JP2002036001A - Cutting method, cutting device, tool holding device, optical element, and molding die for optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cutting device capable of providing good surface roughness in a short time. SOLUTION: This cutting device comprises exciting parts 5a and 5b for vibrating a cutting tool 2 and a work piece 1 relatively in the main component force direction and the rear component force direction, and a driving device 9 for moving the cutting tool 2 so that an axis in the rear component force direction of ellipse, a trajectory of vibration of the tip of the cutting device, directs in the normal direction of a curved machined surface of the workpiece 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cutting a workpiece having a small radius of curvature or a workpiece having a free-form surface having a non-uniform radius of curvature. The present invention relates to a cutting method and a cutting apparatus.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG.
With the longitudinal direction as the generatrix direction (X direction) and the transversal direction as the sagittal direction (Y direction), a toric or other optical component having a different radius of curvature between the generatrix direction and the sagittal direction or a mold for molding the optical component is cut. In the case of machining, a cutting tool 2 composed of a diamond tip 2a and a shank 2b is attached to a tool holder 3, and the cutting tool 2 is rotated by a main shaft 4. On this occasion,
The tip radius of the diamond tip must be smaller than the radius of curvature of the sagittal wire of the workpiece, and the turning radius R1 of the cutting tool must be smaller than the radius of curvature R2 of the generatrix of the workpiece. In this state, the cutting tool and the workpiece are relatively moved in the sagittal direction, so that one minute line is fly-cut, then moved in the generatrix direction at a feed pitch P, and this is repeated. , Cut the entire surface.

On the other hand, in order to improve machining accuracy, a vibration cutting method for forcibly vibrating a cutting tool is used. In this method, it is possible to suppress the heat generation of the tool edge, prevent the formation of the constituent edge, and reduce the cutting resistance, thereby suppressing chatter vibration. In particular, as shown in FIG. 17, the cutting tool is two-dimensionally vibrated in the main component force direction (X direction) and the back component force direction (Z direction), and an ellipse that gives a phase difference of about 90 ° to both vibrations. Vibration cutting has a great effect of reducing cutting resistance. In such a vibration cutting method as well, the entire surface can be cut by moving the workpiece and the cutting tool relative to each other in the same manner as in the above-described fly cut method. In addition, 1a is an unprocessed surface and 1b is a target processed surface.

[0004]

However, in recent years, various demands have been made on the shape of optical components, and in particular, with the miniaturization of products, optical components having a small radius of curvature have been required. In addition, there are various demands for the shape of optical components, and the adoption of free-form surfaces can reduce the number of components and improve optical performance, so the radius of curvature changes from several mm to several tens of mm. Such optical components are required. For this reason, it has been necessary to reduce the turning radius of the cutting tool in the fly-cut method. However, in order to perform processing such that the radius of curvature is 10 mm or less, the protrusion of the tool holder for fixing the cutting tool to the main spindle is required. It is necessary to reduce the diameter of the portion 3a in order to avoid interference with the workpiece, and the cutting resistance tends to cause chattering, and high-precision processing with a surface roughness of the order of several tens nm cannot be substantially performed.

On the other hand, elliptical vibration cutting in which a cutting tool is vibrated two-dimensionally has a vibration amplitude of several μm to several tens μm, and can sufficiently cope with the radius of curvature. However, the only applications of vibration cutting so far have been applied to plane machining and turning.In these machinings, the angle between the workpiece and the cutting tool is kept constant, and optical cutting is performed. When processing a curved surface that satisfies the relationship of the formula, the normal direction of the processed surface of the workpiece changes. Therefore, when the above-mentioned curved surface is applied while the angle between the workpiece and the cutting tool is kept constant as in the past, as shown in FIG. 17, the tip of the cutting tool moves along the target processing surface 1b of the workpiece. Even if it is moved, the trajectory processed by the elliptical motion becomes a shape like 1c, and a shape error occurs. This shape error is determined by the degree of change in the inclination angle of the workpiece and the shape of the elliptical trajectory of the cutting tool.

In the case of elliptical vibration cutting, in actual mass production, as shown in FIG. 10, a method is employed in which the tool edge is moved elliptically in the sagittal direction, and after one line is processed, the pitch P is fed in the generatrix direction. Since the radius of curvature of the locus is very small, when trying to obtain a surface roughness of several tens of nanometers, the feed pitch P becomes as small as several μm, and the processing time becomes enormous,
Mass production is practically impossible.

[0007] For example, the theoretical surface roughness Rth when processing the planar vibration cutting with circular motion, Rth = f ^2/8
r (f = feed pitch P, r = radius of tool vibration trajectory). When Rth is 20 nm and r is 5 μm, f becomes 0.89 μm, and when the generating line is 100 mm, 100 mm / 0. It is necessary to send 89 μm = 112360 times in the generatrix direction. If it takes 5 seconds to process one line, the total processing time is 156 hours.

