JP2010110799A - Apparatus and method for machining hard and brittle material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve such problems that, when machining a hard and brittle material, i.e., a hard-to-work material such as cemented carbide and diamond, the material is broken by the buckling and cannot be machined in the mechanical finish by polishing or grinding when the shape is slender, and that an optional fore end shape is hardly formed in a non-contact machining method. <P>SOLUTION: An optional fore end shape is formed by applying femtosecond laser beam via an optical system including a condensing lens while rotating and moving an object to be machined consisting of a hard and brittle material. Further, the finish surface roughness of the object can be controlled by changing the ellipticity of the femtosecond laser beam by operation of the optical system. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a processing apparatus and a processing method for hard and brittle materials such as cemented carbide and diamond which are difficult to process materials.

Conventionally, when processing hard and brittle materials such as cemented carbide and diamond, which are difficult to process, linear processing by grinding and grinding, processing by a grinding die created in the processing shape, or focused ion of non-contact processing method Beam (FIB), ultrasonic processing, etching processing, and electric discharge processing have been used. However, in mechanical finishing, when the shape is elongated, there is a problem that it cannot be processed because it breaks due to buckling. In addition, there is a problem that it is difficult to produce an arbitrary tip shape by the non-contact processing method.

In general, a femtosecond laser, which is an ultra-short pulse laser, enables sub-micron fine processing inside a workpiece by a multi-photon absorption process without contact. Further, since the pulse width of the laser beam is very short compared with the time required for thermal diffusion at the time of energy injection, there is little thermal damage to the periphery of the processed portion, and non-thermal processing can be performed. Therefore, microfabrication with a femtosecond laser has been used to fabricate a new device having a three-dimensional structure.
Regarding processing on a workpiece using such a femtosecond laser, Japanese Patent No. 3283265 (see Patent Document 1), Japanese Patent No. 3824622 (see Patent Document 2), Japanese Patent Application Laid-Open No. 2005-210037 (Patent). Document 3) discloses a method of performing line or spot (drilling) processing on a metal material using a femtosecond laser.

Japanese Patent Laid-Open No. 2001-68899 (see Patent Document 4) discloses a method of forming a large number of hemispherical projections having a particle diameter of 1 μm to 100 μm on the surface of a refractory metal plate such as tungsten using a femtosecond laser. It is disclosed. However, none disclose a technique for processing the tip of a hard and brittle material such as cemented carbide or diamond into an arbitrary shape.
Japanese Patent No. 3283265 Japanese Patent No. 3824622 JP 2005-210037 A JP 2001-68899 A

As mentioned above, as a method for easily processing hard-brittle materials such as hard metal and diamond, which are difficult to process, processing by linear processing by grinding or grinding, or by grinding dies created in processed shapes, etc. It had been.
However, the spherical processing using the above-described processing method to the convex end portion 142 of the hard brittle material 141 made of cemented carbide having a slender length of 1 μm to 1000 μm as shown in FIG. 14 is easy to break. It was very difficult.

In addition, in the prior art relating to processing of a workpiece using a femtosecond laser, there is no description regarding processing of hard and brittle materials such as cemented carbide and diamond.

The present invention has been proposed in view of such a situation. A tip of a hard and brittle material such as cemented carbide or diamond, for example, a minute spherical convex portion having a radius of curvature of 1 μm to 1000 μm can be easily and The present invention provides a processing apparatus and a processing method for a novel hard and brittle material that is processed with high accuracy.

  The invention described in claim 1 includes a rotating means for rotating a workpiece made of a hard and brittle material, a triaxial moving means for moving the rotating means in three axial directions, and a condenser lens on the workpiece. Laser irradiation means for irradiating a femtosecond laser via an optical system, and the optical system determines the ellipticity of the femtosecond laser when the workpiece is irradiated to the finished surface of the workpiece. It is a hard and brittle material processing apparatus provided with the means to change according to roughness.

According to a second aspect of the present invention, in the hard and brittle material processing apparatus according to the first aspect of the invention, the optical system can adjust the ellipticity in a range of 0 to ± 1.

