JPH0825070A - Optical system for laser working - Google Patents

Abstract

PURPOSE:To always perform a working with a desired spot diameter by memorizing, pairing previously the coordinate data of a working point with the focal position of a laser beam, and at the time of a working, correcting the position of a converging optical system so that a correct focal position comes on the surface of an object to be worked. CONSTITUTION:A working is performed by irradiating an object 21 to be worked with a laser beam from a laser oscillator 10 using a working head 40. Before the working, the working head 40 is moved within a working range while irradiating previously the surface of a working table 20 with a laser beam, the focal position of the laser beam at each working point is grasped. Paired coordinate data expressing the position of the working head 40 and focal position data are memorized by a control unit 50. At the time of an actual working, whenever the working head 40 is moved to each working point, the working head 40 is moved in the Z axis direction by a drive device 53 according to the signal of the control unit 50 so that a correct focal position is attained according to the focal position data, and the position of a converging optical system 30 is corrected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical system for laser processing such as welding, cutting and surface modification. More specifically, the present invention relates to a converging optical system in a laser processing machine of optical scanning type or torch moving type. The present invention relates to correction of the focal position of the.

[0002]

2. Description of the Related Art A laser processing machine collects a laser beam emitted from a laser oscillator by using a focusing optical system and irradiates the focused laser beam on a predetermined processing point of a workpiece for processing. Normally, as shown in FIG. 6, the laser light from the laser oscillator (1) is fed into a plurality of bend mirrors (2a-2).
It is bent at d), transmitted to the processing head (3), and emitted from the nozzle via the condensing optical system in the processing head (3).

A processing head (torch) to which a workpiece is fixed
In a torch moving type or optical scanning type laser processing machine in which the moving head moves, for example, the transmission system between the bend mirrors (2a, 2b) and between the bend mirrors (2b, 2c) is configured to be expandable and contractible, and the processing head (3) is It can be moved in the X and / or Y directions. Therefore, the transmission distance from the laser oscillator (1) to the focusing optical system changes greatly in proportion to the movement amount of the processing head (3).

[0004]

Generally, when the diffused light emitted from the light source (5) is condensed through the condensing optical system (6) as shown in FIG. 7, the following relational expression is established. . 1 / f = 1 / a ₁ + 1 / a ₂ ------ where f: focal length of condensing optical system a ₁ : distance from light source (5) to condensing optical system (6) a ₂ : Distance from the focusing position (7) to the focusing optical system (6).

It is recognized that the laser light is a parallel light without divergence because it has a good directivity. However, in reality, a slight amount of light diffuses like the light shown in FIG. For this reason,
If the equation holds for the focusing optical system of the laser processing machine and the distance (a ₁ ) from the laser oscillator (light source) to the focusing optical system changes, the distance from the focusing position to the focusing optical system ( a ₂ ) also changes. Moreover, the divergence of the beam does not always diverge while maintaining a linear relationship with the distance from the light source, and the degree of divergence may vary depending on each position. This means that if the processing position is different, the position where the laser light is focused is also different.

Therefore, as the processing range increases, the focus position of the laser light fluctuates, and the spot diameter of the laser light at each processing point changes. For this reason, the energy density of the laser beam varies depending on the processing point, and the processing quality of the product may be non-uniform.

In order to solve such a problem, conventionally, a condenser lens called a collimation lens or a condenser mirror system having a similar function is arranged in an optical path between a laser oscillator and a condenser optical system to form a beam. Diffusion (divergence angle) is suppressed. However, even if a collimation lens is used, it is not possible to make the laser light perfectly parallel even if the divergence is reduced to a certain extent simply by correcting the divergence of the beam. There is no guarantee that the focal position will remain constant over.

An apparatus has also been proposed in which the distance from the laser oscillator to the farthest position in the processing range is a fixed optical path length and the focal length is kept constant at any position in the processing range. A device that should be called this device for constant optical path length is, for example, as shown in FIG.
And a condenser optical system (6), a pair of bend mirrors (8,
By disposing 9) and sliding the pair of mirrors (8, 9) in conjunction with the movement of the machining head and in the opposite direction to the movement direction, regardless of the position of the machining head.
The transmission distance from the laser oscillator (1) to the condensing optical system (6), that is, the optical path length is always kept constant. However, since this device requires an optical system such as a reflecting mirror structurally, energy loss at the mirror surface is unavoidable, and the mechanism itself becomes large, which increases the cost of the entire laser processing machine. There's a problem.

