JP3544601B2 - Ultra-precision cutting method for crystalline materials - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ultra-precision cutting method for a crystal material, and more particularly to a method for performing high-precision, high-quality and low-cost surface processing of a ZnSe lens or the like used as an optical component for laser.
[0002]
[Prior art]
The surface of a ZnSe lens or the like used in a laser processing apparatus is subjected to ultra-precision cutting (single-point diamond turning, commonly called SPDT processing) using a single crystal diamond tool having a negative rake angle of 35 to 45 degrees. Are made.
[0003]
The SPDT processing is capable of performing aspherical processing and has a short processing time, and is superior to the polishing processing in terms of multi-quality support and securing high precision.
[0004]
[Problems to be solved by the invention]
As shown in FIG. 3, the conventional single-crystal diamond tool used for the SPDT processing has a very sharp cutting edge of the cutting blade 2. The sharp cutting edge is apt to be broken due to the fact that the single crystal diamond 1 itself is small and brittle, and the tool life is short. Therefore, it is difficult to process a large-diameter part having a large processing area by the conventional method using such a cutting tool. In addition, roughing → semi-finishing (this is performed as necessary) → bite replacement is required at each stage of finishing, which increases tool cost and replacement time (1-2 hours / time), resulting in increased processing cost. .
[0005]
In addition, the amount of one cut cannot be increased to protect the cutting edge, and cutting with a minute cut of 1 μm or less is repeated, so that the processing time becomes longer and the processing phenomenon becomes unstable. If the processing phenomenon is not stable, the surface roughness becomes coarse, clouding also occurs, and the optical characteristics of the component deteriorate. Since the performance of the laser processing apparatus depends on the characteristics of the optical components, high-precision and high-quality optical components are required. In this respect, the conventional SPDT processing lacks adequacy.
[0006]
An object of the present invention is to solve the above-mentioned various problems in the SPDT processing of ZnSe or the like.
[0007]
[Means for Solving the Problems]
In order to solve the above problems, in the present invention, a rake angle is set to -20 to 20 degrees, a relief angle is set to 5 to 10 degrees, and a cutting edge has a width of 0.5 to 2 μm. A chamfered single crystal diamond tool is used. In addition, the feeding of the cutting tool is repeated to perform the processing from roughing to finishing with one cutting tool. Furthermore, the depth of cut in rough processing is 5 to 10 μm, the depth of cut in finish processing is 1 to 5 μm, and two or more crystal materials are continuously processed based on the same processing program with one cutting tool. I do.
[0008]
A ZnSe optical component made by using such a processing method has no cloudiness and scratches, and can have a surface roughness of 2 to 3 nmRa.
[0009]
In addition, a laser processing apparatus using this high-precision, high-quality ZnSe optical component as a reflecting mirror or a condensing lens can reduce the converging spot diameter as much as possible to increase the energy density of the laser beam at the focal position. Speeding up the processing and improving the processing quality.
[0010]
[Action]
According to the present invention, the edge of the single crystal diamond tool is chamfered to suppress the chipping of the edge. In addition, by setting the chamfer width of the cutting edge to 0.5 to 2 μm, the sharpness of the cutting edge is also maintained, and both long tool life and good sharpness are achieved.
[0011]
In addition, the rake angle of the cutting blade is set to -20 degrees or more and 20 degrees or less to facilitate the discharge of chips and to increase the strength of the cutting edge.
[0012]
Further, by setting the clearance angle to 5 ° to 10 °, the appropriate contact between the machined surface and the flank of the cutting tool is made smooth while giving appropriate pressure to the created machined surface, and the finish of the machined surface is improved.
[0013]
With the above measures, it is possible to increase the depth of cut and increase the amount of processing with one cutting tool.
[0014]
Therefore, roughing → (medium finishing →) finishing is performed with one tool without changing tools, and the time required for setup (tool replacement, various adjustments) at each stage is greatly reduced.
[0015]
Further, the machining time is shortened by increasing the depth of cut in the roughing process to 5 μm or more, while the depth of cut is reduced to 1 to 5 μm in the finishing process to ensure high-quality finishing accuracy and shorten the processing time.
[0016]
Furthermore, by continuously processing two or more crystal materials with one tool, it is possible to shorten the time for tool replacement, adjustment, re-creation of machining programs, etc. Elimination), the elimination of the effects of individual differences in bite quality, the elimination of human errors, and the reduction of the load on the processing equipment.
[0017]
The ZnSe optical component processed by such a method has no defects (scratch, clouding, etc.) on the surface, is high quality, and has enhanced functions realized by using various surface shapes such as flat, spherical, and aspherical surfaces. .
[0018]
Further, the laser processing apparatus using the ZnSe optical component has improved performance and reliability due to high quality and excellent optical characteristics of the optical component. In particular, there is no change in the processing characteristics associated with the replacement of a worn optical component.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows the shape of the cutting edge of a single crystal diamond tool used in the present invention. 1 is a single crystal diamond, 2 is a cutting edge attached to the diamond, 3 is a chamfer for removing the edge of the cutting edge, 4 is a rake face, 5 is a flank, and 6 supports the single crystal diamond 1. It is a metal. The base metal 6 is provided as needed.