Further, as an example of elliptical vibration cutting, Japanese Patent Application Laid-Open
As disclosed in Japanese Patent Application No. 68401, there is known a method of relatively feeding a cutting tool and a workpiece in a direction of an elliptical motion which is a cutting direction. However, JP-A-7-68
When the method disclosed in Japanese Patent Publication No. 401 is applied to the mirror finishing of a curved surface determined from an optical relationship, it takes twice or more times as long as the case of processing by a fly cut processing method. Because, in this method, as described above, since the cutting tool and the workpiece are relatively sent in the direction of the elliptical motion, when performing reciprocating machining, it is necessary to use up-cut and down-cut in the outward path and the return path. There is. However, there is a difference in the state of the machined surface between up cut and down cut,
When high precision mirror finishing is required, reciprocating processing cannot be performed.

The difference in the finished state of the machined surface between the up cut and the down cut is caused by the following principle. In the case of down cut, back force direction (cutting direction)
Is faster than the speed in the cutting direction, and the approach angle of the tool is close to a right angle. On the other hand, in the case of the up-cut, when the tool enters from the direction in which the cutting is proceeding, the speed in the cutting direction becomes faster than the speed in the back force direction, and the approach angle of the tool can be reduced. In addition, since machining is performed from the direction in which cutting is in progress and the direction in which cutting is not in progress, the state of chip discharge is different, and the state of the finished surface is different.
As described above, when the reciprocating processing is performed, the state of the cut surface is alternately different for each processing line, so that there is regularity, which affects the optical characteristics. The difference between the tool entry angles of the upcut and the downcut is the difference between the points A and B shown in FIG. 6, and as can be seen from the tool trajectories at those points, the entry angle of the point A is lower.

As described above, when processing a workpiece in which a portion having a radius of curvature of 10 mm or less and a larger portion coexist, good surface roughness due to chatter or the like is obtained by the conventional fly cut method. In addition, the elliptical vibration cutting method requires a long processing time, and there is no practical processing method for obtaining good surface roughness in a short time.

Accordingly, the present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a cutting method and apparatus, an optical element, and a molding of an optical element capable of obtaining good surface roughness in a short time. To provide a metal mold.

[0012]

Means for Solving the Problems The above-mentioned problems are solved,
In order to achieve the object, a cutting method according to the present invention is a cutting method for cutting a curved processing surface while vibrating a cutting tool and a workpiece relatively in a main component direction and a back component direction. A machining method, wherein the cutting tool is moved such that an axis of an elliptical back component direction, which is a locus of vibration of a tip of the cutting tool, is oriented in a direction normal to a machining surface of the workpiece. Features.

Further, in the cutting method according to the present invention, the amplitude of a drive source for vibrating the cutting tool in the main component force direction is enlarged and transmitted to the cutting tool.

In the cutting method according to the present invention, a piezoelectric element is used as a drive source for relatively vibrating the cutting tool and the workpiece.

Further, the cutting apparatus according to the present invention comprises: a vibrating means for vibrating a cutting tool and a workpiece relatively in a main component direction and a back component direction; And a drive means for moving the axis of the elliptical back force direction, which is the trajectory of the vibration of the tip of the cutting tool, to be oriented in the normal direction of the processing surface formed of the curved surface of the workpiece. .

Further, the cutting apparatus according to the present invention is further characterized by further comprising an enlarging means for enlarging an amplitude of a drive source for vibrating the cutting tool in a main component direction and transmitting the amplitude to the cutting tool. .

Further, in the cutting apparatus according to the present invention, a piezoelectric element is used as a drive source for relatively vibrating the cutting tool and the workpiece.

Further, the cutting method according to the present invention is a method of cutting a curved surface satisfying an optical relationship while vibrating a cutting tool and a workpiece relatively in a main component direction and a distribution direction. A machining method, wherein the vibration causes the cutting edge of the cutting tool to perform an elliptical motion,
Rotating the cutting tool about an axis parallel to the central axis of the ellipse such that the axis of the elliptical component force direction is oriented in the direction normal to the processing surface of the workpiece. It is characterized by having.

Further, the cutting method according to the present invention is directed to a cutting method for cutting a workpiece while vibrating a cutting tool and the workpiece relatively in a main component direction and a back component direction. In the machining method, the trajectory of vibration of the tip of the cutting tool is changed in accordance with the curvature of the work surface of the work in accordance with the curvature of the work.

Further, in the cutting method according to the present invention, the amplitude and phase of the vibration of the cutting tool in the main component force direction;
And controlling the amplitude and phase of the vibration of the cutting tool in the direction of the back force to control the trajectory of the vibration of the tip of the cutting tool.

The cutting method according to the present invention is characterized in that the tip of the cutting tool is moved elliptically.

Further, the cutting apparatus according to the present invention comprises a driving means for vibrating the cutting tool in the main component force direction and the back component force direction, and for causing the cutting tool to follow a change in the curvature of the processing surface of the workpiece. And a control means for controlling the vibration amplitude of the cutting tool in the main component direction, the vibration amplitude in the back component direction, and the phase of the vibration.

Further, in the cutting apparatus according to the present invention, the control means controls the tip of the cutting tool to perform an elliptical motion.

Further, an optical element according to the present invention is an optical element processed by the above cutting method.

Further, a mold for molding an optical element according to the present invention is characterized in that it is processed by the above-mentioned cutting method.

Further, an optical element according to the present invention is characterized in that it is processed by the above-mentioned cutting apparatus.

Further, a molding die for an optical element according to the present invention is characterized in that it is processed by the above-mentioned cutting apparatus.

