JPH0441090A - Laser drilling method - Google Patents

Abstract

PURPOSE:To improve laser processing quality by packing a mixture formed by dispersing a granular material which scatters a laser beam into a low melting material into the inner side of a hollow body and drilling the same. CONSTITUTION:The mixture composed of the low melting material 31, such as beeswax, and the granular material 32 having a light scattering property is packed into a turbine blade 30 and is heated from ordinary temp., by which the mixture is poured into the turbine blade 30; thereafter, the mixture is returned again to the ordinary temp. to solidify in the drilling of the turbine blade 30. The drilling angle is thereafter fixed to a prescribed value and the drilling is executed by irradiating with a laser beam 34. The neat hole free from sticking of process scrap is formed in this way and the stability of the processing is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Purpose of the Invention (Industrial Application Field) The present invention relates to a laser drilling method, and particularly to drilling of a hollow body.

(Prior Art) When drilling holes in a hollow body using a laser, a problem is how to deal with processing waste generated during drilling. This machining debris may adhere to the inner surface of the hollow body during machining, or may close the minute holes that have already been drilled on the opposite side. To deal with this, for example,
The method disclosed in Japanese Patent No. 133896 is known. That is, in this disclosed technology, a shielding body such as a rod is inserted into a hollow body to prevent problems caused by machining debris as a conventional technique, and in this technology, the shielding body is subjected to secondary processing using a laser and machining debris is generated. However, since the same problem as before the countermeasure occurs, we propose the technique shown in Fig. 3. In FIG. 3, the workpiece (10) is, for example, a small-diameter pipe with a circular cross section, and a condenser lens (I) is arranged at a predetermined distance from the workpiece. On the other hand, a laser beam (12) is irradiated from a laser oscillation device (not shown), and this laser beam (12) passes through a condensing lens (11).
Hole (13) to be drilled in the machining part of the workpiece (10)
The light is focused and irradiated with a size corresponding to the size. Further, a hole (13) is provided inside the workpiece (10).
) through which the laser beam (12) passes.
4a) is formed, and a tubular insert (14) is inserted to receive the laser light passing through the entrance portion (14a) as far away as possible. In the laser drilling process, processing waste adheres to the inner surface of the insert (14), eliminating the above-mentioned problem. However, there are cases where so-called molded bodies such as tubular bodies cannot be inserted. Figure 4 is JP-A No. 6
], In another conventional example disclosed in Japanese Patent No. 199590, when the tube (20) is cut by melting, a space is created inside the tube (20) above the tube body (20), and the particles of the refractory material ( 21) and irradiates a beam (22), such as a laser beam, along the fusing line to fuse it.

(Problem to be solved by the invention) Since granules are used, there is no restriction on the inner shape of the hollow body (or rather, in the process of drilling multiple holes throughout the hollow body, the granules are removed from the holes that have already been drilled). There was a problem in which processing debris adhered to the inner surface of the hollow body due to a lack of filled granules.

The present invention has been made in order to eliminate such problems, and it is an object of the present invention to provide a laser drilling method that can drill multiple holes throughout the hollow body without causing machining debris to adhere to the inner surface of the hollow body. This is the purpose.

[Structure of the invention] (Means and effects for solving the problem) In a laser drilling method for drilling a hole in the hollow body by irradiating the outer surface of the hollow body with a laser beam, the laser beam is scattered inside the hollow body. The above irradiation is carried out by filling a mixture in which granular materials are dispersed in a low melting point substance, and the portion irradiated with the laser light liquefies and scatters the laser light.

(Example) EMBODIMENT OF THE INVENTION Hereinafter, this invention will be explained based on drawing which shows an Example.

FIG. 1 shows an embodiment of the present invention, which is applied to drilling holes in turbine blades. In other words, (30) is a hollow body-shaped turbine blade which is a workpiece and has a dense layer inside.
A mixture of light-scattering granules (32) mixed with a low-melting substance (31) such as edema or paraffin is filled. In this example, the mixing ratio was set to be about 3 parts of the granules (32) to 3 INs of the low melting point substance.Although it is desirable that the ratio of the particulates be larger, the laser beam always 32) may be used.

(33) is a pulse laser oscillator installed at a predetermined location, and the output pulse laser beam (34) is reflected by a folding mirror (
35) and a condensing lens (36), the light is focused onto the outer surface of the turbine blade (30). The turbine plate (30) is fixed to an electromagnetic chuck (38) installed on the XY child table 37). XY
X drive source (38) and Y drive source (child table 37)
39) are each driven by a control signal from a scan control section (40). Further, the folding mirror (35) is supported so as to be angular, and is set at a predetermined angle by a driver (not shown). The particle size of the granules (32) need only be large enough to densely fill the hollow part of the turbine blade (30), and is usually selected from a particle size of several hundred to several tens of μm, and the material thereof is Pulsed laser light (
34) is selected from alumina ceramics, quartz, etc. in the case of YAG relay, and in the case of CO21 noser, it is selected from crystals of rhium chloride, zinc chloride, etc.

Heat the above mixture from room temperature to
0) After pouring it into the container, returning it to room temperature and solidifying it,
The drilling angle with respect to the turbine plate (30) is fixed at a predetermined value and the pulsed laser beam (34) is irradiated to perform drilling. With this irradiation, the hole (41) is simultaneously opened and the hole (4
1) The filled mixture is instantaneously irradiated with a pulsed laser beam (34) in the opening. The pulsed laser beam (34) irradiated on the mixture is scattered by the granules (32) in the mixture, and the energy density rapidly decreases, while the granules (32)
) itself absorbs light and becomes hot. At the same time, the low melting point substance (31) is evaporated into air, and the vapor is suddenly ejected from the machined hole (41). The holes (41) are successively drilled at predetermined positions by driving the XY child table 37).

It goes without saying that the workpiece may be a hollow body other than the above embodiments.

[Effects of the Invention] Since the energy density of the pulsed laser beam (34) is reduced by the scattering effect of the granules, the inner surface of the hollow body is not damaged. In addition, machining debris generated during drilling was expelled from the hole to the outside at once by the ejection of the low melting point substance (31). For this reason, the condensing lens (36) can be made to have a large depth of focus, and the pulsed laser beam (34)
The focusing distance has become longer, and it has become possible to form holes with good parallelism, where the openings at both ends of the hole have approximately the same diameter, and are clean and free of machining debris. Furthermore, since the mixture of the low melting point substance (31) and the granules (32) is solidified unless it is irradiated with the pulsed laser light (34), even if the already machined hole is placed on the lower side, the granules (32)
32) cannot flow out of this hole, for example, a plurality of mutually opposite holes (42a), (42b) on the side of the turbine blade (30) as shown in FIG.
It is now possible to perform stable processing without being hindered by laser light or processing debris.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram for explaining the present invention, FIG. 2 is a partially enlarged perspective view of a workpiece, and FIGS. 3 and 4 are sectional views showing a conventional example. (31), (32), (33), (36), low melting point substance, granular body ψ noggle thread, converging lens oscillator

Claims (1)

[Claims] In the laser drilling method of drilling a hole in the hollow body by irradiating the outer surface of the hollow body with a laser beam, the inside of the hollow body is filled with a mixture in which granules that scatter the laser beam are dispersed in a low melting point substance. A laser drilling method characterized by performing the above irradiation.