JP2007152466A - Cutting vibrator, vibratory cutting unit, machining device, mold , and optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vibratory cutting unit, enabling high-accuracy machining with a holding member having a low efficient of linear expansion and hardly breaking the tool mounting surface even when a cutting tool is repeatedly attached and detached. <P>SOLUTION: A surface coating layer SF having a higher hardness than the primary coat part SB is formed on the inner surface of a groove 21x provided at the tip of a tool part 21. This type of surface coating layer SF forms the tool mounting surface SS on the lower side of the groove 21x, so that the hardness of the tool mounting surface SS can be heightened. In the case where the hardness of the tool mounting surface SS is heightened as in the present embodiment, even if the cutting tool 23 is repeatedly attached and detached, the tool mounting surface SS is hardly damaged and deformed so that the cutting tool 23 can be firmly fixed to reduce heat generation or heating of a vibrating body 82. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a vibration body for cutting, a vibration cutting unit, a processing apparatus, and a molding die produced using the same, suitably used for cutting a material for forming a molding die for an optical element and the like. The present invention relates to a mold and an optical element.

  There is a technique for cutting a hard material such as carbide or glass by vibrating the tip of a cutting tool such as diamond, which is called vibration cutting. This is because the cutting tool blade edge makes a fine cut at a high speed by vibration, and the cutting edge generates a chip by the vibration, so there is less stress on both the cutting tool and the work material. Cutting is realized (see, for example, Patent Documents 1, 2, 3, 4, etc.). By this vibration cutting, the critical cutting amount required in normal ductile mode cutting is improved several times, and difficult-to-cut materials can be cut with high efficiency.

  In such vibration cutting, if the vibration frequency is increased in order to improve the processing efficiency, the above-described effect is increased, and the feed rate of the tool is also increased almost in proportion to the frequency. used. In addition, since this frequency exceeds the human audible range, there is an advantage that the vibrator and the vibrator excited by the vibrator do not produce unpleasant sound.

As a method of generating such high-speed vibration at the cutting tool blade edge, a holding member for holding the tool is excited by a piezo element or a giant magnetostrictive element, and this member is resonated by bending vibration, axial vibration, or the like. Stable vibration as a standing wave has been put into practical use. In such a method, the cutting tool is detachably fixed to the tip of the holding member which is a vibrating body on the base side.
JP 2000-52101 A JP 2000-218401 A Japanese Patent Laid-Open No. 9-309001 JP 2002-126901 A

By the way, as the holding member which is a vibrating body, for example, a material having a relatively high hardness such as chromium molybdenum steel (Vickers hardness of about Hv 370 to 400) can be used, but chromium molybdenum steel has a linear expansion coefficient (11. 0 × 10 ⁻⁶ ) is large, and the position variation of the cutting tool edge tends to be large. In particular, in vibration cutting, a certain amount of heat generation of the holding member is unavoidable due to high-speed vibration of the cutting tool. Therefore, in the case of high-accuracy machining with a unit depth of 100 nm or less, for example, if a material having a relatively large linear expansion coefficient such as chrome molybdenum steel is used, the position variation of the cutting tool edge increases and the machining accuracy is increased. It becomes extremely difficult to do.

  In addition, as a holding member that is a vibrating body, it is possible to use a ceramic material having a low linear expansion coefficient and a high hardness such as silicon nitride, but a normal ceramic material is susceptible to vibration and easily generates cracks. As a result, it was not easy to increase the durability of the holding member.

  In addition, although a low linear expansion coefficient alloy material or the like can be used as a holding member that is a vibrating body, the hardness of these materials is generally low, and scratches and deformations are caused on the tool mounting surface when the cutting tool is repeatedly attached and detached. As a result, it was impossible to fix the cutting tool firmly, and high-speed vibration resulted in frictional heat generation that could not be ignored on the tool mounting surface and mounting screws.

  Accordingly, an object of the present invention is to provide a vibration body for cutting in which the tool mounting surface is not easily damaged even when the cutting tool is repeatedly attached and detached, and a vibration cutting unit incorporating the same.

  Another object of the present invention is to provide a molding die and an optical element that are manufactured with high accuracy using the vibration cutting unit.

  In order to solve the above-described problems, the vibration body for cutting according to the present invention can support a cutting tool via a tool mounting surface, and transmits vibration applied when the cutting tool is supported to the cutting tool. The vibration body for cutting has a surface coating layer having a Vickers hardness larger than that of the base in the support portion including the tool mounting surface.

  In the above-described cutting vibration body, the support portion including the tool mounting surface has a surface coating layer having a Vickers hardness larger than that of the base, so that even if the base is formed of an alloy material having a low linear expansion coefficient and the Vickers hardness is low, the tool The Vickers hardness of the mounting surface can be increased as much as necessary within a certain range, and the cutting vibration body can be provided in which the tool mounting surface and its base are not easily damaged even when the cutting tool is repeatedly attached and detached, and the characteristics are not deteriorated. In the case where the surface coating layer is not provided, if the cutting tool is repeatedly attached and detached, the tool mounting surface may be damaged or deformed, and the cutting tool may not be firmly fixed. In such a case, excessive frictional heat generation occurs with the cutting tool, and the tool mounting portion of the cutting vibrator easily exceeds 100 ° C. Therefore, the cutting vibrator made of a material having a low linear expansion coefficient is used. Even if it exists, since it expand | swells greatly, the cutting tool front-end | tip fixed to the front-end | tip of the vibration body for cutting will be displaced greatly, and the precision of cutting will fall.

  In a specific aspect of the present invention, in the vibration cutting apparatus, the surface coating layer is formed of a material having a Vickers hardness of 400 Hv or more. In this case, it is experimentally confirmed that the tool mounting surface and its base are hardly deteriorated even if the cutting tool is repeatedly attached and detached, and it is possible to extend the life of the cutting vibrator and maintain high processing accuracy. The Vickers hardness of the material for forming the surface coating layer is more preferably 500 Hv or more, but the upper limit is 5000 Hv. The Vickers hardness means the hardness of the material surface measured by using a micro Vickers hardness meter.

In another aspect of the present invention, the base is a material having a linear expansion coefficient of −2 × 10 ⁻⁶ or more and 2 × 10 ⁻⁶ or less (hereinafter simply referred to as “low linear expansion coefficient” or “low linear expansion coefficient material”). ). In this case, since the expansion of the support portion of the cutting tool can be greatly reduced, the displacement of the tip of the cutting tool can be reduced and the accuracy of the cutting process can be improved. In addition, when the main part of the vibration part of the cutting vibration body is formed of a low linear expansion material, the expansion of the cutting vibration body can be greatly reduced, so that the cutting tool tip fixed to, for example, the tip of the cutting vibration member Can be prevented from being greatly displaced during the cutting process, and the accuracy of the cutting process can be improved.

  In still another aspect of the present invention, the base is formed of at least one of invar, super invar, and stainless invar. In this case, the expansion of the cutting vibration body becomes extremely small with respect to the temperature change of the tool mounting portion and the processing environment, and even if the vibration source or the like generates heat, the thermal expansion of the cutting vibration body can be suppressed. Cutting is possible.

  According to still another aspect of the present invention, the apparatus further includes a vibration source that vibrates the cutting tool through the cutting vibration body by applying vibration to the cutting vibration body. In this case, necessary vibration can be generated by supplying electric power or the like to the vibration cutting unit.

  In yet another aspect of the present invention, the surface coating layer is formed by electrolytic plating. In this case, the surface coating layer can be formed relatively easily and the cost can be reduced.

