JP2021133490A - Correction-polishing processing method and correction-polishing processing device - Google Patents

Abstract

To provide a correction-polishing processing method and a correction-polishing processing device which can suppress occurrence of streaks in a static processing trace, and do not cause anisotropy in surface roughness even when increasing scanning pitch of correction-polishing processing, so that efficiency in processing can be improved.SOLUTION: A correction-polishing processing method, which performs scanning processing by numerically controlling a rotary tool 2 that can perform polishing processing locally, while supplying slurry polishing processing liquid 8, processes a work-piece 90 while oscillating the work-piece. A vibration frequency of the oscillation is 0.1 Hz or more and amplitude of vibration is 1 μm or more. In the polishing processing liquid, abrasive grain made of organic particles whose average particle size is 5 μm or more are dispersed in liquid, which is composed mainly of pure water or water.SELECTED DRAWING: Figure 1

Description

The present invention relates to a correction polishing method in which scanning is performed by numerical control using a rotation tool capable of locally polishing.

The surface shape of optical elements such as lenses and mirrors greatly affects the light condensing performance and changes in intensity. On the other hand, the required surface shapes are various. In particular, it is difficult to produce aspherical surfaces and free-form surface shapes by conventional grinding. Therefore, a correction polishing process is performed in which a rotary tool capable of locally polishing process is subjected to numerical control scanning processing over the entire surface while being pressed against a work (workpiece) while supplying a slurry-like polishing processing liquid in between. There is.

In the correction polishing process, a static processing mark is obtained by polishing a material of the same quality as the work in advance without scanning the rotation tool, and a unit processing shape is obtained by replacing the static processing mark per unit time. Then, the residence time (scanning speed) of the rotation tool is calculated by deconvolution (deconvolution integration) of this unit processing shape and the shape error (correction target shape) on the work, and along this residence time distribution. The process of scanning the rotation tool performs correction processing to the desired shape (see, for example, Patent Document 1).

In the corrective polishing process, it is important to suppress the instability of the processing rate caused by tool wear and the method of supplying the processing liquid (slurry). In particular, when general abrasive grains such as cerium oxide and silica are used, poor dispersibility of the abrasive grains causes instability of the processing rate. In response to this problem, the present inventor has already developed Organic Abrasive Machining (OAM method) using organic particles such as acrylic as abrasive particles (see Patent Document 2). The merits of using organic particles are that the specific gravity is close to that of water, so the dispersibility of the particles is very high, it is softer than a workpiece and less likely to be scratched, and it is easy to remove after processing because it dissolves in an organic solvent, and it can be obtained at low cost. The point is that it is easy to do.

In the above OAM method, a correction polishing process having a spatial resolution of 100 μm is achieved using acrylic particles. However, even in this OAM method, as shown in FIG. 6, fringes depending on the rotation direction of the tool are generated in the static machining marks. As a result, when the scanning pitch of the correction polishing process is increased, the surface roughness after the polishing process is anisotropy in the tool rotation direction and is slightly deteriorated. Therefore, there is a problem that the scanning pitch cannot be increased and the processing efficiency cannot be improved.

Japanese Unexamined Patent Publication No. 2005-2205 Japanese Patent No. 6446590

Therefore, in view of the above-mentioned situation, the present invention tries to solve the problem by suppressing the occurrence of fringes in the static processing marks and increasing the scanning pitch of the correction polishing process without anisotropy in the surface roughness. The point is to provide a correction polishing processing method and a correction polishing processing apparatus capable of improving the processing efficiency.

As a result of diligent studies to solve the above-mentioned problems, the present inventor may be able to average the processing by oscillating the work, suppress the generation of fringes and thus anisotropy, and improve the surface roughness. As a result of investigating the change in the static processing mark due to the shaking, the present invention has been completed.

That is, the present invention includes the following inventions.

(1) In a correction polishing method in which a rotary tool capable of locally polishing is scanned by numerical control while supplying a slurry-like polishing liquid in between, the work is processed while swinging. A modified polishing method characterized by.

(2) The modified polishing method according to (1), wherein the frequency of the vibration is 0.1 Hz or higher.