Further, the cutting method according to the present invention is directed to a cutting tool blade for generating an aspherical curved surface composed of a generatrix and a sagittal curved surface on a surface to be processed of a member to be processed. In a cutting method for performing processing by imparting an elliptical motion by vibration in a force direction, the aspherical curved surface to be created is divided into a plurality of areas, and the elliptic motion of the cutting tool blade in the divided areas is divided. Lowermost point P1, machining start point P
2. Obtain the short diameter H of the ellipse that coincides with the curved surface of the bus formed by the machining end point P3, and determine the condition under which the feed pitch of the cutting tool blade in the bus direction in the area is the maximum as the movement locus of the tool blade. It is characterized by:

A tool holding device according to the present invention is a tool holding device for performing vibration cutting by applying vibration to a tool blade for cutting an aspherical curved surface on a surface to be processed of a member to be processed. First vibration generating means for applying vibration in the main component force direction to the tool blade, second vibration generating means for applying vibration in the back component force direction to the tool blade, and a holding member for holding the tool blade And an enlargement mechanism for increasing the displacement in the main component force direction is formed on the holding member.

In the cutting apparatus according to the present invention, a vibration in a main component force direction and a vibration in a back component force direction are applied to a tool blade for cutting an aspherical curved surface on a processing surface of a workpiece. A cutting device for processing, wherein first vibration generating means for applying vibration in the main component direction to the tool blade, and second vibration generating means for applying vibration in the distributed force direction to the tool blade. A holding member for holding the first and second vibration generating means and the tool blade, an indexing operation member for indexing the tool blade to a processing position on the surface to be processed via the holding member, It is characterized by comprising control means for controlling the drive of the first and second vibration generating means, and index control means for controlling the drive of the index operation member.

[0031]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

(First Embodiment) FIG. 1 is a view showing the configuration of a first embodiment of a vibration cutting apparatus according to the present invention.
The mechanical diagram on the left side in the figure shows a front view of the cutting apparatus, and the mechanical diagram on the right side shows a side view of the mechanical diagram on the left as viewed from the right.

In FIG. 1, reference numeral 2a denotes a diamond tip, and the sagittal direction (Y direction) is arc-shaped. 5a is a piezoelectric element for vibrating the cutting tool 2 in the main component direction, and 5b is a piezoelectric element for vibrating in the back component direction. One ends of the piezoelectric elements 5a and 5b are fixed to the base member 6 with elastic hinges 6a and 6b, respectively. The other ends of the piezoelectric elements 5a and 5b are
It is adhesively fixed to the vibration transmitting member 6e via c and 6d. The base member 6 and the vibration transmitting member 6e are originally the same member, and a flat plate is formed by electric discharge machining to form a base portion (base member 6), hinge portions (hinges 6a, 6b, 6c, 6d),
Piezoelectric element insertion portion (between hinges 6a and 6c, and hinge 6
b and 6d) and a vibration transmitting section (vibration transmitting member 6e). Further, in order to constitute an enlargement mechanism for enlarging the displacement in the main component direction, the elastic hinge 6f,
6 g are provided.

Here, the operation of the enlargement mechanism for increasing the displacement in the main component force direction will be described.

FIG. 7A shows the initial state.
When the piezoelectric element 5a is energized and displaced by the drive control device 7 in this state, the hinge 6a is not displaced and the hinge 6c is displaced.
The side moves to the state shown in FIG. That is, a lever is formed in which the hinge 6c is the point of action and the hinge 6f is the fulcrum, and the tip of the cutting tool moves by the amount indicated by S1 with the displacement of the piezoelectric element enlarged by the ratio of the distances l1 and l2. At this time, a compressive force or a tensile force and a bending moment are applied to the hinges 6a, 6c, 6f, and 6g, and a bending moment is mainly applied to the hinges 6b and 6d. Since it is flexible, there is almost no displacement transmission loss in the displacement direction of the piezoelectric element and little loss of the generated force of the piezoelectric element due to bending of the rigid hinge, and the amount of displacement is small. Similarly, when the piezoelectric element 5b is energized and displaced, the hinge 6b is not displaced, the hinge 6d is moved, and the state shown in FIG. At this time, the force for reducing the displacement of the piezoelectric element is mainly generated by the hinges 6a, 6c, 6f,
The bending moment applied to 6 g has only a small effect on the reduction of the displacement. FIG. 7B and FIG.
An elliptical motion (rotational motion) is performed by superimposing the states of (c).

When a voltage of 150 V is applied to the piezoelectric elements 5a and 5b,
The displacement is 0 μm. A current of about 75 V ± 55 V is applied to this by the drive control device 7 to obtain a displacement of about 20 μm. The service life can be extended more than when the rated voltage is fully applied. When a sine-wave voltage having a phase difference of 90 ° is applied to the two piezoelectric elements 5a and 5b by the drive control device 7, a long elliptical trajectory of the tip of the cutting tool 2 according to the ratio between l1 and l2 is obtained. . The higher the frequency of vibration, the higher the effect as vibration cutting and the higher the processing efficiency. However, the allowable current of the drive control device 7, the life of the piezoelectric element, the vibration transmission member 6
500 Hz or less is appropriate in consideration of the resonance frequency of e.

