JP2010228086A - Surface processing method and surface processing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform highly accurate surface processing in a wide space wave length area, in polishing processing of using a processing fluid including a polishing particle. <P>SOLUTION: A plurality of nozzles 3a-3c different in a nozzle diameter are arranged on a head 4 for scanning in the direction indicated by an arrow to a workpiece 2, and a removing quantity in a space wave length area different with respective nozzles 3a-3c is set. Scanning is performed while injecting the processing fluid by successively selecting from a nozzle corresponding to a large space wave length area, and the wide space wave length area is accurately polished by respectively and independently controlling a supply quantity of a polishing undiluted solution so as to become the removing quantity adjusted to the respective nozzle diameters. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a surface processing method and a surface processing apparatus for processing a surface of an optical element such as a lens and a mirror and a mold with high accuracy.

  Conventionally, as a method of processing the surface of a workpiece, there is a method of processing a surface of a workpiece by ejecting a machining fluid that is a mixture of abrasive particles and a fluid such as water or air from a nozzle. In such processing, by changing the injection pressure of the processing fluid, the speed at which the nozzle or workpiece is moved, the distance between the nozzle and the workpiece surface, the type and amount of abrasive particles contained in the processing fluid, etc. A desired machining area on the workpiece surface is machined with a desired machining amount.

  For example, a method is known in which the distance between the fluid jet and the nozzle can be controlled to be changed, and the processing conditions are adjusted in accordance with the type of fluid used, the pressure, the particle size of the abrasive particles, the specific gravity, and the like. (See Patent Document 1).

  In addition, a plurality of gas blast nozzles are arranged in the plate width direction of the steel plate to be continuously conveyed, and the steel particle surface is adjusted by adjusting the spraying conditions of abrasive particles from each nozzle individually or for each preset combination. A processing method for processing is also known (see Patent Document 2).

JP-A-06-055551 JP 2003-305647 A

  However, the configuration disclosed in Patent Document 1 is characterized in that the spot shape formed by processing for a certain period of time without changing the relative position between the nozzle and the workpiece surface is isotropic. When processing a free-form surface using such a nozzle, the nozzle and the surface to be processed are moved relative to each other to perform partial removal in a straight groove shape with a uniform depth. Further, the surface of the workpiece is processed by overlapping the processing surface or nozzle while shifting the position by the feed pitch while maintaining the state. When this processing method is applied to optical elements such as lenses and mirrors or high-precision processing of the mold surface, problems of processing time and processing accuracy arise.

  For example, when high-precision processing is performed in the spatial wavelength range of 0.3 to 300 mm, two methods are conceivable. The first is a method of processing with a spot diameter equal to or shorter than the shortest spatial wavelength. The second method is a method of processing with several spot diameters.

  When processing with one nozzle, it is necessary to use a tool size that matches the shortest wavelength in the first method, and therefore processing takes a long time when processing a wide area. In the second method, the spot diameter cannot be changed to 1 to 1000 times even if the spot diameter is changed according to the injection conditions such as the workpiece-nozzle distance and the injection pressure. In general, when the diameter of a spot shape close to a cosine shape is d, it is known that the spatial wavelength at which the surface of the workpiece can be processed is mainly d / 2 or more. For this reason, it is not possible to cope with the case where the spatial wavelength range requiring high-precision processing is 0.3 to 300 mm. Moreover, the processing amount per unit time will also change by changing injection conditions.

  As a solution to the problem of processing time, it is conceivable to install a plurality of nozzles as disclosed in Patent Document 2. However, this method also cannot change the spot diameter to 1 to 1000 times when the nozzle diameter is constant, and cannot cope with processing in a wide spatial wavelength region of 0.3 to 300 mm. Moreover, the processing amount per unit time will also change by changing injection conditions. Furthermore, this machining method of machining with nozzles that exist discretely can easily perform planar machining, but it is very difficult to machine a free-form surface.