(3) The modified polishing method according to (1) or (2), wherein the swing amplitude is 1 μm or more.

(4) The correction polishing process according to any one of (1) to (3), wherein the polishing process solution is a polishing process solution in which abrasive grains composed of organic particles having an average particle size of 5 μm or more are dispersed in the liquid. Method.

(5) The modified polishing method according to any one of (1) to (4), wherein the liquid is a liquid containing pure water or water as a main component.

(6) A rotary tool for polishing workpieces that can locally polish workpieces in a stationary state without scanning,
A processing liquid supply means for supplying a slurry-like polishing processing liquid between the rotating tool and the work, a work holding mechanism for holding the work movably in the XYZ direction, and a work held by the work holding mechanism. A correction polishing processing apparatus provided with a swinging means for swinging the work, and scanning the work swinging by the swinging means by numerically controlling the work holding mechanism.

(7) The swinging means comprises a guide mechanism for guiding the holding body holding the work along the swinging direction, and a vibrating actuator for vibrating the holding body along the swinging direction. (6) The modified polishing apparatus according to (6).

According to the invention of the present application as described above, by processing the work while swinging the work in a direction intersecting the rotation direction of the rotation tool, it is possible to suppress the occurrence of fringes on the static processing marks by the rotation tool. Therefore, even if the scanning pitch is increased during the scanning process by numerical control, the surface roughness does not become anisotropic, and the efficiency of the correction polishing process can be improved.

The front view which shows the correction polishing processing apparatus which concerns on the typical embodiment of this invention. The left side is a surface observation image of static processing marks without shaking, and the right side is a graph showing the depth profile. The left side is a surface observation image of a static processing mark having a swing amplitude of 1 μm, and the right side is a graph showing a depth profile. The left side is a surface observation image of a static processing mark having a swing amplitude of 5 μm, and the right side is a graph showing a depth profile. The left side is a surface observation image of a static processing mark having a swing amplitude of 10 μm, and the right side is a graph showing a depth profile. The left side is a surface observation image of a static processing mark having a swing amplitude of 20 μm, and the right side is a graph showing a depth profile. The left side is a surface observation image of a static processing mark having a swing amplitude of 30 μm, and the right side is a graph showing a depth profile. The left side is a surface observation image of static processing marks without shaking, and the right side is a graph showing the depth profile. The left side is a surface observation image of a static processing mark with a vibration frequency of 0.1 Hz, and the right side is a graph showing a depth profile. The left side is a surface observation image of a static processing mark with a vibration frequency of 1 Hz, and the right side is a graph showing a depth profile. The left side is a surface observation image of a static processing mark with a vibration frequency of 10 Hz, and the right side is a graph showing a depth profile. The left side is a surface observation image of scanning traces with a scanning pitch of 10 μm without shaking, and the right side is an enlarged image. The left side is oscillating, and the surface observation image of scanning marks with a scanning pitch of 10 μm, and the right side is an enlarged image. The left side is a surface observation image of scanning traces with a scanning pitch of 50 μm without shaking, and the right side is an enlarged image. The left side is oscillating, and the surface observation image of scanning marks with a scanning pitch of 50 μm, and the right side is an enlarged image. (A) is a PSD in a 10 μm pitch scanning process, and (b) is a PSD in a 50 μm pitch scanning process. (A) is a surface observation image of static processing marks in the conventional OAM method, and (b) is an image showing surface roughness before and after scanning processing. Explanatory drawing which shows the method of scanning processing.

Next, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 1, the correction polishing apparatus 1 according to a typical embodiment of the present invention includes a rotation tool 2 for polishing a work that is locally pressed against the work 9, and the rotation tool 2 and the work 9. In between, the machining fluid supply means 3 for supplying the polishing fluid in the form of a slurry, the work holding mechanism 4 for holding the work 9 so as to be movable in the XYZ direction, and the work 9 held by the work holding mechanism 4 are swung. It is provided with a swinging means 5.

