JP2016144859A - Elliptic vibration cutting processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a processing method for cutting a ferrous material into a mirror surface with elliptic vibration cutting processing, especially ultrasonic elliptic vibration cutting processing.SOLUTION: An elliptic vibration cutting processing method for processing a flat surface or free-form surface on a cutting object material 11 by elliptically vibrating a tip 14 of a cutting tool 10 relatively to the cutting object material 11 performs the elliptic vibration cutting processing by making the cutting direction of the cutting tool 10 and the rolling direction of the cutting object material 11 substantially vertical to each other. As the cutting tool 10, any cutting tool among a single crystal diamond coated tool, a nano-polycrystalline diamond coated tool and a polycrystalline diamond coated tool can be used.SELECTED DRAWING: Figure 5

Description

The present invention relates to a machining method for cutting a steel material into a mirror surface by elliptical vibration cutting, particularly ultrasonic elliptical vibration cutting.

Conventionally, in the production of optical lens molds for cameras, etc., an electroless nickel phosphorous plating surface is used by using a processing machine called nanometer-order precision called an ultra-precision machine and a high-precision diamond cutting tool. The mirror surface is obtained by cutting.

However, the hardness of electroless nickel phosphorus plating is 400 HV to 500 HV in terms of Vickers hardness, which is lower than 500 HV to 900 HV of the heat-treated steel material. Also, electroless nickel phosphorus plating loses luster as the surface oxide film grows over time in an environment where the humidity is not controlled. That is, the surface roughness and accuracy are greatly impaired by rust.

In recent years, there has been an increasing need for a mold having a mirror surface on a large-area free-form surface having a surface roughness of Ra 20 nm or less, and having a durability and corrosion resistance. There is a tendency that martensitic stainless steel, which is a steel material, is preferred as the required mold material.

Grinding wheels and cutting tools are used to manufacture this mold, but it is difficult to obtain a mirror surface on the mold surface by grinding and cutting alone. I get a mirror. In order to cope with the recent increase in resolution, it is necessary to minimize the distortion and distortion of the mold. For this reason, it is necessary to eliminate a polishing step that impairs processing accuracy and obtain a mirror surface only by cutting.

For example, in order to obtain a mirror surface by cutting, the accuracy of the processing machine and the cutting tool is a necessary condition, but the accuracy of the cutting tool is determined by the hardness and uniformity of the tool material. Therefore, for example, a tool coated with single crystal diamond or a tool coated with nano-polycrystalline diamond disclosed in Patent Document 1 can achieve nanometer-order accuracy, and is therefore used in the manufacture of molds for optical components. I came.

However, carbon constituting diamond has high solubility in iron, and when steel material is processed with the diamond tool, significant wear occurs. Thus, conventionally, a steel material is not used for a mold for an optical component manufactured by a diamond tool, and electroless nickel phosphor plating has been used.

On the other hand, as shown in FIG. 10, Patent Document 2 discloses an elliptical vibration cutting method in which the cutting edge 103 of the cutting tool 100 draws an elliptical orbit 102 when the work material 101 is oxygen-free copper. By this processing method, the contact time between the cutting tool 100 and the work material 101 is reduced, and at the same time, the cutting tool 100 is relatively moved in the chip discharging direction to reduce the cutting resistance. A chemical reaction between the temperature rise and the work material 101 can be suppressed.

By using this elliptical vibration cutting method, mirror cutting can be performed even when a diamond tool, which has been difficult in the past, is used as the cutting tool 100 and a steel material is used as the work material 101.

JP 2003-292397 A Japanese Patent No. 3500434

The inventors cut martensitic stainless steel by an elliptical vibration cutting method using a single crystal diamond tool for the purpose of producing a free-form optical mold. As a result, no serious problem occurred immediately after the start of processing. However, it was found that when the cutting distance is 500 m or more, white streaks (swells) 110 are irregularly generated on the processed surface of the work material 101 as shown in FIG. 11, and a good mirror surface cannot be obtained.

In view of the above-described problems, an object of the present invention is to provide a machining method for machining a steel material into a mirror surface by elliptical vibration cutting, particularly ultrasonic elliptical vibration cutting.

As a result of intensive studies on various cutting conditions, the inventors have found that the cause of white streaks is elongated carbides distributed in parallel to the cutting direction.

