The present disclosure relates to a single-crystal diamond cutting tool. This application claims priority based on Japanese Patent Application No. 2020-005599 filed on Jan. 17, 2020. The entire contents of the description in this Japanese patent application are incorporated herein by reference.
Conventional single-crystal diamond cutting tools are disclosed in PTL 1 (Japanese Patent Laying-Open No. 2014 -012310) and PTL 2 (Japanese Patent Laying-Open No. 2006 -015412).
[PTL 1] Japanese Patent Laying-Open No. 2014-012310 [PTL 2] Japanese Patent Laying-Open No. 2006-015412
A single-crystal diamond cutting tool according to an aspect of the present disclosure is a single-crystal diamond cutting tool provided with a flank and a rake face, a cutting edge being provided at a boundary between the flank and the rake face, an inclined surface being provided at a location distant from the cutting edge, the inclined surface being contiguous to the rake face and inclined at 0.05 degrees or more and 80 degrees or less with respect to the rake face, the rake face having a roughness Ra of 1 µm or less, the cutting edge being provided with a chamfered surface or round honing having a width of 1 µm or less, the cutting edge having projections and depressions having a width of 100 nm or less and smaller than that of the chamfered surface or round honing.
Conventional single-crystal diamond cutting tools are required to have further increased service life in high-accuracy cutting.
According to the present disclosure, a single-crystal diamond cutting tool capable of cutting with high accuracy and having a long service life can be provided.
Initially, embodiments of the present invention will be enumerated and described.
A single-crystal diamond cutting tool according to an aspect of the present disclosure is a single-crystal diamond cutting tool provided with a flank and a rake face, a cutting edge being provided at a boundary between the flank and the rake face, an inclined surface being provided at a location distant from the cutting edge, the inclined surface being contiguous to the rake face and inclined at 0.05 degrees or more and 80 degrees or less with respect to the rake face, the rake face having a roughness Ra of 1 µm or less, the cutting edge being provided with a chamfered surface or round honing having a width of 1 µm or less, the cutting edge having projections and depressions having a width of 100 nm or less.
The single-crystal diamond cutting tool configured as described above has an inclined surface inclined at 0.05 degrees or more and 80 degrees or less with respect to the rake face and can thus have the rake face with roughness Ra of 1 µm or less. If the inclined surface has an inclination of less than 0.01 degrees, the inclination is too small and it is difficult to polish the rake face. If the inclined surface has an inclination exceeding 80 degrees, and the rake face is polished, the boundary between the inclined surface and the rake face will have a large roughness, and the rake face cannot have surface roughness of 1 µm or less.
Preferably, the rake face forms an angle of 0 degrees or more and 15 degrees or less with respect to a (110) plane. Within this range, the single-crystal diamond cutting tool has a particularly increased service life.
Preferably, the inclined surface has roughness Ra of 5 µm or less. When the inclined surface has a roughness of 5 µm or less, the rake face contiguous to the inclined surface will have small roughness, and the single-crystal diamond cutting tool has a long service life.
Preferably, the single-crystal diamond cutting tool provides a relief angle of 0 degrees or more and 30 degrees or less. Within this range, the single-crystal diamond cutting tool has a particularly long service life as the cutting tool can maintain the cutting edge’s strength while preventing the flank from coming into contact with a workpiece.
Rake face 10 has a roughness Ra of 1 µm or less. Roughness Ra of rake face 10 can be measured for example with a white light interferometer. When rake face 10 has roughness Ra exceeding 10 µm, a rough processed surface is provided, resulting in a reduced tool service life.
Rake face 10 is not particularly limited in plane orientation. Rake face 10 preferably forms an angle of 0 degrees or more and 15 degrees or less with respect to a (110) plane of single-crystal diamond 3. The most distal end portion of rake face 10 is a cutting edge 20. Cutting edge 20 has an arcuate shape in
Inclined surface 12 preferably has roughness Ra of 5 µm or less. When inclined surface 12 has a roughness of 5 µm or less, rake face 10 contiguous to inclined surface 12 will have small roughness, and single-crystal diamond cutting tool 1 will have a particularly long service life. Roughness Ra of rake face 10 can be measured for example with a white light interferometer.
Flank 11 has an angle θ2 (a relief angle) with respect to a direction in which a workpiece is moved, as indicated by an arrow 3a. Angle θ2 is not particularly limited. Relief angle θ2 can be measured with a projector.
Preferably, angle θ2 is 5 degrees or more and 25 degrees or less, more preferably 10 degrees or more and 20 degrees or less. Single-crystal diamond 3 has a lower surface with an angle θ3 with respect to the direction in which a workpiece is moved, as indicated by arrow 3a. Angle θ3 is not particularly limited.
