JPH05212568A - Laser beam machine and method for controlling height of condenser lens thereof - Google Patents

Abstract

PURPOSE:To simply, surely and automatically set the positions of focus and machining torch as preparatory work for laser beam machining. CONSTITUTION:A condenser lens 4, machining torch 18, servomotor 9a for changing the interval between the condenser lens 4 and a workpiece 7, numerical controller 21 with which the servomotor 9a, working table 10b and laser beam oscillator 1 are controlled and profiling device which is attached to the machining torch 18 and with which the distance between the condenser lens 4 and the workpiece 7 is detected are provided. A guide bearing is provided between a profiling sensor part 19 and a machining torch 18 to move the profiling sensor part 19 along the machining torch 18 coaxially with the optical axis of laser beam 1a, and is provided with a taper-like hole along the laser beam 1a which is condensed with the condenser lens 4 of the part 19 through which the laser beam 1a and auxiliary gas are passed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser processing apparatus such as a carbon dioxide gas laser for welding, cutting or drilling a steel sheet or the like, and in particular, shortens the processing preparation time and stabilizes the processing conditions to improve the yield. The present invention relates to an improved laser processing apparatus and a method of controlling the height of a condenser lens thereof.

[0002]

2. Description of the Related Art FIG. 6 shows the configuration of a conventional laser processing apparatus for cutting a steel plate or the like. In FIG. 6, 1 is a laser oscillator, 1a is a laser beam, 2 is a laser light guide, 3 is a bending mirror, 4 is a condenser lens, 5 is a lens guide, and 6 is a total length including the lens guide 5. A processing torch having a length substantially matching the focal length of the lens 4, 7 is a workpiece, 8a
Is an auxiliary gas pipe, 8b is an auxiliary gas cylinder, 9a is a servomotor for moving up and down the processing torch 6 having the condenser lens 4, 9b is a worm, 9c is a rack, and the servomotor 9a and the processing torch 6 are a worm 9b and a rack 9c. Engaged. Reference numeral 10a is a processing table base, 10b is a processing table, 10c is a sword mountain for supporting a workpiece, 10d is a servomotor for driving the operation of the processing table 10b, 11 is a numerical controller, 12 is a scanning sensor unit, and 12a is a scanning sensor. A support rod, 13 is a signal converter, 14 is a laser output command signal, 15 is a servo command signal that determines the machining shape and machining speed, 16 is a servo command signal that sets the lens height, 1
Reference numeral 7 is an output of the copying apparatus.

Next, the operation of the conventional laser processing apparatus having the above structure and the preparatory work up to the processing before the start of processing will be described. The laser oscillator 1 excites a laser medium and outputs a laser beam 1a. The laser light 1a that has passed through the laser light guide 2 is reflected by a bending mirror 3 provided in the middle of the optical path, the optical axis is bent in the direction of the condenser lens 4, and enters the condenser lens 4, and the condenser lens 4 The object 7 to be processed which is focused by the laser beam 4 and placed near the focal point of the focusing lens 4 is irradiated.
The workpiece 7 is placed on the blade 10c for supporting the workpiece on the machining table 10b, and the servomotor 10d drives the machining table 10b to move the workpiece 7. Between the condenser lens 4 and the workpiece 7, a processing torch 6 having a tapered inner diameter as it approaches the workpiece 7 is formed.
Is provided, and the auxiliary gas supplied by the gas cylinder 8b is sprayed onto the laser-irradiated portion of the workpiece 7 so as to be coaxial with the focused laser beam 1a through the gas pipe 8a. The numerical control device 11 to which the processing conditions such as the processing shape, the moving speed of the workpiece 7 and the laser output are input, outputs the laser output command signal 14 to the laser oscillator 1 to obtain a predetermined laser output and perform the processing. The servo command signal 15 is sent to the servo motor 10d according to the shape and the required moving speed, and the workpiece 7 on the processing table 10b is moved to machine it into a predetermined shape.

