JP4771052B2 - Vibration cutting apparatus, molding die, and optical element - Google Patents

Description

  The present invention relates to a vibration cutting apparatus suitably used for cutting a material for forming a molding die for an optical element and the like, and a molding die and an optical element manufactured using the vibration cutting device.

  There is a technique for cutting a hard material such as cemented carbide or glass by vibrating the tip of a tool such as diamond, which is called vibration cutting. This is because the cutting edge of the tool performs fine cutting at a high speed by vibration, and the cutting edge generates a chip by the vibration, and the cutting process generates less stress on both the tool and the work material. (For example, refer to Patent Documents 1, 2, 3, etc.).

  As a result, the critical depth of cut required for normal ductile mode cutting is improved several times, and difficult-to-cut materials can be cut with high efficiency.

  In this vibration cutting process, in order to improve the processing efficiency, if the vibration frequency is increased, the above-described effect is increased, and further, the feed rate of the tool is increased in proportion to the frequency. used. Further, since this frequency exceeds the human audible range, there is also 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 tool edge, a standing wave is generated by exciting a member holding the tool by a piezo element or a giant magnetostrictive element, and resonating the member with bending vibration or axial vibration. It has been put to practical use as a stable vibration. In such a method, a member for holding a tool, that is, a vibrating body is fixed to a member connected to an apparatus housing, a tool stand of a processing machine, or the like at a resonance node.
JP 2000-52101 A JP 2000-218401 A Japanese Patent Laid-Open No. 9-309001

  However, in the vibration cutting as described above, the plate-shaped shank that supports the tool blade edge is inserted into the tip holder, and the plate-shaped shank is simply pressed and fixed from one side with a screw. Although it is simple, the tool blade tip is easily loosened, and the loosening tends to reduce the machining accuracy of vibration cutting. In addition, since the tool edge is not firmly fixed, energy loss tends to increase during vibration cutting.

  Therefore, the present invention enables a highly accurate vibration cutting by securely fixing the tool blade edge, and a vibration cutting apparatus capable of reducing energy loss during vibration cutting, and a molding manufactured using the vibration cutting apparatus. An object is to provide a mold and an optical element.

In order to solve the above-mentioned problems, a vibration cutting apparatus according to the present invention includes (a) a cutting tool that supports a machining tip at the tip, (b) a vibration source for vibrating the cutting tool, and (c) a tip portion. When holding the cutting tool, the vibrating body that transmits the vibration from the vibration source to the cutting tool, (d) a fastening member that fixes the cutting tool to the tip of the vibrating body, and preventing the fastening member from coming off Fixing means having a locking member.
In the above apparatus, not only the cutting tool is fixed to the tip of the vibrating body by the fastening member, but also the fastening member is prevented from coming off by the locking member, so that the cutting tool is securely fixed to the tip of the vibrating body. Therefore, vibration cutting with high accuracy and low loss can be realized.
In the above apparatus, the tip portion of the vibrating body has a recess for receiving a fixing portion provided at one end of the cutting tool, and a first fixing hole extending so as to intersect the recess, and the fastening member is a cutting member. The screw member includes a screw portion that is inserted into an opening provided in a fixing portion of the tool and is screwed into a first fixing hole, and a head portion that presses a peripheral portion of the opening against the inner surface of the recess. In this case, the fixing portion of the cutting tool is inserted into the recess provided at the tip of the vibrating body, and the screw member is simply screwed into the first fixing hole, and the fixing portion is sandwiched between the head portion and the inner surface of the recess. The cutting tool can be fixed by tightening. In the above-described first fixing hole, the inner diameter of the portion screwed with the screw portion is smaller than the inner diameter of the portion screwed with the plug-like screw.
Further, in the above apparatus, the locking member is plugged into the second fixing hole extending in the same direction as the first fixing hole toward the head portion side of the screw member screwed into the first fixing hole. It is a screw. In this case, the screw member and the plug-like screw are screwed and fixed sequentially into the first fixing hole and the second fixing hole. If it fixes in this way, it will embed a plug-like screw using the space of the remaining part to which the screw member was attached among the 1st and 2nd fixing holes, and securing of a screw member will be secured. It can be fixed securely in a space-saving manner. Note that the plug-like screw includes not only a grub screw but also a screw having a normal outer shape having a screw portion and a head portion.