Here, electroless nickel phosphor plating conventionally used as a mold for optical components is microcrystalline or amorphous, and there is no segregation of carbides or large crystal grains unlike steel materials. Furthermore, since it is manufactured by a plating process, the material surface is uniform in all directions and the hardness is also uniform. Also, there is no elongated carbide in the oxygen-free copper disclosed in Patent Document 2.

On the other hand, when a steel material is manufactured by melting, it usually undergoes processes such as casting, forging, and rolling. For this reason, crystal grains and carbides are remarkably deformed in the material in the direction stretched during rolling (hereinafter referred to as the rolling direction), and the shapes of the crystal grains and carbides are elongated in the rolling direction.

Steel materials contain various components, and the hardness varies locally depending on the components contained. In particular, carbides in which carbon such as vanadium, chromium, tungsten, and molybdenum is bonded to carbon are harder than the matrix (base) portion. Further, the carbide is usually dispersed in a size of 10 μm to 100 μm in the material before rolling. However, the carbide after the rolling process has a shape elongated in the rolling direction.

Accordingly, in the present invention, there is provided an elliptical vibration cutting method for machining a mirror surface that forms a flat surface or a free-form surface on a work material while causing the cutting edge of the cutting tool to vibrate elliptically relative to the work material. The above-described problems have been solved by providing an elliptical vibration cutting method in which the cutting direction of the workpiece and the rolling direction of the work material are substantially perpendicular.

That is, the contact time between the cutting tool and the carbide in the work material is shortened by making the direction in which the cutting tool advances while being elliptically vibrated (cutting direction) and the rolling direction of the work material, thereby reducing the elliptical orbit. Reduces the time that the cutting tool is affected by hard carbides. Thereby, in the whole area | region which a cutting tool passes, the carbide | carbonized_material becomes cutting resistance, and the influence which it has on the escape state of a tool, a constituent blade edge, the resonance state of ultrasonic vibration, etc. is reduced.

The cutting tool used may be any of a tool coated with single crystal diamond, a tool coated with nano-polycrystalline diamond, and a tool coated with polycrystalline diamond. That is, by using any one of the above cutting tools among the cutting tools, the cutting tool has durability and heat resistance, becomes less susceptible to hard carbides, and stabilizes the elliptical orbit of elliptical vibration cutting.

Further, the work material is a work made of martensitic stainless steel, and the work is a work having a surface hardness of 300 HV to 700 HV in terms of Vickers hardness. The martensitic stainless steel conforms to JIS standards. It can be limited to martensitic stainless steel which is the same component as SUS420J1 or SUS420J2 and contains one or more of trace metals or metalloids at 1.0 wt% or less. That is, when cutting the martensitic stainless steel by the elliptical vibration cutting method by limiting the work material to a specific steel type, the elongated island-shaped convex portions made of carbides are scattered in the mirror surface, and By forming a concave and convex curved surface with a regular period in the matrix, there is no white streaks on the mirror surface of the workpiece, and distortion can be reduced.

In the present invention, by making the cutting direction of the cutting tool substantially perpendicular to the rolling direction of the work material, the influence of hard carbide on the cutting tool in the entire cutting tool path can be reduced. This makes it possible to reduce cutting resistance such as cutting tool escape, component cutting edge and ultrasonic vibration resonance state, so that cutting can be performed without generating white streaks on the surface of the work material. A small number of optical parts can be manufactured.

Moreover, by using any one of a single crystal diamond tool, a nano-polycrystalline diamond tool, and a polycrystalline diamond tool as the cutting tool, the cutting tool has durability and heat resistance, and is less susceptible to hard carbides. . In addition, the elliptical trajectory of the elliptical vibration cutting process is stabilized, white streaks are not generated on the surface of the work material, the cutting precision is improved, and an optical part with less distortion can be manufactured.

Furthermore, by limiting the work material to a martensitic stainless steel workpiece, etc., it is applied to an optical component such as a lens, which is produced by an elliptical vibration cutting method with less distortion. It is possible to provide an optical product, an optical instrument, and the like having excellent optical characteristics.