  An object of the present invention is to provide a surface processing method and a surface processing apparatus capable of processing a surface of an optical element such as a lens and a mirror or a mold with high accuracy over a wide spatial wavelength range. is there.

  In order to achieve the above object, the surface processing method of the present invention provides a target processing amount to be polished and removed in a surface processing method for processing the surface of a workpiece by ejecting a processing fluid containing abrasive particles from a nozzle. A process of dividing a plurality of spatial wavelength ranges of 0.3 mm or more, selecting a different nozzle diameter for each spatial wavelength range, and injecting a processing fluid from the nozzle having the nozzle diameter, And a step of processing the surface of the workpiece with a target processing amount divided for each spatial wavelength region by scanning the surface.

  The surface processing apparatus of the present invention is a surface processing apparatus for processing a surface of a workpiece by ejecting a processing fluid containing abrasive particles from a nozzle, and a head having a plurality of nozzles each having a different nozzle diameter, A mechanism for supplying a processing fluid to each nozzle, a mechanism for adjusting the abrasive particle content of the processing fluid supplied to the plurality of nozzles for each nozzle, and a mechanism for scanning the head on the surface of the workpiece The plurality of nozzles have nozzle diameters selected so as to respectively correspond to a plurality of spatial wavelength regions of 0.3 mm or more.

  By dividing the target processing amount into a plurality of spatial wavelength ranges of 0.3 mm or more and processing the divided target processing amounts using nozzles having different nozzle diameters for each spatial wavelength range, a wide range of spatial wavelengths Enables high-precision surface processing in the area.

It is a schematic diagram which shows the surface processing apparatus by 1st Embodiment. It is a figure which shows the scanning locus | trajectory of the head at the time of the process of the apparatus of FIG. It is a schematic diagram which shows the surface processing apparatus by 2nd Embodiment. It is a figure which shows the scanning locus | trajectory of the head at the time of the process of the apparatus of FIG. It is a figure which shows the nozzle structure used for 1st and 2nd embodiment. It is a graph for demonstrating the determination method of the removal amount with respect to a spot diameter. It is a graph which shows the relationship between the density | concentration of the abrasive particle contained in a processing fluid, and a removal rate. It is a figure which shows the surface shape of the to-be-processed object before a process. 3 is a graph showing the results of measuring the surface shape of a workpiece after processing according to Example 1. It is a graph which shows the result of having measured the surface shape of the workpiece after processing by Example 2. FIG.

  FIG. 1 shows a surface processing apparatus according to a first embodiment, in which a workpiece 2 is placed on a stage 1 which is a scanning mechanism movable in the X and Y axial directions and faces the workpiece 2. The head 4 including a plurality of nozzles 3a to 3c having different nozzle diameters is installed at the position where the nozzles are to be mounted. Each of the nozzles 3 a to 3 c is provided with an ejection fluid supply pipe 5, and is connected to an ejection fluid supply mechanism 6 via an ejection pressure adjusting valve 7. Further, a polishing stock solution supply pipe 8 is disposed in each of the nozzles 3 a to 3 c, and is connected to a polishing stock solution supply mechanism 9 via a supply amount adjusting valve 10. A polishing stock solution containing abrasive particles is supplied from the polishing stock solution supply mechanism 9 through the polishing stock solution supply pipe 8 to the nozzles 3a to 3c. In each of the nozzles 3a to 3c, the working fluid 11 is formed by mixing the jetting fluid and the polishing stock solution. The injection pressure of the working fluid 11 is generated by the injection fluid supply mechanism 6 and adjusted by the injection pressure adjusting valve 7 for each nozzle. Further, by adjusting the amount of the stock polishing solution supplied by the supply amount adjusting valve 10, the concentration of abrasive particles (abrasive particle content) contained in the processing fluid 11 supplied to each nozzle is adjusted.

