JPS6390379A - Groove machining method for ceramic - Google Patents

Abstract

PURPOSE:To perform accurate groove machining without increasing the depth and width of a formed groove by adjusting the focusing position of a laser beam projected on the surface of a ceramic member and moving the laser beam and ceramic part relatively in the axial directions. CONSTITUTION:The ceramic member (silicon nitride, etc.) 1 is rotated around an axis X. The surface of said member 1 is irradiated with, for example, CO2 laser beam A from above through a condenser lens 2 so that the irradiation direction accords with the tangential direction. Then, the laser beam is moved so that the focusing position Y of the laser beam A moves away from the axis X by a specified offset angle theta. Therefore, even if the surface temperature of the ceramic member 1 rises according to machining, the heat value at the irradiation position is held constant because of a decrease in the irradiation energy. The fused body of ceramic is blown away with the laser beam A. This method reduces an error in the size of the formed groove and provides the accurate machining.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for forming grooves on the surface of a columnar silicon nitride-based ceramic member, and particularly relates to measures for improving groove processing accuracy.

(Prior Art) Ceramics have recently been widely used in various industrial fields because they have high high-temperature strength and excellent thermal shock resistance. As a method for processing the surface of a ceramic member, electric discharge machining 1 machining and the like have been generally employed.

On the other hand, for example, as disclosed in Japanese Patent Application Laid-Open No. 55-45593, a laser beam is irradiated onto the surface of the workpiece while the workpiece is rotated around its axis, and the irradiated area is melted. A method of forming stepped portions having partially different diameters is known.

(Problems to be Solved by the Invention) However, in the former conventional method, if the ceramic is silicon nitride-based, the electric discharge machining cannot be performed because silicon nitride is insulating. In addition, silicon nitride ceramic is a difficult-to-process material, so it is generally machined using a Guiemondo grindstone, but since there are restrictions on the shapes that can be machined, it is difficult to process it into complex shapes, or in particular, with high dimensional accuracy such as thread cutting. It is unsuitable for groove machining that requires.

Therefore, when performing groove processing that requires high dimensional accuracy, such as thread cutting as described above, on a columnar silicon-based ceramic member, the conventional latter method described above is adopted. While rotating the ceramic member around its axis, a laser beam is irradiated and scanned on the surface of the ceramic member, and the irradiation energy is used to melt and melt the beam irradiated area of the ceramic member.
It is conceivable to perform groove processing such as thread cutting on the surface of the silicon nitride ceramic member by sublimation.

However, in the groove machining method using a laser beam as described above, the surface temperature of the ceramic member increases as the machining progresses. As a result of the increased thermal mass at the irradiated area compared to the previous beam irradiation, the depth and width of the grooves formed on the ceramic surface gradually increase from the initial stage to the final stage of beam irradiation, making it impossible to precisely process the grooves. is necessary.

The present invention has been made in view of the above, and an object of the present invention is to apply a laser beam to the columnar silicon nitride ceramic member when groove processing such as thread cutting is performed on the surface of the columnar silicon nitride ceramic member as described above. By controlling the amount of beam irradiation energy to vary from the beginning to the end of beam irradiation, even if the surface temperature of the ceramic member increases as the HO process progresses, the irradiation area remains stable from the beginning to the end of beam irradiation. The heat content can always be kept constant, and as a result, the depth and width of the grooves formed on the surface of the ceramic member do not gradually increase from the beginning to the end of beam irradiation, making it possible to form grooves with high precision. It's about trying to get it.

(Means for Solving the Problems) In order to achieve the above object, the solving means of the present invention is directed to a method of forming grooves on the surface of a columnar silicon nitride ceramic member. A laser beam is irradiated onto the surface of the ceramic member while it is being rotated around its axis so that the irradiation direction is tangential, and the beam focusing position of the laser beam and the ceramic member gradually moves away from the axis of the ceramic member. This method involves relatively moving the ceramic member in the axial direction.