According to a third aspect of the present invention, in the hard and brittle material processing apparatus according to the first or second aspect, the rotating means controls the circumferential speed of the object to be processed within a range of 0.01 mm / second to 100 mm / second. It is possible.

According to a fourth aspect of the present invention, in the hard and brittle material processing apparatus according to any one of the first to third aspects, the hard and brittle material is diamond or a cemented carbide.

The invention according to claim 5 is an end portion of a hard and brittle material which is irradiated with femtosecond laser light while rotating and moving a workpiece made of a hard and brittle material, thereby processing the end portion of the workpiece into a convex shape. A method for processing an end portion of a hard and brittle material, characterized in that the ellipticity of the femtosecond laser applied to the workpiece is adjusted according to the finished surface roughness.

The invention according to claim 6 is the method of processing an end portion of the hard and brittle material according to claim 5, wherein the end portion of the hard and brittle material is previously processed into a desired shape by grinding or polishing. And

A seventh aspect of the invention is characterized in that the ellipticity is in the range of 0 to ± 1 in the end portion processing method of the hard and brittle material according to the sixth or seventh aspect.

The invention according to claim 8 is the method of processing an end portion of the hard and brittle material according to any one of claims 5 to 7, wherein the shape of the end portion is processed into a spherical shape with a radius of curvature of 1 μm to 1000 μm. It is characterized by.

The invention according to claim 9 is the method for processing a hard and brittle material according to any one of claims 5 to 8, wherein the hard and brittle material is diamond or a cemented carbide.

According to the present invention, a minute spherical convex portion having a tip curvature radius of 1 μm to 1000 μm, for example, can be processed with high accuracy at the end portion of the hard and brittle material.
Further, the hard and brittle material whose end portion is processed according to the present invention can be used for terminals of various measuring instruments, micro tools for processing, and the like.

A hard brittle material processing apparatus and this processing method according to the present invention will be described below in detail with reference to the accompanying drawings.
The drawings show an embodiment relating to a processing apparatus and processing method for hard and brittle materials such as cemented carbide and diamond of the present invention. FIG. 1 is a schematic diagram showing the stage of tip processing of a hard and brittle material, FIG. 2 is a schematic diagram of a femtosecond laser processing apparatus, FIG. 3 is a plan view of a lathe apparatus attached to the femtosecond laser processing apparatus and used for processing, FIG. Is a block diagram of a lathe device, FIG. 5 is an enlarged photograph when the end of a round bar of cemented carbide is processed into a spherical shape, FIG. 6 is a three-dimensional observation image by a laser microscope when viewed from the direction of the arrow in FIG. 7 is a cross-sectional shape in the XY coordinates shown in FIG. 5, FIG. 8 is a cross-sectional shape in which a part of FIG. 7 is enlarged, FIG. 9 is a surface roughness of a hemispherical portion of cemented carbide, and FIG. 11 shows the relationship between the ellipticity indicating the degree of polarization and the surface roughness of the processed part of the cemented carbide, FIG. 11 is an enlarged photograph of the spherical part obtained by processing the end of the square of the diamond into a spherical shape, and FIG. 12 is a cross section taken along the XY coordinates shown in FIG. Fig. 13 shows the surface roughness of the hemispherical part of Fig. 12 A.

FIG. 1 shows one embodiment of a processing stage according to a processing method of a hard and brittle material such as a cemented carbide or diamond according to the present invention. The rotating body 11 of a hard and brittle material such as cemented carbide or diamond is processed into a conical shape having a tapered surface 12 having a predetermined angle obtained by cutting the head 13 in advance. The pre-processing may be performed by grinding or polishing.

While rotating the rotating body 11 of a hard and brittle material such as a hard metal or diamond pre-processed in this way, for example, a round bar, the tip is irradiated with a femtosecond laser, and the curvature radius of the tip is 1 μm to 1000 μm. A spherical shape 14 having a curved surface is formed. The femtosecond laser irradiation is to sequentially scrape a predetermined thickness while rotating a rotating body 11 of a hard and brittle material such as a cemented carbide or diamond using a lathe described later.