  FIG. 2 shows a scanning trajectory of the head 4 with respect to the workpiece 2 during processing by the apparatus of FIG. While feeding the head 4 from the scanning start position 12 in the + X direction at a constant interval P, the head 4 scans in the ± Y direction, and until the head 4 reaches the scanning end position 13, the working fluid 11 is fed from one of the nozzles 3 a to 3 c. The surface to be machined is processed by spraying. With the scanning start position 12 as the origin, the X and Y coordinate positions of the reference position (center of gravity position) of the head 4 are measured by a position sensor (not shown) during scanning. The measured center-of-gravity coordinates of the head 4 are transmitted to the processing control device via a transmission cable (not shown), and the processing conditions of the nozzles 3 a to 3 c are determined by the position of the center of gravity of the head 4. The determined processing conditions are transmitted to the supply amount adjusting valve 10 via the transmission cable, and the polishing stock solution amount is adjusted so that a desired removal amount is obtained for each spatial wavelength region.

  For the plurality of nozzles 3a to 3c, a target processing amount to be polished and removed on the surface of the workpiece 1 is divided so as to correspond to a plurality of spatial wavelength regions of 0.3 mm or more, and nozzles different for each spatial wavelength region Select the caliber.

  The process of scanning the surface of the workpiece 2 while ejecting the machining fluid using one of the nozzles 3a to 3c is divided into the target machining amount (removal amount) in each of a plurality of spatial wavelength ranges. By repeating the above, surface processing of the workpiece 2 is performed.

  FIG. 3 shows a surface processing apparatus according to the second embodiment. A workpiece 22 is installed on a stage 21 that can move in the X and Y axial directions, and a head 24 having a plurality of nozzles 23 a to 23 e with different nozzle diameters is installed at a position facing the workpiece 22. ing. The stage 21 is scanned in the arrangement direction of the nozzles 23a to 23e. It arrange | positions so that the nozzle aperture of each nozzle 23a-23e may change gradually toward the scanning direction of the head 24 shown by the arrow. An ejection fluid supply pipe 25 is disposed in each of the nozzles 23 a to 23 e, and is connected to an ejection fluid supply mechanism 26 via an ejection pressure adjustment valve 27. The polishing stock solution supply pipe 28 connected to each of the nozzles 23 a to 23 e is connected to the polishing stock solution supply mechanism 29 via a supply amount adjusting valve 30. A polishing stock solution containing abrasive particles is supplied from the polishing stock solution supply mechanism 29 via the polishing stock solution supply pipe 28 to the nozzles 23a to 23e. In each of the nozzles 23a to 23e, the working fluid 31 is formed by mixing the jetting fluid and the polishing stock solution. The injection pressure of the processing fluid 31 is generated by the injection fluid supply mechanism 26 and adjusted by the injection pressure adjustment valve 27. By adjusting the amount of the polishing stock solution supplied by the supply amount adjusting valve 30, the concentration of abrasive particles (abrasive particle content) contained in the processing fluid 31 is adjusted.

  The nozzles 23a to 23e have a nozzle diameter that changes in the scanning direction, maximize the nozzle diameter of the central nozzle 23c, and gradually decrease the nozzle diameter toward the end nozzles 23a and 23e.

  FIG. 4 shows a scanning trajectory of the head 24 during processing by the apparatus of FIG. The head 24 is scanned from the scanning start position 32 in the + X direction at a constant interval P while scanning in the ± Y direction, and the surface to be processed is processed until the head 24 reaches the scanning end position 33. For example, in the scanning in the −Y direction, the nozzles 23 a, 23 b, and 23 c are selected so that the nozzle diameter increases in the scanning direction of the head 24. With the scanning start position 32 as the origin, the X and Y coordinate positions of the center of gravity of the head 24 are measured by a position sensor (not shown) during scanning. The measured barycentric coordinates of the head 24 are transmitted to the machining control device via a transmission cable (not shown), and the nozzles 23a to 23e are arranged according to the barycentric position of the head 24 and the positions of the nozzles 23a to 23e from a predetermined barycentric position. The processing conditions of 23e are determined. The determined processing conditions are transmitted to the supply amount adjusting valve 30 via the transmission cable, and the amount of the polishing stock solution is adjusted so as to obtain a desired removal amount that is a target processing amount divided for each nozzle.