Inclination angle θ1 can be measured with a white light interferometer. Relief angle θ2 and angle θ3 can be measured with a projector.
Chamfered surface 20c is formed by chamfering. Chamfered surface 20c is formed in an arcuate shape between first cutting edge 20a and second cutting edge 20b. Cutting edge 20 and chamfered surface 20c formed in an arcuate shape allow predetermined cutting performance to be exhibited even if a portion of cutting edge 20 coming into contact with a workpiece varies.
Chamfered surface 20c has the width in the
When cutting edge 20 is not arcuate and is for example instead square and the first cutting edge and the second cutting edge meet at the tip end, the chamfered surface’s width is defined by an average value in width of the chamfered surface in a cross section taken through the center of each of the first and second cutting edges and perpendicular to a direction in which the first and second cutting edges extend.
(1) A 3D-SEM set in 2D is used to observe cutting edge 20 in a direction perpendicular to rake face 10, as shown in
(2) Subsequently, a cross section of cutting edge 20 is obtained through the 3D-SEM at the location of dotted line 20g selected in step (1). It should be noted that this cross section indicates positional information of a surface of cutting edge 20, rake face 10 and flank 11, and does not include internal information of cutting edge 20. Chamfered surface 20c is imaged while the cross section is observed with the 3D-SEM.
(3) Subsequently, width L1 of chamfered surface 20c of each cross section is measured based on an image obtained in step (2).
(4) Subsequently, an average value of 10 points measured in step (3) is defined as width L1 of the chamfered surface.
(1) A 3D-SEM is used to image the cutting edge, as observed on the side of the tip of the cutting edge in a direction forming 45° with respect to rake face 10 and forming 45° with a direction perpendicular to rake face 10.
(2) A ridge line 220a of a portion of the boundary between flank 11 and chamfered surface 20c with no projections/depressions 200a observed serves as a reference. A curve 201a passing by an outermost projection of projections and depressions 200a and parallel to ridge line 220a is determined. A curve 202a parallel to ridge line 220a and passing by an innermost depression of projections and depressions 200a is drawn. The distance between the two curves 201a and 202a serves as a width of projections and depressions 200a. A ridge line 220b of a portion of the boundary between rake face 10 and chamfered surface 20c with no projections/depressions 200b observed serves as a reference. A curve 202b passing by an outermost projection of projections and depressions 200b and parallel to ridge line 220b is determined. A curve 201b parallel to ridge line 220b and passing by an innermost depression of projections and depressions 200b is drawn. The distance between the two curves 201b and 202b serves as a width of projections and depressions 200b.
(3) Measurement can be done in the above method as what has projections and depressions with a width of 10 nm or more can have the projections and depressions observed through a 3D-SEM. Projections and depressions having a width of less than 10 nm are unobservable. Therefore, it is determined that a size which is not observed as projections/depressions is less than 10 nm.
(4) The width of the projections and depressions is defined as an average value of both A1 of the boundary between rake face 10 and chamfered surface 20c and A2 of that between flank 11 and chamfered surface 20c, i.e., (A1 + A2)/2. That is, A1 and A2 obtained through calculation have the same value, that is, A1 = A2 = (A1 + A2)/2.
As shown in
(1) A 3D-SEM set in 2D is used to observe cutting edge 20 in a direction perpendicular to rake face 10 to randomly select ten points free of large chipping, similarly as done in the first embodiment.
(2) Subsequently, a cross section of cutting edge 20 is obtained through the 3D-SEM at each location selected in step (1). It should be noted that this cross section indicates positional information of a surface of cutting edge 20, rake face 10 and flank 11, and does not include internal information of cutting edge 20. Round honing 20h is imaged while the cross section is observed with the 3D-SEM.
(3) Subsequently, based on an image obtained in step (2), a circle 20R is formed at a portion overlapping round honing 20h, as shown in
(4) Subsequently, a radius R of circle 20R obtained in step (3) is measured. (5) Subsequently, width L2 of round honing 20h is determined from radius R obtained in step (4), and a cutter angle E of rake face 10 and flank 11.
(1) A 3D-SEM set in 2D is used to observe cutting edge 20 in a direction perpendicular to rake face 10 to randomly select ten points free of large chipping, similarly as done in the first embodiment.
(2) Subsequently, a cross section of cutting edge 20 is obtained through the 3D-SEM at each location selected in step (1). It should be noted that this cross section indicates positional information of a surface of cutting edge 20, rake face 10 and flank 11, and does not include internal information of cutting edge 20. Round honing 20h is imaged while the cross section is observed with the 3D-SEM.
