JP2006326833A - Method of machining aspheric surface - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for machining an aspheric surface capable of quickly grinding and cutting a considerably uneven workpiece with high quality through the use of a conventional aspheric surface machining device in a simple control method, and an apparatus therefor. <P>SOLUTION: A workpiece 208 to be machined rotating around the rotation axis as the center and a rotary tool 214 relatively movable with the workpiece in the same direction as the rotary axis of the workpiece and in the direction orthogonal to the rotary axis of the workpiece are provided. The rotary tool moves in a constant direction with a predetermined feed pitch over a partial or entire region from the center of the rotary axis of the workpiece to the outer periphery of the workpiece in the direction orthogonal to the rotary axis of the workpiece for machining the workpiece into a non-axisymmetrical aspheric surface. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an aspherical surface processing method, and more particularly, to an aspherical surface processing method, an aspherical surface forming method, and an aspherical surface processing apparatus capable of rapidly grinding and cutting an aspherical surface having a large uneven surface.

  As a spectacle lens for correcting presbyopia, a so-called progressive power lens without a border is often used. In recent years, so-called inner surface progressive lenses have been proposed in which a concave surface on the eyeball side is provided with a curved surface obtained by combining a progressive surface or a progressive surface toric surface. This inner surface progressive lens can reduce fluctuations and distortions, which are disadvantages of a progressive power lens, and can dramatically improve optical performance.

  Prior art document information relating to a technique for creating a non-axisymmetric aspheric surface such as a concave progressive surface of a spectacle lens includes those shown in Patent Document 1 and Patent Document 2.

  A three-axis controlled aspherical processing device that creates a non-axisymmetric aspherical surface uses an X-axis table, a Y-axis table, and a workpiece rotating means to continuously position a rotary tool at a predetermined position, and perform grinding and grinding. Create a shape based on the lens design shape by cutting.

  The outline of the control method is that while rotating the workpiece, the rotation position of the workpiece is indexed by an encoder, and the three axes of the X-axis table, the Y-axis table, and the workpiece rotation means are controlled in synchronization with the rotation position.

  A normal control processing method that is a conventional shape creation control method using this aspherical processing apparatus will be described with reference to FIGS. 12, 13, and 14. FIG. FIG. 12 is a schematic view showing a processed surface of a lens in the normal control processing method. 12A is a front view of the lens, and FIG. 12B is a cross-sectional view taken along the line BB ′ of FIG. FIG. 13 is a conceptual diagram showing a normal control processing method. FIG. 14 is a conceptual diagram showing the position of the rotary tool center in the X-axis direction in the normal control machining method.

  Numerical data for NC control in the normal control machining method will be described using an arbitrary point Qx shown in FIG. The numerical data for NC control of the normal control processing method assumes a spiral defined by a feed pitch P from the outer periphery of the circular lens to the rotation center, and the radiation and spiral at a predetermined angle from the rotation center of the lens. The coordinate value of each intersection is given by the rotation angle (θ) of the lens and the distance (radius Rx) from the rotation center. Further, the height (y) corresponding to the surface shape in the Y-axis direction passing through each intersection not shown is obtained. These three points are obtained as coordinate values (θ, Rx, y) of the machining points.

  The toric surface has a curve with a minimum curvature along the line AA ′ (base curve) and a curve with the maximum curvature along the line BB ′ orthogonal to the line AA ′ (cross curve). It has a curved surface. When the difference in curvature between the base curve and the cross curve is large, as shown in FIG. 12B, the cross section cut along the cross curve has a curved surface shape having extremely thick end portions and a thin central portion. Each time the rotary tool 214 rotates 180 degrees, it reciprocates between the height of the minimum thickness portion and the height of the maximum thickness portion. That is, it reciprocates in the Y axis direction. For example, as shown in FIG. 13, when the lens is rotated 90 degrees from the AA ′ cross-section to the BB ′ cross-section, an arbitrary processing with the maximum height from an arbitrary processing point Qn in the minimum thickness portion. The rotary tool 214 moves to the plus side in the Y-axis direction up to the point Qnm.

  The tip of the rotary tool 214 used for grinding and cutting is formed in a cross-sectional arc shape (hereinafter referred to as a round shape). In the normal control, for example, the center of the rounded portion of the tip of the rotary tool 214 is positioned in the normal direction set up at the processing point Qn of the lens.