The base member 6 is fixed to a spacer 8, and the spacer is fixed to an indexing board 9. The indexing board 9 includes a rotating part rotor 9a and a fixed part housing 9b.
The rotor 9a is driven by a DC brushless motor or the like, and the rotation angle is detected by an encoder. The indexing board 9 is mounted on a Z slider 10 that moves up and down. The work is moved by the hiring 11 in the horizontal plane X
It is fixed to the Y slider 12. XY slider 12,
The Z slider 10 is a high-precision slider that is supported by a static pressure bearing, driven by a linear motor, and whose position is detected by a laser length measuring device.

In the above configuration, the NC unit 13
In the machining program in the figure, the generatrix shape and sagittal shape of the workpiece, the distance from the rotation center of the indexing board 9 to the tip of the cutting tool 2 (diamond tip 2a), the sagittal direction of the cutting tool 2 (diamond tip 2a) Is input, and NC data for processing the shape of the workpiece is created. The NC signal created by the machining program is sent to the arithmetic and control unit from the synchronization signal creating unit at a constant clock interval, and the command values assigned to the XY slider, the Z slider, and the index axis (rotor 9a) are sent therefrom. Sent to Each axis (X, Y,
Z and the rotor), as shown in FIG. 2, the condition that the axis of the elliptical locus of the tip of the cutting tool 2 (diamond tip 2a) in the back force direction coincides with the normal direction of the generatrix. Is calculated under Also in the sagittal direction, the condition that the normal direction of the sagittal shape at the point of contact between the cutting tool 2 and the workpiece 1 matches the radial direction of the arc of the cutting tool 2 (diamond tip 2a) is taken into account. I have. A current is supplied from the servo controller 14 to each of the linear motors and the rotary motors to move them to the command position. The position of each axis is detected by the laser length measuring device and the encoder, and the position detection unit transmits this to the arithmetic control unit. , A servo system that makes the error with the command zero.

The actual machining procedure will be described with reference to FIGS. 4 and 5. In a state where the cutting tool 2 is always subjected to elliptical vibration,
The workpiece 1 and the cutting tool 2 are moved relative to each other at a point a1 on an extended line that applies an optical relationship to the generatrix direction (X direction) end b1 of the workpiece 1 and move in the sagittal direction (Y direction). Processing is performed (the cutting tool and the workpiece are relatively moved so that movement in the Y direction is mainly performed), and processing for one line is performed.
The actual tool path is L1 in FIG. 4, and a1 → b1 → c1
→ d1 → e1, and since the direction of the back force of the cutting tool coincides with the normal direction of the processing surface and changes in the Z direction, in order to satisfy a tool trajectory that follows the shape, , X, and Z are processed while moving in one line. Thereafter, the normal angle is moved by the movement of the feed pitch moving from the point e1 to e2 in the generatrix direction and the rotation axis 9 for performing the rotation index of the cutting tool, and the machining feed is performed in the sagittal direction (e2 → d2). → c2 → b2 → a2). By repeating this operation, the entire surface of the workpiece 1 is processed, and as a result, a target processed surface is obtained. By such processing,
It is possible to obtain a high shape accuracy on the order of 0.1 μm, which is equivalent to the device movement accuracy.

The machining procedure will be described with reference to FIG. 2 which is a side view of the workpiece. In a state where the cutting tool 2 is always oscillated in an elliptical manner, the cutting tool 2 is moved from the point b1 in the sagittal direction (Y direction). Processing is performed, and processing for one line is performed. After that, it is moved by the feed pitch p1 in the generatrix direction, and is machined in the sagittal direction. By repeating this operation, the entire surface of the workpiece 1 is processed, and as a result, the target processed surface 1b is obtained. By such a processing, 0.1 which is equivalent to the movement accuracy of the apparatus can be obtained.
High shape accuracy on the order of μm can be obtained. However, in order to obtain a surface roughness of several tens of nm required as a mold of an optical component by such a processing method, the feed pitch in the generatrix direction must be extremely fine, and the processing time becomes long. For example, when the vibration amplitude of the elliptical vibration is 20 μm,
When the generatrix has a theoretical surface roughness of 50 nm as a flat surface, the feed pitch is as small as 6 μm. Therefore, FIG.
As shown in the above, the enlargement mechanism using the lever principle
When the displacement in the main component force direction is enlarged, the elliptical shape of the tool tip is also enlarged in the main component force direction as shown in FIG. Under the condition that the theoretical surface roughness is the same, the ratio between P1 and P2 is almost proportional to the ratio between l1 and l2.

Therefore, when the displacement of the piezoelectric element 5a is enlarged four times by the enlargement mechanism, P2 can be made four times as large as P1.
As a result, the processing time can be reduced to 1/4. However, if the enlargement ratio is too large, the vibration transmission member 6e becomes longer, the rigidity of this member is reduced, and the trajectory of the vibration becomes unstable due to resonance with the frequency of the elliptical vibration. Must be a rate. Also, the piezoelectric element 5b
When the displacement of is reduced, the ellipse becomes more crushed,
Since the radius of curvature of the ellipse in the cutting area is increased, the feed pitch P2 can be increased and the processing time can be reduced. The feed pitch can be increased almost in inverse proportion to the square root of the decreasing ratio of the amplitude in the back force direction. For example, when the amplitude of the piezoelectric element 5b is reduced from 20 μm to 5 μm, the feed can be approximately doubled.