It is a schematic diagram which shows the cutting direction of the cutting tool 10 in case the to-be-cut material 11 is a round steel. It is a schematic diagram which shows the cutting direction of the cutting tool 10 in case the to-be-cut material 11 is a square steel. It is a schematic diagram of the surface of the work material 11 cut by the method of the present invention. FIG. 4 is a sectional view taken along line AA shown in FIG. 3. FIG. 4 is a sectional view taken along line BB shown in FIG. 3. It is an external view of the surface of a workpiece (die) 60 cut by the method of the present invention. It is an external view which shows the metal mold | die 60 processed by the processing method of this invention, and the molded article 70 shape | molded using the said metal mold | die 60. FIG. It is the elements on larger scale of the workpiece 60 edge part shown in FIG. In an Example, (a) The microscope picture of the workpiece surface cut elliptically by the method of this invention, (b) The microscope picture of the workpiece surface cut elliptically by the conventional method. It is a schematic diagram which shows the locus | trajectory 102 of the cutting tool 100 to which elliptical vibration was added with respect to the to-be-cut material 101. FIG. It is a microscope picture which shows the surface state after cutting the workpiece 101. FIG. When the length of the carbide in the rolling direction is 1, the angle between the rolling direction and the cutting direction when the width of the carbide is 1/5, 1/10, 1/20, and 1/100. It is a graph which shows the relationship between (theta) and the maximum length L which crosses one carbide | carbonized_material. It is the elements on larger scale of FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram showing the cutting direction of the cutting tools 10A and 10B when the work material 11 is round steel, and FIG. 2 is a schematic diagram showing the cutting direction of the cutting tools 10A and 10B when the work material 11 is square steel. It is. As shown in FIG. 1, when the work material 11 has a cylindrical shape such as a round steel, the rolling direction 21 is parallel to the longitudinal direction of the work material 11. Therefore, when the end surface 12 or the side surface 13 of the cylindrical work material 11 is cut by the cutting tools 10A and 10B, the cutting direction 30 by the cutting tools 10A and 10B and the rolling direction 21 of the work material 11 are always perpendicular. Become. For example, when the work material 11 is applied to a lens mold application, when the work material 11 is cut while rotating in the rotation direction 20, the work material 11 is also a rotationally symmetric body. The cutting direction 30 of 10B and the rolling direction 21 of the work material 11 are perpendicular to each other.

On the other hand, when the work material 11 has a rectangular parallelepiped shape such as a square steel, the cutting directions 30 and 31 by the cutting tools 10A and 10B are the rolling direction of the work material 11 (the length of carbide) as shown in FIG. (Direction) 21 is not necessarily perpendicular to each other. That is, the relationship between the rolling direction 21 of the work material 11 and the cutting directions 30 and 31 may be a vertical relationship as in the cutting direction 30 or a parallel relationship as in the cutting direction 31. .

FIG. 7 is an external view showing a mold 60 processed by the processing method of the present invention and a molded product 70 molded using the mold 60. The mold 60 having a free curved surface as shown in FIG. 7 is produced by moving the cutting tool 10A in the depth direction according to the target shape while moving the cutting tool 10A in the cutting direction 30 as shown in FIG. By taking in and out, the locus is processed into the desired free-form surface. That is, when the X axis is parallel to the rolling direction 21, the Y axis is parallel to the cutting direction 30, and the Z axis is parallel to the direction in which the cutting tool 10 </ b> A is deeply inserted into the work material 11, the target shape is X, Y, Obtained as each coordinate of Z, the cutting tool 10A is moved to the Z coordinate corresponding to the X coordinate and the Y coordinate while moving the cutting tool 10A in the Y-axis direction.

As shown in FIG. 2, after the cutting tool 10 </ b> A moves from end to end of the workpiece 11 in the Y coordinate, the Z coordinate is moved in the minus direction to release the cutting tool 10 </ b> A, and the Y coordinate is returned to the original cutting start position. return. At the same time, the X coordinate is moved by the set index pitch P2 shown in FIG. 5, and the cutting tool 10A is moved in the Y direction while controlling the Z coordinate corresponding to the X and Y coordinates again to perform cutting. By repeating this, the entire surface of the work material 11 is cut.

Depending on the shape, the entire surface processing may be repeated several times in the order of roughing, intermediate finishing, and finishing while changing the cutting depth in the Z-axis direction, the indexing pitch P2, and the cutting speed. By reducing the indexing pitch P2 shown in FIG. 5, the surface roughness of the work material 11 decreases, but the processing time increases. Therefore, generally, the indexing pitch P2 at the time of roughing is increased or the indexing pitch P2 at the time of finishing is decreased.