In another aspect of the present invention, the fixing means has a linear expansion coefficient substantially equal to that of the vibrating body (specifically, a linear expansion coefficient of about 0.75 to 1.25 times the linear expansion coefficient of the vibrating body). It is formed with the material which has. In this case, the distal end portion of the vibrating body and the fixing means expand similarly, and the cutting tool can be fixed stably and reliably regardless of the temperature change. In addition, it is desirable that the material for forming the tip portion and the fixing means has a linear expansion coefficient of 6 × 10 ⁻⁶ or less. In this case, even if the vibration source or the cutting tool generates heat, the thermal expansion of the vibrating body can be suppressed, the cutting tool can be placed at the target position with high accuracy, and high-precision cutting can be performed.

  In another aspect of the present invention, the fixing means is formed of a material having substantially the same specific gravity as the vibrating body (specifically, a specific gravity of about 075 to 10.25 times the specific gravity of the vibrating body). In this case, the tip of the vibrating body has a mass balance corresponding to the shape, and the vibrating body can be vibrated as intended, and the cutting tool can be vibrated with high accuracy.

  Usually, since the linear expansion coefficient and specific gravity of the fixing means and the vibrating body are made to coincide with each other and vibration characteristics are not biased, the material of the fixing means is the same as the material of the vibrating body. In this case, the fixing means has the same linear expansion coefficient as that of the vibrating body and has the same specific gravity as that of the vibrating body.

  In another aspect of the present invention, the fastening member and the locking member are attached to the distal end portion of the vibrating body so as to fill the fixing hole. In other words, the fastening member and the locking member are embedded in the fixing hole with almost no excess or deficiency so that almost no concave portion or convex portion remains at the position of the fixing hole. In this case, the distal end portion of the vibrating body can be formed into a shape that does not waste externally, and mass unbalance due to the fixing hole can be reduced to ensure stable vibration of the cutting tool.

  In another aspect of the present invention, the cutting tool includes a plate-like support member that extends in the distal direction from the fixed portion and supports the machining tip, and the concave portion is a slit-like groove that fits with the fixed portion. In this case, the cutting tool can be securely fixed by the fixing means while keeping the cutting tool lightweight.

  In another aspect of the present invention, the machining tip has a tip disposed on an extension of the tool axis of the vibrating body. In this case, since the machining point is arranged on the extension of the tool axis, the machining tip is displaced about the extension line of the tool axis, and the symmetry of vibration is improved on the tool axis. Therefore, the surface to be processed is cut more smoothly, and the processing accuracy can be improved. Moreover, it is easy to grasp the arrangement of the cutting tool and the tip of the vibrating body with respect to the work surface, and the workability by the vibration cutting device can be improved.

  The molding die according to the present invention has an optical surface created by machining using the vibration cutting device. In this case, a mold having a concave surface and other various optical surfaces can be efficiently and simply processed with high accuracy.

  The optical element according to the present invention is formed of, for example, plastic, glass or the like, and is molded by the molding die. In this case, a high-precision optical element can be obtained with a high-precision mold.

[First Embodiment]
Hereinafter, a vibration cutting apparatus according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram illustrating the structure of a vibration cutting apparatus that processes the optical surface of a molding die for molding an optical element such as a lens.

  As shown in FIG. 1, the vibration cutting device 10 includes a vibration cutting unit 20 for cutting a workpiece W that is a workpiece, an NC control mechanism 30 that supports the vibration cutting unit 20 with respect to the workpiece W, A stage driving device 40 that controls the operation of the NC control mechanism 30, a vibrator driving 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 a main controller 70 that controls the overall operation of the apparatus.

  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 lower portion, and cuts the workpiece W by high-frequency vibration of the cutting tool. Details of the vibration cutting unit 20 will be described later.

  The NC control mechanism 30 has a structure in which a column 33 is provided on a pedestal 31, and includes a head 37 that is attached to the column 33 and moves up and down in the Z direction. The vibration cutting unit 20 is attached to the head 37, and the tool portion 21 is exposed at the bottom. The head 37 supports the vibration cutting unit 20 and can be moved to a desired position in the XY plane at a desired speed, and the vibration cutting unit 20 is rotated by a desired angle around the tip position and the tool axis. Can be made. A stage 35 is provided on the pedestal 31 so as to face the vibration cutting unit 20. The stage 35 supports the workpiece W, can be arranged and fixed at an appropriate position in the XY plane, and can rotate the workpiece W around a vertical axis parallel to the Z axis at a desired speed. it can.