The mechanism for expanding the displacement of the tool tip will be further described.

The theoretical surface roughness of fly cutting is determined by the following equation.

Theoretical surface roughness Ry = P ² / (8 × R) P: feed pitch in the generatrix direction R: length from the tool rotation axis to the tool edge From this formula, P = √ (Ry × 8 × R) Becomes

In the mirror processing of fly cut processing, Ry =
50 nm and R = about 10 to 50 mm are used.
Is 63.2 μm to 141.1 μm.

On the other hand, as shown in FIG. 6, the surface roughness and the feed pitch when using vibration cutting are such that Ry1 in the figure is the surface roughness because the tool locus is transferred to the processing surface. , L is the feed pitch. Therefore, in order to make the processing time realistic and superior to fly cut, L
Need to be longer. In addition, P
Considering the size and stroke of ZT and the like, the stroke is 15 μm and the length is 20 mm. Considering the size in consideration of mounting, the stroke is considered to be about 45 μm as a limit, and a displacement enlargement mechanism is required.

In the above embodiment, the cutting tool is subjected to the elliptical vibration. However, the workpiece may relatively vibrate, and an enlargement mechanism in the main component force direction is also provided on the workpiece. May be. Further, a rotation indexing mechanism for matching the direction of the back force of the elliptical motion with the direction of the normal to the generatrix is XY.
It may be on the slider side. Further, the function of the piezoelectric element can be performed by the magnetostrictive element.

As described above, according to the first embodiment, while the tip of the cutting tool is oscillated in an elliptical shape, the axis of the ellipse, which is the trajectory of the vibration of the cutting tool, in the direction of the back force component, By moving the workpiece so that it always faces in the normal direction of the processing surface of the workpiece, and expanding the vibration amplitude in the main component direction of the elliptical vibration obtained by the piezoelectric element, etc., using a magnification mechanism, the workpiece with a small radius of curvature can be processed. In fly cut processing of an object, extremely high shape accuracy can be obtained, and the feed pitch can be increased without deteriorating the theoretical surface roughness, so that the processing time can be reduced.

(Second Embodiment) FIG. 8 is a block diagram showing a configuration of a vibration cutting apparatus according to a second embodiment of the present invention.

The workpiece 101 has such a shape that the radius of curvature in the generatrix direction (X direction) varies from a minimum of several hundred μm to a maximum infinity, that is, a plane. Reference numeral 102a denotes a diamond cutting tool, which has an arc shape in the sagittal direction (Y direction) and has a radius of curvature smaller than the minimum value of the sagittal radius of curvature in the entire workpiece. Reference numeral 105a denotes a piezoelectric element for vibrating the cutting tool in the main component force direction (X direction).
b is a piezoelectric element for vibrating in the back force direction (Z direction). One end of each piezoelectric element is connected to a base member 106.
Are bonded and fixed via elastic hinges 106a and 106b. The other end of the piezoelectric element is connected to an elastic hinge 106c,
It is adhesively fixed to the vibration transmitting member 106e via 106d. The base member 106 and the vibration transmission member 106e are originally the same member, and are configured as a base portion, a hinge portion, a piezoelectric element insertion portion, and a vibration transmission portion by subjecting a flat plate to electric discharge machining. Further, the elastic hinge 10 is used to constitute an enlargement mechanism for increasing the displacement in the main component force direction.
6f and 106g are provided.

In this state, the PZT drive control device 107a
When the piezoelectric element 105a is energized and displaced, the hinge 106a side is not displaced, and the hinge 106c side is moved.
As a result, the hinge 106c becomes the point of action, and the hinge 106f
A lever is formed with the portion as a fulcrum, and the tip of the cutting tool 102 moves with the displacement of the piezoelectric element 105a enlarged at a ratio of the distances l1 and l2. At this time, the hinges 106a, 106c,
A compressive or tensile force and a bending moment are applied to 106f and 106g, and a bending moment is mainly applied to the hinges 106b and 106d. However, since the elastic hinge is rigid for compression and tension and flexible for rotational moment, There is almost no displacement transmission loss in the displacement direction of the piezoelectric element 105a and no loss in the generated force of the piezoelectric element 105a due to bending of the rigid hinge, and the amount of displacement is small. Similarly, PZT
When the piezoelectric element 105b is energized and displaced by the drive control device 107b, the hinge 106b is not displaced and the hinge 10b is displaced.
The 6d side moves. At this time, the force for reducing the displacement of the piezoelectric element is mainly generated by the hinges 106a, 106c, 106f, 10
The bending moment applied to 6 g has only a small effect on the reduction of the displacement.

The piezoelectric elements 105a and 105b are such that they are displaced by 30 μm when 150 V is applied. A current of about 75 V ± 55 V is supplied to the drive control devices 107a and 107b to obtain a displacement of about 20 μm. The service life can be extended as compared to applying the full rated voltage. Two piezoelectric elements 1
PZT drive control devices 107a and 107b
According to 7b, when a sine wave voltage having a phase difference of 90 degrees is applied, an elliptical trajectory at the tip of the cutting tool according to the ratio of l1 and l2 is obtained. If the vibration transmitting member 106e is made too long, the rigidity of the member is reduced, and the vibration resonates with the frequency of the elliptical vibration and the trajectory of the vibration becomes unstable.