(3) Subsequently, based on an image obtained in step (2), circle 20R is formed at a portion overlapping a tip portion of round honing 20h, as shown in
(4) Subsequently, radius R of circle 20R obtained in step (3) is measured. A radius line 402 is drawn from the center of circle 20R toward the boundary portion between rake face 10 and curved surface 400 (such that radius line 402 and rake face 10 form an angle of 90°). An intersection point 401 between radius line 402 and circle 20R is determined. A radius line 502 is drawn from the center of circle 20R toward the boundary portion between flank 11 and curved surface 500 (such that radius line 502 and flank 11 form an angle of 90°). An intersection point 501 between radius line 502 and circle 20R is determined.
(5) Subsequently, from radius R obtained in step (4), and cutter angle E of rake face 10 and flank 11, the distance between intersection points 401 and 501, or width L2 of round honing 20h, is determined
Cutting edge 20 is provided with projections and depressions 200c. Projections and depressions 200c have a width A3 of 100 nm or less. Width A3 of projections and depressions 200c of round honing 20h can be measured with a 3D-SEM.
(1) A 3D-SEM is used to image the cutting edge, as observed on the side of the tip of the cutting edge in a direction forming 45° with respect to rake face 10 and forming 45° with a direction perpendicular to rake face 10.
(2) A ridge line of a portion of round honing 20h with no projections/depressions 200c observed serves as a reference. A first curve passing by an outermost projection of projections and depressions 200c and parallel to the ridge line is determined. A second curve parallel to the ridge line and passing by an innermost depression of projections and depressions 200c is drawn. The distance between the first and second curves serves as a width of projections and depressions 200c.
(3) Measurement can be done in the above method as what has projections and depressions with a width of 10 nm or more can have the projections and depressions observed through a 3D-SEM. Projections and depressions having a width of less than 10 nm are unobservable. Therefore, it is determined that a size which is not observed as projections/depressions is less than 10 nm.
Initially, there were prepared samples which were formed as shown in
These samples were used to mirror-finish a mold for a lens (a workpiece: formed of a material which is a steel material plated with Ni-P). The mold has a cylindrical shape having a diameter φ of 5 mm with a tip having a spherical surface. It was determined that a tool in mirror-finishing the spherical surface reached its end of service life when an iridescent surface appeared on a finished surface.
The processing was done under the following conditions: Processing speed: 500 mm/sec at maximum (As the spherical surface is processed at a fixed rotational speed, the processing speed varies depending on the processed site.)
Sample Nos. 16 to 20 having rake face 10 with a plane orientation of (110) have a longer service life than a sample having rake face 10 with a plane orientation of (100). This is because a crystal orientation with high abrasion resistance is located at the cutting edge.
Samples Nos. 17 to 24 having inclined surface 12 with surface roughness Ra of 5 µm or less have a longer service life than a sample having inclined surface 12 with surface roughness Ra exceeding 5 µm. This is because when inclined surface 12 is rough, rake face 10 will be rough, and the cutting edge will have large projections and depressions.
Sample Nos. 19, 20, and 23 to 26 having relief angle θ2 of 30 degrees or less have a longer service life than a sample having relief angle θ2 exceeding 30 degrees. This is because falling within this range allows the cutting edge to maintain strength while avoiding contact between the flank and the workpiece.
There were prepared samples which were formed as shown in
These samples were used to mirror-finish a mold for a lens (a workpiece: formed of a material which is a steel material plated with Ni-P). The mold has a cylindrical shape having a diameter φ of 5 mm with a tip having a spherical surface. It was determined that a tool in mirror-finishing the spherical surface reached its end of service life when an iridescent surface appeared on a finished surface.
The processing was done under the following conditions: Processing speed: 500 mm/sec at maximum (As the spherical surface is processed at a fixed rotational speed, the processing speed varies depending on the processed site.)
It should be understood that the embodiments and examples disclosed herein are illustrative and not restrictive in all respects. The scope of the present invention is indicated by the appended claims rather than by the embodiments described above, and is intended to include all modifications within the scope and meaning equivalent to the claims.
The present disclosure is applicable in the field of single-crystal diamond cutting tools.
1 single-crystal diamond cutting tool, 2 shank, 3 single-crystal diamond, 10 rake face, 11 flank, 12 inclined surface, 15 boundary, 20 cutting edge, 20a first cutting edge, 20b second cutting edge, 20c chamfered surface, 20h round honing, 200a, 200b, 200c projections and depressions
Number | Date | Country | Kind |
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2020-005599 | Jan 2020 | JP | national |
Filing Document | Filing Date | Country | Kind |
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PCT/JP2020/047858 | 12/22/2020 | WO |