  More specifically, at an arbitrary machining point Qn on the minimum thickness curve (base curve, AA ′ cross section), the center point Pn of the rotary tool 214 is positioned in the normal direction established from the machining point Qn. At an arbitrary processing point Qnm on the maximum height curve (cross curve, BB ′ cross section) obtained by rotating the lens 90 degrees from the processing point Qn, the center of the rotary tool 214 in the normal direction established from the processing point Qnm. Point Pnm is positioned. Here, the processing point Qnm moves from the processing point Qn by a quarter pitch toward the center side in the X-axis direction. While moving from the machining point Qn to the machining point Qnm, the rotary tool 214 moves ΔY in the plus direction in the Y-axis direction, and relatively moves Xm toward the center side in the X-axis direction. At an arbitrary processing point Qnr on the minimum height curve (base curve, AA ′ cross section) obtained by further rotating the lens by 90 degrees, the rotary tool 214 moves in the negative direction of the Y-axis direction (not shown). Yes. At this time, in the X-axis direction, since the thickness decreases and the speed toward the outside is larger than the speed toward the center side of the feed pitch, the rotary tool 214 moves toward the outer periphery as shown in FIG. Move relative to Xr. That is, the cross curve of the BB ′ cross section becomes an inflection point where the sign of the moving direction is forward and reverse, and the rotary tool 214 has the opposite direction of motion with respect to the cross curve of the BB ′ cross section. Perform reciprocal movement in the Y-axis direction and the X-axis direction.

  In the processing method by normal control, as shown in FIG. 12, the intersection of the spiral and the radiation is used as a processing point, and the center position of the tip of the rotary tool 214 is controlled in the normal direction set at this processing point. . That is, in the machining method based on normal control, the rotary tool 214 repeats that the direction of motion is opposite to the opposite direction as described above, and grinds and cuts the workpiece while drawing a complicated zigzag spiral path.

Japanese Patent No. 3367102 Japanese Patent Laid-Open No. 10-175149

  In the normal control processing method using the aspherical surface processing apparatus described above, the X-axis table causes the workpiece to reciprocate in the X-axis direction, and the Y-axis table causes the rotary tool to reciprocate in the Y-axis direction. Therefore, the reciprocating motion control of the X-axis table and the reciprocating motion control of the Y-axis table are intertwined, and the control of both tables is complicated. Therefore, when grinding and cutting a toric surface or the like that corrects high-level astigmatism with uneven steps, the control method employed in normal lens processing uses grinding and cutting shapes due to backlash associated with reciprocating motion. Collapse has occurred. Therefore, there is a problem that a complicated control method and a high-function control device for operating the method are required.

  Further, since the X-axis table needs to move at least the distance of the radius of the workpiece, there is a limit to making it small, and the inertial force is large and heavy. Therefore, it is difficult to make the workpiece reciprocate at a high speed in the X-axis direction. Therefore, when the toric surface or the like is ground and cut, the X-axis table cannot follow the rotational speed of the workpiece employed in normal lens processing. If an ultra-high output motor is used, the X-axis table may be reciprocated at high speed, but this is not practical. Therefore, the number of rotations of the workpiece is reduced to the extent that the X-axis table can follow. As a result, the problem that productivity falls will arise.

  The present invention has been made in view of the above circumstances, and an aspherical surface processing capable of grinding and cutting a workpiece having a large unevenness with a simple control method with a simple control method using a conventional aspherical surface processing device. It is an object to provide a method, an aspherical surface forming method, and an aspherical surface processing apparatus.

  In order to achieve the above-mentioned object, an aspherical surface processing method according to the present invention includes a workpiece to be rotated about a rotation axis, a direction identical to the rotation axis of the workpiece, and a direction orthogonal to the rotation axis of the workpiece. A rotary tool that can move relative to the workpiece, and the rotary tool is a part or all from the center of the rotation axis of the workpiece to the outer periphery of the workpiece in a direction orthogonal to the rotation axis of the workpiece. In this area, the workpiece is processed into a non-axisymmetric aspherical surface by moving in a predetermined direction at a predetermined feed pitch.

  According to the aspherical surface processing method of the present invention, the rotary tool moves in a predetermined direction at a predetermined feed pitch to process the workpiece, and therefore the rotary tool draws a simple spiral trajectory that is not zigzag-shaped. While grinding and cutting the workpiece. That is, the rotary tool always moves relatively in a fixed direction without reciprocating in the direction orthogonal to the rotation axis of the workpiece.

  Therefore, since the X-axis table of the aspherical surface processing apparatus moves in a fixed direction without reciprocating the workpiece, the control method of the X-axis table is simplified, and it is not necessary to improve the performance of the control apparatus. Further, it is possible to follow even if the number of rotations of a workpiece having a large unevenness is increased, and it is possible to perform grinding and cutting quickly with high quality by a simple control method as compared with the conventional example.

  Further, the present invention provides an aspherical machining method characterized in that the position of the rotary tool is controlled so that the rotation center axis of the tip of the rotary tool is positioned in the normal direction set at the machining point of the workpiece.

  Further, the machining with the rotary tool is performed when the distance between the rotation center of the workpiece and the tip of the rotary tool in the direction orthogonal to the rotation axis of the workpiece is zero or near zero, or with the outer peripheral edge of the workpiece and the rotation. Provided is an aspherical surface processing method characterized in that control is performed so that the distance from the tool tip starts from zero or near zero.

  The rotating tool is a grindstone that rotates about a rotation axis.

  The rotating tool is a cutting tool that rotates about a rotation axis.

