JP2001300838A - Large ultraprecise elid aspherical work device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a large ultraprecise ELID aspherical work device capable of highly accurately holding a relative position of a workpiece and a tool by minimizing deformation by work resistance and influence of thermal expansion, capable of polishing and shape measurement on a machine without removing and installing the workpiece and capable of highly accurately and highly efficiently working a large ultraprecise X-ray mirror in excellent surface roughness. SOLUTION: This large ultraprecise ELID aspherical work device is provided with a machine bed 12 having a horizontal upper surface and being slender in the X axis direction, an X axis table 14 installed on the machine bed and numerically controllable in the X axis direction by fixing the workpiece 4 to the upper surface, a gate-shaped fixed column 16 extending in the horizontal Y axis direction orthogonal to the X axis by striding over the X axis table and having both leg parts fixed to the machine bed, a Y axis stage 18 installed on the gate-shaped fixed column and numerically controllable in the Y axis direction, a Z axis column 20 suspended by the Y axis stage and numerically controllable in the vertical Z axis direction, an ELID grinding attachment 22 installed on the Z axis column, a polishing device 24 and a shape measuring device 26.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a large ultra-precision ELI.
The present invention relates to a D aspherical surface processing device.

[0002]

2. Description of the Related Art With the development of science and technology in recent years, the demand for ultra-precision machining has been drastically enhanced, and as a mirror surface grinding means that meets this demand, an electrolytic in-process dressing grinding method (Electrolytic In-pro
ESS Dressing: ELID grinding method) has been developed and published by the applicant of the present invention (RIKEN symposium “Latest Technology Trend of Mirror Surface Grinding”, held on March 5, 1991).

In this ELID grinding method, as schematically shown in FIG. 6, an electroconductive grinding wheel 1 is used in place of an electrode in a conventional electrolytic grinding, and an electrode 2 opposed to the grinding wheel with a gap therebetween. And applying a voltage between the grinding wheel 1 and the electrode 2 while flowing the conductive liquid 3 between the grinding wheel and the electrode,
The work is ground by the grindstone while dressing the grindstone by electrolysis. In other words, by using the metal bond grindstone 1 as an anode and the electrode 2 opposed to the grindstone surface with a gap therebetween as a cathode and performing the electrolytic dressing of the grindstone at the same time as the grinding operation, the grinding performance can be maintained and stabilized. Is the law. In this drawing, reference numeral 4 denotes a work (material to be ground), 5 denotes an ELID power supply, 6 denotes a power supply,
Reference numeral 7 denotes a conductive liquid nozzle.

In this ELID grinding method, even if the abrasive grains are made fine, clogging of the grindstone does not occur due to the sharpening of the abrasive grains by electrolytic dressing. Therefore, by grinding the abrasive grains, an extremely excellent processed surface such as a mirror surface is ground. It can be obtained by processing. Therefore, the ELID grinding method can maintain the sharpness of the grinding wheel from high-efficiency grinding to mirror surface grinding, and can perform various grinding processes as a means that can create a highly accurate surface in a short time, which was impossible with the conventional technology. Is expected to be applied.

[0005]

In recent years, large ultra-precision X
Line mirrors, hologram optical elements or other optical elements, mechanical structures, optoelectronic devices (hereinafter referred to as large ultra-precision X
Processing requirements for large and ultra-precision devices such as line mirrors) are increasing in the fields of scientific instruments such as synchrotron radiation facilities and large astronomical telescopes, optoelectronic devices, high-density and high-speed information devices,
There is a growing need in industries such as flat displays.

In such a large ultra-precision X-ray mirror or the like, the conventional processing means reduces the surface roughness by lapping or ordinary grinding to a processing limit of Rmax1 to 2 μm (1000 to 2 μm).
000 nm), and then polishing to the required surface roughness (for example, several Å). However, the removal allowance by polishing usually requires about 10 times the surface roughness before processing.
It is necessary to process 0 to 20 μm by polishing, and there is a problem in that the removal amount (processing amount) by polishing is large. For this reason, a tool that elastically deforms is lightly pressed against the surface of the optical element so as not to damage the surface, and a conventional polishing method in which a slurry containing fine abrasive grains is supplied and polished is used to process a large mirror surface of 10 to 20 μm. Required a long period of several months.