(Function) With the above configuration, in the present invention, the laser beam is irradiated onto the surface of the ceramic member while the ceramic member is rotated around the axis so that the irradiation direction is tangential. In this case, the laser beam and the ceramic member are moved relative to each other in the axial direction of the ceramic member so that the beam focus position gradually moves away from the axis of the ceramic member, so that the surface temperature of the ceramic member increases as the machining progresses. Even if the irradiation energy of the laser beam on the ceramic member is reduced in proportion to the increased temperature, the heat d of the irradiated area remains constant from the beginning to the end of the beam irradiation. . Therefore, the depth and width of the grooves formed on the surface of the ceramic member do not gradually increase from the initial stage to the final stage of beam irradiation, so that groove processing can be performed with high precision.

(Example) Embodiments of the present invention will be described below based on the drawings.

Figures 1 and 2 show the case where the ceramic groove processing method according to the embodiment of the present invention is applied to thread cutting.To explain the processing procedure, first, the thread cutting target is 25 mm in diameter and 25 mm in length. A pressureless sintered silicon nitride ceramic member 1 consisting of 150 round bars is prepared. Then, the ceramic member 1 is set horizontally in a processing device (not shown), and while the ceramic member 1 is rotated around the axis X at a rotation speed of 7.96 rpm by the operation of the processing device, the surface of the ceramic member 1 is While irradiating the CO2 laser beam A with an output of 800 W from above through the condensing lens 2 so that the irradiation direction is tangential, it is parallel to the axis X of the ceramic member 1 in the direction of the axis from the state shown by the solid line in Figure 1. Scanning is performed to the state shown by the imaginary line in the figure.

As a feature of the present invention, as the CO2 laser beam A is moved in the direction of the axis X of the ceramic member 1, it is moved so as to gradually move away from the axis X by a predetermined offset angle θ.

Specifically, the offset angle θ is arbitrarily set depending on the thread shape such as the root diameter of the thread and the length of the threaded portion, and in this example, the offset angle θ is set to 5°. Also,
The beam feeding speed (scanning speed) of the above CO2 laser beam A is set to 7.96 s/mi, and this CO2
The laser beam A is passed through a condensing lens 2 whose focal length is set to 127 cm, and is directed toward the axial center from the surface of the ceramic member 1 corresponding to the threaded portion formation location, that is, from the shaft end.
The surface is irradiated over a distance of 5 cm. Simultaneously with the irradiation with this C02 laser beam A, argon gas as an assist gas is sprayed onto the surface of the ceramic member 1 at a gas pressure of 2.0 KI/cm to spray the ceramic melt melted by the C02 laser beam A. Make it fly. At this time, the condenser lens 2 is placed on the ceramic member 1 so that the beam focal position Y of the CO2 laser beam A is located at a predetermined distance Ω1, for example, 3 m, above the axis X of the ceramic member 1. Place it above.

Then, CO2L/
'ft,' - The optical axis C of the beam A is the initial position of the beam irradiation (the position shown by the solid line in Figure 1) and the final position of the beam irradiation (the position shown by the imaginary line in Figure 1) of the CO2L'-the beam A. The predetermined pressure 112 is offset radially outward by, for example, 0.5 m.

The finished state of the threaded part according to this embodiment <I>, which was threaded in this way, is shown at the offset 1lfl above.
Example in which z is set to 0.28 and 0.7 m, respectively (
Table 1 below shows the data compared with the machining finish state of a comparative example in which (In> and offset g2 are set to zero. (a) is the first one counting from the screw tip,
(b) indicates the 25th one, and (0> indicates the 50th one.) In general, the units of numerical values shown in Table 1 are m.