  FIG. 5 shows the nozzle configuration used in the first and second embodiments. The nozzle 101 is supplied with an ejection fluid 102 from an ejection supply pressure mechanism. Further, the polishing stock solution 103 is supplied to the nozzle 101 through the supply nozzle 104 from the polishing liquid supply mechanism. The polishing stock solution 103 is mixed with the jetting fluid 102 to become a processing fluid 105 and is jetted from the nozzle 101.

  FIG. 6 shows a method for determining the removal amount of each nozzle in the first and second embodiments. As shown in FIG. 6A, when machining the pre-machining shape A into the target shape B, the powers spectral density (PSD) representing the amount of the swell component for each spatial frequency is used for the shape evaluation of the surface to be machined. . The spatial wavelength region to be processed is divided into 30 mm or more, 3 mm or more, and 0.3 mm or more, and the spot diameter is set to 30 mm, 3 mm, or 0.3 mm for each spatial wavelength region. The relationship between the removal amount and PSD is obtained in advance for each spot diameter. For example, as shown by graphs C1 and C2 in FIG. 6B, the PSD for the removal amounts of 200 nm and 400 nm with respect to the spot diameter of 3 mm is obtained. In this way, from the relationship between each removal amount and PSD obtained in advance for each spot, the removal amount (divided target processing amount) that achieves a target shape in each spatial wavelength region with respect to the spot diameter to be used. Ask for. Further, the removal amount at each position on the surface to be processed is determined in accordance with the shape of the processed surface measured in advance.

  FIG. 7 is a graph showing the relationship between the concentration of abrasive particles contained in the working fluid used in the first and second embodiments and the removal rate. FIG. 8 shows the surface shape of the workpiece before processing. The spatial wavelength region is not limited to three, and may be divided into a plurality of arbitrary regions. An electromagnetic valve, an electric valve, a pinch valve, or the like can be used as the flow rate adjustment valve. An axial flow type, a centrifugal type, a reciprocating type, a rotary type, etc. can be used for the jetting fluid supply mechanism and the polishing stock solution supply mechanism. As a stage driving method for moving the workpiece, an ultrasonic method, an electromagnetic method, a piezoelectric element method, or the like can be used. For the stage guide, an air system, a ball system, a roller system, or the like can be used. Instead of using a plurality of nozzles having different nozzle diameters, it is possible to use nozzles having variable nozzle diameters.

  Surface processing was performed using the surface processing apparatus of FIG. As the polishing stock solution, water was used as the main solvent and cerium oxide (30% by weight, average particle size of 0.25 μm) was dispersed. Water was used as the jet fluid. The spatial wavelength region to be processed is divided into 30 mm or more, 3 mm or more, and 0.3 mm or more, and spot diameters of 30 mm, 3 mm, and 0.3 mm are used for each wavelength region. The initial injection pressure was 5 Mpa, and the nozzle diameters of the three nozzles were such that the spot diameters were 0.3 mm, 3 mm, and 30 mm at an injection pressure of 5 Mpa, respectively. Quartz glass was used as the workpiece. The processing evaluation area was in a circle with a diameter of 60 mm. Processing was performed in the order of spot diameters of 30 mm, 3 mm, and 0.3 mm. The feed pitch was set to 0.03 mm, 0.3 mm, and 3 mm for the spot diameters of 0.3 mm, 3 mm, and 30 mm, respectively. The moving speed (scanning speed) of each nozzle was fixed at 5 mm / sec, and the concentration of abrasive particles contained in the sprayed working fluid was changed according to the amount of removal at each position on the work surface.