  Further, by roughing the workpiece into a shape that approximates a desired shape, and processing the workpiece using the aspherical surface processing method according to claim 1 to claim 3, following the roughing step, A method of forming an aspherical surface, comprising: a finishing cutting step for forming the workpiece into a desired shape.

  An aspherical surface processing apparatus incorporating the aspherical surface forming method according to claim 6 is provided.

  Examples of the aspherical surface processing method according to the present invention will be described below.

== Description of the processing apparatus ==
An aspherical surface processing device (also referred to as an NC control device) used in the aspherical surface processing method of the present invention will be described with reference to FIG. FIG. 1 is an elevation view showing an aspherical surface processing apparatus used in the aspherical surface processing method of the first embodiment.

  The aspherical surface processing apparatus 200 includes an X-axis table 202 and a Y-axis table 203 on a bed 201. The X-axis table 202 is driven to reciprocate in the X-axis direction by an X-axis drive motor 204. The position in the X-axis direction is determined by an encoder (not shown) incorporated in the X-axis drive motor 204. A workpiece axis rotating unit 205 as a workpiece axis rotating means is fixed on the X axis table 202. A workpiece chuck 206 is attached to the workpiece axis rotation unit 205, and is rotated by a workpiece rotation axis driving motor 207 with the main axis in the Y axis direction orthogonal to the X axis as a rotation axis. The rotation position of the work chuck 206 is determined by an encoder (not shown) incorporated in the work rotation shaft driving motor 207. A workpiece (eyeglass lens) 208 to be processed is attached to the workpiece chuck 206 via a block jig (not shown). The Y-axis table 203 is driven to reciprocate by a Y-axis drive motor 209 in a substantially horizontal Y-axis direction orthogonal to the X-axis table 202. The position in the Y-axis direction is determined by an encoder (not shown) incorporated in the Y-axis drive motor 209. A Z-axis table 210 is provided on the Y-axis table 203. The Z-axis table 210 is driven to reciprocate in the Z-axis direction by a Z-axis drive motor 211. The position in the Z-axis direction is determined by an encoder (not shown) incorporated in the Z-axis drive motor 211. On the Z-axis table 210, a rotary tool rotating unit 212 as a rotary tool rotating means is fixed. A rotating tool 214 is attached to the rotating tool shaft 213 of the rotating tool rotating unit 212, and is rotated by a Z-axis driving motor 211 about the main axis in the Z-axis direction orthogonal to the X-axis as a rotating shaft.

  The aspherical surface processing apparatus 200 fixes the workpiece axis rotating unit 205 and replaces the Y axis table 203 with the X axis table 202 instead of reciprocating the workpiece axis rotating unit 205 in the X axis direction by driving the X axis table 202. The rotary tool 214 may be reciprocated in the X-axis direction by the X-axis table 202.

  Further, a linear scale may be used in place of the encoder as the X axis, Y axis, and Z axis position detecting means.

  Here, a control method will be described.

  First, the rotation center of the rotary tool 214 in the Z-axis direction determined by the encoder is aligned with the rotation center of the workpiece 208. Next, while rotating the workpiece 208, the rotation position of the workpiece 208 is indexed by an encoder. Next, the relative position of the rotary tool 214 in the Y-axis direction, which is the rotation axis of the workpiece 208 indexed by the encoder, and the workpiece 208 are synchronized with the rotation of the workpiece 208, and the rotation in the X-axis direction indexed by the encoder is performed. The distance between the rotation center of the tool shaft 213 and the rotation center of the workpiece 208 is synchronized with the rotation of the workpiece 208. In this way, the rotary tool 214 is positioned at the machining point using the three axes of the X-axis table 202, the Y-axis table 203, and the workpiece axis rotation unit 205. The shape creation based on the lens design shape is performed by continuously positioning the rotation center coordinate of the rotary tool shaft 213 corresponding to the machining point.

  The numerical data necessary for the aspherical surface processing apparatus 200 to process the workpiece (eyeglass lens) 208 is calculated by the calculation computer 400 based on the prescription data of the eyeglass lens input from the input device 300 that is an input means. Then, it is stored in the storage device inside the aspherical surface processing apparatus 200 via the host computer 500 or transmitted from the host computer 500 to the aspherical surface processing apparatus 200 during the processing.

== Description of grinding and cutting procedures ==
Here, grinding and cutting procedures for creating an aspheric surface will be described with reference to FIG. FIG. 2 is a cross-sectional view of a lens which is an example of a workpiece.

  The grinding and cutting method includes outer diameter machining, approximate machining roughing machining, finishing machining, chamfering machining, and the like. As shown in FIG. 2, the outer diameter machining is a slightly thick lens 208 (hereinafter referred to as “semi-finish lens 208”) having a post-processing allowance (cutting allowance, grinding allowance) as an example of the workpiece 208. In this process, the unnecessary outer peripheral portion 208a is cut and reduced to a predetermined outer diameter. The external shape processing is also processing for shortening roughing processing and finishing processing. The approximate machining surface roughing process is a roughing process in which the semifinished lens 208 is quickly ground to a predetermined approximate surface shape 208b. In the finish machining, a desired lens surface shape 208c is precisely created by machining from the approximate surface shape 208b. The chamfering process is a process in which the edge of the lens after the finishing process is sharp and dangerous, and is easily chipped, so that the edge chamfering 208d is performed by the rotary tool 214 (for finishing).