The movement of the cutting tools 10A and 10B described here indicates a relative movement with respect to the work material 11. Depending on the machine configuration, the work material 11 may be fixed with the cutting tools 10A and 10B being fixed. Sometimes moved. In addition, this is the case where each of the X, Y, and Z axes moves, for example, the cutting tool 10 moves in the Y axis direction to move the X axis direction, and the workpiece 11 moves in the Z axis direction. There can be.

In addition, as shown in FIG. 2, the work material 11 (rolled material) generally has a long shape in the rolling direction (carbide longitudinal direction). In many cases, the direction of the longest side (longitudinal direction of the work material 11) is the rolling direction 21 unless it is extreme.

For example, when cutting by planar processing, the direction of the longest side of the work material 11 is generally set as the cutting direction 31 in order to minimize the time of air cut and to facilitate the setup. That is, the cutting direction is often parallel to the rolling direction 21 like the cutting direction 31.

As shown in FIG. 3, in the elliptical vibration cutting method of the present invention, the cutting direction 30 of the cutting tool 10 is substantially perpendicular to the rolling direction 21 of the work material 11 (square steel). Thereby, the contact time of the cutting tool 10 and the carbide | carbonized_material 41 becomes short, and the time when the cutting tool 10 receives the influence of the carbide | carbonized_material 41 harder than the matrix 42 is shortened.

For example, it is 200 μm or more and 1000 μm or less in the direction perpendicular to the cutting direction 30 (rolling direction 21), is 10 μm or more and 50 μm or less in the direction parallel to the cutting direction 30, and is in the height direction (Z direction: depth direction on the paper surface). A carbide 41 having a size of 0.02 μm or more and 0.06 μm or less in which elongated island-shaped convex portions are formed is scattered on the surface of the work material 11. As a result, white stripes (swells) 110 as shown in FIG. 11 do not occur.

Further, as shown in FIG. 4, the cutting tool 10 is vibrated on an elliptical orbit 52 in the cutting direction 30 relative to the work material 11 (square steel) in the vertical direction (in the YZ plane of FIG. 4) to cut the work. By cutting the material 11, a mirror surface forming a flat surface or a free curved surface is processed on a workpiece (die) 60 as shown in FIG.

Thereby, the contact time between the cutting tool 10 and the work material 11 is reduced, the cutting resistance is greatly reduced, and the temperature rise of the cutting edge 14 of the cutting tool 10 and the work material 11 are reduced as shown in FIG. Chemical reaction can be greatly suppressed. Moreover, the periodic uneven | corrugated curve 53 is formed in the mirror surface by the cutting direction pitch P1 by the vibration period and cutting speed of the cutting tool 10. FIG.

Furthermore, as shown in FIG. 5, the contact time of the cutting edge 14 of the cutting tool 10 and the carbide | carbonized_material 41 can be shortened by making a cutting direction perpendicular | vertical with respect to the rolling direction 21 (paper surface front direction). Further, a periodic uneven curve 54 corresponding to the indexing pitch P2 of the cutting tool 10 is formed on the surface of the work material 11 in a direction perpendicular to the cutting direction (rolling direction 21).

Therefore, as shown in FIG. 6, the surface of the workpiece 60 is 10 μm or more and 1000 μm or less in the direction perpendicular to the cutting direction 30 (rolling direction 21), and 0.01 μm or more and 10 μm parallel to the cutting direction 30. A concave-convex curved surface having the following regular cycle can be formed. That is, the white streak 110 as shown in the work material 11 of FIG. 11 does not appear, a good mirror surface can be obtained, and a workpiece with a small surface roughness Ra of 20 nm or less, such as a mold or a lens. Optical parts such as can be manufactured.

The elongated island-shaped convex portions made of carbide are in the range of 200 μm or more and 1000 μm or less in the longitudinal direction of the carbide, and the island-shaped projections scattered in a dimension in the range of 10 μm or more and 50 μm or less in the direction perpendicular to the longitudinal direction of the carbide And a range of 10 μm or more and 1000 μm or less in a direction parallel to the carbide longitudinal direction, and a regular period that is a range of 0.01 μm or more and 10 μm or less in a direction 30 perpendicular to the carbide longitudinal direction. An optical product having excellent optical characteristics, an optical device, and the like are provided by using an optical component having a concave and convex curved surface formed in a matrix in which the island-shaped convex portions are distributed in a concave and convex curved surface. It becomes possible.