When performing the above processing, first the lens guide 5 is moved in advance so that the interval 0 at which the tip of the processing torch 6 contacts the surface of the workpiece 7 is set between the condenser lens 4 and the workpiece 7. The origin is set in the numerical controller 11 as the origin of the coordinate of the distance. After that, the distance between the tip of the processing torch 6 and the workpiece 7 is set to several mm, and the distance between the tip of the processing torch 6 and the workpiece 7 is adjusted while performing a machining test to obtain the best cutting performance. Set the distance to the copying device.

Generally, when performing welding, cutting or drilling of a mild steel plate or the like with this type of laser processing apparatus, when the workpiece 7 is placed near the focal position focused by the condenser lens 4, The cutting speed can be increased and the cut surface roughness can be reduced. Further, the tip of the processing torch 6 and the workpiece 7
When the distance is set to several mm, the auxiliary gas promotes the removal of the workpiece 7 melted by the laser beam 1a, and the processing speed increases. Since the distance between the focus position and the workpiece 7 is determined by the plate thickness and material to be processed, it is necessary to set the position of the processing torch 6 every time the workpiece 7 or the condenser lens 4 is replaced. there were.

[0006]

In the conventional laser processing apparatus described above, the distance between the focus position and the workpiece 7 and the distance between the processing torch 6 and the workpiece 7 are the same as those of the workpiece 7 and the light condensing unit. Since it has to be set every time the lens 4 is replaced, it takes a lot of time to prepare for the start of processing, resulting in a markedly low work efficiency. Further, since the length of the processing torch 6 is fixed with respect to the variation of the focal length of the condenser lens 4, if the distance between the processing torch 6 and the workpiece 7 is fixed, the focal position and the workpiece are not processed. There is a problem that the relative position of 7 shifts from the optimum position, the irradiation condition of the laser beam 1a with which the workpiece 7 is irradiated changes, the processing quality varies, and the yield decreases.

The present invention solves such a conventional problem and simplifies the setting of the focus position and the position of the processing torch as a preparatory work for laser processing, improves the work efficiency and improves the processing yield. It is an object of the present invention to provide a laser processing apparatus capable of realizing stable processing quality.

[0008]

To achieve the above object, a laser processing apparatus of the present invention comprises a laser oscillator, a laser light guide, a bending mirror, a condenser lens, and a processing torch for blowing an auxiliary gas. , An auxiliary gas source, a machining table that holds and moves the workpiece, a servo motor that changes the distance between the condenser lens and the workpiece, and numerical control that controls the servo motor, the machining table, and the laser oscillator. An apparatus, a copying apparatus equipped with a processing torch, which includes a scanning sensor unit for detecting a distance between a condenser lens and an object to be processed, and a signal converter, and a laser beam focused by the condenser lens. A scanning sensor section having a tapered hole for passing laser light and auxiliary gas, and a guide bearing for moving the scanning sensor section along the machining torch coaxially with the optical axis of the laser light. In which it provided between the support portion and the processing torch.

Further, the method of controlling the height of the condenser lens of the laser processing apparatus of the present invention comprises a laser oscillator, a condenser lens, a processing torch, a processing table for holding and moving a workpiece, and a condenser lens. A servo motor for changing the distance between the workpieces, a numerical controller for controlling the servo motor, the machining table, and the laser oscillator, and an optical sensor for detecting the light emitted from the laser beam irradiation section on the surface of the workpiece. In the laser processing apparatus, wherein the numerical control device is provided with a storage device for storing the distance between the condensing lens and the object to be processed according to the change in the output of the optical sensor, in the range including the condensing lens focal length. By irradiating the work piece with laser light while changing the distance between the optical lens and the work piece, and by changing the laser light irradiation position while moving the work piece, The maximum distance and the minimum distance between the object and the object are stored in a storage device, and the substantially central position of the stored maximum distance and the minimum distance between the condenser lens and the workpiece is set as the coordinate origin of the servo motor. It is a thing.