  A process for grinding and cutting the semi-finished lens 208 using the aspherical surface processing apparatus 200 shown in FIG. 1 will be described. A semi-finished lens 208 fixed to a block jig (not shown) is fixed to the work chuck 206, and the outer diameter of the semi-finished lens 208 is set to a predetermined diameter based on outer diameter processing data given to the semi-finished lens 208. Until the rotating tool 214 (for roughing) is ground and cut. Subsequently, the surface roughness Rmax is 100 μm or less with a free curved surface, a toric surface or a spherical surface shape approximated to the desired lens surface shape 208c based on the rough surface processing data of the approximate surface processing surface using the rotary tool 214 (for roughing). The approximate surface shape 208b is ground and cut. Subsequently, prescription data for a spectacle lens whose surface roughness Rmax is about 1 to 10 μm by further grinding and cutting about 0.1 to 5.0 mm based on the finishing machining data using the rotary tool 214 (for finishing). To the lens surface shape 208c based on the above. Subsequently, the chamfering 208d based on the chamfering data is performed using the rotary tool 214 (for finishing).

== Explanation of grinding and cutting conditions ==
The grinding and cutting conditions are as follows.
<For grinding>
Rotary tool: Whetstone Bond type: Metal, Resin. The number of rotations of the workpiece is 1 to 300 rpm for roughing and 1 to 300 rpm for finishing. The feed pitch is 0.05 to 5.0 mm / rev for roughing and 0.005 to 1.0 mm / rev for finishing. The cutting depth is 0.1 to 5.0 mm / pass for roughing. In the finishing process, 0.001 to 0.5 mm / pass (depending on the mesh of the grindstone).
<For cutting>
Rotary tool: Cutter Material: Monocrystalline / polycrystalline diamond. The number of rotations of the workpiece is 1 to 300 rpm for roughing and 1 to 300 rpm for finishing. The feed pitch is 0.05 to 5.0 mm / rev for roughing and 0.005 to 1.0 mm / rev for finishing. The cutting depth is 0.1 to 10.00 mm / pass in rough cutting. In finishing, 0.05 to 3.0 mm / pass.

  Most of the machining is performed under the condition that the feed pitch is constant, but the feed pitch may be changed during the machining. As an example, when the astigmatism is 2.00 D or more regardless of the refractive index of the lens, chipping at the outer periphery of the lens is likely to occur. When processing such a lens, the lens is processed at a small feed pitch P1 at the outer peripheral portion of the lens, and is processed at a large feed pitch P0 at the inner peripheral portion near the center of the lens (P1 <P0). Specifically, P1 is determined in the range of 0.01 mm / rev to 0.07 mm / rev, and P0 is determined in the range of 0.03 mm / rev to 0.10 mm / rev. Moreover, the outer peripheral part of the lens which processes with the feed pitch P1 is the range of 5-15 mm from the outermost periphery of a lens.

  The first embodiment of the aspherical surface processing method of the present invention will be described with reference to FIGS. 3, 4, 5, 6, and 7 by taking processing of a spectacle lens (hereinafter referred to as “lens”) as an example. explain. FIG. 3 is a schematic view showing a processed surface of a lens in the aspherical processing method. 3A is a front view of the lens, and FIG. 3B is a cross-sectional view taken along the line BB ′ of FIG. 3A. FIG. 4 is a conceptual diagram of three-dimensional coordinates divided into a lattice pattern on the surface of the tip of the rotary tool. 4A is an elevation view, a plan view, and a side view showing the positional relationship between the workpiece and the rotary tool, and FIG. 4B is an enlarged view of the rotary tool in FIG. 4A. FIG. 5 is a conceptual diagram showing three-dimensional coordinates on the workpiece surface and the surface of the tip of the rotary tool. FIG. 6 is a conceptual diagram showing an aspherical surface processing method. FIG. 7 is a conceptual diagram showing the position of the center of the rotary tool in the X-axis direction in the aspherical surface processing method.

  In the aspherical surface processing method of the first embodiment, the grindstone of the rotary tool 214 is ground while the rotational center of the rotary tool shaft 213 draws a spiral trajectory as shown in FIG. In the conventional normal control, the machining point represented by the rotation angle of the lens and the distance from the rotation center is determined in advance. In the aspherical machining method of the first embodiment, the rotation center position of the rotary tool shaft 213 is determined. The spiral shape to be drawn is predetermined. That is, the spiral trajectory drawn by the rotation center of the rotary tool shaft 213 is determined by a predetermined feed pitch in a direction (X axis) orthogonal to the rotation axis of the workpiece 208. In this example, when the distance (Rx) from the rotation center of the workpiece 208 to the rotation center of the rotary tool shaft 213 is continuously decreased at a predetermined feed pitch, that is, from the outer peripheral direction of the lens toward the central direction. It is a spiral shape to draw.