[0020]
R in FIG. 1A is a nose radius of the cutting edge portion, α in FIG. 1B is a rake angle, β is a clearance angle, and W is a chamfer width of a cutting edge, where R = 1.5 mm and α = 0 °, β = 7 °, and W = 0.8 μm.
[0021]
Reference numeral 8 in FIG. 2 denotes a cutting tool constituted by fixing the single crystal diamond 1 having the cutting edge shape of FIG. In the present invention, the single-crystal diamond tool 8 is cut into the rotating crystal material A by feeding, and the tool is repeatedly fed from the outer diameter portion to the center portion of the material, thereby cutting at the time of roughing and finishing. The rough machining to the finishing machining are performed with the same one bite by changing the amount.
[0022]
Also, a plurality of crystal materials are processed using the same cutting tool without changing the conditions. Hereinafter, specific examples of the processing will be described.
[0023]
-Example 1-
Five ZnSe polycrystals (CVD material) having a diameter of 50 mm and a plate thickness of 5 mm were prepared, and the nose radius R was 1.5 mm, the rake angle α was 0 °, the clearance angle β was 7 °, and the bevel was chamfered. It was processed with a single crystal diamond tool having a width W = 0.8 μm. One byte was used. The ZnSe polycrystal was replaced by a second unprocessed product after the completion of the first process, and finished up to the finish under the same conditions based on the same processing program as the first process, and this method was repeated.
The processing conditions were as follows.
Processing surface shape: Plane processing conditions Roughing: 2000 rpm, feed 5 mm / min, depth of cut 10 μm
Semi-finished: 〃 〃, ２．５2.5 mm / min, 〃5 μm
Finish: 〃 〃, 〃 〃, 〃 1μm
The properties of the processed surface obtained by the above processing were as follows.
Surface roughness: 2-3 nmRa
Finish: No cloudiness or scratches Surface accuracy: 0.5 μm or less.
[0024]
Example 2
The single-crystal diamond tool used in Example 1 was continuously used without replacement, and an aspheric ZnSe lens having a diameter of 50 mm, a thickness of 4 mm, and a focal length of 127 mm was processed. This processing is performed on the ZnSe polycrystal which has been flattened on one side in Example 1, and the other surface of the polycrystal is processed into a convex aspheric surface to finish the lens. The processing conditions were the same as in Example 1.
The convex aspheric surface obtained by this processing is
Surface roughness: 2-3 nmRa
Surface accuracy: 0.5 μm or less Wavefront aberration: 1 μm or less, and the quality was very good, like the plane on the opposite side.
[0025]
Further, in the aspheric ZnSe lens obtained through the processing of Examples 1 and 2, it was confirmed by a laser light focusing test that the focused spot diameter was almost reduced to the diffraction limit.
[0026]
Example 3
One bite of the same ZnSe polycrystal that was processed in Example 1 under the same conditions as in Example 1 except that the cutting depth was changed to 1.5 μm (specifications were the same as those of Example 1) As a result, almost the same results as in Example 1 were obtained. The results when the cutting depth of the finishing was 3 μm and 5 μm were almost the same.
[0027]
The present invention is also effective for processing a crystal for an optical component other than ZnSe.
[0028]
【The invention's effect】
According to the method of the present invention described above, the life of the tool is extended by improving the tool used. For example, in the SPDT processing of a ZnSe lens, the number of work pieces that can be processed when using a conventional bite is one per bite, whereas in the present invention, ten or more lenses can be processed with one bite, thereby increasing the magnification by 10 times. The above life was shown.
[0029]
In addition, the cutting time is greatly reduced by improving the cutting tool to increase the depth of cut in the rough machining, and by improving the machining procedure to reduce setup changes and the like.
[0030]
In addition, the chamfer width is limited for strengthening the cutting edge, the clearance angle is set so that pressure can be applied to the machined surface without difficulty, and the continuous machining of multiple crystal materials with a single cutting tool increases the accuracy and quality of the machined surface. And the reliability of processing is improved.
[0031]
In addition, cutting costs are also reduced due to reductions in tool costs and processing time.
[0032]
Further, the ZnSe optical component processed by the method of the present invention has excellent optical characteristics and improves the performance and reliability of a laser processing device and the like.
[Brief description of the drawings]
1A is a plan view showing the shape of a cutting edge of a single-crystal diamond tool used in the method of the present invention; FIG. 2B is a side view of the cutting edge of the same tool; FIG. FIG. 3 is a side view of a cutting edge of a polycrystalline diamond tool used in a conventional method.
DESCRIPTION OF SYMBOLS 1 Single crystal diamond 2 Cutting edge 3 Chamfered part 4 Rake face 5 Flank 6 Base metal 7 Holder 8 Single crystal diamond tool R Nose radius α Rake angle β Relief angle W Chamfer width A of cutting edge Crystal material

Claims (1)

As a working tool, a single-crystal diamond tool having a rake angle of -20 to 20 degrees, a clearance angle of 5 to 10 degrees, and a beveled edge having a width of 0.5 to 2 μm is used. The feed is repeated to perform roughing to finishing with a single cutting tool. The cutting depth in roughing is 5 to 10 μm, and the cutting depth in finishing is 1 to 5 μm. An ultra-precision cutting method for a ZnSe crystal material used for an optical component for laser, wherein two or more crystal materials are continuously processed by a cutting tool based on the same processing program.

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