  In yet another aspect of the present invention, the surface coating layer is formed by hard Cr plating. In this case, sufficient hardness as the surface coating layer can be obtained.

  In yet another aspect of the present invention, the surface coating layer is formed by electroless plating. In this case, since the plating proceeds by a chemical reaction between the base and the plating material, a surface coating layer having a uniform film thickness can be obtained regardless of the shape of the base.

  In still another aspect of the present invention, the surface coating layer is formed by plating containing at least Ni and P, or is formed by electroless plating containing at least Ni and B. In this case, sufficient hardness as the surface coating layer can be obtained. Electroless Ni-B plating has high Vickers hardness and is hard to cause cracks in the plating film, electroless Ni-P plating is low cost and economical, and electroless Ni-P / SiC plating has high Vickers hardness and resistance Abrasion is good.

  In still another embodiment of the present invention, the surface coating layer is cured by heat treatment. In this case, the Vickers hardness of the surface coating layer made of a plating layer can be increased. Specifically, for example, the surface coating layer is heat-treated at 300 ° C. for several hours. In this case, when the underlying material is a low linear expansion material, the structure of the surface is not transformed by the heat treatment temperature, so that the hardness of the surface coating layer made of the plating layer can be increased without deteriorating the linear expansion coefficient. . Further, the material of the base and the plating layer diffuses to improve the adhesion strength of the plating layer.

  In still another aspect of the present invention, the surface coating layer is subjected to a surface processing treatment. In this case, the surface coating layer can be smoothed by surface processing, the adhesion between the cutting tool and the tool mounting surface can be further increased, and heat generation on the tool mounting surface can be reduced.

  The vibration cutting unit according to the present invention includes (a) the above-described cutting vibration body, (b) a cutting tool supported by the cutting vibration body, and (c) a cutting tool that is detachably fixed to the cutting vibration body. Fixing means.

  In the vibration cutting unit, since the cutting vibrator has a surface coating layer having a Vickers hardness larger than that of the base in the support portion for the cutting tool, the tool mounting surface and the base are not easily damaged even when the cutting tool is repeatedly attached and detached. Deterioration of cutting characteristics can be suppressed.

  The processing apparatus according to the present invention includes (a) the above-described vibration cutting unit, and (b) a drive device that is displaced by driving the vibration cutting unit.

  In the above processing apparatus, since the vibration cutting unit described above is displaced by the driving device, highly accurate processing can be realized by the vibration cutting unit having high durability.

  The molding die according to the present invention has a transfer optical surface for forming an optical surface of an optical element, which is created by using the vibration cutting unit described above. In this case, a mold having a concave surface and other various optical surfaces can be processed efficiently and with high accuracy.

  The optical element according to the present invention is created using the above-described vibration cutting unit. In this case, a highly accurate optical element having a concave surface and other various optical surfaces can be obtained.

[First Embodiment]
Hereinafter, a vibration body for cutting and a vibration cutting unit according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view illustrating a structure of a vibration cutting unit used when processing an optical surface of a molding die for molding an optical element such as a lens.

  As shown in FIG. 1, the vibration cutting unit 20 includes a cutting tool 23, a vibrating body 82, an axial vibrator 83, a bending vibrator 84, a counter balance 85, and a housing 86.

  Here, the cutting tool 23 is fixed so as to be embedded in the distal end portion 21 a of the tool portion 21 that is the distal end side of the vibrating body 82. As will be described in detail later, the cutting tool 23 has a diamond tip cutting edge 23a, and vibrates with the vibrating body 82 as an open end of the vibrating body 82 in a resonance state. That is, the cutting tool 23 generates a vibration that is displaced in the Z direction with the vibration of the vibrating body 82 in the axial direction, and a vibration that is displaced in the Y-axis direction (or the X-axis direction) with the bending vibration of the vibrating body 82. . As a result, the tip 23a of the cutting tool 23 is displaced at high speed, for example, exaggeratingly drawing an elliptical orbit EO as illustrated.

The vibrator 82 is a cutting vibrator integrally formed of a material having an absolute value of linear expansion coefficient of 2 × 10 ⁻⁶ or less. Specifically, the vibrator 82 is an invar material, a super invar material, a stainless invar material, or the like. Are preferably used. The vibrating body 82 has a thin outer diameter at the tool portion 21 on the distal end side, and a thick outer diameter on the root side. A first fixing flange 87, which is a plate-like portion, is formed at an appropriate location on the side surface of the vibrating body 82, and the vibrating body 82 is fixed to the housing 86 via the first fixing flange 87 with, for example, screws 93. Has been. The vibrating body 82 is oscillated by the axial vibrator 83 and enters a resonance state in which a standing wave that is locally displaced in the Z direction is formed. The vibrating body 82 is vibrated by the flexural vibrator 84 and enters a resonance state in which a standing wave is locally displaced in the Y-axis direction (or X-axis direction). Here, the position of the first fixing flange 87 is a common node for the vibrating body 82 in the axial vibration and the bending vibration, and by fixing the vibrating body 82 via the first fixing flange 87, It is possible to prevent the axial vibration and the bending vibration from being hindered.

  The first fixing flange 87 can be, for example, a disk-shaped fixing member. In this case, the outer peripheral portion is fixed to the casing 86 to seal the casing 86, and the structure has no ventilation. Become. The first fixing flange 87 may be a fixing member having a plurality of openings, or a fixing member having an elongated support member extending in three directions, for example. In this case, the first fixing flange 87 is fixed to the housing 86. In addition, sufficient ventilation inside and outside the casing 86 can be secured.

  The axial vibrator 83 is a vibration source that is formed of a piezo element (PZT), a giant magnetostrictive element, or the like and is connected to the base-side end face of the vibrating body 82, and a vibrator drive device ( To be described later. The axial vibrator 83 operates based on a drive signal from the vibrator driving device and gives a longitudinal wave to the vibrating body 82 by stretching and vibrating at a high frequency. The axial vibrator 83 is displaceable in the Z direction but is not displaced in the XY direction.

  The bending vibrator 84 is a vibration source that is formed of a piezo element, a giant magnetostrictive element, or the like and is connected to the base side surface of the vibrating body 82, and is connected to a vibrator driving device (described later) via a connector that is not shown. Has been. The bending vibrator 84 operates based on a driving signal from the vibrator driving device, and vibrates at a high frequency to give a transverse wave, that is, vibration in the Y direction in the illustrated example.

  The counter balance 85 is connected to the opposite side of the vibrating body 82 with the axial vibrator 83 interposed therebetween. A second fixing flange 88 is formed at an appropriate position on the side surface of the counter balance 85, and the counter balance 85 is fixed to the housing 86 via the second fixing flange 88. For example, the second fixing flange 88 may be a fixing member having a plurality of openings or a fixing member having an elongated support member extending in three directions, for example. In this case, the second fixing flange 88 is fixed to the housing 86. However, sufficient ventilation inside and outside the housing 86 can be secured. Note that the counter balance 85 is in a resonance state in which a standing wave that is vibrated by the axial vibrator 83 and locally displaced in the Z direction is formed. Here, the position of the second fixing flange 88 is a node of axial vibration for the counter balance 85, and the axial vibration of the vibrating body 82 is prevented by fixing the second fixing flange 88 via the second fixing flange 88. Can be prevented. The counter balance 85 is also formed of the same material as that of the vibrating body 82.

