JP2014061552A - Method of producing tool for polishing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of producing a grindstone which enables production of a tool for polishing having different contents of pores according to the radial direction through simple steps.SOLUTION: A method of producing a tool for polishing comprises a lower punch arrangement step S2 of arranging a lower punch in a cylindrical die for powder molding, a powder arrangement step S3 of arranging a powder of raw materials containing a polishing material in the die in such a way that the height from the upper surface of the lower punch increases from the central axis toward the outer periphery of the die, an upper punch arrangement step S4 of arranging an upper punch in the die and a molding step S5 of carrying out compression molding by pressing the powder with the upper and lower punches.

Description

  The present invention relates to a method for manufacturing a polishing tool used for grinding or polishing an optical element such as a lens.

  When grinding or polishing an optical element having a rotationally symmetric shape such as a lens, a processing surface of a polishing tool (grinding stone) formed in a spherical shape (concave spherical shape or convex spherical shape) having a desired curvature is provided on the optical element. The surface to be processed is processed by contacting the surface to be processed, rotating the polishing tool and swinging the optical element.

  In such a rotating polishing tool, since the peripheral speed on the circumferential side is faster than the central axis side of the processing surface, the distance rubbed in contact with the processing surface per unit time is more on the circumferential side. become longer. As a result, the processing surface is worn faster on the circumferential side than on the central axis side. In this way, since the wear of the polishing tool is not uniform on the processing surface, the shape of the processing surface changes from the original spherical shape in the process of using the polishing tool, which affects the processing accuracy of the optical element. End up.

  In order to make the amount of wear on the processed surface uniform, Patent Document 1 describes that the grindstone itself is easily worn by changing the composition (content ratio) of the air bubbles (pores) between the central axis side and the circumferential side of the grindstone. A technique for giving a distribution to the length has been proposed. Specifically, the pore-containing structure in the grindstone is made smaller on the circumferential side than on the central axis side. As a result, the circumferential side is less likely to be worn compared to the central axis side, and therefore, the wear of the grindstone can be made uniform when the processed surface is brought into contact with the optical element and rotated.

JP-A-61-103768

  However, Patent Document 1 does not disclose a specific method for changing the content of pores in the grindstone in the radial direction. As a method of incorporating pores in the grindstone, for example, a method of mixing a foaming agent into the raw material powder (abrasive grains) before molding can be considered. By such a method, the pore content is changed in the radial direction. Is very difficult and complicates the manufacturing process.

  This invention is made | formed in view of the above, Comprising: It aims at providing the manufacturing method of the grindstone which can manufacture the polishing tool from which the content rate of a pore differs in a radial direction by a simple process.

  In order to solve the above-described problems and achieve the object, a method for manufacturing a polishing tool according to the present invention includes a lower punch arranging step of arranging a lower punch on a cylindrical powder forming die, and the die A powder disposing step of disposing a raw material powder containing an abrasive in the die so that a height from the upper surface of the lower punch increases from a central axis of the die toward an outer periphery; and an upper punch on the die And an upper punch placement step of placing the upper punch and the lower punch, and a molding step of compressing the powder by applying pressure to the powder.

  In the method for manufacturing a polishing tool, in the powder arranging step, the powder is put into the die and the die is rotated with the central axis as a rotation axis.

  In the method for manufacturing a polishing tool, the lower punch includes an outer peripheral portion in which a hole passing through the central axis of the die in the direction of the central axis is formed, and a plug that can be inserted into and removed from the hole. The powder disposing step includes removing the plug after discharging the powder into the die, discharging a part of the powder from the hole, and then removing the plug from the hole. It is characterized by being inserted into.

  According to the present invention, the raw material powder is placed in the die so as to form a so-called mortar shape in which the height from the upper surface of the lower punch increases from the central axis of the die toward the outer periphery, and compression molding is performed. Therefore, it becomes possible to manufacture polishing tools having different pore content ratios in the radial direction by a simple process.