If l1 is 10 mm, l2 is 50 mm
Since the degree is considered appropriate, the stroke in the main component force direction is 100 μm. The higher the frequency of vibration, the higher the effect as vibration cutting and the higher the processing efficiency. However, the allowable current of the PZT drive control devices 107a and 107b, the piezoelectric element 105
500 Hz or less is appropriate in consideration of the life of the a and 105b, the resonance frequency of the vibration transmitting member 106e, and the like. Generally, an ultrasonic vibration frequency of 10 kHz to 40 kHz is used. This is to increase the vibration amplitude by using the resonance of the vibrator or the structure. Since the vibration amplitude is likely to change due to a system change in the resonance state due to contact of an object or the like, the tool locus may deviate from the intended one, and the shape accuracy may be deteriorated.

The base member 106 is fixed to a spacer 108, and the spacer 108 is fixed to an indexing board 109. The indexing board 109 is a rotating part rotor 109a.
And a fixed portion housing 109b.
09a is driven by a motor such as a DC brushless, and the rotation angle is detected by an encoder. The indexing board 109 is mounted on a Z slider 110 that moves up and down. The workpiece is fixed to the XY slider 112 that moves in a horizontal plane by the hiring 111. The XY slider 112 is a high-precision slider that is supported by a static pressure bearing, driven by a linear motor, and whose position is detected by a laser length measuring device.

In the above construction, the cutting tool is continuously fed in the sagittal direction while vibrating in the main component force direction and the back component force direction, and is fed by the feed pitch P in the generatrix direction after processing one line. The operation is repeated to process the entire area.

In order to make such a motion, the machining program creating unit in the NC device 113 informs the generating line shape and the sagittal line shape of the workpiece 101 and the distance from the rotation center of the indexing board 109 to the tip of the cutting tool 102. Then, the radius of curvature in the sagittal direction of the cutting tool 102 is input, and NC data for processing the shape of the workpiece is created.

The NC data created by the machining program is sent from the synchronizing signal creating unit to the arithmetic and control unit at a constant clock interval, from which the two piezoelectric elements 105a and 105b are sent.
X, Y, Z, and the command values assigned to the index axes are sent to the respective PZT drive control devices 107a and 107b and the servo controller 114.

PZT drive control unit 107 in operation control unit
The command values to a and 107b are calculated by calculating the displacement amounts of the piezoelectric element 105a vibrating in the main component direction and the piezoelectric element 105b vibrating in the back component direction, and the phases of both, so as to correspond to the curvature change of the bus. ing. PZT drive control device 107a, 1
Reference numeral 07b amplifies the given command value to a voltage having a sinusoidal shape and supplies the voltage to the piezoelectric elements 105a and 105b. As a result, as shown in FIG.
Even if it changes to 1d and 101e, the tool tip trajectory shape is adjusted to 102c, 102d and 10 according to the radius of curvature of the workpiece.
2e.

Specifically, the trajectory calculation is performed on condition that the feed pitch in the generatrix direction becomes maximum. According to FIG. 10, the stroke L in the main component force direction is 100 μm at the maximum by the displacement enlarging mechanism, and 80% of the stroke is used for shape creation, and the lowest point P1 at the tip of the cutting tool and the machining start point At P2 and the machining end point P3, the short diameter H of the ellipse that matches the generatrix shape is determined, and the cutting tool tip trajectory shape 1
02f so that the PZT drive control devices 107a and 107
b.

For example, if the radius of curvature of the bus bar is 0.4 mm, H
= 10.00 μm. Piezoelectric element 105 in this case
The voltage waveforms applied to a and 105b are as shown in FIG.
When the radius of curvature is 1 mm, H = 4.00 μm and the radius of curvature is 10
In mm, H is reduced to 0.40 μm, but when the stroke in the direction of the back force is reduced, the advantage of vibration cutting is impaired, for example, because the dischargeability of chips is reduced. For this reason, when the radius of curvature of the bus bar is larger than 0.4 mm, after the machining end point P3, the displacement after the machining end point P3 is larger than the elliptical locus so that H = 10 μm as shown in the bite locus 102g in FIG. To start the intrusion operation and make a large displacement to the machining start point P2, and then apply the voltage for the elliptical orbit. The voltage waveform to the piezoelectric element at this time is as shown in FIG.

The radius of curvature is 50, which is the length l2 of the arm of the enlargement mechanism.
If it is larger than mm, the maximum vibration amplitude is given only in the main component force direction, and a command is given so that H = 10 μm in the non-machining direction without vibration during machining in the back component force direction. That is,
When the radius of curvature is larger than 50 mm, the turning radius of the cutting tool is always 50 mm, and escapes by 10 μm in the direction of the back force when not machining. When the radius of curvature is 0.2 mm or less, if the main component direction stroke is maximized, the back component direction stroke is insufficient at 20 μm, so the back component direction stroke is fixed at 20 μm, and the main component direction stroke is reduced. To go. Further, when the radius of curvature is 0.01 mm or less, both the main component force direction stroke and the back component force direction stroke assume a value twice the radius of curvature.