  The housing 86 is a member having a cylindrical inner space, and is a portion that supports and fixes the vibrating body 82 and the counter balance 85 via the first and second fixing flanges 87 and 88. The above-mentioned first fixing flange 87 is attached to one end of the housing 86 so as to block all or part of the opening, and an air supply pipe 92 connected to the opening on the end surface is provided on the other end. ing. The air supply pipe 92 is connected to a gas supply device (described later), and pressurized dry air set to a desired flow rate and temperature is supplied.

  In the vibration cutting unit 20 described above, the vibrating body 82, the axial vibrator 83, and the counter balance 85 are joined and fixed to each other by brazing so that the axial vibrator 83 can be vibrated efficiently. It has become. In addition, a through-hole 91 is formed in the shaft center of the vibrating body 82, the axial vibrator 83, and the counter balance 85 so as to pass through these joint surfaces. Of pressurized dry air flows. That is, the through-hole 91 is a supply path for sending out pressurized dry air, and constitutes a cooling means for cooling the vibration cutting unit 20 from the inside together with a gas supply device and an air supply pipe 92 (not shown). The front end portion of the through hole 91 is also used as a holding hole for inserting and fixing the cutting tool 23, and the pressurized dry air introduced into the through hole 91 can be supplied to the periphery of the cutting tool 23. Yes. Further, the tip of the through hole 91 leaves a gap even when the cutting tool 23 is fixed, and pressurized dry air is jetted at a high speed from the opening 91a formed adjacent to the cutting tool 23, and cutting is performed. Not only can the machining point at the tip of the tool 23 be efficiently cooled, but also the machining point and chips adhering to the periphery of the machining point can be reliably removed by an air flow.

  2A is a plan view of the tip of the tool portion 21 shown in FIG. 1, FIG. 2B is a front view of the tip of the tool portion 21, and FIG. It is a side view.

  As is apparent from the drawing, the tip 21a provided in the tool portion 21 has a tapered shape that is wedge-shaped in plan view. Further, the cutting tool 23 held at the tip of the tip portion 21a includes a shank 23b having a triangular tip, a hexagonal base at the base, and a plate-like shape as a whole, and a triangular machining tip fixed to the tip of the shank 23b in an inclined state. 23c. Among these, the shank 23b is formed of a super hard material, a ceramic material, high-speed steel, or the like, and is difficult to bend while being lightweight. The processing tip 23c is a diamond tip, and is fixed to the tip of the shank 23b by brazing or the like. The cutting tool 23 itself is fixed so as to be embedded in the tip portion 21a, and the tip 23a of the machining tip 23c is disposed on the extension of the tool axis AX.

  The cutting tool 23, that is, the fixed portion 23e of the shank 23b is formed along the XZ plane including the tool axis AX at the tip 21a and inserted into the groove 21x. The groove 21x has a trapezoidal side surface along the XY plane and a rectangular cross section along the YZ plane. The fixing portion 23e held in the groove 21x is detachably and firmly fixed to the tip portion 21a by two fixing screws 25 and 26 and a nut 27 formed of the same material as the material of the tool portion 21. Has been. One fixing screw 25 filling the fixing hole 21h is a flat head screw, and functions as a fastening member for fixing the cutting tool 23 in cooperation with the nut 27. The other fixing screw 26 filling the fixing hole 21g is a flat screw and functions as a locking member for preventing the fixing screw 25 from coming off. The inner diameter of the fixing hole 21g is larger than the inner diameter of the fixing hole 21h in order to pass the fixing screw 25. The fixing holes 21h and 21g extend in the Y-axis direction, and the tightening direction by the fixing screws 25 and 26 and the nut 27 is orthogonal to the tool axis AX.

  When assembling, first, the fixing screw 25 is inserted into the hole 23f of the shank 23b and the fixing hole 21h provided on the lower side through the fixing hole 21h provided on the upper side of the tip portion 21a, and the nut 27 is screwed on the tip side. Let At this time, the fixing portion 23e of the cutting tool 23 is clamped between the head portion of the fixing screw 25 and the inner surface of the groove 21x, and the fixing portion 23e is fixed from the upper surface side, so that the cutting tool 23 is prevented from being separated. Fixing of the cutting tool 23 to the tip 21a is ensured. Next, the fixing screw 26 is screwed into the fixing hole 21h provided on the upper side of the distal end portion 21a to be fixed. The fixing screw 25 is tightened from the upper end by the tip portion of the fixing screw 26 screwed in this way, and the fixing screw 25 is prevented from loosening, so that the cutting tool 23 can be fixed more reliably, and the vibration of the cutting tool 23 can be reduced. Looseness can be reduced. Further, the fixing screw 26 has an effect of arranging the weight of the tool mounting portion in the Y direction symmetrically with respect to the tool axis AX, and realizes stable basic vibration by preventing generation of unnecessary vibration of the tool mounting portion.

  As the fixing screws 25 and 26 and the nut 27 which are fixing means for fixing the cutting tool 23 to the tip end portion 21 a of the vibrating body 82, it is desirable to use a material having the same linear expansion coefficient as that of the vibrating body 82. Specifically, although depending on other processing conditions, about 0.75 to 1.25 times the linear expansion coefficient of the vibrating body 82 is practical. In this case, the tool portion 21 and the fixing screws 25 and 26 are similarly expanded, and the cutting tool 23 can be fixed stably and reliably regardless of the temperature change. Furthermore, as materials for the fixing screws 25 and 26 and the nut 27, considering the ease of processing and the like, ceramic materials, high-speed steel, etc. are suitable in addition to cemented carbide as well as the shank 23b, but silicon nitride, sialon, Invar materials, stainless invar materials, and the like can also be used. The fixing screws 25 and 26 and the nut 27 are preferably formed of a material having a specific gravity substantially equal to the specific gravity of the material of the vibrating body 82 from the viewpoint of not giving noise or the like to the vibration of the vibrating body 82. Specifically, although depending on other processing conditions, about 0.75 to 1.25 times the specific gravity of the vibrating body 82 is practical. In general, the fixing screws 25 and 26 and the vibrating body 82 are made of the same material. However, the fixing screws 25 and 26 and the nut 27 and the vibrating body 82 can be formed of different materials.

  The inner dimension of the groove 21x into which the fixed part 23e of the cutting tool 23 is inserted is slightly larger than the outer dimension of the fixed part 23e of the cutting tool 23 with respect to the width in the Y-axis direction. In addition, an opening 91 a is formed in the center of the bottom surface of the groove 21 x to discharge the pressurized dry air sent from the through hole 91 to the tip portion 21 a of the tool portion 21. Thereby, the upper side surface of the cutting tool 23 can be directly and efficiently cooled from the fixed portion 23e side that is fitted into and supported by the tip portion 21a. Moreover, since pressurized dry air is injected toward the front-end | tip of the cutting tool 23 from the opening 91a close | similar to the process point on a workpiece | work, the temperature rise of a workpiece | work can be suppressed and processing accuracy can be improved. Moreover, since pressurized dry air can be sprayed from the opening 91a to the processing point on the workpiece, the workpiece can be reliably cooled, and chips adhering to the processing point of the workpiece and its vicinity can be quickly removed. Therefore, the processing accuracy by the cutting tool 23 can be increased.