  The stage driving device 40 is capable of high-precision numerical control, and the head 37 and the stage 35 are driven by driving a motor, a position sensor and the like built in the NC control mechanism 30 under the control of the main control device 70. Is operated as appropriate. Thereby, the three-dimensional position and angle of the tip of the tool portion 21 of the vibration cutting unit 20 with respect to the workpiece W and the rate of change thereof can be freely adjusted. Furthermore, the workpiece W can be rotated around the vertical axis at a high speed while moving the tip of the tool portion 21 of the vibration cutting unit 20 at a low speed (feed operation), and the NC control mechanism 30 is utilized as a high-precision lathe. be able to.

  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. Processing with the tool portion 21 tip, that is, the cutting tool 23 directed to the surface of the workpiece W by vibration or three-dimensional vibration is possible.

  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 that adjusts the temperature of the gas and a flow rate adjusting unit 65 that adjusts 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. 2 is a cross-sectional view illustrating the structure of the vibration cutting unit 20. 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 of the cutting tool 23 is displaced at high speed, for example, exaggeratingly drawing an elliptical orbit EO as illustrated.

The vibrating body 82 is formed of a material having a linear expansion coefficient of 6 × 10 ⁻⁶ or less. Specifically, silicon nitride, sialon, carbide, invar material, stainless invar material, or the like is 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 bending vibrator 84 and enters a resonance state in which a standing wave that is locally displaced in the Y-axis direction or the X-axis direction is formed. 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.

  FIG. 3 illustrates the shape of the first fixing flange 87. The first fixing flange 87 shown in FIG. 3A is a perfect disk-shaped fixing member, and the outer peripheral portion is fixed to the casing 86 of FIG. It has no structure. The first fixing flange 87 shown in FIG. 3B is a fixing member having an opening 87a, and even if the outer peripheral portion is fixed to the casing 86 of FIG. It has become. The first fixing flange 87 shown in FIG. 3C is a fixing member having a supporting member 87b extending in three directions at an equal angle, for example. Even if the tip of the supporting member 87b is fixed to the casing 86 in FIG. Sufficient ventilation inside and outside the body 86 can be secured.

  Returning to FIG. 2, 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 end face on the base side of the vibrating body 82, and is connected via a connector or the like not shown. Are connected to the vibrator driving device 50 of FIG. The axial vibrator 83 operates based on a drive signal from the vibrator driving device 50 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. The bending vibrator 84 is connected to the vibrator driving device 50 of FIG. It is connected. The bending vibrator 84 operates based on a drive signal from the vibrator driving device 50, and applies a transverse wave, that is, a vibration in the Y direction in the illustrated example, to the vibrating body 82 by vibrating at a high frequency.

  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. The shape of the second fixing flange 88 is the same as that of the first fixing flange 87 shown in FIG. 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 casing 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 first fixing flange 87 is attached to one end of the housing 86 so as to close the opening, and an air supply pipe 92 connected to the opening on the end surface is provided on the other end. The air supply pipe 92 is connected to the gas supply device 60 of FIG. 1, and is supplied with pressurized dry air set to a desired flow rate and temperature. That is, the air supply pipe 92 is for cooling the vibration cutting unit 20 from the inside together with the gas supply device 60.

  In the vibration cutting unit 20 described above, the vibrating body 82, the axial vibrator 83, and the counter balance 85 are fixed to each other by brazing, and the axial vibrator 83 can be efficiently vibrated. Yes. Further, a through hole 91 is formed through the vibrating body 82, the axial vibrator 83, and the counter balance 85, and pressurized dry air from the air supply pipe 92 circulates therethrough. . The tip of the through hole 91 is a fine hole 91a that branches into two or more branches, and the pressurized dry air introduced into the through hole 91 can be discharged to the vicinity of the tip part 21a of the tool part 21.

  FIGS. 4A and 4B are a side sectional view and a plan sectional view of the tip of the tool portion 21 shown in FIG.