FIG. 1 is a flowchart showing a method for manufacturing a polishing tool according to Embodiment 1 of the present invention. FIG. 2A is a schematic diagram for explaining the lower punch arrangement step and the raw material powder arrangement step shown in FIG. 1. FIG. 2B is a schematic diagram for explaining a raw material powder arranging step shown in FIG. 1. FIG. 2C is a schematic diagram showing a state in which the raw material powder is arranged in a mortar shape. FIG. 2D is a schematic diagram for explaining an upper punch arranging step and a compression molding step shown in FIG. 1. FIG. 3 is a diagram showing the green compact obtained by the compression molding process shown in FIG. 1 and the density distribution in the green compact. FIG. 4 is a schematic view showing a cylindrical grindstone member obtained by the heating step shown in FIG. FIG. 5A is a schematic diagram illustrating a raw material powder arranging step in the method for manufacturing a polishing tool according to Embodiment 2. FIG. 5B is a schematic diagram illustrating a raw material powder arranging step in the method for manufacturing a polishing tool according to Embodiment 2. FIG. 5C is a schematic diagram illustrating a compression molding step in the method for manufacturing a polishing tool according to Embodiment 2. FIG. 6 is a diagram showing the green compact obtained by the compression molding process shown in FIG. 5C and the density distribution in the green compact. FIG. 7 is a graph showing an example of a rotation pattern given to the die in the first modification of the second embodiment. FIG. 8 is a schematic diagram for explaining a method for manufacturing a polishing tool according to the second modification.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited by these embodiments. Moreover, in description of each drawing, the same code | symbol is attached | subjected and shown to the same part. It should be noted that the drawings are schematic, and the dimensional relationships and ratios of each part are different from the actual ones. Also between the drawings, there are included portions having different dimensional relationships and ratios.

(Embodiment 1)
FIG. 1 is a flowchart showing a method for manufacturing a polishing tool according to Embodiment 1 of the present invention. 2A to 2D are schematic diagrams for explaining the method for manufacturing the polishing tool according to Embodiment 1. FIG.

  In step S1, raw material powder is produced. In Embodiment 1, a composite powder in which an abrasive is bound with a resin is used as a raw material. For this purpose, first, a resin solution is prepared by dissolving a powder or flaky resin material in a solvent. As the resin material, phenol resin, epoxy resin, polyimide resin, polyamide resin, etc. are used. If necessary, silane, titanium coupling agent, fluorocarbon, molybdenum disulfide, ethylene fluoride, A reinforced resin or the like is added. As the solvent, organic solvents such as NMP, monoglyme, diglyme, butyl lactone, toluene, acetone, and trichrene are used.

  Subsequently, abrasive mud (slurry) is produced by mixing and stirring the powdery abrasive (abrasive grains) in the resin solution. As the abrasive, cerium oxide, zirconium oxide, aluminum oxide, chromium oxide, diamond and the like are used. Then, the abrasive mud is stretched thinly, the solvent is volatilized and dried to produce a sheet-like composite material. Furthermore, this sheet-like composite material is pulverized into flakes, and pulverized using a mixer, a ball mill, a mortar or the like until it becomes powdery. This is the raw material powder. The particle size of the powder is not particularly limited and is preferably in the range of about 1 μm to about 500 μm.

  In the subsequent step S2, as shown in FIG. 2A, the lower punch 11 is set in the lower opening of the powder forming die 10. Here, the die 10 is a processing tool generally used in powder compression molding processing, and has a cylindrical shape. On the other hand, the lower punch 11 is a punch that can be fitted to the inner periphery of the die 10 and has an outer peripheral portion 11a in which a hole that passes through the central axis R1 of the die 10 in the direction of the central axis R1 is formed. And an inner peripheral part 11b that can be inserted into and removed from the hole part of the outer peripheral part 11a. By fitting the lower punch 11 into the die 10, a cylindrical cavity is formed in the die 10. The inner peripheral portion 11 b functions as a plug on the bottom surface of the die 10 that is closed by the lower punch 11.

  In the subsequent step S3, the raw material powder 1 is arranged in a mortar shape in the die 10. Here, the mortar shape is a state in which the height of the raw material powder 1 as viewed from the upper surface of the lower punch 11 increases from the vicinity of the central axis R1 of the die 10 toward the outer periphery.

  For this purpose, first, as shown in FIG. 2A, the powder 1 is put into the die 10, and then the inner peripheral portion 11b of the lower punch 11 is pulled out as shown in FIG. 2B. Thereby, a part of the powder 1 is discharged from the area near the central axis R1 of the die 10, and the powder 1 remaining in the die 10 becomes a mortar shape having a recessed central part. Then, as shown to FIG. 2C, the inner peripheral part 11b is again fitted in the outer peripheral part 11a, and it plugs.

  In step S4, as shown in FIG. 2D, while maintaining the mortar state of the powder 1, the die 10 and the lower punch 11 are placed on the base 13 of the compression molding apparatus, and the upper punch 12 is placed in the upper opening of the die 10. Place.