  FIG. 3A is a partial enlarged cross-sectional view for explaining the state of the groove 21x formed in the tip portion 21a of the tool portion 21, and FIG. 3B is an enlarged side view of the cutting tool 23. FIG. The lower side of the groove 21x is a support portion 21s for supporting the cutting tool 23, and transmits the vibration by supporting the cutting tool 23. That is, the lower surface 23u of the fixed portion 23e of the cutting tool 23 is supported in close contact with the lower surface of the groove 21x, that is, the tool mounting surface SS that is the upper surface of the support portion 21s. Note that the cutting tool 23 is fastened to the support portion 21s by the fixing screws 25, 26 and the like in FIG. 2, and the lower surface 23u of the cutting tool 23 is pressed against the tool mounting surface SS. If the lower surface 23u of the cutting tool 23 is not in close contact with the tool mounting surface SS, considerable frictional heat is generated on the tool mounting surface SS due to vibration of the vibrating body 82, and the temperature of the vibrating body 82 may fluctuate greatly. . When the temperature of the vibrating body 82 fluctuates in this way, the vibrating body 82 expands or contracts, so that the position of the tip 23a of the cutting tool 23 is greatly displaced in the tool axis AX direction. As a result, it becomes difficult to control the vibration position of the tip 23a of the cutting tool 23, and the machining accuracy on the workpiece is lowered.

  On the inner surface of the groove 21x, a surface coating layer SF having a Vickers hardness larger than that of the base portion SB is formed. Such a surface coating layer SF forms a tool attachment surface SS on the lower side of the groove 21x. That is, in the surface coating layer SF, the lower surface of the groove 21x is the tool mounting surface SS, and the Vickers hardness of the upper surface of the support portion 21s is increased. Assuming that the Vickers hardness of the tool mounting surface SS is low, if the mounting and dismounting of the cutting tool 23 is repeated, the tool mounting surface SS is deformed by scratches and screw tightening, and the cutting tool 23 cannot be firmly fixed. The vibrator 82 is greatly heated or heated. On the other hand, when the Vickers hardness of the tool mounting surface SS is increased as in this embodiment, even if the cutting tool 23 is repeatedly attached and detached, the tool mounting surface SS is not easily damaged or deformed. The heat generation or heating of the vibrating body 82 can be reduced.

  In the vibration cutting unit 20 of the present embodiment, the material of the main body portion of the vibrating body 82, in particular, the base portion SB, is a material having a low linear expansion coefficient such as an invar material, a super invar material, or a stainless invar material, as already described. Is formed.

Here, the invar material is an alloy containing Fe and Ni, and is an iron alloy containing 36 atomic% of Ni, but usually has a linear expansion coefficient of 1 × 10 ⁻⁶ or less at room temperature. The Young's modulus is as low as about half that of steel, but by using this as the material of the vibrating body 82, thermal expansion and contraction of the vibrating body 82 is suppressed, and the temperature drift of the cutting edge position of the cutting tool 81 held at the tip is reduced. Can be suppressed.

The super invar material is an alloy containing at least Fe, Ni, and Co, and is an iron alloy containing 5 atomic% or more of Ni and 5 atomic% or more of Co, respectively, and has a linear expansion coefficient of room temperature. In general, it is a material that is about 0.4 × 10 ⁻⁶ and is more difficult to thermally expand and contract than the aforementioned invar. The Young's modulus is as low as about half that of steel, but by using this as the material of the vibrating body 82, thermal expansion and contraction of the vibrating body 82 is suppressed, and the temperature drift of the cutting edge position of the cutting tool 81 held at the tip is reduced. Can be suppressed.

Further, the stainless steel invar material is an alloy material in which the main component of 50 atomic% or more is Fe and the incidental material containing 5 atomic% or more is at least one of Co, Cr, and Ni. Point to. Therefore, here, Kovar material is also included in this stainless steel invar material. The stainless steel invar material has a linear expansion coefficient of 1.3 × 10 ⁻⁶ or less at room temperature. Young's modulus is as low as about half that of steel, but by using this as a material for the vibrating body, thermal expansion and contraction of the vibrating body 82 is suppressed, and temperature drift at the cutting edge position of the cutting tool 81 held at the tip is suppressed. it can. Furthermore, the stainless steel invar material has a much higher resistance to moisture than the invar material, and has an excellent feature that rust does not occur even when subjected to a processing coolant or the like. Therefore, it is suitable as a structural material for holding and fixing the cutting tool 81. Yes.

  However, the low linear expansion material such as Invar material described above has a relatively low Vickers hardness of about 200 Hv, and when the cutting tool 23 is directly supported on these surfaces, the surface is likely to be damaged. Therefore, the surface coating layer SF having a higher Vickers hardness than these low linear expansion materials is formed on the surface of the base portion SB made of a low linear expansion material such as invar material, super invar material, stainless invar material, etc. The strength of the mounting surface SS, that is, the groove 21x can be increased. The surface coating layer SF is desirably formed of a material having a Vickers hardness of 400 Hv or higher, particularly 550 Hv or higher (upper limit of 5000 Hv) from the viewpoint of durability, and various protective films formed by plating are versatile and simple in the manufacturing method. Suitable from the point of view. For example, electrolytic plating can be used as the plating protective film. In the electrolytic plating, the surface coating layer SF can be formed relatively easily and the manufacturing cost can be suppressed. In addition, electroless plating can be used as the plating protective film. In the electroless plating, the plating proceeds by a chemical reaction between the base portion SB and the plating material. Therefore, even when the base portion SB has a recessed shape like the groove 21x, the surface coating layer SF having a uniform film thickness is obtained. be able to. When the surface coating layer SF is formed by plating, the thickness is preferably 1 μm or more, but there is no particular upper limit. If the surface coating layer SF is 1 μm or more, the strength of the surface coating layer SF can be maintained for the cutting tool 23 for a certain period of use or number of replacements.

  When the surface coating layer SF is used as a plating protective film, the surface coating layer SF may be completed by forming a plating layer on the surface of the base portion SB and then subjecting the plating layer to heat treatment at an appropriate temperature and time. it can. The heat treatment of the plating layer is preferably performed at a temperature of 100 ° C. or higher and 800 ° C. or lower for a processing time of about 1 to 3 hours. However, in the case where the heat treatment is continuously performed for about one hour, if the heat treatment temperature is set too high, the experimental result that the low linear expansion material of the base portion SB, that is, the vibrator 82 is transformed to increase the thermal expansion coefficient. When the base portion SB is an invar material, a super invar material, a stainless invar material or the like, the heat treatment temperature is desirably 400 ° C. or lower. In particular, it is more desirable to heat-treat the plating layer at a temperature of about 300 ° C. for a processing time of about 1 to 3 hours. In addition, when the surface coating layer SF is used as a plating protective film, whether or not cracks are likely to occur on the surface may be a problem. This is because, when cracks are formed on the surface of the surface coating layer SF, the strength of the surface coating layer SF decreases as a result. For this reason, it is necessary to consider a film forming material and a film forming process that are less likely to cause cracks in both electrolytic plating and electroless plating.

  When the surface coating layer SF is formed by electrolytic plating, for example, hard Cr plating is suitable. Hard Cr plating has a Vickers hardness of about 800 to 900 Hv.

  When the surface coating layer SF is formed by electroless plating, for example, electroless Ni—B plating, electroless Ni—P plating, electroless Ni—P / SiC plating, electroless Ni—Co plating, or the like is suitable.

