JP3230157B2 - Beam absorber for laser processing of tubes - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to processing of a pipe by an industrial laser.

2. Description of the Related Art Conventionally, laser processing has been used for welding, cutting,
It was developed for drilling, etc., and has been rapidly developed as a machine for various metals and non-metals due to its high use. However, in the processing of pipes, especially small-diameter pipes can be cut or drilled with a laser. For example, a laser beam emitted perpendicular to the processing surface of the tube passes through the thickness of the material and reaches the inner wall of the tube on the other side while the power density of the beam does not decrease, causing deep processing damage to the inner wall. In many cases, they were not widely used for processing pipe materials.

SUMMARY OF THE INVENTION Accordingly, the present invention provides a laser beam passing through a processing surface of the above-mentioned conventional tube, and reaches the opposite inner wall of the tube while the power density of the beam does not decrease.
An object of the present invention is to provide a method for improving machining defects caused by laser machining by avoiding machining scratches on its inner wall, and particularly for facilitating laser machining of small-diameter pipes.

In order to achieve the above object, the present invention provides a mechanism for inserting a beam absorbing material into a tube to thermally extinguish a laser beam passing through the thickness of the material inside the absorbing material. In addition, the present invention is characterized in that a laser beam can be easily processed by laser processing on the inner wall of the material by avoiding processing scratches on the inner wall of the material.

According to the above-mentioned feature of the present invention, a laser beam having a high power density, which is vertically irradiated on a processing surface of a pipe and passes through the thickness of the material to reach the inside, is absorbed by the beam absorbing material. In this case, it is possible to avoid processing flaws caused by heating of the passing beam applied to the inner wall of the material and scattering of the melted scattered material.

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
This will be described in detail with reference to FIG. Fig. 1 shows the structure around the processing head and the processing surface in the cutting process of the laser processing machine.
Shown in The processing head 2 mainly includes a lens holder and a nozzle for blowing the assist gas 3.
The lens holder is cooled with water 4 to prevent the condenser lens 5 from being heated. In FIG. 1, parameters related to the setting of the nozzle height 9 and the focal length 8 of the condenser lens are shown in FIG. The distance between the focal position of the irradiation laser beam 6 and the processing surface is referred to as a defocus distance 10, and the defocus distance 10 is not set on the + side (the focal position is higher than the processing surface) in normal laser processing. In the cutting process, the defocus distance 10 is set to the minus side (the focal position is lower than the processing surface) in order to reduce the molten splatters 7, and the defocus distance is set so as to pass through the cutting surface at a place where the beam power density is high. I have. Therefore, when processing the tube material, especially in the case of a thin wall such as a small-diameter tube, the focal point of the beam falls below the thickness of the material and reaches the opposite side of the tube while the power density of the beam does not decrease. Consequently, the inner wall of the tube is heated at the same power density as when the defocus distance 10 is on the + side. That is, the inner wall of the tube shown in FIG. 3 has a flaw similar to the processing surface, and the molten scattered substance 7 scatters and adheres to the inner surface of the tube, resulting in processing defects. However, by inserting the beam absorber 12 of the present invention inside the tube, the laser beam that has passed through the thickness of the material as shown in FIG.
The beam absorbing material 12 is a rod-shaped unfired insulator whose main component is magnesium oxide, which is heated by laser beam irradiation. However, since it is an unfired metal oxide, it does not emit harmful gas, etc. While sintering occurs, the laser beam is extinguished as heat for firing the metal oxide.
By shaping the rod-shaped unsintered insulator of the beam absorbing material 12 into an outer diameter corresponding to three-fourths of the inner diameter of the pipe to be processed, the work of inserting the inside of the pipe can be easily performed. Also, even if the pipe to be processed is rotated during laser processing, the porosity relative to the inner diameter of the pipe is large, so that the insulator rolls inside and the distance from the processing surface to the insulator is kept constant. Therefore, the laser processing can be performed in a stable condition without obstructing the flow path of the assist gas 3. After processing, the beam absorber 12
When removing the beam, the beam absorbing material 12 is contracted in volume due to the dehydration reaction and the sintering of the surface, so that the beam absorbing material 12 can be easily removed similarly to the operation at the time of insertion.

According to the laser processing method of the present invention having the above construction and operation, the laser beam is thermally extinguished inside the beam absorbing material. Thereby, it is possible to avoid processing flaws caused by heating of the passed beam on the inner wall of the material and scattering of molten scattered substances, thereby improving the defect of laser processing, and in particular, facilitating processing of small-diameter pipes with remarkable processing flaws.

[Brief description of the drawings]

FIG. 1 shows a schematic structural diagram of a laser beam machine.

FIG. 2 shows the state of parameters during processing.

FIG. 3 shows an operation schematic diagram before loading according to the present invention.

FIG. 4 is a schematic diagram showing the operation of the present invention when loading.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cutting surface 2 Processing head 3 Assist gas 4 Cooling water 5 Condensing lens 6 Laser beam 7 Melted and scattered object 8 Focal length of a condensing lens (f) 9 Nozzle height (g) 10 Defocus distance (fd) 11 Tube material 12 Beam absorber

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-57-9590 (JP, A) JP-A-5-205678 (JP, A) JP-A-56-1289 (JP, A) JP-A-1 228695 (JP, A) Japanese Utility Model 60-46983 (JP, U) Japanese Utility Model Hei 1-177088 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B23K 26/00-26 / 18

Claims (1)

(57) [Claims] 1. A laser for machining, such as cutting or drilling with an industrial laser, for facilitating machining by avoiding scratches on the inner wall of the material due to a laser beam inserted into the inside of the tube and passing through the thickness of the material. .A beam absorbing material that absorbs and annihilates the beam, and the beam absorbing material includes three quarters of the inner diameter of the tube.
A beam absorber used for laser processing of a tube using an unsintered insulator of magnesium oxide whose main component has a considerable outer diameter.