JPS61232085A - Method and apparatus for laser beam cutting - Google Patents

Abstract

PURPOSE:To make possible the cutting to a sharp angled shape and to make uniform the roughness of a cut surface by detecting the moving speed of a laser beam relative to a work, changing over the laser from continuous output to pulse output and controlling the pulse frequency. CONSTITUTION:An arithmetic control unit 13 calculates the relative moving speed of the laser beam 3 with respect to the work 1 in accordance with the speed change in the X-, Y-directions of a processing table 10 detected by a speed detector 12 in the stage of cutting. The laser output is changed over from the continuous output to the pulse output by a laser output control means 14 and the pulse frequency is controlled when the processing speed drops to the critical speed or below in the angular part of the cutting shape. The cutting to the sharp angle shape is thus made possible and the roughness of the cut surface is made uniform.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a cutting method and apparatus using a laser beam.

[Conventional technology]

Laser beams have extremely high energy density and are widely used for welding, cutting, heat treatment, etc. Conventionally, laser cutting has been carried out using a laser cutting acid as shown in Figure I-7. As shown in the figure, the workpiece (1) is set on the processing table αQ.

This processing table can be freely moved in the X and Y directions by an X-axis drive motor (11a) and a Y-axis motor (i i b). Laser beam (3)
is taken out from the laser oscillator (2) and passed through the beam duct (
4) and irradiates the workpiece (1).

Along the way, the light is focused by a mirror (5) and a lens (7).

The processing head (6) is equipped with a gas inlet (8) that supplies assist gas (not shown) necessary during cutting,
Assist gas is injected onto the workpiece (1) through the nozzle hole (9).

[Problem that the invention seeks to solve]

When laser cutting is performed using the above-mentioned device under nine preset processing conditions, if the processed shape has an acute angle as shown in Figure 8 (,A), the parts a and b in the figure (101 )
, The melt falls off at the part indicated by (102), Fig. 8 (B)
It is difficult to cut into an acute angle shape as shown in IIC.

The reason for this is as shown in Figure 9 (A) (a) and (b).
, (+').

Laser beam (3) at corners such as (d) and (e)
This is because the relative movement speed between the object (1) and the workpiece (1) shows a time change as shown in FIG. 9(B). In other words, at the corners where the speed has decreased, relatively excessive heat input occurs, as shown in Fig. 8 (A).
The melting shown in Figure 9 is the ninth that will cause a drop. Also, the true roughness of the cut surface at this part is a % b
There are many problems such as the fact that the surface roughness tends to be finer than the regular parts such as the part and c-d part, and it is not possible to maintain a constant surface roughness over the entire surface of the cut part.

[Means for solving problems]

In order to solve the above problems, the present invention detects the change in speed when cutting various shapes with a laser beam and controls the laser output when the processing speed decreases at the corner. The laser output mode is set to pulse output when the speed is below a preset value, and when the speed falls below the critical speed within this pulse output range, @ lowers the average output of the pulse output and further increases the pulse output. The present invention provides a laser cutting method and apparatus characterized in that frequency control is added.

[Effect]

When laser cutting is performed according to preset conditions, the processing speed is reduced at the corners of the cut shape, and by controlling the laser output at the corners, the amount of heat input to the corners is prevented from becoming excessive. Further, by adding pulse output and pulse frequency control according to the speed during machining using pulse output, the machined surface roughness can be kept constant.

〔Example〕

FIG. 1 is a block diagram of an apparatus according to an embodiment of the present invention.

In the present invention, a speed detector (6) and a speed detector (2) are used to detect the moving speed of the processing table αQ during cutting.
) is provided with an arithmetic and control unit Q which calculates the optimum value of the laser output based on the signal from the laser output control unit Q and a laser output control means 4 which controls the laser output into a continuous output and a pulse output.

Next, the present invention will be explained in detail. When the speed detector (6) detects the speed change in the X direction and the Y direction, the relative moving speed of the laser beam (3) on the workpiece (1) is immediately determined by the arithmetic control unit (2). When this speed is equal to or higher than the critical speed, the laser output mode is continuous output, and the output is controlled according to each speed. That is, as shown in the cutting condition example of FIG. 2, when the cutting speed exceeds point P, the straight line LtK is used to control the average output. In case the cutting speed becomes lower than the speed corresponding to point P, the laser output form is changed to Norms output, and the output is controlled in a straight line. Figure 3 shows these relationships according to time changes. In Figure 6, the vertical axis (rn/-) represents the relative movement speed, (4) represents the average output, and the horizontal axis (sec)
indicates time. By controlling the average output and changing the laser output form in this way, the angle f! shown in FIG. 8(B) can be obtained! Its (part a) and (part b) can perform good laser cutting without any welding.