Electroless Ni-B plating was applied to the tool mounting surface of the vibrator made of stainless invar material.
Electroless Ni-B plating has high Vickers hardness among electroless plating, and cracks are unlikely to occur in the plating film. In the case of electroless Ni—B plating, the surface coating layer SF had a Vickers hardness of 985 Hv after a film thickness of 25 μm, a processing temperature of 300 ° C., and a processing time of 1 hour. The surface coating layer SF had a Vickers hardness of 650 Hv after a film thickness of 35 μm, a processing temperature of 300 ° C., and a processing time of 2 hours. As a result, the hardness of the tool mounting surface SS was improved.
Note that when the cutting tool 23 is fastened to the vibrator 82, the cutting tool 23 bites in with a fastening torque of 100 cN · m, the tool mounting surface is deformed, and the edge portion of the tool is caught. Entered, and it sometimes became a burr. Further, when the cutting tool 23 does not adhere to the vibrator 82 due to the deformation of the tool mounting surface, the cutting tool 23 is displaced during vibration, and frictional heat is generated between the tool mounting surface and the cutting tool 23. When the temperature near the tool mounting surface of the vibrator 82 at that time was measured with a radiation thermometer, the temperature rose to 80 ° C. or more in several tens of seconds. In this case, it is easily predicted that the position of the tool blade edge 23a will change greatly.
However, by applying the electroless Ni-B coating according to the present embodiment, even if the screw is strongly tightened with a torque of 240 cN · m, the cutting tool 23 does not bite into the tool mounting surface SS, and the cracks and the tool mounting surface SS are deformed. No longer occurs. Furthermore, since the tool mounting surface SS is not deformed according to the present embodiment, the cutting tool 23 is brought into close contact with the vibrator 82, and the temperature rise during vibration remains at 1.1 ° C. Further, since the deformation of the tool mounting surface SS is suppressed, even if the cutting tool 23 is repeatedly attached and detached, the cutting tool 23 can always be firmly fixed, so that fluctuations in the tool edge position can be suppressed as much as possible, and the optical surface and transfer High-precision processing of an optical surface (hereinafter, the transfer optical surface is also simply referred to as an optical optical surface) could be performed. As a verification of the effect, when a concave R3 mm spherical surface was processed, optical mirror surface processing with a shape accuracy of 50 nm PV could be achieved. In addition, it is no longer necessary to disassemble the vibrator 82 and rework the tool mounting surface SS in order to regenerate the tool mounting surface SS.

Next, electroless Ni—P plating was applied to the tool mounting surface SS of the vibrator made of invar material.
The electroless Ni—P plating has a lower Vickers hardness than the electroless Ni—B plating, but is economical at a low cost. In the electroless Ni—P plating, if the Vickers hardness is equal to that of the electroless Ni—B plating, a long-time heat treatment is required, so that the plating film is crystallized and cracks are likely to occur. In the case of electroless Ni—P plating, the surface coating layer SF had a Vickers hardness of 550 Hv after a film thickness of 25 μm, a processing temperature of 300 ° C., and a processing time of 3 hours.
As a result, the hardness of the tool mounting surface SS was increased, and the tool mounting surface SS that had been deformed with a fastening torque of 100 cN · m as described above vibrated normally up to a torque of 160 cN · m. However, when tightened with a torque of 170 cN · m and vibrated, the temperature in the vicinity of the tool mounting surface SS suddenly increased for several tens of seconds as in the case of insufficient adhesion with the electroless Ni—B plating described above. It became 80 degreeC or more. When the cutting tool 23 was removed and the tool mounting surface SS was confirmed, there were innumerable cracks in the electroless Ni—P plating layer, and the plating layer, that is, the surface coating layer SF was peeled off in some places. Many cracks occurred because the heat treatment time after plating was as long as 5 hours at 300 ° C. As a result, the plating layer was peeled off due to vibration, the cutting tool 23 and the tool mounting surface SS were not firmly adhered, and frictional heat was generated. I think that the. When the heat treatment time was 1 hour at 300 ° C., the hardness was as small as 500 Hv, but cracks did not occur, and no burrs or deformation occurred even when fastened with a torque of 170 cN · m.
Therefore, it is conceivable that the appropriate temperature and time of the heat treatment after plating differ depending on the plating material. In the electroless Ni-P plating of this example, the heat treatment at 300 ° C. is good for 1 hour, and when the tool is vibrated, When the temperature in the vicinity of the mounting surface SS was measured with a radiation thermometer, the temperature rise during vibration was 1.3 ° C. Therefore, even when the cutting tool 23 is fixed with a tightening torque larger than that of the conventional tool, the tool mounting surface is not deformed and is firmly fixed and fixed, and the effect of the present invention is seen.

Next, electroless Ni—P / SiC plating was applied to the tool mounting surface SS of the vibrator 82 formed of a super invar material.
The electroless Ni—P / SiC plating has a relatively high Vickers hardness and contains SiC particles, so that the wear resistance is improved. However, the electroless Ni—P / SiC plating increases the Vickers hardness by co-depositing SiC fine particles, the fracture toughness of the plating film is small, and cracks are likely to occur. In the case of electroless Ni—P / SiC plating, the surface coating layer SF had a Vickers hardness of 805 Hv after a film thickness of 35 μm, a processing temperature of 300 ° C., and a processing time of 2 hours.
As a result, the tool mounting surface SS has been increased in hardness, and as described above, the tool mounting surface that has been deformed with a fastening torque of 100 cN · m has oscillated normally up to a torque of 190 cN · m. . However, when tightened with a torque of 200 cN · m and oscillated, the temperature in the vicinity of the tool mounting surface SS suddenly increased and exceeded 80 ° C. in several tens of seconds, as in the case of the electroless Ni—P plating described above. It became. The cutting tool 23 is removed and the tool mounting surface SS is confirmed. There were innumerable cracks in the electroless Ni—P / SiC plating layer, and the plating layer, that is, the surface coating layer SF was peeled off in some places. Furthermore, countless scratches were also seen on the tool mounting surface SS side of the cutting tool 23. This is considered to be caused by the fact that the shank 23b was made of superhard having a lower hardness than SiC or ceramics such as silicon nitride with respect to the SiC particles on the surface of the electroless Ni—P / SiC plating layer. Moreover, since the crack contains SiC particles, the fracture toughness of the plating layer, that is, the surface coating layer SF is small, and stress concentration occurs on the plating layer at the edge portion on the tool mounting surface SS side of the cutting tool 23, and from there It is thought that it occurred. In the present embodiment, the fastening torque of the cutting tool 23 has a limit of 190 cN · m, and is practically used at 170 cN · m in view of the safety factor. At this time, there were no cracks, and no scratches on the cutting tool 23 and no burrs or deformations on the tool mounting surface SS were observed. Here, the temperature in the vicinity of the tool mounting surface SS was measured, but the temperature during vibration increased only by 1.2 ° C. Also from this, even if the cutting tool 23 is fixed with a tightening torque larger than that of the conventional tool, the tool mounting surface is not deformed and is firmly fixed and fixed, and the effect of the present invention is seen.

  In addition, electroless Ni—Co plating, electroless Ni—P—Co plating, electroless Ni—B—W plating, electroless Ni—P—B plating, and electroless Co—P plating can also be used. Depending on the conditions and heat treatment, a Vickers hardness of about 600 to 950 Hv can be obtained.

  Further, the method of forming the surface coating layer SF is not limited to plating, but can be thermal spraying using plasma or a high-speed flame. As the material for thermal spraying, SiC, WC, Al2O3, zirconia, or the like can be used. In addition, as the surface coating layer SF, a DNF (diamond near film) or a DLC film can also be used. The temperature at which the DNF or DLC film is formed is 200 ° C. or less, and damage to the underlying portion SB is small, and a high Vickers hardness of about 4200 to 5000 Hv is obtained.