[0007] Further, when 10 to 20 µm is removed by polishing, the processing distortion of the surface during lapping or grinding is removed, so that there is a problem that the shape accuracy between the surface and the reference surface changes, and the ultra-precision mirror surface is required. Shape accuracy (λ / 4 or less)
In order to obtain, after polishing, re-work the reference plane,
It was necessary to repeat the polishing again until the required precision was obtained. Further, there is a problem that the reference surface of the optical element is likely to be displaced when the work is repeatedly removed / attached.

On the other hand, although the above-mentioned ELID grinding method is suitable in principle for high-efficiency and high-precision grinding processing, even if it is simply increased in size, it is affected by deformation due to processing resistance and thermal expansion. There was a problem that the relative position between the workpiece and the tool could not be maintained with high accuracy. In addition, this E
Even if the LID grinding method is simply applied, it is necessary to repeat the removal / attachment of the work for the above-mentioned polishing, and at this time, there has been a problem that the reference surface of the optical element is shifted.

The present invention has been made in order to solve such a problem. That is, an object of the present invention is to minimize the influence of deformation and thermal expansion due to machining resistance, to maintain the relative position of a work and a tool with high precision, and to perform removal / attachment of a work without removing the work. Provides a large-sized ultra-precision ELID aspherical surface processing device that can perform polishing and shape measurement on a machine, and thereby can efficiently process large-scale ultra-precision X-ray mirrors and the like with high accuracy and excellent surface roughness. Is to do.

[0010]

According to the present invention, a machine bed (12) elongated in the X-axis direction having a horizontal upper surface.
An X-axis table (14) mounted on the machine bed and fixed on the upper surface to fix the work (4) and capable of performing NC control in the X-axis direction; and a horizontal Y-axis straddling the X-axis table and orthogonal to the X-axis. A gate-type fixed column (16) extending in the axial direction and having both legs fixed to a machine bed; a Y-axis stage (18) mounted on the gate-type fixed column and capable of performing NC control in the Y-axis direction; A Z-axis column (20) suspended on a stage and capable of NC control in a vertical Z-axis direction, and an ELID grinding device (22), a polishing device (24), and a shape measuring device (26) attached to the Z-axis column The present invention provides a large-sized ultra-precision ELID aspherical surface processing apparatus, comprising:

According to the configuration of the present invention, since the frame structure is such that the gate-shaped fixing column (16) is fixed in the width direction of the elongated machine bed (12), the frame has high rigidity and symmetry. Due to the structure, the influence of thermal deformation can be minimized. Further, the X-axis table (14) is mounted on the elongated machine bed (12), and the Y-axis stage (18) and the Z-axis column (20) are mounted on the portal fixed column (16). In addition, it is possible to efficiently process a mirror having an elongated toroidal surface used in a facility utilizing radiation light. Further, since the ELID grinding device (22), the polishing device (24), and the shape measuring device (26) are mounted on the same Z-axis column, the workpiece can be removed on the same machine by performing ELID grinding, polishing, and shape measurement. / It can be repeated while making corrections without performing mounting, and it is possible to process large and large ultra-precision X-ray mirrors and the like with high accuracy and excellent surface roughness with high efficiency.

According to a preferred embodiment of the present invention, there is provided an ultra-precision VV roller guide for guiding the X, Y, and Z axes by a pair of V-shaped roller guides. With this configuration, the pair of V-shaped roller guides enhances the guide accuracy and guide rigidity, and enables a super-precision linear motion without any backlash.