The action of the femtosecond laser is removal processing by laser ablation on the surface portion of the rotating body 11 of a hard and brittle material such as cemented carbide or diamond, and performs extremely high precision processing on a very small workpiece. Can do. Laser ablation means the removal of the solid surface by laser irradiation.

The removal speed of the workpiece surface by femtosecond laser varies depending on the laser fluence. Laser fluence refers to the amount of energy per unit area and is expressed in J / cm ² or W / cm ² . The greater the laser fluence, the greater the amount removed by laser ablation and the greater the amount of plasma generated. The larger the laser fluence, the greater the influence on the points other than the condensing processing point, so that the surface roughness of the processed part deteriorates. Therefore, there is an appropriate laser fluence regarding the processing speed and processing accuracy.

FIG. 2 shows an outline of a femtosecond laser processing apparatus, and FIG. 3 shows an outline of a lathe apparatus used for lathe processing using a femtosecond laser.
In FIG. 2, the femtosecond laser processing apparatus used in the present invention includes a lathe apparatus 21 to which a rotating body 11 of a hard and brittle material such as cemented carbide or diamond is attached, and a lathe apparatus 21 mounted thereon and moves in the xyz axis direction. The three-axis orthogonal electric linear stage 22 made possible, and a rotating body 11 of a hard and brittle material such as cemented carbide or diamond held by a lathe device 21 on the three-axis orthogonal electric linear stage 22 via an optical system 23. A collection disposed between a femtosecond laser light source 24 for irradiating a femtosecond laser, and a rotating body 11 of a hard and brittle material such as cemented carbide or diamond held by the optical system 23 and a three-axis orthogonal electric linear stage 22. And an optical lens 25.
The optical system 23 has a configuration in which an optical axis is changed by a mirror 26 and a polarization type attenuator 27, a polarizing element (λ / 4 wavelength plate) 28, and a neutral density filter 29 are arranged. By adjusting the polarization type attenuator 27 and the neutral density filter 29, the laser fluence can be changed. Further, the polarization state of the laser beam can be changed by adjusting the polarization element 28.
Polarized light refers to light in which the vibration direction of light, that is, the intensity of light is not uniform and is always limited to a certain plane. Polarized light can be classified into linearly polarized light, elliptically polarized light, and circularly polarized light. Linearly polarized light is when the vibration (intensity) of light is limited to a straight line on a plane perpendicular to the optical axis. Circularly polarized light refers to a case in which the vibration (intensity) of light is always constant on a plane perpendicular to the optical axis and a circle is drawn. The elliptically polarized light is a case where an ellipse whose light vibration (intensity) is intermediate between linearly polarized light and circularly polarized light is drawn. The ellipticity indicates the ratio between the major axis and the minor axis of elliptically polarized light. From this, when the ellipticity is 0, linearly polarized light, when the ellipticity is ± 1, circularly polarized light, and the intermediate ellipticity is elliptically polarized light. Here, ± corresponds to the case where + is clockwise, and the case where − is counterclockwise.

FIG. 3 shows an apparatus configuration of the lathe apparatus 21. The lathe device 21 is provided on a PC-controlled three-axis orthogonal electric linear stage 22, and positioning control in the xyz direction is possible.
In FIG. 3, a lathe device 21 of an independent control system is mounted on a three-axis orthogonal electric linear stage 22 for processing a round bar. That is, the lathe device 21 is composed of a brushless DC motor 31 and a spindle 32, both of which are transmitted power by pulleys 33, 33 projecting from the end in the same direction and a flat belt 34 connecting them.
In the figure, reference numeral 35 denotes a chuck for holding a workpiece attached to the tip of the spindle 32.

FIG. 4 is a diagram showing an optical path from when the femtosecond laser beam is converged by the condensing lens 25, condensed at the tip of the rotating body 11 attached to the chuck 35 at the end of the spindle 32, and removed.
If the structure as described above is employed, the rotating body 11 made of a hard and brittle material such as a cemented carbide or diamond, which is a workpiece, can be processed with very high accuracy.