[0010]

According to the above configuration and method, for example, when the workpiece is mild steel or stainless steel, the intensity of the laser beam is 1
Utilizing the fact that when the intensity exceeds the limit of 10 ⁶ W per cm ^2, the color emitted from the surface of the workpiece changes from orange to blue, and the light emitted from the surface of the workpiece is detected by an optical sensor with a blue filter. When monitoring and moving the processing torch up and down while changing the position of the workpiece, blue light emission is detected in the upper and lower range including the focus of the condenser lens. This operation is performed several times by changing the position of the work piece, and the center of the upper and lower limits of the range where blue light emission is detected is set as the focus of the condenser lens in the numerical control device to automatically set the focus position. Can be done on a regular basis.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of an embodiment of the laser processing apparatus of the present invention. In FIG. 1, the same parts as those in FIG. 6 are designated by the same reference numerals, and the description thereof will be omitted. Different parts will be described.

In FIG. 1, 18 is a processing torch, 19 is a copying sensor with a nozzle, 20 is a copying sensor support rod, and 21
Is a numerical controller, 22 is an optical sensor, and 22a is an optical sensor output. 2 is a cross-sectional view showing the detailed structure of the nozzle tip portion. In FIG. 2, 19a is a guide roller and 1 is a guide roller.
Reference numeral 9b is a tapered hole, 19c is an opening for looking through the laser light irradiation portion, 22b is a blue filter, 23 is a guide bearing, 24 is an assist gas packing, and 25a and 25b are for preventing the copy sensor 19 with a nozzle from falling. It is a stopper.

In the laser processing apparatus shown in FIGS. 1 and 2, one end of the laser light guide 2 is connected to the output port of the laser oscillator 1, and the bending mirror 3 is provided in the middle of the laser light guide 2.
Is provided, and the other end of the laser light guide 2 has a cylindrical shape with a circular cross section, and the lens guide 5 to which the condenser lens 4 is attached is inserted. An elevating rack 9c is attached to a side surface of the lens guide 5, and an elevating worm 9b coupled to a servo motor 9a is attached to the elevating rack 9c.
The lens guide 5 is engaged by the servo motor 9a.
Raise and lower. Further, the signal converter 13 is attached to the side surface of the processing torch 18 connected to the lens guide 5, and the side surface of the processing torch 18 is connected to the auxiliary gas cylinder 8b by the auxiliary gas pipe 8a.

A processing torch 18 is attached to the tip of the lens guide 5.
Is attached. As the processing torch 18 moves away from the condensing lens 4, the inner diameter becomes thin to about half the diameter of the condensing lens 4, and then the processing torch 18 becomes cylindrical up to the tip. Processing torch 18
The guide bearing 23 is attached to the inner surface of the tip of the, and the nozzle-equipped copy sensor 19 is inserted into the guide bearing 23. Further, on the inner surface of the processing torch 18, a gas packing 24 that keeps the auxiliary gas airtight between the scanning sensor with nozzle 19 and the processing torch 18 and a nozzle stopper 25b for preventing the nozzle sensor from falling off the scanning sensor with nozzle 19 are attached. A nozzle stopper 25a for preventing the copy sensor 19 with a nozzle from coming off is provided on the 19 side so as to face the nozzle stopper 25b with a nozzle to prevent the copy sensor 19 from coming off. Further, an optical sensor 22 is attached to the outer wall of the processing torch 18, and an optical sensor output 22a is connected to the numerical controller 21.

The scanning sensor with nozzle 19 is provided with a tapered hole 19b along the laser beam condensed inside, and the central axis of the tapered hole 19b and the laser optical axis are aligned with each other so that the center of the auxiliary gas flow is almost the same. To match. A guide roller 19a for keeping a constant distance from the workpiece 7 is embedded in the lower surface of the copying sensor with nozzle 19, and the processing torch 18 is provided.
The opening 19c is provided so as not to block the space between the optical sensor 22 attached to the side surface and the laser light irradiation portion.

The numerical control device 21 receives the processing conditions such as the processing shape of the workpiece 7, the moving speed and the laser output, and outputs the laser output command signal 14 to the laser oscillator 1 according to the processing shape and the moving speed. The servo command signal 15 is sent to the servo motor 10d, and the workpiece 7 is moved by the machining table 10b.