  Further, in the aspherical surface processing method of the first embodiment, the numerical data of the coordinate Cx of the rotational axis center of the rotary tool shaft 213 is the rotational position (θ) of the workpiece 208 and the direction orthogonal to the rotational axis of the workpiece 208 (X Machining the workpiece 208 in the same direction as the rotation axis of the workpiece 208 (not shown) (Y-axis) and the distance (Rx) from the rotation center of the workpiece 208 when continuously decreasing at a predetermined feed pitch in the axis) The point is represented by three points (θ, Rx, y) of the position (y) where the tip of the rotary tool 214 contacts. The shape creation based on the lens design shape is performed by continuously positioning the rotation axis central coordinates of the rotary tool shaft 213. Note that the coordinates may constitute numerical data for processing using an absolute value of each point or a relative value with respect to the previous coordinate point.

  As shown in FIG. 4B, the three-dimensional coordinates of the lattice points that are divided into a lattice pattern according to a predetermined rule are obtained at predetermined positions on the surface of the rotary tool 214 having a radius R and a rounded shape.

  Further, as shown in FIG. 5, the three-dimensional coordinates of the tip surface of the rotary tool 214 are transferred to the surface of the workpiece 208 along the origin direction of the Y axis, and the surface of the rotary tool 214 is transferred to the surface of the workpiece 208. The three-dimensional coordinates of the surface of the workpiece 208 divided in a grid pattern according to the same predetermined rule as the original coordinates are obtained.

  Thereby, the distance between the surface of the workpiece 208 and the surface of the rotary tool 214 is calculated for each grid point corresponding to the three-dimensional coordinate of the surface of the workpiece 208 and the three-dimensional coordinate of the surface of the rotary tool 214, and the distance between the grid points is calculated. Find the combination of grid points that minimizes the distance. The coordinates (Lxn, Lym) of the lattice points become contact points.

  In addition, if the length of one side of the lattice is lengthened, the accuracy of deriving a machining point becomes rough, and if the length is shortened, the accuracy increases but the calculation time is lengthened. Actually, it is about 0.001 to 0.1 mm.

  As shown in FIGS. 6 and 7, for example, on an arbitrary point Cn of the minimum thickness portion (base curve, AA ′ cross section), the direction orthogonal to the rotation axis of the workpiece 208 at the tip of the rotary tool 214 ( When the central axis (hereinafter referred to as “the central axis of the tip portion”) exists in the X axis), the position of the central axis of the tip portion of the rotary tool 214 in the Y-axis direction is as shown in FIG. The point Qs (Lxns, Lyms) at which the corresponding grid point first contacts between the three-dimensional coordinates of the surface of the tip of the rotary tool 214 and the three-dimensional coordinates of the surface of the workpiece 208 by freely moving 214 in the Y-axis direction. It becomes a contact point (processing point). As shown in FIGS. 6 and 7, the central axis of the tip of the rotary tool 214 is located on the normal line set up at the point Qs.

  When the lens rotates 90 degrees and the rotation center axis of the tip of the rotary tool 214 exists on an arbitrary point Cnm of the maximum thickness portion (cross curve, BB ′ cross section) from the point Cn, the rotary tool The position of the central axis of the tip of 214 in the Y-axis direction is determined by the three-dimensional coordinates of the surface of the tip of the rotary tool 214 and the three-dimensional coordinates of the surface of the workpiece 208 by freely moving the rotary tool 214 in the Y-axis direction. Thus, the central axis of the tip of the rotary tool 214 is positioned on the normal line set up at the point Qsm (contact point) where the corresponding lattice point first contacts. When the lens rotates 90 degrees and the rotating tool 214 moves from Cn to Cnm, the rotating tool 214 moves ΔY in the positive direction of the Y-axis direction, while the rotating tool 214 accurately moves to the center side in the X-axis direction. Relatively move by X nm for 1/4 pitch. In other words, the workpiece 208 is accurately moved to the outside in the X-axis direction by X-axis by the X-axis table 202 to Xnm.

  When the lens further rotates 90 degrees and the center of the tip of the rotary tool 214 exists on an arbitrary point Cnr of the minimum thickness portion from the point Cnm, the rotary tool 214 moves in the negative direction of the Y-axis direction. On the other hand, it moves relative to the center side in the X-axis direction exactly by 1/4 pitch Xnr. That is, the workpiece 208 is accurately moved to the outside in the X-axis direction by X-axis by Xnr by the X-axis table 202.

  In the aspherical surface processing method of the first embodiment, a distance Rx between the rotation center of the workpiece 208 and the center axis of the tip of the rotary tool 214 in a direction (X axis) orthogonal to the rotation axis of the workpiece 208 is set to a predetermined feed rate. By controlling so as to decrease continuously with the pitch, the X-axis table 202 of the aspherical surface processing apparatus 200 moves only in a certain direction without reciprocating the lens 208. In addition, if the rotation speed of the workpiece | work 208 is constant and a feed pitch is also constant, it will become constant velocity motion. Thus, the locus drawn by the rotary tool 214 on the lens 208 is a simple spiral that is not a conventional zigzag shape, and can be followed even if the number of revolutions of the workpiece 208 with a large unevenness is increased. Become. In other words, it is possible to perform grinding at an increased grinding speed.