  As is apparent from the drawing, the tip 21a provided on the tool portion 21 has a quadrangular shape in a side view and a triangular wedge shape in a plan view. The cutting tool 23 held by the tip 21a of the tip 21a includes a shank 23b having a triangular tip and a plate-like shape as a whole in plan view, and a machining tip 23c fixed to the tip of the shank 23b. Among these, the shank 23b is a support member formed of, for example, a super hard 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 end surface 21d of the distal end portion 21a, and the tip of the processing tip 23c is disposed on the extension of the tool axis AX extending in the cutting depth direction. Further, the processing chip 23c and the shank 23b that supports the processing chip 23c are accommodated in a wedge-shaped space having an opening angle θ extending from the wedge side surface (left and right side surfaces) of the tip portion 21a. Here, the opening angle θ of the tip portion 21a is in the range of 20 ° to 90 °. By setting the opening angle θ to 20 ° or more, the bending strength and the like of the distal end portion 21a can be secured at a sufficiently high level. Further, by setting the opening angle θ to 20 ° or more, it is possible to suppress the tendency of the vibration mode to change in the vicinity of the tip portion 21a, and to prevent the cutting accuracy of the cutting tool 23 from being lowered by unintended vibration. . On the other hand, by setting the opening angle θ of the tip end portion 21a to 90 ° or less, the tip end portion 21a is less likely to interfere with the workpiece surface SA of the workpiece W. Therefore, the restriction on the processing shape is reduced and the shape is arbitrarily determined be able to.

  The cutting tool 23, that is, the root portion 23e of the shank 23b is inserted in a state of fitting into a slit-like groove 21f having a rectangular cross section cut in the XZ plane along the tool axis AX from the end surface 21d of the tip 21a. In addition, the two fixing screws 25 and 26 formed of the same material as the material of the tool portion 21 are detachably and firmly fixed to the distal end portion 21a. Specifically, fixing screws 25 and 26 are sequentially screwed into fixing holes 21h and 21g that penetrate between the upper and lower side surfaces of the tip 21a. These fixing holes 21h and 21g extend, for example, in the Y-axis direction, and the tightening direction of both is orthogonal to the tool axis AX. Both the fixing holes 21h and 21g have different inner diameters, and the inner diameter of the fixing hole 21g is larger than the inner diameter of the fixing hole 21h. Both fixing holes 21h and 21g are filled by screwing both fixing screws 25 and 26. That is, deep concave portions are not left or high convex portions are not formed at the positions of the fixing holes 21h and 21g. One fixing screw 25 screwed into the fixing hole 21h is a fastening member for fixing the cutting tool 23, and is a Torx screw including a male screw portion 25b and a head portion 25a. By screwing the head portion 25a with an appropriate tool while the male screw portion 25b is inserted into the fixing hole 21g, the male screw portion 25b passes through the opening 23h formed in the root portion 23e, and the fixing hole 21g It is screwed with a female screw on the inner surface of the fixing hole 21h formed at the back. At this time, the root portion 23e of the cutting tool 23 is clamped between the head portion 25a and the inner surface of the slit-shaped groove 21f, and the root portion 23e is fixed from the main surface side, so that separation of the cutting tool 23 is prevented. Fixing of the cutting tool 23 is ensured. The other fixing screw 26 screwed into the fixing hole 21g is a so-called potato screw and functions as a locking member for preventing the fixing screw 25 from coming off. The fixing screw 26 is screwed into the fixing hole 21g by being screwed into the female screw on the inner surface of the fixing hole 21g by turning the upper end to the fixing hole 21g and turning the upper end with an appropriate tool, thereby filling the fixing hole 21g. . Since the fixing screw 25 is tightened from the upper end by the fixing screw 26 screwed in this way and the fixing screw 25 is prevented from loosening, the cutting tool 23 is more securely fixed, and the vibration of the cutting tool 23 is reduced. be able to.

  FIG. 5A is a plan view of the cutting tool 23, and FIG. 5B is a side view of the cutting tool 23. As is apparent from the figure, the machining tip 23c is fixed to the pointed end side of the plate-like cutting tool 23, and a fixing opening 23h is provided to the other end side of the cutting tool 23. FIG. 5C is a plan view of the fixing screw 25, and FIG. 5D is a side view of the fixing screw 25. On the side surface of the male screw portion 25b of the fixing screw 25, a screw thread 25c that is screwed with the inner surface of the fixing hole 21h in FIG. 4 is formed. FIG. 5E is a plan view of the fixing screw 26, and FIG. 5F is a side view of the fixing screw 26. On the side surface of the male screw portion 25b of the fixing screw 26, a screw thread 26c that is screwed with the inner surface of the fixing hole 21g in FIG. 4 is formed.