  As for the surface coating layer SF formed on the surface of the vibrating body 82, that is, the base portion SB, the surface of the surface coating layer SF, that is, the tool mounting surface, for example, by polishing the surface layer obtained by electrolytic plating, electroless plating, or thermal spraying. It is desirable to smooth the SS. Thus, by smoothing the surface of the tool mounting surface SS and increasing the parallelism of the tool mounting surface SS, the adhesion between the cutting tool 23 and the tool mounting surface SS can be further increased. The heat generation can be reduced. In the case of polishing the surface of the surface coating layer SF, it is desirable that the film formation by electrolytic plating, electroless plating, thermal spraying, etc. is 50 μm or more, and the process of increasing the parallelism by polishing is facilitated. In the present embodiment, the groove 21x is formed in the tip 21a of the tool portion 21 and the cutting tool 23 is fixed to the groove 21x. However, when the cutting tool 23 is fixed to a step instead of the groove 21x, Since the tool mounting surface SS faces outward, polishing becomes easy. The means for smoothing the tool mounting surface SS is not limited to polishing, and various surface processing methods such as grinding and cutting can be used. Low linear expansion materials such as Invar material, Super Invar material and Stainless steel Invar material are soft and difficult to grind, and it was not easy to improve the processing accuracy of the tool mounting surface SS, but surface coating with high Vickers hardness The grinding of the layer SF is easy and it is easy to ensure accuracy.

  In addition, as a method of forming the surface coating layer SF, a thin plate material such as carbide, SiC, zirconia, or alumina can be brazed to the surface of the base portion SB using high-frequency heating or the like. The Vickers hardness of the layer SF can be about 1800 Hv. Similarly, a conductive thin plate material such as carbide or SiC can be brazed to the surface of the base portion SB using spot welding or the like, and the Vickers hardness of the surface coating layer SF is set to about 1800 Hv. it can.

  In the above embodiment, the inner surface of the groove 21x formed in the tip portion 21a of the tool portion 21 is protected by the surface coating layer SF. However, the inner surface of the fixing hole 21g screwed with the fixing screw 26 is also surface-coated. It can be protected by the layer SF. Thereby, the friction at the time of fastening the fixing screw 26 can be reduced, and the effect of protecting the thread is recognized.

  In addition, the vibrator 84 is preferably formed of a low linear expansion material such as an invar material, a super invar material, or a stainless invar material that is common to the main body portion of the vibrating body 82.

[Second Embodiment]
Hereinafter, a processing apparatus according to a second embodiment of the present invention will be described with reference to the drawings. FIG. 4 is a block diagram conceptually illustrating the structure of a processing apparatus of a vibration cutting type that processes an optical surface of a molding die for molding an optical element such as a lens.

  As shown in FIG. 4, the processing apparatus 10 includes a vibration cutting unit 20 for cutting a workpiece W that is a workpiece, an NC drive mechanism 30 that supports the vibration cutting unit 20 with respect to the workpiece W, A drive control device 40 that controls the operation of the drive mechanism 30, a vibrator drive device 50 that applies desired vibration to the vibration cutting unit 20, a gas supply device 60 that supplies a cooling gas to the vibration cutting unit 20, and an apparatus And a main controller 70 that controls the overall operation in an integrated manner.

  The vibration cutting unit 20 is a vibration cutting tool in which a cutting tool 23 is embedded at the tip of a tool portion 21 extending in the Z-axis direction, and efficiently cuts the workpiece W by high-frequency vibration of the cutting tool 23. The vibration cutting unit 20 has the structure described in the first embodiment.

  The NC drive mechanism 30 is a drive device having a structure in which a first stage 32 and a second stage 33 are placed on a pedestal 31. Here, the first stage 32 supports the first movable part 35, and the first movable part 35 indirectly supports the workpiece W via the chuck 37. The first stage 32 can move the workpiece W, for example, to a desired position along the Z-axis direction at a desired speed. The first movable portion 35 can rotate the workpiece W around the horizontal rotation axis RA parallel to the Z axis at a desired speed. On the other hand, the second stage 33 supports the second movable part 36, and the second movable part 36 supports the vibration cutting unit 20. The second stage 33 supports the second movable part 36 and the vibration cutting unit 20 and can move them to a desired position along, for example, the X-axis direction or the Y-axis direction at a desired speed. Further, the second movable portion 36 can rotate the vibration cutting unit 20 at a desired speed by a desired angular amount around the vertical turning axis PX parallel to the Y axis. In particular, the vibration cutting unit 20 is positioned at its tip by arranging the tip point of the vibration cutting unit 20 on the vertical pivot axis PX by appropriately adjusting the fixed position and angle of the vibration cutting unit 20 with respect to the second movable portion 36. It can be rotated around the point by a desired angle.

  In the NC drive mechanism 30 described above, the first stage 32 and the first movable unit 35 constitute a workpiece drive unit that drives the workpiece W, and the second stage 33 and the second movable unit 36 are A tool driving unit that drives the vibration cutting unit 20 is configured.

  The drive control device 40 enables high-precision numerical control, and drives the motor, the position sensor, and the like built in the NC drive mechanism 30 under the control of the main control device 70, thereby allowing the first and first control. The two stages 32 and 33 and the first and second movable parts 35 and 36 are appropriately operated to a target state. For example, the first and second stages 32, 33 follow a predetermined locus in which the machining point at the tip of the cutting tool 23 provided at the tip of the tool portion 21 of the vibration cutting unit 20 is set at a low speed in a plane parallel to the XZ plane. Thus, the workpiece W can be rotated around the horizontal rotation axis RA at a high speed by the first movable portion 35 while moving (feeding operation) relative to the workpiece W. As a result, the NC drive mechanism 30 can be utilized as a highly accurate lathe under the control of the drive control device 40. At this time, the second movable portion 36 can appropriately rotate the tip of the cutting tool 23 around the vertical turning axis PX around the processing point corresponding to the tip of the cutting tool 23, Thus, the tip of the cutting tool 23 can be set to a desired posture (tilt).

  The vibrator driving device 50 is for supplying electric power to a vibration source built in the vibration cutting unit 20, and the tip of the tool unit 21 is controlled by the main controller 70 by a built-in oscillation circuit or PLL circuit. It can be vibrated at a desired frequency and amplitude. Although details will be described later, the tip of the tool portion 21 is capable of bending vibration perpendicular to the axis (that is, the tool axis extending in the cutting depth direction) and axial vibration along the axis. Fine and efficient machining with the tip of the tool portion 21, that is, the cutting tool 23, directed to the surface of the workpiece W is enabled by simple vibration or three-dimensional vibration.

  The gas supply device 60 is for cooling the vibration cutting unit 20, and passes a gaseous fluid source 61 for supplying pressurized dry air and the pressurized dry air from the gaseous fluid source 61. Are provided with a temperature adjusting unit 63 as a temperature adjusting unit for adjusting the temperature of the gas and a flow rate adjusting unit 65 as a flow rate adjusting unit for adjusting the flow rate of the pressurized dry air that has passed through the temperature adjusting unit 63. Here, the gaseous fluid source 61 dries air by, for example, sending the air to a dryer using a thermal process, a desiccator, or the like, and pressurizes the dry air to a desired pressure with a compressor. Although not shown, the temperature adjustment unit 63 includes, for example, a flow path in which the refrigerant is circulated around and a temperature sensor provided in the middle of the flow path. By adjusting the temperature and supply amount of the refrigerant, The pressurized dry air passed through the flow path can be adjusted to a desired temperature. Furthermore, the flow rate adjusting unit 65 has, for example, a valve and a flow controller (not shown), and can adjust the flow rate when supplying pressurized dry air whose temperature is adjusted to the vibration cutting unit 20. Yes.