Therefore, an object of the present invention is to enable a workpiece to be machined with a constant spot diameter in the entire range of the processing region without increasing cost and increasing energy loss. .

[0010]

In order to achieve the above object, in the present invention, the coordinate data of the processing point and the focal position of the laser beam at the processing point are paired in advance over a part or the whole of the laser processing range. The position of the condensing optical system is corrected so that an accurate focus position is located on the surface of the workpiece during processing of each processing point.

At the time of machining each machining point, the focal position may be calculated from the stored coordinate data and automatically corrected, or the coordinate data of the machining point and the focal position of the laser beam at the machining point may be obtained. It is also possible to record and as a pair and to manually apply the correction.

Further, in the case of intentionally defocusing (defocusing) depending on the processing conditions, the defocusing is performed after obtaining the accurate focus for each processing point.

In order to correct the position of the condensing optical system, the condensing optical system itself may be moved, but it is relatively easy if the processing head containing the condensing optical system is moved. It can be realized by configuration.

In this case, since the nozzle attached to the lower end of the machining head also moves as the machining head moves,
It is desirable to adjust the distance between the tip of the nozzle and the work piece.

[0015]

According to the present invention, in consideration of the divergence of the laser beam, the distance from the focusing system capable of obtaining the minimum spot diameter in advance over the range expected for laser processing is measured and stored together with the position data. Every time, when processing at each processing point, an appropriate focus position is obtained based on the data.

Measuring the distance from the condensing system that can obtain the minimum spot diameter also includes obtaining it by optical calculation. Also, here is the memory
In addition to storage by electronic or magnetic storage means, recording on paper or the like is also included.

It should be noted that it is not always necessary to cover the entire range of the processing region, but for example, a part of the processing conditions may be targeted.

In this way, if the distance (focus) from the converging system that can obtain the minimum spot diameter at the position where processing is expected, that is, the processing point, is known, when processing is performed at that position, It is possible to accurately bring the light collecting system to the focal position. Further, if the distance between the converging system and the focus is measured in advance over the entire processing range and stored (recorded) together with the position data, the focus position can be obtained over the entire processing range, thus obtaining uniform processing conditions. be able to.

[0019]

EXAMPLES First, as shown in FIG. 1, a general laser processing machine comprises a laser oscillator (10), a processing table (20), a beam transmission system (30), a processing head (40), and the like. A plurality of bend mirrors (30a to 30c) that constitute the beam transmission system (30) using the laser light from the laser oscillator (10).
It is bent by and is transmitted to the processing head (40), and is emitted from the nozzle (43) via the condensing optical system (42) in the processing head (40). This laser processing machine is an optical scanning type in which the processing head (40) moves. Therefore, the transmission system between the bend mirror (30b) and the processing head (1) is configured to be expandable and contractable, and the processing head (40) can be moved in the Y direction. Note that FIG. 1 exemplifies a case where the processing table (20) is movable in the X direction. As each drive device (51, 52, 53) in the X, Y, and Z axis directions, a combination of a servo motor and a ball screw is illustrated in FIG. 1, and each is electrically connected to the control unit (50). ing.

The processing head (40) comprises a housing (41) connected to a driving device, a condensing optical system (42) and a nozzle (43) attached to the housing (41). Although a lens (transmission optical system) is illustrated as the condensing optical system (42), a reflective optical system such as a parabolic mirror (see FIGS. 2 and 3) or another condensing optical system may be used. Of course it is possible.

Considering the case where the surface of the flat work piece (21) fixed on the work table (20) is subjected to laser processing, the work piece (21) is not placed prior to the working. In this state, the processing head (40) is moved within the processing range while irradiating the laser light, and the focus position of the laser light at each processing point is grasped. For example, the focus position is obtained by actually measuring with a suitable focus position detecting means, and the focus position thus obtained is paired with the coordinate data representing the position of the machining head (40) as the focus position data as a control unit. Store in (50).

In actual machining, each time the machining head (40) moves to each machining point, the accurate focus position at the machining point matches the desired machining position based on the stored focal position data. Control unit (5
The drive device (53) moves the machining head (40) in the Z-axis direction based on the signal from (0). As a result, the distance (a _{2 in} FIG. 7) from the condensing optical system (42) to the welding location changes, and the focus position is corrected.