In the present embodiment, the OAM method (local polishing method described in Japanese Patent No. 6446590) and the swinging means 5 will be described in combination, but the present invention uses such an OAM method. The EEM processing (Elastic Emission Machining) method, the ferrofluid polishing processing method (Japanese Patent Publication No. 2-25745), and various other local polishing processing methods are combined with the swinging means. Is possible. In particular, it is effective to combine it with a correction polishing method capable of swinging at high speed without direct contact between the tool and the work surface or generating a strong contact force. Regarding the configuration of the OAM method of the present embodiment, the description of Japanese Patent No. 6446590 is incorporated by reference.

The rotating tool 2 includes a rotating body 20 made of an elastic material such as rubber, a shaft body 21 provided with the rotating body 20 at the tip and long in the axial direction for rotating the rotating body 20, and the shaft body on the proximal end side. It is composed of a rotation support portion 22 that rotates the center of the shaft while supporting the 21. By pressing the outer peripheral surface of the rotating body 20 against the work 9, the shaft body 21 is curved, and the curved shaft body 21 is curved. The rotating body 20 is pressed against the work 9 side and urged by the elastic restoring force of. Reference numeral 70 in the figure is an electronic balance of the weight and 71, and is configured so that the pressing load (and load change) of the rotating body 20 on the work 9 can be measured in detail by the electronic balance 71 and recorded on the personal computer 10. ..

The rotating body 20 is configured so that the outer diameter (maximum diameter in the region) of the polishing action region on the outer peripheral surface facing the work 9 is 5.0 mm or less, and the diameter of the rotating body (maximum diameter of the outer peripheral surface) is The diameter is set smaller than the diameter of the conventional rotating tool. As a specific elastic material, it is preferable to use fluororubber. As the shape of the rotating body 20, various shapes such as a spherical shape, a partial spherical shape, a ring shape having a circular cross section (toroidal shape), and the like can be adopted.

As the shaft body 21, a metal shaft such as stainless steel can be used. In the present embodiment, the rotation tool 11 is configured by fitting and fixing the tip end portion of the shaft body 21 into the toroidal-shaped rotating body 20 and fixing the base end portion of the shaft body 21 to the rotation support portion 22. ing. An electric motor or the like can be used for the rotation support portion 22. Then, the abrasive grains interposed between the rotating body 20 and the work surface 90 are rolled on the work surface 90 while being pressed by the rotating body 20 to polish the work surface 90.

The processing liquid supply means 3 is provided in the ejection nozzle 30 and the recovery tank 31 around the ejection nozzle 30 and the recovery tank 31 which receive the polishing processing liquid 8 which is ejected from the nozzle and hits the workpiece surface 90 and falls. A machining fluid injection unit including a slurry circulation pump 35 that supplies the receiving and recovered polishing fluid 8 to the ejection nozzle 30 again and ejects it upward is configured. The polishing liquid 8 circulates between the ejection nozzle 30, the workpiece surface 90, the recovery tank 31, and the pump 35.

The liquid of the polishing liquid 8 is preferably a liquid containing pure water or water as a main component in terms of the dispersibility of organic particles. Various organic particles can be adopted, and in particular, those having a density close to 1 g / cm3, such as acrylic particles, urethane particles, and styrene particles made of a polymer material, are preferable. Of these, urethane and acrylic (both densities are 1.2 g / cm3) are more preferable. Organic particles of different materials may be mixed. The average particle size of the organic particles is preferably 5 μm or more and 30 μm or less.

The work holding mechanism 4 is composed of a three-axis automatic stage of an X-axis stage 41, a Y-axis stage 43, and a Z-axis stage 42 that holds the work 9 with the work surface 90 facing downward so as to be movable in the XYZ direction at an upper position. Has been done. If the work holding mechanism 4 is provided with a rotating mechanism (rotating stage; θ stage) that rotates the work 9 while holding it, the posture can be changed in addition to the position of the work, and the degree of freedom in processing can be further increased. Can be done. By numerically controlling the operation of the work holding mechanism 4 and the support base 60 of the rotation tool 2 by a computer (not shown), the work 9 in contact with the rotation tool 2 is moved, and the surface 90 to be machined is automatically scanned. It is configured in.