Further, the apparatus has a ball screw for driving each of the X, Y, and Z axes, and at least one of the ball screws is formed as a water-cooled hollow. With this configuration, it is possible to prevent the heat generated by the ball screw (for example, the X axis) that is driven at high speed, and to prevent the accuracy from being deteriorated due to the thermal expansion of the ball screw and the adverse effect due to the temperature rise of the work and the guide.

An NC controller for controlling the X, Y, and Z axes by NC and a personal computer connected to the NC controller by HSSB are stored in the personal computer. With this configuration,
The memory capacity of the expensive NC control device can be reduced, and the simulation of the NC control program can be freely simulated by a general-purpose personal computer (PC), thereby reducing bugs and preventing erroneous processing.

Further, the ELID grinding device (22) includes:
Grinding spindle (2) that can change the axis of rotation horizontally or vertically
2a) a conductive grindstone (22b) rotatably mounted on the grinding spindle; an electrode facing the grindstone at an interval; a nozzle for flowing a conductive liquid between the grindstone and the electrode; It consists of a power supply and a power supply that applies a voltage between the electrodes, and while applying a conductive liquid between the grindstone and the electrode, while applying a voltage between the grindstone and the electrode, the grindstone is dressed by electrolysis. The work (4) is ground. With this configuration, the grinding spindle (22
By converting the rotation axis of a) to horizontal or vertical, a disc-shaped grindstone, a ball nose grindstone, or another conductive grindstone can be used as the conductive grindstone (22b). A line mirror or the like can be ground to high efficiency, high precision and high quality surface roughness by ELID grinding.

Further, the polishing apparatus (24)
A polishing head (24a) having a polishing pad at a lower end thereof; and a rotary driving device (2) for rotating the polishing head about a vertical axis while supporting the polishing head in a swingable manner.
4b) and a pressing cylinder (24b) for pressing the polishing head downward against the work. With this configuration, while the polishing head (24a) is pressed with a predetermined pressing force by the pressing cylinder (24b), the polishing head is rotated by the rotary drive device (24b), and the soft polishing head is swung along the processing surface. By rotating, polishing can be performed efficiently.

The shape measuring device (26) includes a probe (26a) having a spherical contact at a lower end, and an urging guide device (26b) for supporting the probe so as to be vertically movable and urging it downward. And a position detector (26c) for detecting the position of the probe. With this configuration, for example, a laser type position detector is used for the position detector (26c), and the probe (26a) is supported by an air bearing, thereby improving the dynamic characteristics of the probe and allowing the machined surface shape of the workpiece to be machined. Can be measured with high accuracy.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. In the drawings, common parts are denoted by the same reference numerals.

FIG. 1 shows a large super precision ELID according to the present invention.
It is the whole perspective view of an aspherical surface processing device. As shown in this figure, a large-sized ultra-precision ELID aspherical surface processing apparatus 10 of the present invention
Are a machine bed 12, an X-axis table 14, a gate-shaped fixed column 16, a Y-axis stage 18, a Z-axis column 20, and a Z-axis.
It comprises an ELID grinding device 22, a polishing device 24, and a shape measuring device 26 mounted on a shaft column. Further, in this example, the machine bed 12 is further provided with a rotary truer 28, and the processing surface of the grindstone 2 is trued by bringing the outer peripheral surface thereof into contact with the grindstone 22b. Further, the large-sized super-precision ELID aspherical surface processing apparatus 10 is installed in a constant temperature chamber (not shown), the constant temperature chamber is always maintained at a constant temperature, displacement due to thermal expansion of the work 4 and the components is suppressed, and high accuracy is maintained. It has become.