The focal position can be obtained by actual measurement as described above, or can be calculated by optical calculation based on coordinate data representing the position of the processing head (40). In that case, workability can be improved as compared with the case where the focal position is actually measured at each processing point prior to processing.

Alternatively, as described above, the focus position data is stored in the control unit (50) and the correction of the focus position is automatically executed during machining. For example, when the machining range is small or the machining point is When there are few,
The focus position data obtained in advance may simply be recorded on a recording medium such as paper, and the focus position may be manually corrected during processing.

By the way, particularly in the cutting process, the assist gas pressure used during the process has a great influence on the quality, but in order to keep this constant, the distance between the workpiece and the nozzle at the tip of the processing head is kept constant. I have to However, when the machining head (40) is moved in the Z-axis direction to correct the focus position as described above, the distance between the tip of the nozzle (43) and the workpiece (21), that is, the gap, also changes. Therefore, the processing head (40) and the condensing optical system (42) are moved by separating the nozzle (43) from the condensing optical system (42), strictly speaking, and moving it in the Z-axis direction. However, it is necessary to prevent the gap from changing.

FIG. 2 shows an embodiment in which this point is taken into consideration. The nozzle position adjusting unit (60) is attached to the machining head (40).
Is provided. In the embodiment of FIG. 2, the condensing optical system (4
A parabolic mirror, which is a reflection and focusing system, is used in 2). The housing (41) is connected to a member that houses the bend mirror (30c) immediately before the condensing optical system (42) as shown by the chain double-dashed line, and both move integrally in the Z-axis direction. .

A sleeve (44) is attached to the lower end of the housing (41) so as to be vertically slidable with respect to the housing (41), and a nozzle (43) is joined to the lower portion of the sleeve (44). The structure for supplying the shield gas and the assist gas to the nozzle (43) is omitted in the drawing. Then, the nozzle position adjusting unit (60) is provided with the nozzle (43).
For moving up and down independently of the housing (41), including a ball nut (61) fixed to the flange (45) of the sleeve (44) and a ball screw (62) screwed to the ball nut (61). , A motor (63) fixed to the housing (41) side and having an output shaft coupled to one end of a ball screw (62).

When the ball screw (62) is rotated by the motor (63), the sleeve (44) and the nozzle (43) are integrally moved up and down, and the space between the tip of the nozzle (43) and the workpiece (21) is increased. The gap (G) changes. Therefore, the machining head (4
Nozzle (43) in the direction and amount that offset the vertical movement amount of (0)
By moving up and down, it is possible to maintain the gap (G) at a constant value over the entire range of the processing area. The configuration of the nozzle position adjusting unit (60) is arbitrary, and it is possible to use a ball screw (62) as shown in the figure, or a combination of a rack and a pinion.

FIG. 3 schematically showing the drive control system of the laser processing machine in the embodiment of FIG. 2 shows a processing head (40).
Of the drive devices for moving in the respective axial directions, only the Z-axis direction drive device (53) is shown. The drive unit in each axial direction (see FIG. 1) including this drive unit (53) is controlled by the control unit (50), and the control unit (50) sends the laser beam machine controller each axis position data of the processing head (40). Will be sent. With the laser processing machine controller,
Based on the axis position data, coordinate data representing the current position of the machining head (40) is calculated and input to the nozzle position controller. The nozzle position control controller sends a nozzle position control signal to the motor drive unit of the nozzle position adjustment unit (60) to adjust the position of the nozzle (43).

In the embodiment shown in FIG. 4, the height sensor (64) fixed to the flange (45) detects the distance between the workpiece (21 ') and the nozzle (43) based on the detected value.
The position is adjusted. That is,
Of the processing head (40) and thus also the focusing optics (42)
Of the nozzle (43) and the work piece (2
The height sensor (64) detects a change in the distance to the gap 1 ') and drives the nozzle position adjusting unit (60) based on the detected value to maintain the gap (G) at a constant value. . As the height sensor (64), for example, a capacitance type sensor is practically used in order to avoid the influence.

When processing a three-dimensionally shaped work piece (21 ') as shown in FIG. 4, first, teaching is performed prior to the working, and the shape data of the work piece (21') is controlled by the control device. To memorize. On the other hand, as described above, the focus position data at each processing point is obtained by actual measurement or optical calculation. Then, the processing head (40) is moved up and down based on the shape data and the focus position data, so that the focus of the laser beam and the processed portion coincide with each other. At the same time, the gap (G) is calculated from the elevation amount of the processing head (40) and the shape data, and the nozzle position adjustment unit (60) is driven so that the gap (G) becomes a predetermined value, and the nozzle (43 ) Position adjustment.