A femtosecond laser processing apparatus having a pulse width of 90 fs (femtosecond), a maximum laser fluence of 3.6 W / cm ² , a wavelength of 800 nm, and an oscillation frequency of 1 kHz was used.
As specific processing conditions, the laser fluence in the femtosecond laser processing apparatus having the above specifications is 530 mW / cm ² , and a cemented carbide that is a workpiece is used by using a 5 × objective condensing lens (focal length 36 mm). Processing was performed with the rotational speed of the alloy rotating body set to 7.8 rpm.
In addition, the xy electric stage was scanned so that the laser condensing point of the lathe device 22 and the xy plane including the machining axis were the same.

As shown in FIG. 1, the machining procedure includes a cone having a tapered surface 12 of a predetermined angle obtained by cutting the head 13 by grinding or polishing at the tip of a rotating body 11 made of cemented carbide that has been machine-finished. The shape is processed and attached to the chuck 35 of the lathe device 21. Then, the brushless DC motor 31 is driven to rotate the spindle 32, and the tapered surface 12 at the tip of the rotating body 11 rotating at a predetermined speed is irradiated with a femtosecond laser to remove the surface so that it becomes spherical. processed.
Specifically, as the rotating body 11, a tip portion of a polished round bar having a diameter of 1.0 mm and a length of 30 mm, about 5 mm, was ground in advance to a diameter of 0.6 mm, and the tip portion was spherically processed.
Note that the shape of the processed sample of the rotating body 11 was observed with a confocal laser microscope.

FIG. 5 shows an external appearance of a sample processed by the lathe device 21. It can be confirmed that the tip of the rotating body 11 is processed into a spherical shape. The diameter of the tip sphere was φ400 μm.
FIG. 6 shows a three-dimensional observation image of the spherical portion viewed from the observation direction indicated by the arrow in FIG. From this figure, it is confirmed that it is processed into a roughly spherical shape.

Next, FIG. 7 shows the relationship between the distance in the X direction and the height in the Y direction at the center of the sphere indicated by the XY coordinates in FIG. FIG. 8 is an enlarged view of a part of FIG.
FIG. 9 shows the arithmetic average roughness Ra specified by JIS of the surface obtained from FIG. 6 (the total including the portion obtained by folding the portion of the cross section appearing below the average line of the extracted portion of the cross section with the average line) The value obtained by dividing the area by the reference length is expressed in μm), and the error line is the standard deviation (the number of measurements is 5). From FIG. 9, the arithmetic average roughness Ra of the surface is about 0.6, which satisfies the surface roughness of the superfinished surface.

The ellipticity of the laser beam affects the surface roughness of the sphere.
FIG. 10 shows the relationship between the ellipticity of the laser beam and the surface roughness. From the figure, it can be seen that the surface roughness is the largest for linearly polarized light with an ellipticity of 0, the surface roughness decreases as the ellipticity increases, and the surface roughness is the smallest for circularly polarized light with an ellipticity of +1. The result corresponding to FIG. 10 was also obtained when the ellipticity was negative.

FIG. 11 shows an enlarged photograph of an example in which spherical processing is applied to the diamond end using the same processing apparatus as in Example 1 above. The diameter of the sphere at the tip of the diamond is about 870 μm and is processed into a spherical shape. The processing conditions and processing procedures at this time are the same as those of the cemented carbide of Example 1, except that the laser fluence is 710 mW / cm ² .

Next, FIG. 12 shows the relationship between the distance in the X direction and the height in the Y direction at the center of the sphere indicated by the XY coordinates in FIG.
FIG. 13 shows the arithmetic average roughness Ra of the surface obtained from FIG. 11, and the error line is the standard deviation (the number of measurements is 5). From FIG. 13, the arithmetic average roughness of the surface is Ra = 1.1, which satisfies the surface roughness of the superfinished surface.

In the above embodiment, the processing conditions of the femtosecond laser processing apparatus are shown as those with a pulse width of 90 fs, a maximum laser fluence of 3.6 W / cm ² , a wavelength of 800 nm, and an oscillation frequency of 1 kHz. However, the processing conditions are limited to these conditions. It is not something.
In addition, the laser fluence in the femtosecond laser processing apparatus having the above specifications is 530 mW / cm ² or 710 mW / cm ² , and a cemented carbide which is a workpiece using a 5 × objective condenser lens (focal length 36 mm). And the rotation speed of the diamond rotating body was 7.8 rpm, but the processing conditions should be changed as appropriate depending on the material of the hard and brittle material rotating body 11 that is the workpiece, the required accuracy, and the like. Can do.