  FIG. 9 is a graph showing measurement results obtained by measuring the shape of the machined surface after scanning by each nozzle in the machining process according to Example 1. The total processing time required about 7.4 hours, and was about 0.23 nm RMS in the spatial wavelength range of 0.3 to 30 mm. The head positioning accuracy was ± 2 μm, and the relative position error of each nozzle center was ± 3 μm.

  Surface processing was performed using the apparatus of FIG. As the polishing stock solution, water was used as the main solvent and cerium oxide (30% by weight, average particle size of 0.25 μm) was dispersed. Water was used as the jet fluid. The spatial wavelength region to be processed is divided into 30 mm or more, 3 mm or more, and 0.3 mm or more, and the spot diameters of 30 mm, 3 mm, and 0.3 mm are used for each wavelength region. Six nozzle diameters were used such that the initial injection pressure was 5 Mpa and the spot diameters were 0.3 mm, 3 mm, 30 mm, 3 mm, and 0.3 mm, respectively, at an injection pressure of 5 Mpa. Quartz glass was used as the workpiece. The processing evaluation area was in a circle with a diameter of 60 mm. Processing was performed using three types of spot diameters simultaneously. The feed pitch was 0.03 mm. The moving speed (scanning speed) of the head was constant at 5 mm / sec, and the concentration of abrasive particles contained in the ejected working fluid was changed according to the amount of removal at each position on the work surface.

  FIG. 10 is a graph showing the result of measuring the processed surface shape after scanning the head in Example 2. The total processing time required about 6.7 hours, and was about 0.19 nm RMS at a spatial wavelength of 0.3 to 30 mm. The head positioning accuracy was ± 2 μm, and the relative position error of each nozzle center was ± 3 μm. A white interferometer was used to measure the processing results.

1, 2, 21 Stage 2, 22 Workpieces 3a-3c, 23a-23e, 101 Nozzle 4, 24 Head 5, 25 Injection fluid supply pipe 6, 26 Injection fluid supply mechanism 7, 27 Injection pressure adjustment valve 8, 28 Polishing stock solution supply pipe 9, 29 Polishing stock solution supply mechanism 10, 30 Supply amount adjustment valve

Claims (7)

In a surface processing method for processing the surface of a workpiece by spraying a processing fluid containing abrasive particles from a nozzle,
Dividing the target processing amount to be polished and removed so as to correspond to a plurality of spatial wavelength ranges of 0.3 mm or more, and selecting a different nozzle diameter for each spatial wavelength range; and
Processing the surface of the workpiece with a target processing amount divided for each spatial wavelength region by scanning the surface of the workpiece while ejecting a processing fluid from the nozzle having the nozzle diameter. The surface processing method characterized by the above-mentioned.   The surface processing method according to claim 1, wherein the abrasive particle content of the processing fluid ejected from the nozzle is controlled in accordance with a target processing amount in each spatial wavelength region and the nozzle diameter.   The surface processing method according to claim 1, wherein the processing is performed using a plurality of nozzles having different nozzle diameters.   The surface processing method according to claim 3, wherein the processing fluid is simultaneously ejected from the plurality of nozzles for processing.   The surface processing method according to claim 4, wherein the plurality of nozzles are scanned side by side so that the nozzle diameter increases in the scanning direction. In a surface processing apparatus for processing the surface of a workpiece by ejecting a processing fluid containing abrasive particles from a nozzle,
A head having a plurality of nozzles each having a different nozzle diameter;
A mechanism for supplying a processing fluid to each of the plurality of nozzles;
A mechanism for adjusting the abrasive particle content of the processing fluid supplied to the plurality of nozzles for each nozzle;
A mechanism for scanning the head with the surface of the workpiece,
The surface processing apparatus, wherein the plurality of nozzles have nozzle diameters selected so as to respectively correspond to a plurality of spatial wavelength regions of 0.3 mm or more.   The surface processing apparatus according to claim 7, wherein the plurality of nozzles are arranged so that a nozzle diameter increases toward a scanning direction of the head.

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