The machine bed 12 is an elongated main body frame having a horizontal upper surface and extending horizontally in the X-axis direction.
It has an integral structure with high rigidity. X axis table 14
Is mounted on the machine bed 12, and the work 4 is fixed on the upper surface thereof so that the work can be moved at high speed and with high accuracy in the X-axis direction by NC control. The gate-shaped fixed column 16 extends in the horizontal Y-axis direction orthogonal to the X-axis across the X-axis table 14, and both legs are fixed to the machine bed 12. The gate-shaped fixed column 16 is also a part of the main body frame similarly to the machine bed 12, and has an integral structure with high rigidity. The Y-axis stage 18 is mounted on the upper surface of the portal fixed column 16 in this example, and can be moved at high speed and with high accuracy by NC control in the Y-axis direction. The Z-axis column 20 is suspended from the Y-axis stage 18 so that it can be moved at high speed and with high precision in the vertical Z-axis direction by NC control.

With the above-described structure, the frame structure is such that the gate-shaped fixing column 16 is fixed in the width direction of the elongated machine bed 12, so that the frame has high rigidity.
In addition, due to the symmetrical structure, the influence of thermal deformation can be minimized. In particular, as in the embodiment described later, the X-axis stroke is increased (for example, 1400 m).
m), by making the Y-axis and Z-axis strokes relatively short (for example, 550 mm and 200 mm, respectively), while maintaining high frame rigidity, large large-scale ultra-precision X-ray mirrors etc. Mirrors with a slender toroidal surface used in such applications) can be machined with high precision.

The X, Y, and Z axes are guided by an ultra-precision VV roller guide 32 shown in FIG. The super-precision V-V roller guide 32 is composed of a pair of V-shaped roller guides 34 supported by a high-accuracy needle bearing 33, which increases the guide accuracy and guide rigidity, and realizes an ultra-precise linear motion without play. Has been realized. Further, it has ball screws (not shown) for driving the X, Y, and Z axes, respectively.
The book (for example, for the X axis) is formed in a water-cooled hollow in order to prevent heat generation at the time of high-speed driving, to prevent a decrease in accuracy due to thermal expansion of the ball screw, and to avoid an adverse effect due to a rise in temperature of the work or guide.

An NC controller (not shown) for performing NC control of the X, Y, and Z axes, and a personal computer connected to the NC controller by an HSSB are provided. In this personal computer, the memory capacity of an expensive NC control device is reduced, and the NC control program is freely simulated by a general-purpose personal computer (PC) to reduce bugs and prevent erroneous processing. In order to prevent this, a program for NC control is stored.

In FIG. 1, the ELID grinding device 22 comprises:
Grinding spindle 22 that can change the axis of rotation horizontally or vertically
a, a conductive grindstone 22b rotatably mounted on the grinding spindle 22a, an electrode (not shown) facing the grindstone at an interval, and a nozzle for flowing a conductive liquid between the grindstone and the electrode (FIG. And a power supply (not shown) for applying a voltage between the grindstone and the electrode. With this configuration, by converting the rotation axis of the grinding spindle 22a to horizontal or vertical, a disc-shaped grindstone, a ball nose grindstone, and other conductive grindstones can be used as the conductive grindstones 22b. Can process ultra-precision X-ray mirrors. In addition, similarly to the conventional ELID grinding apparatus, a voltage is applied between the grindstone and the electrode while flowing a conductive liquid between the grindstone and the electrode, and the work 4 is subjected to ELID grinding while dressing the grindstone by electrolysis. Grinding can be performed with high efficiency, high precision and high quality surface roughness.

FIG. 3 is a configuration diagram of a polishing apparatus mounted on a Z-axis column. As shown in this figure, the polishing apparatus 24 includes a polishing head 24a having a polishing pad at a lower end, a rotation driving device 24b for rotating and driving the polishing head 24a about a vertical axis while swingably supporting the polishing head 24a, 24
and a pressing cylinder 24c for pressing a downwardly against the work. The rotation drive device 24b includes, for example, an electric motor, a pulley, and a belt. With this configuration, after the ELID grinding by the conductive grindstone 22b, the polishing head 24a is rotated by the rotation driving device 24b while pressing the polishing head 24a with a predetermined pressing force by the pressing cylinder 24c, and the soft polishing head is moved along the processing surface. By swinging and rotating, polishing can be performed efficiently.