Next, the operation will be described. In the embodiment shown in FIG. 1, the laser oscillator 1 excites a laser medium and outputs a laser beam 1a according to a command from the numerical controller 21. The laser light 1a that has passed through the laser light guide 2 is bent by the bending mirror 3 in the direction of the condenser lens 4, is incident on the condenser lens 4, and is condensed. Irradiate the placed workpiece 7. Workpiece 7
Is placed on the workpiece supporting sword mountain 10c on the machining table, and the servomotor 10d drives the machining table 10b to move the workpiece 7. Processing torch 1 with auxiliary gas from gas cylinder 8b through gas pipe 8a
8, the processing torch 18 and the copy sensor 1 with nozzle
Numeral 9 is an auxiliary gas which is coaxial with the focused laser light and which is a workpiece 7
To the laser light irradiation part of. As described above, the laser processing is performed on the workpiece 7 placed on the processing table 10b.

Laser light 1a for performing laser processing in this way
FIG. 4A shows the relationship between the beam diameter of the laser light 1 a and the distance from the lens 4 when the light is condensed by the condenser lens 4.
FIG. 4B shows the relationship between the laser intensity and the distance from the lens 4.
Further, FIG. 4C shows the relationship between the change in the emission color observed on the surface of the workpiece 7 and the distance from the lens 4 when the workpiece 7 is further irradiated with the focused laser beam 1a. Figure 4
As shown in (A), the beam diameter changes in proportion to the distance between the lens position and the focal position. On the other hand, the beam intensity increases in inverse proportion to the beam cross-sectional area. That is, the beam intensity changes in inverse proportion to the square of the distance between the lens position and the focal position. When the beam intensity gradually increases and exceeds the limit intensity I _o which is about 10 6 W or more per square centimeter in the case of mild steel or stainless steel, the emission color changes from orange to blue. In FIG. 4B, the limit intensity I is obtained when the output is a and the distance is Za from the lens.
_Thus , blue light emission is obtained in the range from the distance Za to the focus position Zf and in the range from the focus position Zf to a position symmetrical to the focus position Zf at the point Za. In the case of the output b, blue light emission is obtained in the range from the distance Zb from the lens to the focus position Zf and in the range from the focus position Zf to a position symmetrical with respect to the focus position Zf at the Zb point.
At the output c, blue light is emitted only at one point of the focus position.

In the first embodiment, the numerical control device 21 first makes the position of the focal length of the condenser lens 4 about 10% higher than the height and the height of the focal length about 10%.
% While the laser oscillator 1 is instructed to output the laser beam 1a and the workpiece is moved to gradually shift the laser irradiation position, the servo motor 9a causes the condenser lens 4 to move. It is lowered or raised within a range of ± 10% of the focal length with respect to the focused position. At this time, the laser output has a value in which the distance from the lens exceeding the limit intensity I _o has a width, as in the output a or b shown in FIG. 4B.

As the condenser lens 4 moves up or down and approaches the focus position, the laser light is focused and the intensity of the laser light applied to the surface of the workpiece 7 is inversely proportional to the beam cross-sectional area. The color of the light emitted from the laser irradiation point changes from orange to blue. Further, when the condensing lens 4 passes through the focal position and is moved up or down, the condensing lens 4 passes through the focal position, and then the laser light is diffused and the laser light intensity is lowered. The color of the light emitted from blue changes to orange.

An optical sensor 22 mounted on the processing torch 18
The orange filter is blocked by the blue filter 22b of the light receiving section and does not sense the orange color. When the color of the light emitted from the laser light irradiation point changes from orange to blue during the laser light irradiation, the blue light passes through the blue filter 22b of the light receiving section, and the optical sensor 22 detects the light passing through the blue filter 22b. To output the output signal 22a. Numerical control device 2
1 stores the height of the condenser lens 4 at which the optical sensor 22 starts to output the output signal 22a and the height of the condenser lens 4 at which the output signal 22a is no longer output, and the center value of the two heights. Is calculated, the servo motor 9a is controlled, and the light receiving lens 4
Is moved up and down, and the height of the central value of the two heights is set as the reference height of the light receiving lens 4, and the light receiving lens 4 is set to that height. Since the focus position of the condenser lens 4 is at the center of the range in which the emission color is blue, the work 7 is processed by the above operation.
The focus of the condenser lens 4 is set on the surface of the. The position of the condenser lens 4 is used as the coordinate origin of the servo motor 9a for raising and lowering the processing torch 18.