  FIG. 5 is an enlarged plan view for explaining the machining of the workpiece W using the machining apparatus 10 shown in FIG. The tip portion 21a of the tool portion 21 vibrates at high speed, for example, in the YZ plane as already described. Further, the tip end portion 21a of the tool portion 21 is gradually moved by the NC drive mechanism 30 shown in FIG. 4 while drawing a predetermined locus in the XZ plane, for example, with respect to the workpiece W that is a workpiece. That is, the feeding operation of the tool unit 21 is performed. Further, the workpiece W, which is a workpiece, is rotated at a constant speed around the rotation axis RA parallel to the Z axis by the NC drive mechanism 30 in FIG. 4 (see FIG. 4). As a result, the workpiece W can be turned, and the workpiece SA is rotationally symmetric about the rotation axis RA with respect to the workpiece W, for example, a curved surface such as an uneven spherical surface or an aspheric surface, a phase element surface, or the like. Can be formed. At this time, by using the second stage 33, the tip of the cutting tool 23 of the tool portion 21 is rotated around the turning axis PX parallel to the Y-axis direction, so that the vibration surface OS at the tip of the cutting tool 23 becomes the workpiece W. It is made to be substantially perpendicular to the surface SA to be formed. As a result, the machining point of the cutting edge of the tool can be maintained at approximately one point during machining, so that efficient vibration transmission to the machining point and high-accuracy vibration cutting independent of the cutting edge shape can be realized. And the processed surface SA can be made smoother. Further, during the processing of the workpiece W, since the pressurized dry air is injected at high speed from the opening 91a at the tip of the tool portion 21 toward the tip of the cutting tool 23, the cutting tool 23 and the work surface SA can be efficiently cooled. Not only can the temperature of the cutting tool 23 and the surface SA to be processed be within a certain range depending on the temperature and flow rate of the pressurized dry air. The pressurized dry air is introduced through a through hole 91 that penetrates the axis of the tool portion 21 and flows inside the vibrating body 82, the axial vibrator 83, the counter balance 85, and the like. The temperature can be adjusted by the temperature and flow rate of the pressurized dry air. As described above, the temperature of the vibrating body 82 can be stabilized by adjusting the temperature of the pressurized dry air. As a result, the temperature drift of the cutting edge position of the cutting tool 23 held at the tip thereof is reduced. Therefore, a highly accurate and highly reproducible cutting surface can be obtained.

Here, details of a working example in the vibration cutting apparatus 10 in which the tool mounting surface SS of the vibrator 82 according to the present embodiment is electroless Ni-B plated will be described. The processing of the transfer optical surface according to this example was performed by an ultra-precision processing machine having a turning axis shown in the processing apparatus 10.
As the material of the workpiece, that is, the workpiece W, Microalloy F (1850 Hv) manufactured by Tungaloy was used. The shape of the aspherical optical surface to be formed on the workpiece W is a small concave optical surface having an approximate R-concave of about 0.9 mm, a central curvature radius of 1.33 mm, and a maximum prospective angle of 65 °.
The optical surface is pre-processed into a concave spherical surface by electrical discharge machining, and rough cutting from an approximate spherical shape to an aspherical shape is performed using a general-purpose high-precision grinding machine with an axial resolution of about 100 nm. Processing was performed. In this rough grinding process, an electrodeposition grindstone was used, and while repeating shape correction, the shape accuracy was driven to about 1 μm in a short time and finished to an aspherical shape.
Next, cutting finishing was performed by the processing apparatus 10 using the vibration cutting apparatus of the present invention.
The processing tip 23c of the diamond tool, that is, the cutting tool 23 is a sword-shaped cutting tool with a tip rake face sharpened at 30 °, and the rake face S1 of the cutting edge (as shown in FIG. 3B) The tip arc radius of the cutting tool 23 that refers to the surface that contributes to cutting of the cutting material is 1 μm or less, and the clearance angle α of the clearance surface S2 (the clearance angle is the clearance surface S2 as shown in FIG. 3B). Or the angle formed by the tangent of the extension line at the cutting point and the tangent of the machined surface at the cutting point) is 5 °, and the angle formed by the rake face at the cutting point is −25 °. 1 μm. In this vibration cutting, vibrations occur in the axial direction and the bending direction, respectively, and the blade tip trajectory performs a circular motion or an elliptical motion. As a result, since the cutting is performed so as to scoop up on the rake face, the cutting depth can be increased several times even in the ductile mode cutting as compared with the processing that is not the normal vibration cutting. Further, cutting was performed at a spindle rotation speed of 340 rpm with a machining optical surface attached and a feed rate of 0.2 mm / min.
After cutting, the optical surface roughness was measured using a surface roughness measuring device HD3300 manufactured by WYKO. As a result, as shown in FIG. 6, the average surface roughness was Ra 2.58 nm, and a practically sufficient optical mirror surface was obtained. The machining shape accuracy was measured with a three-dimensional shape measuring instrument UA3P manufactured by Matsushita Electric Industrial Co., Ltd., and a machining shape error of about 100 nm PV was obtained in the first machining. When a machining program for correcting the shape error was created and corrected, a result with a shape error of 50 nm PV as shown in FIG. 7 was obtained.
In the cutting process of this embodiment, the second optical surface is cut with the tool used for the first optical surface processing and the NC program with shape correction, and the surface roughness is almost equal to the accuracy of the first optical surface. Shape accuracy was obtained, and excellent process reproducibility was confirmed.
In this way, it is possible to continue machining with one diamond tool, that is, the machining tip 23c, and to cut a total of six optical surfaces, all of which are aspherical surfaces having an average surface roughness of 3 nm or less and a shape error of 50 nm or less. The optical surface could be created and processed. As a result of observing the cutting edge of the diamond tool after machining, that is, the cutting edge of the machining tip 23c by SEM, it was confirmed that tool wear having a width of about 3 μm was observed on the flank, but no chipping occurred.
Furthermore, as a verification of the effect of the present embodiment, a ruby grindstone was passed through the tool mounting surface SS of the vibrator 82, but there was no catching that caused burrs. Further, when the surface profile was measured by applying a surface roughness meter stylus to the tool mounting surface SS, no deformation of the tool mounting surface SS was found.

Another machining example was carried out using the ultra-precision machine shown in the machining apparatus 10 in the same manner as the above-described machining examples. However, in this embodiment, since the blaze structure is processed, the pivot axis is not used. Processing with two axes of XZ is performed.
As the material of the workpiece, Microalloy F <1850Hv) from Tungaloy was used. The shape of the optical surface is a shape having a blazed diffraction groove, and the amount of blaze difference is about 1 μm.
As the diamond tool, that is, the machining tip 23c, a sword tip-shaped bite having a sharp tip apex angle of 30 ° was used. The radius of the cutting edge of the rake face is 1 μm or less, the first flank angle is 5 °, and the angle formed by the rake face at the cutting point is the cutting point on the plane including the relative movement direction of the tool and the workpiece. When the direction parallel to the cutting direction (cutting depth direction) at 0 is 0 ° and the rotation direction of the watch is positive, the cutting amount at this time is 1 μm. Vibration cutting vibrates in each of the axial direction and the bending direction, and the blade locus performs a circular motion or an elliptical motion. As a result, since cutting is performed so as to scoop up on the rake face, the cutting amount can be increased several times even in ductile mode cutting compared to processing that is not normal vibration cutting.
The rotation speed of the main shaft was 500 rpm, the cutting depth was 100 nm, and the feed rate was 0.1 mm / min.
FIG. 8 shows an SEM observation image obtained as a result of processing in this example. As can be seen from the picture, the blaze was processed as intended without sagging or burrs at the edge of the blaze. Further, the processed surface roughness is also a mirror surface in SEM observation. Until now, the diamond tool has been made very sharp, so the blade edge of the diamond tool broke during blazing and could not be processed to the target blaze step. However, the intermittent cutting, which is a feature of vibration cutting, can reduce the cutting resistance applied to the diamond cutting edge, so that the durability of the diamond tool cutting edge can be increased and the desired blaze shape can be machined. It was.
Further, as a verification of the effect of the present invention, a ruby grindstone was passed through the tool mounting surface SS of the vibrator, but there was no catching that caused burrs. Further, when the surface profile was measured by applying a surface roughness meter stylus to the tool mounting surface SS, no deformation of the tool mounting surface SS was found.
Further, a glass optical element capable of correcting chromatic aberration resistant to environmental changes was obtained by glass molding using the optical element molding die of the high hardness material.