FIG. 4 is a configuration diagram of a shape measuring device attached to a Z-axis column. As shown in this figure, the shape measuring device 26 has a probe 2 having a spherical contact at the lower end.
6a, an urging guide device 26b that supports the probe 26a so as to be vertically movable and urges the probe 26a downward, and a position detector 26c that detects the position of the probe 26a. Further, in this example, the position detector 26c is a laser type position detector, and the probe 26a is supported by an air bearing to enhance the dynamic characteristics of the probe and to precisely process the processed surface of the workpiece on the machine. Can be measured.

[0027]

Table 1 shows the large ultra-precision ELID actually manufactured.
This is the specification of the aspherical surface processing device.

[0028]

[Table 1]

As is clear from this table, the X, Y, and Z axes each have a positioning resolution of 10 nm. Also, the straightness of each axis is 0.5 μm / 1400 mm on the X axis and 0.2 μm / 550 mm and 0.2 μm / 200 mm on the Y and Z axes by employing the ultra-precision VV roller guide. Therefore, with this device, 1200 mm x
A large ultra-precision X-ray mirror of 500 mm × 200 mm can be processed. In addition, as described above, in this apparatus, since the ELID grinding device 22, the polishing device 24, and the shape measuring device 26 are attached to the same Z-axis column, ELID grinding, polishing, and shape measurement are performed on the same machine. The work can be repeated while making corrections without removing / attaching the work, and a large large-sized ultra-precision X-ray mirror can be machined with high precision and excellent surface roughness with high efficiency.

FIG. 5 is a diagram showing an example of machining control by the apparatus of the present invention, and shows a step movement position on the X-axis when a command of a 10 nm step is repeated. From this result, it can be seen that the command value accurately follows the command value in 10 nm steps. In addition, the repetition position accuracy is set to 0.
It was 1 μm or less, and it was confirmed that it had the precision required for ultra-precision processing.

It should be noted that the present invention is not limited to the above-described embodiment, but can be changed to a main type without departing from the gist of the present invention.

[0032]

According to the above-described large-sized super-precision ELID aspherical surface processing apparatus, (1) processing of a non-axisymmetric aspherical surface such as a toroidal surface by using a super-hard material such as fused silica or SiC;
(2) Processing such as formation of a holographic optical element / holographic grating with a single crystal diamond tool can be performed.

A rotary table is provided on the X-axis table, and this axis (C-axis) is NC-controlled to obtain (3)
Processing of a large cylindrical optical element, (4) processing of an axisymmetric large lens / reflector, (5) processing of a large non-axisymmetric aspheric surface by simultaneous control of four axes including the C axis, and the like can also be performed.

Therefore, the large super-precision ELID aspherical surface processing apparatus of the present invention can maintain the relative position of the workpiece and the tool with high precision while minimizing the influence of deformation and thermal expansion due to processing resistance, and Polishing and shape measurement are possible on the machine without removing / attaching the workpiece.
Thereby, there is an excellent effect that a large-sized ultra-precision X-ray mirror or the like can be processed with high accuracy and excellent surface roughness with high efficiency.

[Brief description of the drawings]

FIG. 1 is an overall perspective view of a large-sized ultra-precision ELID aspherical surface processing apparatus according to the present invention.

FIG. 2 is a configuration diagram of an ultra-precision VV roller guide.

FIG. 3 is a configuration diagram of a polishing apparatus.

FIG. 4 is a configuration diagram of a shape measuring device.

FIG. 5 is a diagram showing an example of processing control by the apparatus of the present invention.

FIG. 6 is an explanatory diagram of an ELID grinding method.