As shown and described above, according to the present invention, according to the processing apparatus and processing method for cemented carbide and diamond, which are hard and brittle materials, any cemented carbide or diamond rotating body can be used for any purpose. Can be applied.

For example, the processing apparatus and processing method for cemented carbide and diamond of the present invention are suitable for processing applications such as pressure terminals of hardness testers, other fine terminals, and micro tools for processing various metals. It is possible to use.

It is the schematic which shows the cemented carbide alloy and diamond processing apparatus of this invention, a machine finishing surface, and a laser processing surface. It is the schematic which shows the outline of a femtosecond laser processing apparatus. It is a top view of the lathe apparatus used for a process. It is a related figure of the to-be-processed object attached to the lathe apparatus, and the condensed laser. It is the optical microscope image which processed the round bar end of the cemented carbide into a spherical shape. 6 is a three-dimensional observation image by a laser microscope viewed from the direction of the arrow in FIG. 5. 6 is a cross-sectional shape in the XY coordinates of the center of the sphere in FIG. It is the cross-sectional shape obtained by enlarging a part of FIG. It is the surface roughness in the processing spherical surface of FIG. The relationship between the ellipticity of the laser (degree of polarization) and the processed surface roughness in the cemented carbide is shown. It is an optical microscope image of the spherical surface of a diamond edge part. It is a cross-sectional shape in the XY coordinates of the sphere center part of FIG. It is the surface roughness of the processed spherical surface of FIG. It is the schematic of the conventional elongate processed cemented carbide tip part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Rotating body 12 Tapered surface 13 Head 14 Spherical shape 21 Lathe device 22 Three-axis orthogonal type electric linear stage 23 Optical system 24 Femtosecond laser light source 25 Condensing lens 26 Mirror 27 Polarization type attenuator 28 Polarization element (λ / 4 wavelength plate )
29 Neutral density filter 31 Brushless DC motor 32 Spindle 33, 33 Pulley 34 Flat belt 35 Chuck 141 Slender cemented carbide workpiece 142 Convex end

Claims (9)

A rotating means for rotating a workpiece made of a hard and brittle material;
Triaxial moving means for moving the rotating means in three axial directions;
Laser irradiation means for irradiating a femtosecond laser through an optical system including a condenser lens on the object to be processed;
The optical system includes means for changing an ellipticity of the femtosecond laser when the workpiece is irradiated in accordance with a finish surface roughness of the workpiece. Processing equipment.   The hard and brittle material processing apparatus according to claim 1, wherein the optical system is adjustable in the ellipticity range of 0 to ± 1. The hard and brittle material processing apparatus according to claim 1, wherein the rotating means is capable of controlling a circumferential speed of the processing object within a range of 0.01 mm / second to 100 mm / second. 4. The hard / brittle material processing apparatus according to claim 1, wherein the hard / brittle material is diamond or a cemented carbide. An end processing method for a hard and brittle material that irradiates femtosecond laser light while rotating and moving a processing target made of a hard and brittle material, and processing the end of the processing target into a convex shape,
A method for processing an end portion of a hard and brittle material, wherein the ellipticity of the femtosecond laser irradiated to the workpiece is adjusted according to the finished surface roughness.   6. The method for processing an end portion of a hard and brittle material according to claim 5, wherein the end portion of the hard and brittle material is previously processed into a desired shape by grinding or polishing. The method for processing an end portion of a hard and brittle material according to claim 6 or 7, wherein the ellipticity is in a range of 0 to ± 1. The method of processing an end portion of a hard and brittle material according to any one of claims 5 to 7, wherein the shape of the end portion is processed into a spherical shape with a radius of curvature of 1 µm to 1000 µm.   The method for processing a hard and brittle material according to claim 5, wherein the hard and brittle material is diamond or a cemented carbide.