JPH09141483A - Laser cutting nozzle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To cut off air, expand an assist gas injection area, and improve laser cutting precision by gradually increasing the gas flow passage surrounding diameter of a curtain nozzle which injects inert gas toward the tip of a main nozzle. SOLUTION: The nozzle tip part 1 of the laser cutting machine consists of the main nozzle 2 which injects the assist gas 4 surrounding laser beam and the curtain nozzle 3 which injects gas for a curtain surrounding the assist gas 4. With the negative pressure that the assist gas injected together with the laser beam irradiating the surface of a cut material 5 generates by self- jetting, air at the periphery of the nozzle tip part 1 is convoluted outward together with the assist gas 5. The gas 6 for the curtain is jetted from the curtain nozzle 3 slanting outward at an angle θ nearby the nozzle tip part. Consequently, the curtain gas 6 and air flowing in the jet area of the assist gas 4 are cut off and the assist gas of high purity is supplied to improve the laser cutting precision.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a curtain nozzle of a laser cutting machine.

[0002]

2. Description of the Related Art A nozzle of a laser cutting machine for cutting a steel material using a curtain gas is generally known in which a tip opening portion as shown in FIG. 3 is formed. The nozzle 11
Surrounds the main passage with the curtain gas 16 (inert gas)
Since the curtain nozzle 13 that guides the air is vertically provided toward the tip opening of the main nozzle 12, the air around the tip opening where the ejected inert gas flows into the ejection region of the assist gas 14 is blocked, As a result, the high-purity assist gas 14 is sent to improve the cutting speed of the material to be cut.

[0003]

However, in the case of the above-mentioned curtain nozzle 13, since the ejection port is vertically provided toward the tip opening of the main nozzle 12, it is sprayed vertically on the material 15 to be cut with high pressure. The generated curtain gas 16 strongly collides with the material to be cut 15 to generate a gas flow both in the outer direction on the side opposite to the main nozzle 12 and in the inner direction on the side of the main nozzle 12 with respect to the ejection axis. At this time, the curtain gas flow 16a that has flowed in the outward direction entrains the air around the tip opening to block the invasion of air into the ejection region of the assist gas 14, but the curtain gas 16b that has flowed inward is The assist gas 14 flows into the ejection area, which causes the flow of the assist gas 14 to be disturbed. For this reason, it becomes difficult to stabilize the pressure when the assist gas 14 is jetted, and the high-purity assist gas 14 cannot be supplied. As a result, the material to be cut 1 is cut.
There was a problem that dross adhered to the cut surface of No. 5 so that good quality cutting could not be performed and the cutting speed was also reduced.

An object of the present invention is to improve the cutting speed of the material to be cut by preventing the air around the tip opening and the gas for curtain from flowing into the assist gas jetting region,
The point is to make good quality cutting.

[0005]

According to a first aspect of the present invention, a laser beam is guided to an opening at the tip of a laser cutting machine, and a main passage for surrounding the optical path of the laser and ejecting the assist gas coaxially is formed. In a laser cutting nozzle composed of a main nozzle having and a curtain nozzle surrounding the main nozzle to eject an inert gas, the curtain nozzle has a surrounding diameter of the curtain gas flow path in a main nozzle tip direction. It is characterized by being gradually expanded.
According to a second aspect of the present invention, the ejection angle of the laser cutting nozzle according to the first aspect is 45 ° ± 30 with respect to the central axis of the main nozzle.
It is characterized by having been made °.

[0006]

FIG. 1 shows an embodiment of the present invention.
This will be described below with reference to FIG. The laser cutting machine of this embodiment cuts the material to be cut by using high-purity oxygen gas as the assist gas and nitrogen gas as the inert gas for the curtain gas.

FIG. 1 shows the structure of a nozzle in a laser cutting machine according to this embodiment. Reference numeral 1 in the figure indicates the nozzle tip of the laser cutting machine of the present invention. The nozzle tip portion 1 guides the laser light and surrounds the laser light to eject the assist gas 4 (oxygen gas) coaxially with the main nozzle 2. The curtain nozzle 3 ejects 6 (nitrogen gas). The main nozzle 2 is provided on the central axis of the nozzle tip portion 1, and is usually used with its tip opening oriented vertically to the material to be cut 5. The curtain nozzle 3 is provided with the axis line in common (concentrically) with the main nozzle 2, and the surrounding diameter thereof is gradually increased toward the tip. That is, the curtain nozzle 3
Has a cylindrical shape from the upper end of the base end, and gradually expands in the vicinity of the opening of the distal end to form a conical shape. Reference numeral 5'denotes a cutting groove generated by the laser beam emitted from the main nozzle 2.

Next, the main nozzle 2 and the curtain nozzle 3
The flow of each gas ejected further will be described. First,
The flow of the assist gas 4 ejected from the main nozzle 2 will be described. The assist gas 4 ejected at the same time as the laser beam applied to the surface of the material to be cut 5 is vertically sprayed onto the surface of the material to be cut 5 with high pressure. At this time, the air around the nozzle tip 1 is entrained together with the assist gas 4 in the outward direction with respect to the ejection axis of the main nozzle 2 by the negative pressure generated by the self-injection flow of the assist gas 4.