[Explanation of symbols]

Reference Signs List 1 conductive whetstone, 2 electrodes, 3 conductive liquid, 4 work (material to be ground), 5 ELID power supply, 6 feeder, 7 nozzle, 10 large super precision ELID aspherical processing device, 12
Machine bed, 14 X-axis table, 16 fixed columns, 18 Y-axis stage, 20 Z-axis column, 2
2 ELID grinding device, 22a grinding spindle, 22
b conductive grindstone, 24 polishing device, 24a polishing head, 24b rotation drive device, 24c pressing cylinder, 26 shape measuring device, 26a probe, 26b urging guide device, 26c position detector, 2
8 rotary truer, 32 super precision V-V roller guide, 33 needle bearing, 34 V-type roller guide

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Minoru Moriya 2-20-3 Kaga, Itabashi-ku, Tokyo High Corp. Jujo 403 (72) Inventor Weimin Hayashi 716-1-203 Shimookubo, Urawa-shi, Saitama (72) Inventor Shinya Morita Park Heights 4-46-9 Itabashi, Tokyo, Itabashi-ku, Tokyo 202 F F-term (reference) 3C029 BB01 3C047 AA13 AA25 AA27 3C049 AA03 AA11 AC02 BA01 BA07 BB06 BB09 CA02 CB01 3C059 AA02 AB01 GC01 HA08

Claims (7)

[Claims] 1. A machine bed (12) having a horizontal upper surface and elongated in the X-axis direction, and an X-axis table mounted on the machine bed and having a work (4) fixed on the upper surface and capable of NC control in the X-axis direction. (14) a portal-type fixed column (16) extending in the horizontal Y-axis direction orthogonal to the X-axis across the X-axis table and having both legs fixed to a machine bed, and mounted on the portal-type fixed column; A Y-axis stage (18) that can be NC-controlled in the Y-axis direction, and a Z-axis column (2) that is suspended from the Y-axis stage and that can be NC-controlled in the vertical Z-axis direction.
0) and an ELID grinding device (22), a polishing device (24), and a shape measuring device (26) attached to the Z-axis column.
LID aspherical surface processing equipment. 2. The large-sized ultra-precision E according to claim 1, further comprising an ultra-precision VV roller guide for guiding each of the X, Y, and Z axes by a pair of V-shaped roller guides.
LID aspherical surface processing equipment. 3. The apparatus according to claim 2, further comprising a ball screw for driving each of the X, Y, and Z axes, wherein at least one of the ball screws is formed as a water-cooled hollow.
3. A large-sized ultra-precision ELID aspherical surface processing apparatus according to item 1. 4. An NC controller for performing NC control on the X, Y, and Z axes, and a personal computer connected to the NC controller by HSSB, wherein a program for NC control is stored in the personal computer. The large-sized ultra-precision ELID aspherical surface processing apparatus according to claim 1, wherein: 5. The grinding spindle (22), wherein the ELID grinding device (22) is capable of converting a rotation axis horizontally or vertically.
a), a conductive grindstone (22b) rotatably mounted on the grinding spindle, an electrode facing the grindstone at an interval, and a nozzle for flowing a conductive liquid between the grindstone and the electrode;
It consists of a power supply and a power supply that applies a voltage between the grindstone and the electrode, and while applying a conductive liquid between the grindstone and the electrode, applies a voltage between the grindstone and the electrode to dress the grindstone by electrolysis. 2. The large ultra-precision E according to claim 1, wherein the workpiece (4) is ground while grinding.
LID aspherical surface processing equipment. 6. A polishing head (2) having a polishing pad at a lower end thereof.
4a) and a rotation driving device (24) for rotating the polishing head about a vertical axis while swingably supporting the polishing head.
2. A large-sized ultra-precision ELID aspherical surface processing apparatus according to claim 1, comprising: b) and a pressing cylinder (24b) for pressing the polishing head downward against the workpiece. 7. The shape measuring device (26) includes a probe (26a) having a spherical contact at a lower end, and an urging guide device (26b) supporting the probe so as to be vertically movable and urging it downward. The large super-precision ELID aspherical surface processing apparatus according to claim 1, comprising: a position detector (26c) for detecting a position of the probe.