  In the aspherical surface processing method of the first embodiment, the productivity is about 1.3 times that of the conventional normal control method.

  As described above in detail, according to this embodiment, the following effects can be obtained.

  According to the aspherical surface processing method, the aspherical surface forming method, and the aspherical surface processing apparatus of the present invention, since the table having a large inertial force can be controlled simply so as to move only in a certain direction without reciprocating, the followability of the table. Even a workpiece 208 having a large uneven surface can be quickly processed with high quality by rotating at high speed.

  A second embodiment of the aspherical surface processing method of the present invention will be described with reference to FIGS. FIG. 8 is a schematic view showing the processed surface of the lens in the aspherical surface processing method of the second embodiment. 8A is a front view of the lens, and FIG. 8B is a cross-sectional view taken along the line BB ′ of FIG. 8A. FIG. 9 is a conceptual diagram showing an aspherical surface processing method.

  In the aspherical surface processing method of the second embodiment, the grindstone of the rotary tool 214 performs grinding while drawing a spiral trajectory as shown in FIG. In this example, the distance (Rx) from the rotation center of the workpiece 208 to the center axis of the tip of the rotary tool 214 is increased at a predetermined feed pitch. That is, grinding is started from a processing point near the rotation center of the workpiece 208 or near the rotation center, and is ground to the outer peripheral side of the workpiece 208. The grinding data is created along a spiral from the rotation center of the workpiece 208 toward the outer periphery of the workpiece 208.

  In the aspherical surface processing method of the second embodiment, the numerical data of the coordinate of the central axis of the tip portion of the rotary tool 214 is a direction orthogonal to the rotation axis of the workpiece 208 instead of the distance Rx described in the first embodiment ( The distance (Rx) from the center of rotation of the workpiece 208 when increasing at a predetermined feed pitch in the X axis).

  As shown in FIG. 8 and FIG. 9, in the aspherical surface processing method of the second embodiment, the normal line set at the processing point So of the rotation center of the workpiece 208 indicated by the Y axis (main axis) at the start of grinding. The central axis of the tip of the rotary tool 214 is positioned in the direction. Machining is started from the machining point So at the rotation center of the workpiece 208, and the central axis of the tip of the rotary tool 214 exists on an arbitrary point Sn of the maximum thickness portion (cross curve, BB ′ cross section), for example. Sometimes, the position of the central axis of the tip of the rotary tool 214 in the Y-axis direction is determined by freely moving the rotary tool 214 in the Y-axis direction and the surface of the workpiece 208. The center axis of the tip of the rotary tool 214 is located on the normal line set at the point Qt (contact point) where the corresponding lattice point first contacts with the three-dimensional coordinates.

  When the lens 208 is rotated 90 degrees and the central axis of the tip of the rotary tool 214 exists on an arbitrary point Snm of a portion (base curve, AA ′ cross section) having a minimum thickness from the point Sn, the rotary tool The position of the central axis of the tip of 214 in the Y-axis direction is determined by the three-dimensional coordinates of the surface of the tip of the rotary tool 214 and the three-dimensional coordinates of the surface of the workpiece 208 by freely moving the rotary tool 214 in the Y-axis direction. Is the position where the corresponding grid point first touches, and the processing point is the first touch of the corresponding grid point between the three-dimensional coordinate of the surface of the tip of the rotary tool 214 and the three-dimensional coordinate of the surface of the workpiece 208. This is a point Qtm (contact point). When the lens 208 rotates 90 degrees and the rotary tool 214 moves from Sn to Snm, the rotary tool 214 moves ΔY in the negative direction of the Y-axis direction, while the rotary tool 214 has an outer periphery of the lens 208 in the X-axis direction. Relatively moves to the side by exactly 1/4 pitch Xnm. In other words, the workpiece 208 is accurately moved to the center side in the X-axis direction by the X-axis table 202 to the X pitch by X nm.

  Thus, in the aspherical surface processing method of the second embodiment, the distance Rx between the rotation center of the workpiece 208 and the central axis of the tip of the rotary tool 214 in the direction (X axis) orthogonal to the rotation axis of the workpiece 208 is set. By controlling so as to increase at a predetermined feed pitch, the locus drawn by the rotary tool 214 on the lens 208 is made a simple spiral that is not a conventional zigzag shape.