Table 1 As can be seen from this data, in Example (1), the maximum variation value of the thread diameter was 0.07 m, and the maximum variation value of the thread diameter was 0.
．． Although it was possible to cut a thread uniformly over the length of the screw section, which was as small as 12 m, in the comparative example, the maximum variation in the peak diameter was 0.78 m, and the maximum variation in the root diameter was large, at 2.19 m. Moreover, as thread cutting progresses, both the thread diameter and the root diameter become smaller, making it impossible to cut threads uniformly over the length of the threaded portion. This is because the offset g2 of the COz laser beam A is zero, so the surface temperature of the ceramic member increases as processing progresses, and the heat content of the irradiated area increases at the end of the beam irradiation compared to the beginning of the beam irradiation. This is because the depth and width of the thread grooves formed on the surface of the ceramic member 1 gradually increase as the beam irradiation progresses from the initial stage to the final stage.

In addition, in the example (I [>), the maximum variation value of the mountain diameter is 0.5
It can be seen that the maximum fluctuation value of the valley diameter is 1.50 rnM, which is smaller than that of the comparative example. However, as in the case of the comparative example, uniform thread cutting could not be performed over the length of the threaded portion. This is due to the fact that the offset 'M'J2 is smaller than that in Example (I).

Roughly speaking, in Example (III), the maximum variation value of the mountain diameter is 0.
．． 08M, the maximum variation value of the valley diameter is 0.99%, which is smaller than that of the comparative example and example (n), and is not much different from the example (I>); [
＞Contrary to the case above, as the thread cutting process progressed, both the crest and trough diameters increased. This is because the offset ll1D2 of the CO2 laser beam A is large, so that the irradiation energy of the CO2 laser beam A decreases as the machining progresses, particularly as it approaches the final stage of the machining.

In this way, the thread cutting accuracy will vary depending on the offset amount Ω2, but depending on the thread shape to be formed and the laser beam irradiation conditions, the UN offset m
This can be solved by setting H2.

In addition, in the above embodiment, CO2 is not applied to the ceramic member 1.
Although the laser beam A is moved, it is also possible to move the ceramic member 1 in the axial direction while rotating the ceramic member 1 with the CO2 laser beam A positioned at a fixed position. .

Further, in the above embodiment, a case where a thread cutting process is performed on a ceramic member is shown, but the invention is not limited to this. For example, in order to improve the heat resistance characteristics of some engine parts for vehicles such as automobiles, silicon-based ceramics are used. Needless to say, it can also be applied to all other types of groove processing, such as forming irregularities on the ceramic surface in advance to increase the bonding strength between the ceramic and the aluminum alloy when casting this with aluminum alloy. .

(Effects of the Invention) As described above, according to the present invention, the surface of a columnar silicon nitride ceramic member is irradiated with a laser beam while being rotated about its axis. In this case, the laser beam is irradiated in the tangential direction of the ceramic member, and the laser beam and the ceramic member are moved relative to each other in the axial direction of the ceramic member so that the beam focus position gradually moves away from the axis of the ceramic member. Therefore, even if the surface temperature of the ceramic member increases as processing progresses, the heat distribution of the irradiated area can be maintained constant from the initial stage to the final stage of beam irradiation. The grooves formed in the grooves have less dimensional error from the initial stage to the final stage of beam irradiation, so that groove processing can be performed with high precision.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the processing procedure when the ceramic groove processing method according to the embodiment of the present invention is applied to thread cutting, and FIG. 2 is a side view showing the positional relationship of the CO2 laser beam with respect to the ceramic member. 1...Ceramic member, A...CO2 laser beam, C...optical axis, X...axis center, Y...beam focal position, g2...offset amount, θ...offset angle. Two, one! Figure 1 Figure 2

Claims (1)

[Claims] (1) A method of forming grooves on the surface of a columnar silicon nitride ceramic member, in which the ceramic member is rotated around its axis and the surface is irradiated with a laser beam so that the irradiation direction is tangential. A method for machining grooves in ceramic, characterized in that the laser beam and the ceramic member are moved relative to each other in the axial direction of the ceramic member so that the beam focal position gradually moves away from the axial center of the ceramic member.