26 …… Control device, 27 …… Damper circuit,
28 ... Comparison / determination circuit, 29 ... Lock circuit, 30 ...
Servo controller.

Claims (4)

[Claims] 1. A laser beam is converged by a condenser lens of a processing head, a distance between a workpiece and a nozzle at the tip of the processing head is adjusted by a position adjusting means of the processing head, and an assist gas is supplied from a nozzle hole of the nozzle. In the laser processing apparatus for irradiating the object to be processed with the convergence point of the laser beam while ejecting the laser beam, and performing the desired processing on the object, a fine first detection hole opened on the inner surface at the tip end side of the nozzle hole , Detecting the pressure difference between the fine second detection hole opening on the surface facing the workpiece near the nozzle hole and the first and second detection holes to detect the difference between the nozzle tip and the workpiece. A pressure sensor that generates a pressure signal proportional to the distance, and a control device that receives the pressure signal from the pressure sensor as an input and generates a control signal for always correcting the distance to a predetermined value.
A laser processing head adjusting device comprising: a servo controller that controls the rotation of a servo motor in the position adjusting means by using the control signal as an input. 2. The machining head adjusting device according to claim 1, wherein two or more of the first detection hole and the second detection hole are formed on each surface. 3. The laser processing head adjusting device according to claim 1, wherein a damper circuit for integrating the pressure signal under a predetermined time constant is incorporated in the control device. . 4. A comparison / discrimination circuit for discriminating a pressure signal adjustment range, and a lock circuit for stopping the operation of a servo controller when the pressure signal fluctuates beyond the adjustment range. The laser processing head adjusting device according to claim 1, wherein the laser processing head adjusting device is incorporated.