  Returning to FIG. 2, the tip portion 21a of the tool portion 21 vibrates at a high speed in, for example, the YZ plane. Further, the distal end portion 21a of the tool portion 21 is gradually moved, for example, by drawing a predetermined locus in the YZ plane by the NC control mechanism 30 in FIG. 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 a rotation axis RA parallel to the Z axis by the NC control mechanism 30 in FIG. 1 (see FIG. 4). Thereby, for example, a processed surface SA (for example, a curved surface such as an uneven spherical surface or an aspherical surface, or a stepped surface such as a phase element surface) that is rotationally symmetric about the rotation axis RA with respect to the workpiece W can be formed. . At this time, by using the head 37, 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 tip of the cutting tool 23 is to be formed on the workpiece W. It is made to be substantially perpendicular to the processing surface SA (see FIG. 6). Thereby, the processing accuracy of the processing surface SA can be increased, and the processing surface SA can be made smoother.

  Hereinafter, the material forming the vibrating body 82 will be described. The counter balance 85 is also formed of the same material as that of the vibrating body 82.

As the material of the vibrating body 82, a material having a linear expansion coefficient of 6 × 10 ⁻⁶ or less is used. Specifically, silicon nitride, sialon, carbide, invar material, stainless invar material, or the like is preferably used. Thus, when a material having a linear expansion coefficient of 6 × 10 ⁻⁶ or less is used as the material of the vibrating body 82, the linear expansion coefficient is about half of 10-11 × 10 ⁻⁶ of the most common hardened steel material. Therefore, it is possible to prevent the processing accuracy from being lowered due to the thermal expansion of the vibrating body 82.

There are many materials having a linear expansion coefficient of 6 × 10 ⁻⁶ or less, but broadly divided into alloy materials and ceramic materials. Alloy materials are easier to process than ceramics, but their specific gravity is high and Young's modulus is low, so they are not suitable for resonating at high frequencies. Ceramic materials, on the other hand, have a Young's modulus of about 2 to 3 times that of steel, and the specific gravity is less than half, so it is light and easy to vibrate at a high frequency. It is easy to obtain a resonance frequency with high purity. That is, the Q value of the material is high, and the vibrating body 82 should be manufactured with such a material.

Hereinafter, specific materials of the vibrating body 82 will be described. The vibrating body 82 can be formed of, for example, silicon nitride or sialon. Since silicon nitride and sialon are ceramic materials having almost the same characteristics, the linear expansion coefficient at room temperature is as very small as 1.3 × 10 ⁻⁶ , which is about 1/10 of the steel material. The amount of thermal expansion and contraction is significantly reduced, and the temperature drift of the cutting edge position of the cutting tool 23 held at the tip is dramatically reduced. As a result, stable vibration and a cutting amount can be ensured, so that a highly accurate cutting surface can be obtained efficiently and with good reproducibility in the workpiece W.

  Furthermore, silicon nitride and sialon are very tough among ceramic materials, have a characteristic of being able to obtain a relatively large amplitude at a single vibration frequency with little distortion because they vibrate flexibly. Further, since the specific gravity is very light as 3.3 and the inertia force is small and the Young's modulus is as large as 300 GPa, it is easy to vibrate at a high frequency. Therefore, the load on the vibrators 83 and 84 can be reduced and the amount of generated heat can be kept low, which is very good for reducing the temperature drift of the cutting edge position of the cutting tool 23. In addition, the thermal conductivity is about stainless steel, which is relatively high for ceramics, and has a feature that it propagates without accumulating heat in the vibrating body 82 and suppresses temperature rise. Further, since silicon nitride and sialon are ceramic materials that are resistant to impacts, they are characterized by being less susceptible to cracking due to vibration loads and damage due to accidents during processing of the workpiece W.