  In the subsequent step S5, the upper punch 12 is lowered, and compression molding is performed by applying a predetermined pressure to the powder 1 by the lower punch 11 and the upper punch 12 to obtain a green compact.

  In the subsequent step S6, the green compact is taken out from the die 10 and heated. Thereby, the resins contained in the raw material powder 1 are welded together. The processing conditions such as the heating temperature and the heating time are appropriately set according to the type of resin. Thereby, a cylindrical grindstone member is obtained.

  Here, FIG. 3 is a schematic view showing the green compact obtained in step S5. FIG. 4 is a schematic diagram showing the grindstone member obtained in step S6. In FIG. 4, the difference in porosity is represented by gray shades, and the darker the gray, the lower the porosity.

  As described above, the green compact 2 shown in FIG. 3 is obtained by pressing the powder 1 arranged in a mortar shape in the die 10 in a direction parallel to the central axis R1. For this reason, in the green compact 2, the compression density of the powder 1 is low near the central axis R1, and the compression density of the powder 1 increases toward the outer periphery. Therefore, in the grindstone member 3 after heat treatment of such a green compact 2, the pore content is high in the vicinity of the central axis R1, and the pore content is reduced toward the outer periphery.

  Furthermore, in step S7, a spherical surface is created for the cylindrical grindstone member 3 by curve generator processing or the like, and further lapping is performed to form a processing surface 3a having a spherical shape with a desired curvature. Thereby, the polishing tool according to Embodiment 1 is completed.

  As described above, according to the first embodiment, it is possible to easily manufacture a polishing tool in which the pore content is high in the vicinity of the central axis R1, and the pore content decreases toward the outer periphery. In such a polishing tool, it becomes difficult to wear away from the central axis R1 toward the outer periphery. Therefore, when the polishing tool is rotated and used, the amount of wear on the processed surface is made uniform on the central axis R1 side where the peripheral speed is relatively slow and on the circumferential side where the peripheral speed is relatively fast. Is possible.

(Embodiment 2)
Next, a method for manufacturing a polishing tool according to Embodiment 2 of the present invention will be described.
The manufacturing method of the polishing tool according to the second embodiment is generally the same as that shown in FIG. 1, and the raw material powder arrangement method in step S3 is different from the first embodiment. 5A to 5D are schematic views for explaining a method for manufacturing a polishing tool according to Embodiment 2. FIG.

  In the second embodiment, a die 20 and a lower punch 21 shown in FIG. 5A are used as a mold for compression molding of the powder 1. The die 20 and the lower punch 21 are processing tools generally used in powder compression molding processing. The die 20 has a cylindrical shape, and a cylindrical cavity is formed in the die 20 by fitting the lower punch 21 into the die 20.

  After the lower punch 21 is set on the die 20 (step S2), the raw material powder 1 is arranged in a mortar shape in the die 20 in step S3. At this time, in the second embodiment, first, the raw material powder 1 is put into the die 20 as shown in FIG. 5A. Then, as shown in FIG. 5B, the die 20 and the lower punch 21 are placed on a rotary table 22 provided with a rotary motor 23 and rotated until a predetermined rotational speed (for example, about 500 rpm) is reached. Thereby, a centrifugal force is generated in the powder 1 arranged in the die 20 and moves in the outer peripheral direction, and the powder 1 becomes a mortar shape. At the same time, the density of the powder 1 increases from the central axis R2 toward the outer periphery. Furthermore, the powder 1 is classified by the rotation, and the powder 1a having a large particle size and heavy in the powder 1 moves in the outer peripheral direction, and the powder 1b having a small particle size and light remains in the vicinity of the central axis R2. After the rotary table 22 reaches a predetermined rotational speed, the rotary motor 23 is stopped.

  Thereafter, as shown in FIG. 5C, the die 20 and the lower punch 21 are placed on the base 25 of the compression molding apparatus, and the upper punch 24 is disposed in the upper opening (step S4). Then, the upper punch 24 is lowered, and compression molding is performed by applying a predetermined pressure to the powder 1 by the lower punch 21 and the upper punch 24 (step S5).

FIG. 6 is a schematic diagram showing the green compact obtained in step S5 of the second embodiment. In step S5, as described above, the powder 1 whose height and density are increased and the diameter is increased toward the outer periphery from the central axis R2 is pressed in a direction parallel to the central axis R2. For this reason, in the green compact 4 obtained thereby, the compression density on the circumferential side is very high as compared with the vicinity of the central axis R2. In addition, many abrasives having a large particle size and high polishing ability are present on the circumferential side.
The subsequent step S6 and subsequent steps are the same as those in the first embodiment.