In this case, the height sensor (64)
It is also possible to adjust the position of the nozzle (43) by using. By using this height sensor (64), the gap (G) can be directly measured, so that even if there is a deviation between the shape data due to teaching and the actual shape of the workpiece (21 '), the gap There is an advantage that (G) can be managed more accurately.

In the embodiment shown in FIG. 5, the machining head (4
0), the beam transmission system (30) and the laser oscillator (10) are arranged on a table (22) movable in the Y direction so that they can be slid together. With this structure, even if the processing position changes in the Y direction, the distance from the laser oscillator (10) to the condensing optical system (42) does not change, so the focal position of the laser beam does not change. . Therefore, as in the above-described embodiment, it is possible to perform uniform processing over the entire range of the processing area.

[0034]

As described above, according to the present invention, the focus position of the condensing optical system is corrected by raising and lowering the machining head according to the change of the condensing position accompanying the movement of the machining head. The focus of the laser light can always be made to coincide with the processing location. Therefore, the work piece can be always processed with a desired spot diameter, and the product quality can be made uniform over the entire range of the processing area.

Therefore, the present invention is particularly useful when the processing range is large or when it is strictly required to make the processing conditions equal for all the processing ranges, but in addition to this, the beam diffusion amount (divergence angle) is also increased. It is also effective when a large laser must be used.

Moreover, according to the present invention, an additional mirror is not required unlike the prior art described with reference to FIG. 8, and therefore, the increase in cost and the increase in energy loss do not pose a problem. .

Further, since the position of the focal point itself at each processing point can be accurately known, so-called defocusing, which has been widely used in welding and heat treatment, is not limited to the processing at the focal position. Even when it is performed, there is an effect that a desired defocus amount can be accurately obtained.

If the focus position of the condensing optical system fixed inside the processing head is corrected by moving the entire machining head, an additional drive mechanism is required as compared with the case where the condensing optical system itself is moved. Since it is not necessary, it can be realized with a simple structure, and there is no concern that alignment will be complicated.

Further, in this case, by moving the nozzle with respect to the machining head so as to offset the movement amount of the machining head, the distance from the tip of the nozzle to the workpiece can be maintained at a constant value. Therefore, for example, even when assist gas is used, it is possible to maintain the gas pressure at a processing location at a constant value and suppress variations in processing quality due to changes in gas pressure.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of a general laser processing machine.

FIG. 2 is a vertical sectional view showing an embodiment of the present invention.

FIG. 3 is a block diagram showing a control system of the embodiment of FIG.

FIG. 4 is a vertical sectional view showing another embodiment.

FIG. 5 is a vertical sectional view showing still another embodiment.

FIG. 6 is a schematic diagram showing a conventional technique.

FIG. 7 is a schematic diagram of a condensing optical system.

FIG. 8 is a schematic diagram showing a conventional technique.

[Explanation of symbols]

 10 Laser oscillator 20 Processing table 21 Workpiece 30 Beam transmission system 40 Processing head 41 Housing 42 Condensing optical system 43 Nozzle 50 Control unit 51, 52, 53 Drive unit 60 Nozzle position adjustment unit 64 Height sensor

Claims (6)

[Claims] 1. Coordinate data of a processing point and a focal position of a laser beam at the processing point are previously stored as a pair over a part or the whole of the laser processing range, and an accurate focus position is recorded when processing each processing point. An optical system for laser processing, characterized in that the position of the condensing optical system is corrected so that it is on the surface of the workpiece. 2. The laser processing optical system according to claim 1, wherein, when processing each processing point, a focal position is obtained by calculation from stored coordinate data and correction is automatically performed. 3. The laser processing optical system according to claim 1, wherein the coordinate data of the processing point and the focus position of the laser beam at the processing point are recorded as a pair and manually corrected. 4. The optical system for laser processing according to claim 1, wherein in the case of intentionally defocusing depending on processing conditions, defocusing is performed after obtaining an accurate focus for each processing point. 5. The laser processing optical system according to claim 1, wherein the position of the condensing optical system housed in the processing head is corrected by moving the processing head. 6. The laser processing optical system according to claim 5, wherein the distance between the tip of the nozzle and the workpiece is adjusted as the processing head moves.