Here, the carbide has a difference of 0.02 μm or more and 0.06 μm or less in the height direction (Z-axis direction). This is because the carbide forming the island-shaped convex portions is harder than the matrix portion, so that a cutting tool and a processing machine (not shown) are elastically deformed during cutting.

As shown in FIG. 2, when the cutting direction 30 is changed by 90 ° and processed along the rolling direction (carbide longitudinal direction) 21 like the cutting direction 31, along the cutting direction 31 as shown in FIG. 11. Since white stripes 110 are generated and the quality of the surface of the work material 11 is deteriorated, a good mirror surface cannot be obtained.

This is because the carbide extending long in the rolling direction of the work material contacts the cutting edge of the cutting tool for a long time along the cutting direction, so that the cutting edge of the cutting tool escapes due to cutting resistance, the constituent cutting edge and the resonance of the ultrasonic vibration. This is because it affects the state and the like.

That is, the size of the surface of the workpiece (die) is 200 μm or more and 1000 μm or less in the direction perpendicular to the cutting direction (rolling direction) by the scanning white interference method, and is 10 μm or more and 50 μm or less parallel to the cutting direction. Are elongated island-shaped convex portions formed of carbides scattered in the direction of 10 μm to 1000 μm in the direction perpendicular to the cutting direction (rolling direction) and 0.01 μm to 10 μm in the direction parallel to the cutting direction. It is possible to examine whether or not it has a concave and convex curved surface formed in a matrix in which island-shaped convex portions are distributed with a concave and convex curved surface having a regular period. Thereby, it can be determined whether it is a workpiece (die) manufactured by the elliptical vibration cutting method according to the present invention.

For example, as shown in FIG. 7, the surface of the molded product 70 is 200 μm or more and 1000 μm or less by the scanning white interference method, and the long and slender island-shaped convex portions formed of the carbides 41 scattered in the size of 10 μm or more and 50 μm or less are transferred. The concave-convex curved surface 55 formed on the matrix in which the island-shaped convex portions 41 are distributed with the concave-convex concave portion 71 and the concave-convex curved surface 55 having a regular cycle of 10 μm or more and 1000 μm or less and 0.01 μm or more and 10 μm or less is transferred. It is possible to specify by which processing method the mold 60 used for molding is manufactured by examining whether or not it has the uneven surface 75 made.

In addition, as shown in FIG. 8, the rolling direction 21 of the workpiece 60 can be specified by observing a carbide 41 having a mirror surface elongated by a differential interference microscope. Furthermore, the mirror surface is observed using a corrosive solution such as nitrate alcohol to observe the elongated island-shaped convex carbides 41 and the grain boundaries, and the reflected electron image is observed with a scanning electron microscope. Can be identified.

When the workpiece 60 is a mold as shown in FIGS. 7 and 8, the elongated island-shaped recess 71 and the uneven curved surface 75 transferred to the molded product 70 molded using the mold 60. It is possible to specify whether or not the mold 60 is manufactured by the elliptical vibration cutting method of the present invention.

Furthermore, the concave and convex curved surface 55 of the workpiece (die) 60 has an indexing pitch P2 (see FIG. 5) formed in a direction perpendicular to the cutting direction 30 (rolling direction 21) and a direction parallel to the cutting direction 30. The cutting direction pitch P1 (see FIG. 4) formed in the above can also be measured by focus synthesis of a confocal laser microscope or an optical microscope. Moreover, if the workpiece 60 is small, it can also be measured with an atomic force microscope. The index pitch P2 can also be measured with a stylus type surface roughness meter.

The term “substantially vertical” in the present invention includes a common error range. That is, it is difficult to accurately measure the longitudinal direction of carbide appearing approximately elliptically with respect to the surface of the workpiece, and includes an error within a range of several degrees.

In addition, the present invention also includes a range of material cutout and attachment error to a processing machine. However, as a result of deliberately examining the rolling direction and the cutting direction in detail, the angle between the rolling direction, that is, the direction in which the carbides are elongated and the cutting direction is preferably 80 degrees or more and 100 degrees or less, more preferably 85. It came to the conclusion that it is more than 95 degree | times.