FIG. 3 shows an optical sensor 2 used in the second embodiment.
2 shows a processing circuit for two output signals 22a. In the signal processing circuit in FIG. 3, the output signal 22a of the optical sensor 22 is
To the pulse counter 26 to count the number of pulses of the output signal 22a while the elevation signal of the servo motor 9a is being output, and the output side of the pulse counter 26 is input to one of the signal register 27 and the comparison calculator 28. Connect to the side. The signal register 27 stores and outputs the output of the pulse counter 26 at the beginning of the output of the lift signal 16. Signal register 27
The output side of is connected to the other input side of the comparison operator 28. In this embodiment, not the optical sensor output 22a but the output 29 of the comparison calculator 28 is connected to the numerical controller 21.

The operation of the second embodiment will be described below. Since the beam intensity is proportional to the laser output,
As shown in (B), as the output a decreases to the outputs b and c, the range in which the color of the light emitted from the laser light irradiation point becomes blue decreases, and the beam intensity at the focus position Zf, which is the maximum intensity, becomes the limit intensity. Focus position Zf of output c that matches I _o
A blue emission color is emitted from the surface of the work piece only. When the work piece is irradiated with pulsed laser light while increasing / decreasing the average output and the distance between the condenser lens and the work piece is increased or decreased, the pulsed laser light has a beam intensity exceeding the limit intensity I _o. Is emitted to the work piece only, and the pulse counter 26 counts. Therefore, when the lens position moves and the focus position approaches the work piece, the pulse count number gradually increases, and the focus position increases. The pulse count decreases as the distance from the workpiece increases.

Therefore, in the second embodiment, the numerical controller 21 controls the position of the condenser lens 4 to be 10% higher than the focal length of the condenser lens 4 and higher than the focal length thereof. The servo motor 9a is moved so as to move up and down between the position 10% lower. Next, the laser oscillator 1 is made to output the pulse output while increasing or decreasing the pulse peak output in a constant width. When blue light is emitted on the surface of the workpiece 7 while the pulse peak output increases and decreases by one round trip, the optical sensor 22 outputs a pulsed output signal 22a, and the pulse number of the output signal 22a is pulsed. The counter 26 measures. When the pulse increase / decrease is finished, the condenser lens 4 is lowered or raised. At this time, the signal register 27 sets the pulse counter 2 at the first moment when the ascending / descending signal 16 of the servo motor 9a is output.
6 holds the number of pulses counted. Next, laser oscillator 1
Similarly, the pulse output peak value is increased / decreased and pulse signals are counted in the same manner. When the condenser lens continues to descend or rise,
The laser beam is focused as the workpiece approaches the focus position of the condenser lens 4, and the irradiation laser beam intensity increases even with the same output. Therefore, the limit beam accompanied by blue light emission during one cycle of increasing or decreasing the pulse peak output. The number of pulses exceeding the intensity I _o increases. As a result, the output of the pulse counter 26 continues to increase and reaches its maximum when the focus position is on the workpiece. The output of the pulse counter 26 and the output of the signal register 27 are compared by the comparison calculator 28. Whenever the pulse counter increases in the number of pulses each time the condenser lens 4 is moved, the focus position is on the workpiece 7. When approaching, and conversely, when the pulse counter starts to decrease the number of pulses, the focus position is 7
Will be on top. Therefore, the position of the condenser lens 4 with respect to the workpiece 7 when the positive and negative signs of the output of the comparison calculator 28 are inverted is set as the coordinate origin of the servo motor 9a that moves up and down the processing torch 18.

FIG. 5 shows the beam intensity and the sensor pulse output at each position as the pulse peak output increases and decreases. That is, FIG. 5 (A) is a pattern diagram for increasing / decreasing the output override of the laser light, FIG. 5 (B) is a graph showing changes in beam intensity at three types of work positions with increasing / decreasing pulse peak output, and FIG. ) Is a graph showing sensor pulse outputs at three types of work positions according to increase / decrease in pulse peak output. Za, Zb and Z in the figure are graphs.
f corresponds to Za, Zb, and Zf in FIGS. 4B and 4C.