The vibrating body 82 can be formed of, for example, a super hard material. The term “super hard material” as used herein refers to all alloys containing 80% by weight or more of tungsten carbide. Carbide material has a coefficient of linear expansion of 6 × 10 ⁻⁶ , which is about half that of steel, and has a very high rigidity and high Young's modulus, so the resonance frequency can be made relatively high. Is heavy, it is necessary to supply large energy to the vibrators 83 and 84. On the other hand, since it becomes much harder to break than when the vibrating body 82 is formed of a ceramic material, it is suitable as a structural material for holding and fixing the cutting tool 23, and the reliability of the vibrating body 82 can be increased.

The vibrating body 82 can be formed of an invar material, for example. The invar material here refers to all alloy materials in which the main component containing 50 atomic% or more is Fe and the constituent containing 10 atomic% or more is composed of at least Ni. The invar material as described above is, for example, an iron alloy containing 36 atomic% nickel, and 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 23 held at the tip is reduced. Can be suppressed.

The vibrating body 82 can be formed of, for example, a stainless invar material. As used herein, the term “stainless steel invar material” refers to all alloy materials in which the main component of 50 atomic% or more is Fe and the incidental material including 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. The 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 23 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 applied with a processing coolant or the like, so it is suitable as a structural material for holding and fixing the cutting tool 23. Yes.

  The above is the description of the material of the vibrating body 82, but the fixing screws 25 and 26 that are fixing means for fixing the cutting tool 23 to the distal end portion 21 a of the vibrating body 82 also have the same linear expansion coefficient as that of the vibrating body 82. It is desirable to use a material having 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. As the material of the fixing screws 25 and 26, considering the ease of processing and the like, high-speed steel and the like are suitable in addition to the superhard material as described above, but silicon nitride, sialon, invar material, stainless invar material, etc. It can also be used.

  The fixing screws 25 and 26 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, but the fixing screws 25 and 26 and the vibrating body 82 can also be formed of different materials.

  In summary, according to the vibration cutting apparatus 10 of the present embodiment, not only the cutting tool 23 is fixed to the distal end portion 21a by the fixing screw 25 that is a fastening member, but also by the fixing screw 26 that is a locking member. Since the fixing screw 25 is prevented from coming off, the cutting tool 23 can be reliably fixed to the tip portion 21a of the tool portion 21, and vibration cutting with high accuracy and low loss can be realized. Moreover, since the root portion 23e, which is the fixing portion of the cutting tool 23, is clamped between the head portion 25a of the fixing screw 25 and the inner surface of the slit-like groove 21f, the cutting tool can be fixed without loosening. Vibration cutting can be performed, and generation of ultrasonic frictional heat and energy loss can be reduced during vibration cutting.

  Further, according to the vibration cutting device 10 of the present embodiment, the fixing screws 25 and 26 that are fixing means are formed of a material having substantially the same linear expansion coefficient as that of the tool portion 21. 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. Further, fixing screws 25 and 26 as fixing means are formed of a material having substantially the same specific gravity as the tool portion 21. In this case, the tip portion 21a of the tool portion 21 has a mass balance corresponding to the shape, and the tool portion 21 and the cutting tool 23 can be vibrated as intended. Further, fixing screws 25 and 26 as fixing means are attached so as to fill the fixing holes 21g and 21h. In this case, the distal end portion 21a of the tool portion 21 can be formed into a shape that is not wasteful in outer shape, and the mass unbalance due to the fixing holes 21g and 21h can be reduced to ensure stable vibration of the cutting tool 23. it can.

[Second Embodiment]
Hereinafter, the molding die according to the second embodiment will be described. FIG. 7 is a view for explaining a molding die manufactured using the vibration cutting unit 20 of the first embodiment, and FIG. 7A is a side sectional view of the fixed die, that is, the first die 2A. FIG. 7B is a side sectional view of the movable mold, that is, the second mold 2B. The optical surfaces 3a and 3b of both molds 2A and 2B are finished by a vibration cutting apparatus shown in FIGS. That is, the base material (material is, for example, cemented carbide) of both molds 2A and 2B is fixed on the stage 35 as a work 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 stage driving 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 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 and phase structure surfaces.

  FIG. 8 is a cross-sectional view of a lens L press-molded using the mold 2A of FIG. 7A and the mold 2B of FIG. 7B. The material of the lens L is not limited to plastic but can be glass or the like.