  When grinding is started from the outer peripheral side of the workpiece 208, when the rotary tool 214 starts to be applied to the outer peripheral surface of the workpiece 208 that is rotating at a high speed, the rotary tool 214 is suddenly applied to the outer peripheral surface of the workpiece 208. The rotating tool 214 is first arranged at a position slightly outside the outer peripheral surface of the workpiece 208 so as not to hit the workpiece 208, and then the rotating tool 214 is slowly rotated at the center of rotation at a normal grinding feed pitch. It is necessary to start grinding by applying the rotary tool 214 to the outer peripheral surface. Normally, the rotary tool 214 starts to move from the outside of the outer peripheral surface of the workpiece 208 by about 5 mm. However, at this time, the rotary tool 214 is not ground, resulting in wasted production time.

  In the aspherical surface processing method of the second embodiment, by starting grinding from the rotation center of the workpiece 208, the portion where the rotary tool 214 first hits the workpiece 208 is the rotation center where the peripheral speed is zero or almost zero, or the rotation center. Therefore, the rotary tool 214 can be applied immediately, and the processing is completed when the rotary tool 214 is moved only in the area that requires grinding.

  In this way, by starting grinding from the rotation center of the workpiece 208 or the vicinity of the rotation center, the rotary tool 214 is moved and processed only in an area where processing is necessary without reducing the speed of the rotary tool 214. The grinding time can be shortened compared to the case where the grinding is started from the outer peripheral side of 208.

  Further, the grinding data for processing only needs to correspond to the processed surface of the workpiece 208, and the amount of grinding data can be reduced.

  Note that the aspherical surface processing method that starts grinding from the rotation center of the workpiece 208 starts grinding from the rotation center at which the peripheral speed is zero or almost zero, and therefore can be applied to finishing machining in the processing procedure described later. desirable. If the grinding amount (cutting amount) is about 0.1 to 5.0 mm, grinding can be started by directly applying the rotary tool 214 to the rotation center of the workpiece 208.

  At the start of grinding, the center axis of the rounded portion of the tip of the rotary tool 214 is arranged on the Y axis passing through the machining point So of the locus of the rotation center of the workpiece 208 indicated by the Y axis (main axis). The position of the rotary tool 214 in the Y-axis direction is controlled so as to process the processing point of the lens with which the rotary tool 214 abuts. The shape creation based on the lens design shape is performed by continuously positioning the central axis coordinate of the tip of the rotary tool 214 on the trajectory of the spiral from the rotation center of the workpiece 208 to the outside. Note that the coordinates may constitute numerical data for processing using an absolute value of each point or a relative value with respect to the previous coordinate point.

  As described above, the aspherical surface processing method of the second embodiment can perform processing more rapidly than the first embodiment.

  As described above in detail, according to this embodiment, the following effects can be obtained.

  According to the aspherical surface processing method, the aspherical surface forming method, and the aspherical surface processing apparatus of the present invention, since the table having a large inertial force can be controlled simply so as to move only in a certain direction without reciprocating, the followability of the table. Even a workpiece 208 having a large uneven surface can be quickly processed with high quality by rotating at high speed.

  A third embodiment of the aspherical surface processing method of the present invention will be described with reference to FIG. FIG. 10 is a schematic view showing the rotary tool 214 in the aspherical surface processing method of the third embodiment. FIG. 10A is a front view of the rotary tool 214, and FIG. 10B is a side view of the rotary tool 214.

  In the aspherical surface processing method of the third embodiment, cutters 215 serving as cutting tools are disposed at two positions on the circumferential side surface of the rotary tool 214 with the center interposed therebetween.

  Further, the aspherical surface processing method of the third embodiment is the same as the grinding method using the grindstone with the rotary tool 214 described based on the first and second embodiments.

  As described in detail above, according to the present embodiment, the same effects as those of the first and second examples can be obtained in the form of cutting.

  A fourth embodiment of the aspherical surface processing method of the present invention will be described with reference to FIG. FIG. 11 is a schematic view showing the rotary tool 214 in the aspherical surface processing method of the fourth embodiment. FIG. 11A is a front view of the rotary tool 214, and FIG. 11B is a side view of the rotary tool 214.

  In the aspherical surface processing method of the fourth embodiment, a cutter 215 is arranged at one place on the circumferential side surface of the rotary tool 214.

  Further, the aspherical surface processing method of the fourth embodiment is the same as the grinding method using the grindstone with the rotary tool 214 described based on the first and second embodiments.

  As described above in detail, according to the present embodiment, the same effect as that of the third embodiment can be obtained even if the rotary tool 214 has one cutter 215.

  In addition, this invention is not limited to said Example. For example, it can also be implemented in the following manner.

  (1) The aspherical surface processing method of the present invention may process the entire lens 208. Further, a part of the lens 208 may be processed by the aspherical processing method of the present invention, and a part thereof may be processed by a conventional normal control processing method. In particular, in the case of, for example, a lens with a prism having an inclined portion near the center of the workpiece 208, the machining method of the present invention may cause interference with the prism portion at the center of the workpiece 208 of the rotary tool 214. Accordingly, it is effective to partially grind and cut by the conventional normal control processing method.