To summarize the above, according to the radius of curvature of the bus,
The strokes of the piezoelectric element in the main component direction and the back component direction are commanded as shown in FIG.

The command values for the X, Y, Z and index axes from the arithmetic and control unit are based on the bus feed pitch P according to the bus curvature radius.
Is calculated to be 0.8 times the main component direction stroke. Thus, the maximum feed pitch is always obtained regardless of the radius of curvature of the bus bar, and the processing time can be reduced. In addition, the command value from the arithmetic control unit is calculated under the condition that the axis in the back force direction of the elliptical locus of the tip of the cutting tool coincides with the normal direction of the generatrix. The condition that the normal direction of the sagittal shape at the contact point between the cutting tool and the workpiece coincides with the radial direction of the arc of the cutting tool is also taken into consideration.

Each PZT drive control device 107a, 107b
From, the voltage corresponding to the displacement command is applied to the piezoelectric element in order to make the tip of the cutting tool move elliptically, and a current for moving each linear motor and the rotary motor to the command position is given from the servo controller. A servo system is provided in which the position is detected by a laser length measuring device and an encoder, and the position detection unit transmits this to an arithmetic and control unit to reduce the error from the command to zero.

According to the above configuration, in FIG. 9, for example, the radius of curvature of the portion 101c is 5 mm,
The radius of curvature of the portion is 100 mm, the radius of curvature of the portion 101e is 0.1 mm and the length of the bus bar is approximately 100 mm. Can be processed in about 2 to 3 hours.

In the processing of this method, a shape error from the original shape occurs because the bus shape is approximated by an ellipse.
This amount is, for example, 50 nm for a radius of curvature of 1 mm and 5 nm for a radius of curvature of 10 mm, which is an order that can be almost ignored as a shape error. In order to further reduce the shape error, the arithmetic control unit calculates the distortion rate of the sine waveform according to the radius of curvature of the bus, and the PZT drive control units 107a, 107
In b, a circuit for distorting the waveform may be added.

In the above embodiment, the case where the generatrix shape is mainly concave has been described.
The tool is moved with a turning radius of 50 mm, and the bus feed pitch may be calculated from the turning radius of 50 mm, the radius of curvature of the bus, and the required theoretical surface roughness.

Also, a method has been described in which a line is continuously processed in the sagittal direction by one line and is fed by a certain pitch in the generatrix direction. Processing is also possible. In this case, the PZT drive control device is instructed to continuously change the tool tip trajectory during busbar processing.

Also, in the case of a shape in which a plurality of free-form surfaces are continuous as shown in FIG. 15, it has conventionally been necessary to divide and process the portion 101f. By adding a radius of curvature of about 0.1 mm, it can be processed continuously as one workpiece, reducing component costs, shortening setup and processing time, and preventing shape accuracy deterioration due to positioning errors of multiple components. Became possible.

With these vibration cutting devices and processing methods,
A free-form optical element such as a toric lens or a head-mounted display prism used in a scanner optical system of a laser beam printer can be cut with high precision in a short time. An optical plastic material can be directly cut, and a glass material can be processed if the cut is several μm or less.

Also, since a mold having a nickel-based cutting layer applied to phosphor bronze, brass, steel, or cemented carbide for mass production can be machined,
By plastic molding and glass molding using these,
Mass production of free-form surface optical elements is possible. Further, with these optical elements, the number of optical components can be reduced and the optical performance can be improved, and the product can be reduced in size, performance, and cost.

As described above, the vibrating cutting device and the 4-axis NC device capable of maximally displacing about 100 μm in the main component force direction are used, and the back force is set so that the locus of the cutting tool tip is close to the radius of curvature of the workpiece. By controlling the vibration amplitude in the direction and the vibration amplitude in the main component force direction and the phase of both, a free-form surface optical element having a radius of curvature of several mm or less, which could not be practically manufactured, can be manufactured with a good surface of several tens nm. In a few hours, there is no problem in terms of roughness and mass production, and plastic or glass or its mold can be manufactured, and the radius of curvature can be changed from a few μm to a flat surface, and from concave to convex. A curved element can also be processed.

[0073]

As described above, according to the present invention,
Good surface roughness can be obtained in a short time.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a vibration cutting apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a generation state of a processing shape.

FIG. 3 is a diagram illustrating a generation state of a machining shape and an enlarged feed state.

FIG. 4 is a diagram showing a processing state of a workpiece.

FIG. 5 is a side view of FIG.

FIG. 6 is a diagram showing a trajectory of a cutting edge of a cutting tool.

FIG. 7 is a diagram illustrating an operation of enlarging a displacement of a cutting tool in a main component force direction.

FIG. 8 is a block diagram showing a configuration of a vibration cutting device according to a second embodiment of the present invention.

FIG. 9 is a diagram showing a change in a tool tip trajectory.

FIG. 10 is a diagram showing details of a tool tip trajectory;

FIG. 11 is a diagram showing a voltage applied to a piezoelectric element.

FIG. 12 is a diagram showing details of a tool tip trajectory when a generatrix radius of curvature is large.

13 is a diagram showing a voltage applied to the piezoelectric element in FIG.

FIG. 14 is a diagram illustrating a relationship between a radius of curvature of a bus bar and a displacement amount of a piezoelectric element.

FIG. 15 is a view showing a workpiece whose radius of curvature changes discontinuously.