[Third Embodiment]
Hereinafter, the molding die according to the third embodiment will be described. FIG. 9 is a view for explaining a molding die (optical element molding die) manufactured by using the vibration cutting unit 20 of the first embodiment, and FIG. 9A is a fixed die, that is, a first die. FIG. 9B is a side sectional view of 2A, and FIG. 9B is a side sectional view of the movable mold, that is, the second mold 2B. Optical surfaces 3a and 3b of both molds 2A and 2B are finished by a processing apparatus 10 shown in FIG. That is, the base material (the material is, for example, cemented carbide) of both molds 2A and 2B is fixed to the chuck 37 as a workpiece W, and the standing wave is formed in the vibration cutting unit 20 by operating the vibrator driving device 50 and the like. The cutting tool 23 is vibrated at high speed. In parallel with this, the drive control device 40 is appropriately operated to arbitrarily move the tip of the tool part 21 of the vibration cutting unit 20 with respect to the workpiece W in a three-dimensional manner. Thereby, the transfer optical surfaces 3a and 3b of the molds 2A and 2B are not limited to spherical surfaces and aspheric surfaces, but can be step surfaces, phase structure surfaces, and diffraction structure surfaces.

  FIG. 10 is a cross-sectional view of a lens L press-molded using the mold 2A of FIG. 9A and the mold 2B of FIG. 9B. Although not shown, when the optical surfaces 3a and 3b of the molds 2A and 2B have a step surface, a phase structure surface, a diffractive structure surface, etc., the molding optical surface of the lens L is also a step surface, a phase structure surface, and a diffractive structure. It has a surface. Furthermore, the material of the lens L is not limited to plastic, but may be glass or the like. Note that the lens L can also be directly manufactured by the processing apparatus 10 of the second embodiment.

  As described above, the present invention has been described according to the embodiment, but the present invention is not limited to the above embodiment. For example, in the vibration cutting unit 20, the shape of the tip 21a and the method for attaching the cutting tool 23 can be changed as appropriate.

  In the vibration cutting unit 20, the overall shape and dimensions of the vibrating body 82 and the axial vibrator 83 can be appropriately changed according to the application. In addition, when the vibration cutting unit 20 is not heated so much, it is not necessary to worry about the dimensional change of the vibrating body 82, and therefore supply of pressurized dry air is not necessary. Further, in the gas supply device 60 of FIG. 2, instead of air, a gaseous fluid added as a solvent or particles in which oil or other lubricating elements are misted, an inert gas such as nitrogen gas, or the like can be used.

  In the above vibration cutting apparatus, turning has been mainly described. However, the vibration cutting apparatus shown in FIG. 1 can be modified for ruling.

It is a block diagram explaining the vibration cutting unit of 1st Embodiment. (A), (b), (c) is the top view, end view, and side view of a tool part front-end | tip. (A) is a partial expanded sectional view explaining the state of the groove | channel formed in the front-end | tip part of a tool part, (b) is an enlarged side view of a cutting tool. It is a block diagram explaining the processing apparatus of 2nd Embodiment. FIG. 5 is an enlarged plan view for explaining workpiece processing using the processing apparatus shown in FIG. 4. It is a graph which shows surface measurement data. It is a graph which shows shape error measurement data. It is a SEM observation image of a blaze obtained by processing. (A), (b) is a sectional side view of the molding die concerning a 3rd embodiment. FIG. 7 is a side sectional view of a lens formed by the molding die in FIG. 6.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Vibration cutting apparatus, 20 ... Vibration cutting unit, 21 ... Tool part, 21a ... Tip part, 23f ... Hole, 21x ... Groove, 23 ... Cutting tool, 23b ... Shank, 23c ... Chip for processing, 25 ... Fixing screw, 26 ... Fixing screw, 27 ... Nut, 30 ... Drive mechanism, 32 ... First stage, 33 ... Second stage, 35 ... First movable part, 36 ... Second movable part, 37 ... Chuck, 40 ... Drive control device, DESCRIPTION OF SYMBOLS 50 ... Vibrator drive device, 60 ... Gas supply device, 61 ... Gaseous fluid source, 63 ... Temperature control part, 65 ... Flow control part, 70 ... Main controller, 82 ... Vibrating body, 83, 84 ... Vibrator, 85 ... Counter balance 86 ... Case 91 ... Through hole 91a ... Opening 92 ... Air supply pipe AX ... Tool axis EO ... Elliptical orbital RA ... Rotating axis SA ... Work surface W ... work

Claims (16)

A cutting vibration body capable of supporting a cutting tool via a tool mounting surface and transmitting vibration given when the cutting tool is supported to the cutting tool,
A vibration body for cutting having a surface coating layer having a Vickers hardness larger than that of a base in a support portion including the tool mounting surface.   The vibration body for cutting according to claim 1, wherein the surface coating layer is formed of a material having a Vickers hardness of 400 Hv or more. 3. The cutting vibration body according to claim 1, wherein the base is formed of a material having a linear expansion coefficient of −2 × 10 ⁻⁶ or more and 2 × 10 ⁻⁶ or less.   The cutting vibrator according to claim 3, wherein the base is formed of at least one of invar, super invar, and stainless invar.   The vibration body for cutting according to any one of claims 1 to 4, wherein the surface coating layer is formed by electrolytic plating.   The vibration body for cutting according to any one of claims 1 to 5, wherein the surface coating layer is formed by hard Cr plating.   The vibration body for cutting according to any one of claims 1 to 4, wherein the surface coating layer is formed by electroless plating.   The vibration body for cutting according to claim 7, wherein the surface coating layer is formed by plating containing at least Ni and P.   The cutting vibration body according to claim 7, wherein the surface coating layer is formed by plating containing at least Ni and B.   The vibrator for cutting according to any one of claims 5 to 9, wherein the surface coating layer is hardened by heat treatment.   The vibration body for cutting according to any one of claims 6 to 10, wherein the surface coating layer is subjected to a surface processing treatment. The cutting vibrator according to any one of claims 1 to 11,
The cutting tool supported by the cutting vibrator;
Fixing means for removably fixing the cutting tool to the cutting vibration body;
A vibration cutting unit comprising:   The vibration cutting unit according to claim 12, further comprising a vibration source that vibrates the cutting tool through the vibrating body by applying vibration to the vibrating body. The vibration cutting unit according to any one of claims 12 and 13,
A driving device that is displaced by driving the vibration cutting unit;
A processing apparatus comprising:   A molding die having a transfer optical surface for molding an optical surface of an optical element, created by using the vibration cutting unit according to any one of claims 12 and 13.   An optical element created by processing using the vibration cutting unit according to any one of claims 12 and 13.

Images