  (2) The aspherical surface processing method of the present invention is particularly effective at the outer peripheral portion of the lens where the peripheral speed of the lens is large. In the vicinity of the center of the lens, the difference in unevenness is reduced, so that the productivity does not decrease so much even if the conventional normal control processing method is adopted. Therefore, the aspherical surface processing method of the present invention can be adopted at the outer periphery of the lens, and the normal control processing method can be adopted near the center of the lens.

  (3) The aspherical surface processing method of the present invention is not limited to the final lens surface shape based on the prescription data of the spectacle lens, but, for example, outer diameter processing for reducing the outer diameter by reducing the outer diameter of the lens, and the final lens surface The present invention can also be applied to a free cutting surface that approximates a shape, a rough cutting process that forms a toric surface or a spherical surface shape, and a chamfering process that cuts a sharp end of a lens.

  (4) The workpiece 208 may be another lens instead of the spectacle lens, or a mold that casts and superimposes the lens. The processed surface is not limited to a concave surface, and may be a convex surface.

The elevational view which shows the aspherical surface processing apparatus which uses the aspherical surface processing method of 1st Example. Sectional drawing of the lens which is an example of a workpiece | work. It is the schematic which shows the processed surface of the lens in an aspherical surface processing method, (a) is a front view of a lens, (b) is sectional drawing along the BB 'line of Fig.3 (a). It is the conceptual diagram of the three-dimensional coordinate divided | segmented into the grid | lattice form of the surface of the front-end | tip part of a rotary tool, (a) is the elevation, the top view, and side view showing the positional relationship of a workpiece | work and a rotary tool, (b) is FIG. 5 is an enlarged view of the rotary tool of FIG. The conceptual diagram which shows the three-dimensional coordinate on the workpiece | work surface and the surface of a rotary tool front-end | tip part. The conceptual diagram which shows the aspherical surface processing method. The conceptual diagram which shows the center position of the rotary tool of the X-axis direction in an aspherical surface processing method. It is the schematic which shows the processed surface of the lens in the aspherical surface processing method of 2nd Example, (a) is a front view of a lens, (b) is along the BB 'line of Fig.8 (a). Sectional view. The conceptual diagram which shows the aspherical surface processing method. Schematic which shows the rotary tool in the aspherical surface processing method of a 3rd Example. Schematic which shows the rotary tool in the aspherical surface processing method of a 4th Example. It is the schematic which shows the processed surface of the lens in the normal control processing method as a prior art example, (a) is a front view of a lens, (b) is BB 'sectional drawing of Fig.12 (a). The conceptual diagram which shows a normal line control processing method. The conceptual diagram which shows the position of the rotary tool center of the X-axis direction in a normal control processing method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 200 ... Aspherical surface processing apparatus, 201 ... Bed, 202 ... X-axis table, 203 ... Y-axis table, 204 ... X-axis drive motor, 205 ... Work axis rotating unit as a work axis rotating means, 206 ... Work chuck, 207 DESCRIPTION OF SYMBOLS ... Work rotary shaft drive motor, 208 ... Work and lens (semi-finish lens), 208a ... Outer peripheral part, 208b ... Approximate surface shape, 208c ... Lens surface shape, 208d ... Edge chamfer, 209 ... Y-axis drive motor, 210 ... Z-axis table, 211 ... Z-axis drive motor, 212 ... Rotary tool rotating unit as rotating tool rotating means, 213 ... Rotating tool axis, 214 ... Rotating tool, 215 ... Cutter as cutting tool, 300 ... Input device, 400: computer for calculation, 500: host computer.

Claims (7)

A workpiece to be rotated about a rotation axis, and a rotary tool that can move relative to the workpiece in the same direction as the rotation axis of the workpiece and in a direction orthogonal to the rotation axis of the workpiece,
The rotating tool moves in a predetermined direction at a predetermined feed pitch in a part or all of the region from the center of the workpiece rotation axis to the outer periphery of the workpiece in a direction orthogonal to the workpiece rotation axis. An aspherical processing method comprising processing a workpiece into an axisymmetric aspherical surface.   2. The aspherical surface processing method according to claim 1, wherein the position of the rotary tool is controlled so that a rotation center axis of a tip of the rotary tool is positioned in a normal direction set at a processing point of the workpiece. .   When machining with the rotary tool, the distance between the rotation center of the workpiece and the tip of the rotary tool in the direction orthogonal to the rotation axis of the workpiece is zero or near zero, or the outer peripheral edge of the workpiece and the tip of the rotary tool 3. The aspherical surface processing method according to claim 1, wherein the distance is controlled to start from zero or near zero.   The aspherical surface processing method according to any one of claims 1 to 3, wherein the rotary tool is a grindstone that rotates about a rotation axis.   The aspherical surface processing method according to claim 1, wherein the rotary tool is a cutting tool that rotates about a rotation axis.   6. The rough machining step of forming the workpiece into a shape approximating a desired shape, and the workpiece is machined using the aspherical machining method according to any one of claims 1 to 5, following the rough machining step. And a finishing cutting step of forming the workpiece into a desired shape. An aspherical surface processing apparatus incorporating the aspherical surface forming method according to claim 6.

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