  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 overall shapes and dimensions of the vibrating body 82 and the axial vibrator 83 can be appropriately changed according to the application. Further, the second fixed flange 88 extending from the counter balance 85 can be omitted. Moreover, although the through-hole 91 is provided in axial centers, such as the vibrating body 82, and pressurized dry air is distribute | circulated, the supply method of pressurized dry air is not restricted to the air supply pipe 92 illustrated in FIG. For example, it is possible to supply pressurized dry air around the vibrating body 82 from the side surface of the housing 86. 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. 1, instead of air, a gaseous fluid added by misting oil or other lubricating elements, an inert gas such as nitrogen gas, or the like can be used.

  In addition, the shape, size, and the like of the fixing screws 25 and 26 for fixing the cutting tool 23 can be changed as appropriate. For example, the fixing screw 26 can be a plug-like screw having a head like the fixing screw 25.

It is a block diagram explaining the vibration cutting apparatus of 1st Embodiment. It is a longitudinal cross-sectional view explaining the structure of the vibration cutting unit integrated in the vibration cutting apparatus of FIG. (A)-(c) is an end elevation which illustrates the shape of the 1st fixed flange used for the vibration cutting unit of FIG. (A), (b) is the side sectional drawing and plane sectional drawing of a tool part front-end | tip. (A), (b) is the top view and side view of a cutting tool, (c), (d) is the top view and side view of a fixing screw for fastening, (e), (f) These are a top view and a side view of a fixing screw for locking. It is a top view explaining the movement and turning of a tool part front-end | tip. (A), (b) is a sectional side view of the molding die concerning a 2nd embodiment. FIG. 8 is a side sectional view of a lens formed by the molding die of FIG. 7.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Vibration cutting apparatus, 20 ... Vibration cutting unit, 21 ... Tool part, 21a ... Tip part, 21d ... End surface, 21h ... Fixing hole, 23 ... Cutting tool, 23b ... Shank, 23c ... Chip for processing 25, 26 ... Fixing screw, 25b ... male screw part, 25a ... head part, 30 ... NC control mechanism, 31 ... pedestal, 40 ... stage drive device, 60 ... gas supply device, 82 ... vibrating body, 83, 84 ... vibrator, 84 ... Flexural vibrator, PX ... Swivel axis, RA ... Rotary axis, SA ... Work surface, .theta .... Open angle

Claims (9)

A cutting tool for supporting a processing tip at the tip;
A vibration source for vibrating the cutting tool;
A vibrator that transmits vibration from the vibration source to the cutting tool;
A fixing member having a fastening member for fixing the cutting tool to the distal end portion of the vibrator, and a locking member for preventing the fastening member from coming off;
The tip of the vibrator has a recess for receiving a fixing portion provided at one end of the cutting tool, and a first fixing hole extending so as to intersect the recess.
The fastening member is inserted into an opening provided in the fixing portion of the cutting tool and screwed into the first fixing hole, and a head portion pressing a peripheral portion of the opening against the inner surface of the recess A screw member having
The locking member is a plug-like screw screwed into a second fixing hole extending in the same direction as the first fixing hole toward the head portion side of the screw member screwed into the first fixing hole. There is a vibration cutting apparatus characterized by that.   The vibration cutting apparatus according to claim 1, wherein the fixing unit is made of a material having substantially the same linear expansion coefficient as the vibrating body.   3. The vibration cutting device according to claim 1, wherein the fixing unit is made of a material having substantially the same specific gravity as the vibration body. 4.   The vibration cutting apparatus according to claim 1, wherein the fixing unit is made of the same material as that of the vibrating body.   5. The vibration cutting device according to claim 1, wherein the fastening member and the locking member are attached to the distal end portion of the vibrating body so as to fill the fixing hole. .   The cutting tool includes a plate-like support member that extends in a distal direction from the fixed portion and supports the processing chip, and the concave portion is a slit-like groove that fits the fixed portion. The vibration cutting device according to any one of claims 1 to 5.   The vibration cutting apparatus according to claim 1, wherein the machining tip has a tip disposed on an extension of a tool axis of the vibrating body.   A molding die having an optical surface created by machining using the vibration cutting device according to any one of claims 1 to 7.   An optical element molded by the molding die according to claim 8.

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