The reason for reaching such an angle range will be described below. In FIG. 12, when the length of the carbide in the rolling direction is 1, the width of the carbide is 1/5, 1/10, 1/20, and 1/100 (hereinafter, the aspect ratio is 5 and 10 respectively). , 20, 100) in the case of the rolling direction (the longitudinal direction of the carbide) and the angle θ formed by the cutting direction, the calculation result of the maximum length across one carbide, that is, the length L of the line segment passing through the center Indicates. The carbide was calculated by approximating an ellipse based on the observation results shown in FIG. FIG. 13 is a partially enlarged view of FIG.

12 and 13, when the aspect ratio is 10 or more, the angle L formed by the cutting direction and the longitudinal direction of the carbide is 80 degrees or more and 100 degrees or less, and the length L that the tool crosses the carbide is 0.2 or less. Further, the value of L is 0.15 or less at 85 degrees or more and 95 degrees or less. When the aspect ratio is 5, the angle θ is 80 degrees or more and 100 degrees or less, and L is 0.25 or less.

In order to fully demonstrate the effects of the present invention, it is necessary to sufficiently reduce the length of the tool across the carbide. Specifically, the value of L described above is preferably 0.25 or less, 0.20 or less, or 0.15 or less. Therefore, the angle formed by the rolling direction and the cutting direction is preferably 80 degrees or more and 100 degrees or less, the aspect ratio of the carbide is 10 or more, and the angle θ formed by the longitudinal direction of the carbide and the cutting direction is 85 degrees or more. More preferably, it is 95 degrees or less.

Actually, since the magnitude of the effect of the present invention continuously changes depending on the range of θ, it does not mean that the effect of the present invention cannot be obtained when θ is 80 degrees or less or 100 degrees or more. However, the material is often cut out in a direction perpendicular or parallel to the rolling direction, and if the material is cut in a direction other than parallel or perpendicular to the cutting direction of the material, the air cut time becomes long, which is inefficient. For this reason as well, the claimed range of the present invention is such that the cutting direction is substantially perpendicular to the rolling direction, and the range of the angle θ is in the range of 80 degrees to 100 degrees.

Using the elliptical vibration cutting method according to the present invention (hereinafter referred to as the method of the present invention) and the conventional elliptical vibration cutting method (hereinafter referred to as the conventional method), a cutting test was performed under the following processing conditions. In the method of the present invention, the surface of the work material was subjected to elliptical vibration cutting in a direction perpendicular to the rolling direction of the work material, and in the conventional method, the work material surface was subjected to elliptical vibration cutting. Furthermore, the shape of the work material was a simple plane for accurate evaluation.
・ Vibration conditions: Amplitude 4 (μm) × 50 (kHz)
・ Processing method: Planar processing ・ Processing speed: 1000 (mm / min)
・ Cut amount: 3 (μm)
・ Indexing pitch: 25 (μm)
・ Processing area: 12000 (mm ² )
・ Cutting distance: 600 (m)
・ Cutting time: 10 (h)
・ Processing time: 19.1 (h)
・ Cutting tool: Single crystal diamond tool ・ Chamfering diameter R at cutting tool tip: 5.0 (mm)
・ Cutting fluid: Oil-based cutting fluid ・ Work material: Martensitic stainless steel (surface hardness 52HRC)

Further, the surface of the work material near the cutting distance of 520 m was visually observed, and surface roughness (PV, rms, Ra) was measured with a scanning white interference microscope. Where PV is the height difference between the highest and lowest points of the measured roughness curve, rms is the square root of the average of the squares of the deviations from the average line of the roughness curve to the measurement curve, and Ra is the measurement The average roughness of the curve is shown.

Table 1 shows the results of surface observation (presence or absence of white streaks) and surface roughness measurement of the workpiece after the cutting test performed using the method of the present invention and the conventional method. As shown in Table 1, when cutting was performed using the method of the present invention, no white streaks were observed on the mirror surface. However, in the conventional method, white streaks are recognized on the surface of the workpiece as shown in FIG. From this result, it was found that the quality of the machined surface of the workpiece by the method of the present invention was improved compared to the conventional method.

FIG. 9 (a) is an image obtained by measuring the surface of a workpiece that has been subjected to elliptical vibration cutting according to the method of the present invention with a scanning white interference microscope. The surface roughness (PV) of the D1-D1 cross section of the image is shown in FIG. , Rms, Ra) measurements were made. Further, FIG. 9B is an image obtained by measuring a processed surface that has been subjected to elliptical vibration cutting by a conventional method with a scanning white interference microscope, and the surface roughness (PV, rms, Ra) of the D2-D2 cross section of the image. ) Measurement was performed.