On the other hand, since the curtain gas 6 is ejected from the curtain nozzle 3 which is provided in the vicinity of the tip of the nozzle and is inclined outward by an angle θ, the outside angle on the surface of the material to be cut 5 is smaller than the inside angle. It is always blown up. Therefore, the air around the nozzle tip 1 is entrained in the outward direction together with the curtain gas 6 due to the negative pressure of the self-injection flow of the curtain gas 6 that occurs along the angle when the nozzle is blown. Further, in this case, unlike the case where the gas is ejected vertically on the surface of the material 5 to be cut, a gas flow is also generated in the inward direction. However, the negative pressure of the gas flow generated at this time is the negative pressure of the gas flow flowing in the outward direction. Since the pressure for the curtain 6 is always smaller than the negative pressure, the curtain gas 6 does not flow into the jet area of the assist gas 4 and disturb the air flow in the jet area of the assist gas. In this respect, it can be said that it is better to give the curtain nozzle a jetting angle.

As described above, since the curtain gas 6 and the air around the nozzle tip portion 1 are prevented from flowing into the jetting area of the assist gas 4 more effectively, the high-purity assist gas is supplied to the laser beam irradiation area. 4 can be stably supplied, and a higher quality cut surface can be obtained.

Further, the curtain gas 6 ejected at the ejection angle θ is different from the case where the curtain gas 6 is ejected perpendicularly to the material 5 to be cut.
Since the jetting area of the high-purity assist gas 4 is provided in a wider area, it is possible to further improve the laser cutting speed.

Regarding the ejection angle θ of the curtain gas 6, the influence of the difference in the ejection angle on the material 5 to be cut was determined by measuring the roughness Rz (μm) of the cut surface, as shown in FIG. 2a. I got good results. This is to divide the cut surface 5a of the material to be cut 5 irradiated with laser light into an upper surface A, a cutting middle surface B, and a cutting lower surface C from the upper part, and two cutting surface rough surfaces of the cutting middle surface B and the cutting lower surface C. The roughness Rz (μm) was measured by a roughness meter (FIG. 2b). The broken line in FIG. 2a shows the average value (about 60 μm) of the cut surface roughness Rz that is allowed when the conventional curtain nozzle 13 is used in laser cutting. According to the result of this measurement, the surface roughness Rz (μm) of the middle cutting surface B and the lower cutting surface C
Has the minimum value when the ejection angle is 45 °. This means that the best cut surface can be obtained when the ejection angle θ is 45 °. Further, the surface roughness Rz (about 60 μm) allowed in the laser cutting takes a smaller value when the ejection angle θ is in the range of 45 ° ± 30 ° on the lower surface C of the cutting. Since the cutting middle surface B always takes a smaller value than the cutting lower surface C, the ejection angle θ of the curtain nozzle 3 of the laser cutting machine in this embodiment is 45.
It can be said that when the angle is ± 30 °, it is possible to obtain a cut surface 5a having a better quality than the cut surface allowed by laser cutting.

[0013]

As described above, the laser cutting nozzle according to the present invention is provided with the main passage for guiding the laser light at the opening of the tip thereof, surrounding the laser light path, and ejecting the assist gas coaxially. In a laser cutting nozzle composed of a main nozzle and a curtain nozzle that surrounds the main nozzle and ejects an inert gas, the surrounding diameter of the curtain gas flow path gradually increases toward the tip of the main nozzle. The curtain nozzle is provided such that the surrounding diameter thereof is such that the ejection angle θ of the curtain gas is 45 ° ± 30 °. Therefore, compared to the case where a straight curtain nozzle is used, the effect of blocking the curtain gas and the air at the nozzle tip that flows into the assist gas ejection area is enhanced, and a high-purity assist gas is stably supplied. Is possible. Further, since the assist gas ejection area is enlarged, it is possible to perform laser cutting performed at high speed with high accuracy, and it is possible to obtain a higher quality cut surface.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional side view showing a structure of a curtain nozzle that is an embodiment of the present invention and showing a flow direction of an assist gas and a curtain gas and an ejection angle of the curtain gas.

FIG. 2 is a surface roughness R at a cut surface of a material to be cut when a curtain nozzle is provided with an ejection angle and a curtain gas is ejected.
It is a figure which calculated | required z (micrometer), (a) is the surface roughness Rz of the cutting middle surface and cutting lower surface when changing a jet angle.
(B) shows the measurement points of the surface roughness Rz (μm) on the cut surface of the material to be cut.

FIG. 3 is a partial cross-sectional side view showing a conventional structure of a curtain nozzle and a flow direction of an assist gas and a curtain gas.

[Explanation of symbols]

 1 tip opening, 2 main nozzle, 3 curtain nozzle, 4 assist gas (gas flow), 5 cut material, 6 curtain gas (gas flow).

Claims (2)

[Claims] 1. A main nozzle which guides a laser beam through an opening of a tip of a laser cutting machine and surrounds an optical path of the laser beam to eject an assist gas coaxially therewith, and an inert gas which surrounds the main nozzle. In the laser cutting nozzle including a curtain nozzle for ejecting the curtain nozzle, the curtain nozzle has a surrounding diameter of the curtain gas flow passage that gradually increases toward the tip of the main nozzle. 2. The laser cutting nozzle according to claim 1, wherein the curtain gas is ejected at an ejection angle of 45 ° ± 30 ° with respect to the central axis of the main nozzle.