In the above-mentioned two embodiments, the focus position is searched for by detecting the blue light emission on the surface of the work 7 by the irradiation of the laser light to the work 7 by the optical sensor 22. It is also possible to search for the focus position and set the origin of the servo motor 9a by utilizing the fact that a burst sound is emitted when blue light is emitted on the surface of the workpiece 7 by irradiating the workpiece 7 with a laser beam. it can. That is, a sound collecting sensor is used instead of the optical sensor 22 to detect a plosive sound generated when blue light is emitted on the surface of the workpiece 7,
By using the output of the sound collecting sensor instead of the output of the optical sensor 22, it is possible to realize the above two embodiments in the same manner.

The procedure for adjusting the focus position on the workpiece 7 while changing the position of the condenser lens 4 shown in the above embodiment is stored and fixed in the storage device in the numerical controller 21.
The origin is set by the numerical controller 21.

With the above configuration and method, it is possible to automate the work of setting the focal position of the condenser lens on the surface of the workpiece, and to set the focal position according to the individual difference of the operator who operates the apparatus. The distance between the processing torch and the work piece, and the focus position of the condenser lens and the relative position of the work piece can always be kept optimum regardless of the variation and the variation of the focal length of the condenser lens itself. ..

[0029]

As is apparent from the above description, according to the laser processing apparatus and the method of controlling the height of the condenser lens of the present invention, there are variations in the focus position setting due to individual differences among workers and the condenser lens itself. Laser beam irradiation conditions because the distance between the processing torch and the work piece and the focus position of the condenser lens and the relative position of the work piece can always be kept optimal regardless of the variation in the focal length of the work piece. Does not change, and it is possible to prevent variations in processing quality and reductions in yield due to variations in irradiation conditions. Further, since the work of setting the focus position on the surface of the workpiece is automated, the work preparation time is significantly shortened, and no skill is required to set the focus position on the surface of the workpiece.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of a laser processing apparatus of the present invention.

FIG. 2 is an enlarged sectional view of a nozzle portion of the same embodiment.

FIG. 3 is a processing circuit diagram of an output signal of an optical sensor used in the second embodiment.

FIG. 4A is a relationship diagram between the distance from the lens position and the laser beam diameter. FIG. 4B is a relationship diagram between the distance from the lens position and the laser beam intensity. FIG. 4C is a distance from the lens position and the emission color of the work surface. Relationship diagram

FIG. 5A is a pattern of increase / decrease of laser light output override. FIG. 5B is a graph showing changes in beam intensity at three types of work positions according to increase / decrease of pulse peak output. FIG. 5C is increase / decrease of pulse peak output. Graph showing sensor pulse output at three different work positions

FIG. 6 is a configuration diagram of a conventional laser processing device.

[Explanation of symbols]

 1 Laser Oscillator 1a Laser Light 2 Laser Light Guide 3 Bending Mirror 4 Condensing Lens 7 Workpiece 8b Auxiliary Gas Cylinder (Auxiliary Gas Source) 9a Servo Motor 10b Machining Table 10d Servo Motor 13 Signal Converter 18 Machining Torch 19 Tracing with Nozzle Sensor (copy sensor unit) 19b Tapered hole 21 Numerical control device 22 Optical sensor 23 Guide bearing

Claims (6)