As shown in Table 1, it was found that the surface roughness of the method of the present invention is PV121 nm, rms15 nm, and Ra12 nm, and the processing accuracy is improved as well as quality, while the conventional method is PV572 nm, rms20 nm, and Ra16 nm. .

This is because the contact time between the cutting tool and the carbide of the work material is shortened by making the direction in which the elliptical orbit of the cutting tool advances (cutting direction) and the rolling direction of the work material substantially perpendicular to each other. This is because the time affected by the hard carbide is shortened.

The surface roughness Ra was a difference between Ra 12 nm and Ra 16 nm at a cutting distance of about 520 m. However, if there is no white line, Ra 20 nm or less is sufficient to satisfy the quality as an optical mold. The presence or absence of this is particularly important for quality.

Here, the surface of the work material that has been subjected to elliptical vibration cutting by the method of the present invention is 200 μm to 1000 μm in the direction perpendicular to the cutting direction, 10 μm to 50 μm in the direction parallel to the cutting direction, and 0.02 μm to 0 in the height direction. A long and slender island-shaped convex portion formed of carbides scattered in a size of 0.06 μm or less was observed.

Furthermore, a regular uneven curve corresponding to a cutting direction pitch (0.33 μm) with a cutting speed of 1000 mm and an elliptical vibration period of 50 kHz exists in the cutting direction in the matrix in which the island-shaped convex portions are distributed. In addition, a regular uneven curve corresponding to the index pitch (25 μm) exists in the direction perpendicular to the cutting direction, that is, the direction in which the island-shaped protrusions are elongated (rolling direction).

That is, an uneven curve having a regular cycle of 10 μm or more and 1000 μm or less in a direction perpendicular to the cutting direction and an uneven curve having a regular cycle of 0.01 μm or more and 10 μm or less in a direction parallel to the cutting direction. And an uneven curved surface surrounded by.

The relationship between the cutting speed and the vibration cycle is determined by the following equation.
Cutting direction pitch = (cutting speed) ÷ (vibration period)
= [1000 (mm / min) ÷ 60 (sec / min)] ÷ 50000 (/ sec)
≒ 0.00033 (mm) = 0.33 (μm)

On the other hand, when the cutting test was performed with the cutting direction parallel to the rolling direction as in the conventional method, undulations (white streaks) in the cutting direction (rolling direction) were large, and the islands seen in the method of the present invention were observed. The convex shape was not clearly observed. This is not an island shape in the limited range of the influence of the carbide, but the carbide has a long influence on the cutting tool on the cutting surface and appears as waviness in the cutting direction. As a result, white streaks (swells) were generated on the surface of the work material (see FIG. 11), and the surface roughness PV of the conventional method was four times higher than that of the method of the present invention.

In planar processing with an ultra-precise machine, the cutting time is required because of the return time of the cutting tool, the idling time of the cutting tool provided at every fixed cutting distance, the moving time in the cutting direction, the relief direction, and the indexing direction. However, the actual processing time becomes longer.

DESCRIPTION OF SYMBOLS 10, 100 Cutting tool 11, 101 Workpiece 14 Cutting edge 21 of cutting tool 10 Rolling direction 30 of cutting material 11 Cutting direction 60 of cutting tool 10 Workpiece (die)

Claims (3)

An elliptical vibration cutting method for machining a flat surface or a free-form surface on the work material while causing the cutting edge of the cutting tool to vibrate elliptically relative to the work material, the cutting direction of the cutting tool and the work material An elliptical vibration cutting method characterized in that the rolling direction of the electrode is substantially perpendicular. The elliptical vibration cutting method according to claim 1, wherein the cutting tool is any one of a single crystal diamond-coated tool, a nano-polycrystalline diamond-coated tool, and a polycrystalline diamond-coated tool. The work material is a work made of martensitic stainless steel, and the work is a work having a surface hardness of 300 HV or more and 700 HV or less in terms of Vickers hardness,
The martensitic stainless steel is the same component as SUS420J1 or SUS420J2 defined by the JIS standard, and contains one or more of trace metals or semimetals in an amount of 1.0% by weight or less. The elliptical vibration cutting method according to claim 1, wherein the method is a stainless steel.

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