The swinging means 5 includes a guide mechanism 51 that guides the holding body 40 that holds the work 9 along the swinging direction, and a vibrating actuator 52 that vibrates the holding body 40 along the swinging direction. A linear guide is suitable for the guide mechanism 51, and a piezoelectric actuator is suitable for the vibration actuator 52. By passing a sinusoidal alternating current through the piezoelectric actuator, the displacement of the piezoelectric actuator is transmitted to the work through the guide mechanism 51, and the work is swung along the guide direction of the guide mechanism 51. As the piezoelectric actuator, for example, a displacement expansion mechanism type piezoelectric actuator manufactured by Mechano Transformer Co., Ltd. can be preferably used.

The frequency of vibration is preferably 0.1 Hz or more, and the amplitude is preferably 1 μm or more. In the present embodiment, the guidance direction of the swing by the guide mechanism 51 is a straight direction in the direction orthogonal to the rotation tangential direction along the machined surface 90 of the rotation tool 2, and the swing is made in this direction. However, the present invention is not limited to such a swing direction. In addition to linear reciprocation, various modes of swinging are possible, such as curved reciprocating and endless (loop-shaped) rotary swinging.

<Static machining mark test 1>
The result of an experiment for confirming the difference in static machining marks (machining in which the scanning of the tool is stopped) by changing only the swing amplitude using the machining apparatus shown in FIG. 1 will be described.

(Processing conditions)
・ Work material: Quartz glass ・ Polishing liquid: Slurry of acrylic particles with an average particle size of 10 μm mixed with pure water at 10 wt% ・ Material of rotating body of rotating tool: Fluorine rubber ・ Outer diameter of rotating body of rotating tool: 3mm
・ Pushing depth of rotation tool: 400 μm
-Rotation speed of rotation tool: 2000 rpm
・ Frequency of work swing (frequency of sinusoidal alternating current input to piezoelectric actuator): 1Hz
-Work swing amplitude: 0 μm (no swing) / 1 μm / 5 μm / 10 μm / 20 μm / 30 μm
・ Processing time: 5 minutes (result)
The results are shown in FIGS. 2 (a) and 2 (f). The left side of each figure shows the measurement result of the entire spot processing mark at each amplitude by the scanning white interferometer, and the right side shows the depth profile. Comparing the depth profiles of the tool (rotation tool) rotation and the vertical direction (direction orthogonal to the rotation tangential direction along the machined surface), the surface roughness is very rough without shaking. It was confirmed that the surface became smoother as the swing amplitude was increased. It was also confirmed that the size of the static processing marks increased as the amplitude increased.
<Static machining mark test 2>
Next, the results of an experiment for confirming the difference in static machining marks by changing only the swing frequency using the machining apparatus shown in FIG. 1 will be described.

(Processing conditions)
・ Work material: Quartz glass ・ Polishing liquid: Slurry of acrylic particles with an average particle size of 10 μm mixed with pure water at 10 wt% ・ Material of rotating body of rotating tool: Fluorine rubber ・ Outer diameter of rotating body of rotating tool: 3mm
・ Pushing depth of rotation tool: 400 μm
-Rotation speed of rotation tool: 2000 rpm
・ Amplitude of work swing: 10 μm
-Work swing frequency: 0Hz (no swing) /0.1Hz/1Hz/10Hz
・ Processing time: 5 minutes (result)
The results are shown in FIGS. 3 (a) to 3 (d). The left side of each figure shows the measurement result of the entire spot processing mark at each amplitude by the scanning white interferometer, and the right side shows the depth profile. Comparing the depth profile of the tool (rotation tool) rotation and the vertical direction (direction orthogonal to the rotation tangential direction along the machined surface), the surface roughness is sufficiently improved even at a frequency of 0.1 Hz. Was confirmed. However, even if the frequency was raised further, no further improvement was seen. It is considered that this is because the work reciprocates 30 times during the machining time of 5 minutes even with the fluctuation of 0.1 Hz, and the machining averaging action is sufficiently performed.
<Comparison of scanning marks>
We will explain the results of an experiment in which scanning processing is performed in a certain range while feeding the rotation tool (moving the work), and the difference in scanning pitch and the difference in surface roughness depending on the presence or absence of shaking are confirmed. ..