[Claims] 1. A laser oscillator, a laser light guide, a bending mirror, a condenser lens, a processing torch for blowing an auxiliary gas, an auxiliary gas source, and a processing table for holding and moving a workpiece. A servo motor for changing the distance between the condenser lens and the workpiece, a numerical controller for controlling the servo motor, the machining table and the laser oscillator, and the distance between the condenser lens attached to the machining torch and the workpiece. A laser processing apparatus having a scanning device including a scanning sensor unit for detecting a signal and a signal converter, wherein the scanning sensor unit is provided with a tapered hole along the laser beam condensed by the condenser lens. A guide bearing for passing the laser light and the auxiliary gas and moving the scanning sensor section along the machining torch coaxially with the optical axis of the laser beam between the scanning sensor section and the machining torch. Laser processing equipment. 2. A laser oscillator, a condenser lens, a machining torch, a machining table that holds and moves a workpiece, a servo motor for changing the distance between the condenser lens and the workpiece, and its servo. It is equipped with a numerical control device that controls the motor, processing table, and laser oscillator, and an optical sensor that detects the light emitted from the laser beam irradiation part on the surface of the workpiece, and collects light in relation to changes in the output of the optical sensor. By using a laser processing device in which the numerical control device is provided with a storage device that stores the distance between the lens and the workpiece multiple times, the distance between the condenser lens and the workpiece is set within a range including the focal length of the condenser lens. By irradiating the work piece with laser light while changing it, and changing the laser light irradiation position while moving the work piece, the gap between the condenser lens and the work piece when the output from the optical sensor is output. maximum The distance and the minimum distance are stored in a storage device, and the central point of the maximum distance and the minimum distance between the stored condenser lens and the workpiece is the coordinate origin of the servo motor. Height control method. 3. A laser oscillator, a condenser lens, a machining torch, a machining table which holds and moves a workpiece, a servo motor for changing the distance between the condenser lens and the workpiece, and its servo. The numerical control device that controls the motor, the processing table, and the laser oscillator, the optical sensor that detects the light emitted from the laser light irradiation unit on the surface of the workpiece, the pulse counter that inputs the output of the optical sensor, and the numerical control device A signal register that holds the pulse counter output immediately before the drive signal is output each time the servo motor drive signal is output, and the pulse counter output and the signal register output are input to the comparison calculator and the comparison calculator is provided. Using a laser processing device that inputs the output, the work piece is irradiated with pulsed laser light while increasing or decreasing the average output, and
The interval between the condenser lens and the workpiece is increased or decreased for each cycle, and the position of the condenser lens with respect to the workpiece when the positive and negative signs of the output of the comparison calculator are reversed is the coordinate origin of the servo motor. A method for controlling the height of a condenser lens of a laser processing device. 4. A laser oscillator, a condenser lens, a machining torch, a machining table that holds and moves a workpiece, a servo motor for changing the distance between the condenser lens and the workpiece, and its servo. It is equipped with a numerical control device that controls the motor, the processing table, and the laser oscillator, and a sound collection sensor that detects the sound emitted from the laser light irradiation part on the surface of the workpiece, and collects sound in association with changes in the sound collection sensor output. Using a laser processing device equipped with a storage device that stores the distance between the optical lens and the workpiece multiple times in the numerical controller, the distance between the condenser lens and the workpiece is set within the range including the focal length of the condenser lens. By irradiating the work piece with laser light while changing it, and changing the laser light irradiation position while moving the work piece, the distance between the condenser lens and the work piece when the sound collection sensor output is generated Maximum interval and maximum The height of the condenser lens of the laser processing apparatus is stored in the storage device, and the center position of the maximum distance and the minimum distance between the stored condenser lens and the workpiece is set as the coordinate origin of the servo motor. Method. 5. A laser oscillator, a condenser lens, a machining torch, a machining table for holding and moving a workpiece, a servo motor for changing the distance between the condenser lens and the workpiece, and its servo. Numerical control device that controls the motor, processing table, and laser oscillator, pulse counter that inputs the sound collection sensor output, and pulse counter immediately before the drive signal is output each time the numerical control device outputs the servo motor drive signal Using a laser processing device equipped with a signal register that holds the output, inputting the pulse counter output and the signal register output to the comparison calculator and inputting the comparison calculator output, increase or decrease the average output to the workpiece. While irradiating pulsed laser light, the interval between the condenser lens and the workpiece is increased or decreased for each cycle of increase or decrease of the average output.
A condensing lens height control method for a laser processing apparatus, wherein the position of the condensing lens, which is the distance between the condensing lens and the workpiece when the positive and negative signs of the output of the comparison calculator are reversed, is the coordinate origin of the servo motor. 6. The height of the condenser lens of the laser processing apparatus according to claim 2, wherein the procedure for setting the coordinate origin of the servomotor is stored in a storage device in the numerical controller and executed. Control method.