FIG. 16 is a diagram showing a conventional fly cut processing method.

FIG. 17 is a diagram showing a state in which a processed shape is generated by conventional vibration cutting.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Workpiece 2 Cutting tool 5a, 5b Piezoelectric element 6a, 6b, 6c, 6d, 6g, 6f Elastic hinge 6e Vibration transmission member 7 Drive control device 9 Indexing board 13 NC device 14 Servo controller

Claims (19)

[Claims] 1. A cutting method for cutting a processing surface formed of a curved surface while vibrating a cutting tool and a workpiece relatively in a main component direction and a back component direction, wherein the cutting tool comprises: A cutting method, wherein the axis of the elliptical back force direction, which is the trajectory of the vibration of the tip of the cutting tool, is moved so as to point in the direction of the normal to the processing surface of the workpiece. 2. The cutting method according to claim 1, wherein an amplitude of a drive source for vibrating the cutting tool in a main component direction is enlarged and transmitted to the cutting tool. 3. The cutting method according to claim 1, wherein a piezoelectric element is used as a drive source for relatively vibrating the cutting tool and the workpiece. 4. A vibrating means for vibrating a cutting tool and a workpiece relatively in a main component force direction and a back component force direction, wherein the cutting tool is moved along a locus of vibration of a tip of the cutting tool. A cutting device comprising: driving means for moving an axis of a certain ellipse in the direction of the back force so as to point in a direction normal to a curved surface of the workpiece. 5. The cutting apparatus according to claim 4, further comprising an enlarging means for enlarging an amplitude of a driving source for vibrating the cutting tool in a main component direction and transmitting the amplitude to the cutting tool. . 6. The cutting apparatus according to claim 4, wherein a piezoelectric element is used as a drive source for relatively vibrating the cutting tool and the workpiece. 7. A cutting method for cutting a curved surface that satisfies an optical relationship while vibrating a cutting tool and a workpiece relatively in a main component force direction and a distribution force direction. An elliptical movement step for causing the cutting edge of the cutting tool to perform an elliptical motion; and the elliptical movement of the cutting tool so that an axis of the elliptical back force direction points in a direction normal to a processing surface of the workpiece. A turning step of turning around an axis parallel to the center axis of the cutting process. 8. A cutting method for cutting a workpiece while relatively oscillating a cutting tool and a workpiece in a main component direction and a back component direction, wherein: A cutting method, wherein the trajectory of the vibration of the tip of the cutting tool is changed in accordance with the curvature of the workpiece in accordance with the change in the curvature of the processing surface. 9. The vibration of the tip of the cutting tool is controlled by controlling the amplitude and phase of the vibration of the cutting tool in the main component direction and the amplitude and phase of the vibration of the cutting tool in the back component direction. The cutting method according to claim 8, wherein the trajectory is controlled. 10. The cutting method according to claim 9, wherein the tip of the cutting tool is moved in an elliptical manner. 11. A driving means for vibrating a cutting tool in a main component force direction and a back component force direction, and a main component force of the cutting tool for causing the cutting tool to follow a change in curvature of a processing surface of a workpiece. A cutting device comprising: a control unit that controls a vibration amplitude in a direction, a vibration amplitude in a back force direction, and a phase of the vibration. 12. The cutting apparatus according to claim 11, wherein the control unit controls the tip of the cutting tool to perform an elliptical motion. 13. An optical element processed by the cutting method according to claim 8. Description: 14. A molding die for an optical element, which is processed by the cutting method according to claim 8. Description: 15. An optical element processed by the cutting apparatus according to claim 11. Description: 16. A mold for molding an optical element, which is processed by the cutting apparatus according to claim 11. Description: 17. An elliptical motion due to vibrations in a main component direction and a back component direction is applied to a cutting tool blade for creating an aspherical curved surface including a bus surface and a sagittal surface on a surface to be processed of a member to be processed. In the cutting method to process, the aspherical curved surface to be created is divided into a plurality of areas,
A short diameter H of an ellipse that coincides with a generatrix formed by a lowermost point P1, a processing start point P2, and a processing end point P3 of the elliptical motion in the sectioned area of the cutting tool blade is obtained,
A cutting method characterized in that a condition in which the feed pitch of the cutting tool blade in the generatrix direction is maximum in the area is a movement locus of the tool blade. 18. A tool holding device for performing vibration cutting by applying vibration to a tool blade for cutting an aspherical curved surface on a surface to be processed of a member to be processed, wherein the vibration in the main component force direction is applied to the tool blade. A first vibration generating means for applying a vibration, a second vibration generating means for applying a vibration in the direction of a back force to the tool blade, and a holding member for holding the tool blade. A tool holding device having an enlargement mechanism for increasing displacement in a component force direction. 19. A cutting device for machining a tool blade for machining an aspherical curved surface on a surface to be machined by a main component force direction vibration and a back component force direction vibration. First vibration generating means for applying vibration in the main component direction to the tool blade; second vibration generating means for applying vibration in the distribution force direction to the tool blade; and the first and second vibrations A holding member for holding the generating means and the tool blade, an indexing operation member for indexing the tool blade to a processing position on the work surface via the holding member, and the first and second vibration generating means And a control means for controlling the drive of the indexing operation member.