(Processing conditions)
・ Work material: Quartz glass ・ Polishing liquid: Slurry of acrylic particles with an average particle size of 10 μm mixed with pure water at 10 wt% ・ Material of rotating body of rotating tool: Fluorine rubber ・ Outer diameter of rotating body of rotating tool: 3mm
・ Pushing depth of rotation tool: 400 μm
-Rotation speed of rotation tool: 2000 rpm
・ Work swing: No swing / swing (amplitude 30 μm, frequency 90 Hz)
-Scanning pitch: 10 μm / 50 μm (see Fig. 7 for scanning pitch)
-Scanning range: 690 μm square at a scanning pitch of 10 μm, 650 μm square at a scanning pitch of 50 μm-Processing time: 30 minutes (Result)
The results are shown in FIGS. 4 (a) to 4 (d) and FIG. The left side of each figure of FIG. 4 is the measurement result of the entire processing mark by the scanning white interferometer, and the right side is a magnified image of the processed portion. Without the 50 μm pitch swing, the surface roughness was deteriorated depending on the scanning pitch, whereas with the 50 μm pitch swing, the surface roughness was not deteriorated depending on the scanning pitch, and the surface was not deteriorated. Roughness improved. At a pitch of 10 μm, the surface roughness did not change with or without rocking. That is, no deterioration in surface roughness was observed depending on the scanning pitch, and no further improvement in surface roughness was observed.

FIG. 5 shows a comparison of PSD (power spectral density) of surface roughness in the swing direction. The surface roughness was improved at a low spatial frequency of 50 μm pitch, but the surface roughness was not improved by rocking in the high frequency region of 10 μm pitch.

Inferring from this result, the average speed of rocking is only about 1.7% of the rotation speed of the rotating tool, and the flow of each particle is hardly affected by rocking, so the scanning pitch. Under the circumstances where the influence of the fringes during spot processing was not seen in the first place, the surface roughness could not be further improved by adding the sway. On the other hand, it can be seen that the deterioration of the surface roughness when the scanning pitch is increased can be effectively prevented by the vibration.

1 Corrective polishing equipment 2 Rotating tool 3 Machining liquid supply means 4 Work holding mechanism 5 Swinging means 8 Polishing liquid 9 Work 20 Rotating body 21 Shaft 22 Rotating support 30 Spout nozzle 31 Recovery tank 35 Slurry circulation pump 35 Pump 40 Holder 42 Z-axis stage 41 X-axis stage 43 Y-axis stage 51 Guide mechanism 52 Vibration actuator 70 Weight 71 Load measuring device 60 Support base 90 Work surface

Claims (7)

In a correction polishing method in which a rotary tool capable of locally polishing is scanned by numerical control while supplying a slurry-like polishing liquid in between.
A correction polishing processing method, characterized in that processing is performed while swinging the work. The modified polishing method according to claim 1, wherein the vibration frequency is 0.1 Hz or higher. The modified polishing method according to claim 1 or 2, wherein the swing amplitude is 1 μm or more. The modified polishing method according to any one of claims 1 to 3, wherein the polishing liquid is a polishing liquid in which abrasive grains composed of organic particles having an average particle size of 5 μm or more are dispersed in the liquid. The modified polishing method according to any one of claims 1 to 4, wherein the liquid is pure water or a liquid containing water as a main component. A rotary tool for polishing workpieces that can locally polish workpieces in a stationary state without scanning,
A processing liquid supply means for supplying a slurry-like polishing processing liquid between the rotating tool and the work,
A work holding mechanism that holds the work movably in the XYZ directions,
A swinging means for swinging the work held by the work holding mechanism is provided.
A correction polishing machine that numerically controls the work holding mechanism to perform scanning on a work that swings by the swinging means. The rocking means
A guide mechanism that guides the holding body that holds the work along the swing direction, and
A vibrating actuator that vibrates the holder along the swing direction,
The correction polishing processing apparatus according to claim 6.

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