  As described above, according to the second embodiment, since the centrifugal force is generated in the raw material powder 1 in the die 20, the compression density of the powder 1 increases from the central axis R2 toward the outer periphery, and The green compact 4 having a large particle size and increasing the heavy powder 1a can be easily formed. In the polishing tool produced by further heat-treating such a green compact 4, the content of pores on the circumferential side is very low compared to the central axis R2, and the average particle size of the abrasive is growing. That is, as it goes from the central axis R2 to the outer periphery, it becomes harder to wear and the polishing ability becomes higher. Therefore, when the polishing tool is rotated and used, the amount of wear on the processed surface is made uniform on the central axis R2 side where the peripheral speed is relatively slow and on the circumferential side where the peripheral speed is relatively fast. Is possible.

(Modification 1)
Next, Modification 1 of Embodiment 2 will be described. FIG. 7 is a graph showing an example of a rotation pattern given to the die 20 in step S3 of the second embodiment.
In step S3, after the powder 1 is put into the die 20, the rotary motion of the rotary motor 23 may be controlled as shown in FIG. 7 to rotate the die 20 intermittently. Specifically, after increasing the number of revolutions to N _{max and} then repeating the intermittent pattern that immediately drops to N _min three times, the number of revolutions is again increased to N _max and rotated for a predetermined time.

  Since the flow of the powder 1 is activated by intermittently applying rotation in this manner, the time until the powder 1 becomes a mortar shape can be shortened. In addition, since the degree of classification between the powder 1a having a large particle size and the powder 1b having a small particle size is increased, the difference in the average particle size in the radial direction of the green compact 4 is further increased. Therefore, according to the first modification, the green compact 4 in which the compression density increases from the central axis R2 toward the outer periphery and the powder 1a having a large particle size with high polishing ability increases more efficiently. It becomes possible.

(Modification 2)
Next, a second modification of the second embodiment will be described. FIG. 8 is a schematic diagram for explaining a method for manufacturing a polishing tool according to the second modification.
When the die 20 is rotated in step S3 of the second embodiment, vibration may be applied to the die 20 directly or indirectly. For example, as shown in FIG. 8, an ultrasonic oscillation device 26 is attached to the rotary motor 23, and ultrasonic vibration is applied to the die 20 via the rotary motor 23 and the rotary table 22 while rotating the rotary table 22 and the die 20. . Thereby, ultrasonic vibration is transmitted to the powder 1 and the flow is activated, and the time until the powder 1 becomes a mortar shape can be shortened. Moreover, since the classification degree of the powder 1a with a large particle size and the small powder 1b also becomes high, the difference of the average particle diameter in the radial direction of the green compact 4 becomes larger. Therefore, according to the modified example 2, the green compact 4 in which the powder density 1a increases in compression density and increases in the polishing ability and increases in the particle diameter 1a from the central axis R2 to the outer periphery is more efficiently produced. It becomes possible.
The ultrasonic oscillator 26 may be provided on the rotary table 22 in addition to the rotary motor 23, or may be provided directly on the side surface or upper end of the die 20.

DESCRIPTION OF SYMBOLS 1, 1a, 1b Powder 2, 4 Compact 3 Grinding wheel member 3a Processing surface 10, 20 Die 11, 21 Lower punch 11a Outer peripheral part 11b Inner peripheral part 12, 24 Upper punch 13, 25 Base 22 Rotary table 23 Rotary motor 26 Ultrasonic oscillator

Claims (3)

A lower punch placement step of placing a lower punch on a cylindrical powder forming die;
A powder disposing step of disposing a raw material powder containing an abrasive in the die so as to increase in height from the upper surface of the lower punch from the central axis of the die toward the outer periphery,
An upper punch placement step of placing an upper punch on the die;
A molding step of performing compression molding by applying pressure to the powder by the upper punch and the lower punch;
A method for producing a polishing tool, comprising:   2. The method for manufacturing a polishing tool according to claim 1, wherein in the powder arranging step, the powder is put into the die and the die is rotated about the central axis as a rotation axis. The lower punch includes an outer peripheral portion in which a hole that passes through the central axis of the die in the direction of the central axis is formed, and a plug that can be inserted into and removed from the hole.
In the powder arranging step, the powder is put into the die, the plug is removed, a part of the powder is discharged from the hole, and the plug is inserted into the hole. The method for producing a polishing tool according to claim 1.