Next, when the speed decreases and you switch to pulse output, for speeds below that, the pulse duty is changed to keep the average output constant depending on the degree of speed decrease, but if the frequency remains constant, As shown in FIG. 4, the average surface roughness KZ changes greatly. The horizontal axis N in Fig. 4 represents the number of ridges on the cut surface, that is, the number of unevenness, but in order to keep the surface roughness within a certain range R21 to 84, the number N of ridges is determined.
need to be controlled. In this case, since there is a proportional relationship between the number of peaks N and the pulse frequency as shown in Figure 5,
By controlling the frequency, the surface roughness can be kept within a certain range. For this reason, the arithmetic and control unit (2) is equipped with a frequency control function, and if the critical speed Uc is below the critical speed Uc within the pulse output control range, the frequency will overflow to the preset change line C2 as shown in Figure 6. I'm trying to change the. In the figure, the C1 line indicates a constant frequency, the vertical axis f indicates the frequency, and the horizontal axis V indicates the cutting speed. In addition, although the case of cutting was shown in the said Example, this invention can also be applied to welding and scribing processing.

Further, in the embodiment, only the case where the workpiece is moved two-dimensionally has been explained, but the present invention is not limited to this, and the present invention is also applicable to the case where the workpiece is moved three-dimensionally or more. However, it goes without saying that if the composite speed, that is, the actual speed, is detected in the same way, exactly the same effect can be obtained.

〔Effect of the invention〕

According to the present invention, it is possible to switch from continuous output to pulsed output in laser cutting, and it is also possible to cut acute-angled shapes by frequency control within the pulsed output range, and it is possible to maintain uniform cut surface roughness. .

[Brief explanation of drawings]

Figure 1 is a configuration diagram of the device according to the present invention, Figure 2 is a diagram showing the relationship between cutting speed and laser output form, Figure 6 is a time chart of relative moving speed and average output, and Figure 4 is cutting. An explanatory diagram of surface roughness, Fig. 5 is a diagram of the relationship between pulse frequency and the number of ridges on the cut surface, Fig. 6 is an explanatory diagram of pulse frequency control, Fig. 7 is an explanatory diagram of laser cutting by the conventional method, and Fig. 8 Figure (~, (B
) is a state diagram showing melting of the cut part, Fig. 9(A), (
B) is a diagram showing changes in relative movement speed. 1: Workpiece, 2: Laser oscillator, 3: Laser beam,
4: Beam duct, 5: Mirror, 6: Processing head, 7:
Lens, 8 gas inlets, 9: Nozzle hole, 10: Processing table, 11a: X-axis drive motor, (11b)
Y-axis drive motor, 12: speed detector, 16: arithmetic control unit. In each figure, the same reference numerals indicate the same or similar parts. Agent Patent Attorney Sanro Kimura Fig. 2 Shun Zan: &bottom (m/m1n) Fig. 3 VffP: 1 (sec) N (Ki/) Omm) Fig. 5 F (Sui)

Claims (2)

[Claims] (1) In a laser processing method in which processing is performed by irradiating a laser beam onto a workpiece, the relative movement speed of the laser beam irradiated to the workpiece with respect to the workpiece is detected, and a speed range higher than a preset value is detected. In this case, the laser output is continuous output, and below that, the laser output is pulse output, and when the relative movement speed is less than a preset speed within the relative movement speed range when processing with pulse output, the laser output is set as pulse output. A laser cutting method characterized by changing the pulse frequency. (2) Laser processing equipment that processes a workpiece by irradiating it with a laser beam is equipped with a speed detector that detects the relative movement speed of the processing table, and an optimal means for calculating the average output power of the laser;
A laser cutting device comprising: means for determining pulse output or continuous output; further, arithmetic control means for controlling pulse frequency within a range of pulse output conditions; and laser output control means.