JP3703632B2 - Truing and dressing equipment for grinding tools - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a truing and dressing device for a grinding tool, and more particularly to a truing and dressing device for a grinding tool for accurately truing and dressing a hemispherical grinding tool.
[0002]
[Prior art]
In order to mirror-finish the free-form surface of a mold by performing a displacement cutting type grinding process, a grindstone or a grinding tool including a hemispherical diamond abrasive grain is used. As the grinding stone progresses, the fine chips removed from the workpiece surface are clogged between the abrasive grains on the surface of the grinding stone, and the abrasive grains and the binding material (matrix) of the grinding stone are gradually removed and deformed. In this case, in order to create a highly accurate processed surface, it is necessary to accurately truing (molding) and dressing (sharpening) the grindstone.
[0003]
As a precise surface polishing method, a polishing method using an electrophoretic phenomenon is already known. For example, Japanese Patent Publication No. 59-46739 discloses a method of grinding a workpiece surface by electrophoresis. In this method, in a suspension in which loose abrasive grains are dispersed, the workpiece and the polisher are opposed to each other, and a relative rotational movement is applied while applying a voltage between the two, and the workpiece surface is polished using the electrophoresis phenomenon. To do.
[0004]
Further, Japanese Patent Application Laid-Open No. 8-257912 discloses an in-process dressing method using electrophoresis in which a workpiece is polished and at the same time a grinding wheel is regenerated in a suspension in which free abrasive grains are dispersed.
As described above, truing and dressing with high accuracy are indispensable in high-precision grinding. However, the methods disclosed in the above two publications have a problem that truing and dressing of a hemispherical grinding tool cannot be performed.
[0005]
In order to solve this problem, the present applicant has applied for a patent for the dressing apparatus described in Japanese Patent Application No. 9-221585. As shown in FIG. 4, the dressing apparatus 100 includes a hemispherical grinding tool 102 rotatably supported in a processing tank in which a polishing liquid is stored, and a grinding tool 102. And a positive electrode 104 rotatably supported around a parallel rotation axis O ′. The positive electrode 104 has a shape corresponding to the shape of the tip of the grinding tool 102. A negative electrode 106 is opposed to the positive electrode 104 at a predetermined interval. An electric field is formed between the positive electrode and the negative electrode, and free abrasive grains dispersed in the polishing liquid are electrically At the same time, the grinding tool 102 and the positive electrode 104 are relatively rotated to perform truing and dressing of the grinding tool 102.
[0006]
[Problems to be solved by the invention]
In the dressing apparatus of FIG. 4, the spherical tip of the grinding tool 102 can be dressed to a sphericity of about 1 μm, but it is difficult to dress the surface of the grinding tool 102 uniformly. That is, since the polishing liquid always flows in the same direction with respect to the surface of the grinding tool 102 in the cylindrical side surface region I of the grinding tool, small circumferential mechanical scratches are formed in the side surface region I of the grinding tool 102. Is done. On the other hand, in the spherical tip region II of the grinding tool 102, such a scratch is not formed because the flowing direction of the polishing liquid with respect to the surface of the grinding tool 102 is not constant.
[0007]
The present invention has a technical problem to solve such problems of the prior art. By utilizing the electrophoresis phenomenon, a grinding tool, particularly a grinding tool composed of a hemispherical grindstone, is scratched on the surface with high accuracy. It is an object of the present invention to provide a truing and dressing apparatus for a grinding tool capable of truing and dressing so as not to be formed.
[0008]
[Means for Solving the Problems]
The present invention relates to a grinding tool truing and dressing apparatus, a hemispherical grinding tool that is rotatably supported, and an axis that is immersed in a polishing liquid in a processing tank and is provided at a position of an axis and a twist of the grinding tool. A cylindrical positive electrode rotatably supported around the positive electrode, and a negative electrode having a fixed cylindrical inner face facing the positive electrode at a predetermined interval, the positive electrode and the negative electrode An electric field is formed between the two and the electrophoretic phenomenon of the free abrasive grains dispersed in the polishing liquid is generated between the two and the grinding tool and the positive electrode are relatively rotated, and the grinding tool is The gist of the truing and dressing apparatus for a grinding tool is characterized in that a relative arc motion is performed along the cylindrical outer peripheral surface of the positive electrode to perform truing and dressing of the grinding tool.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.
First, referring to FIGS. 1 and 2, a dressing apparatus 10 according to the present embodiment has a generally cylindrical housing 12 as a processing tank and a columnar shape rotatably supported around a horizontal axis a1 in the housing 12. A positive electrode 18 is provided. More specifically, the positive electrode 18 is connected to the output shaft 14a of the motor 14 through the coupling 16, and is supported by the output shaft 14a and the coupling 16 so as to be rotatable about the horizontal axis a1. The motor 14 is fixed to a support surface 36 such as a table by a motor mount 14b. The motor 14 can change its rotation speed at a predetermined cycle.
[0010]
In the housing 12, the negative electrode 20 is further fixed to the housing 12 by a negative electrode holder 22 made of a nonconductive material. The negative electrode 20 is a member having a semi-cylindrical inner peripheral surface that faces the lower side surface of the positive electrode 18 at an angle of 45 ° over an angle of about 180 from the center. The negative electrode 20 is opposed and fixed at a predetermined interval so that the inner surface thereof is substantially parallel to the outer surface of the positive electrode 18. A DC voltage is applied between the positive electrode 18 and the negative electrode 20 by a power supply device including a DC power supply 32 and a variable resistor 34 as main components.
[0011]
A ball grindstone 26 is inserted into the housing 12 as a grinding tool to be dressed from a tool insertion opening 12 a formed near the top of the housing 12. The ball grindstone 26 is attached to the tip of the spindle device 24 that is rotatable about a vertical axis a2 that is in a vertical twist position with respect to the horizontal axis a1.
[0012]
The main shaft device 24 is configured to be movable in a direction along the rotation axis a2 and in a direction perpendicular to the rotation axis, so that the tip of the ball grindstone 26 can be accurately positioned with respect to the positive electrode 18. . In the present embodiment, the ball grindstone 26 is an ultrafine resin bond grindstone having a diameter of 20 mm, and is formed by combining diamond abrasive grains having an average particle diameter of 4 to 6 μm with a melamine resin and combining a cylinder and a hemisphere. Has been. The ball grindstone 26 may simply be formed in a hemispherical shape.
[0013]
The polishing liquid necessary for dressing is supplied by a polishing liquid circulation apparatus including a polishing liquid circulation pump 30, a polishing liquid discharge pipe 30a, and a polishing liquid discharge pipe 30b as main components. That is, the polishing liquid circulating pump 30 is supplied from above the positive electrode 18 and the negative electrode 20 in the housing 12 through the polishing liquid discharge pipe 30 a, and the polishing liquid supplied in the housing 12 is supplied in the housing 12. After being used for dressing the ball grindstone 26, the polishing liquid discharged from the polishing liquid discharge port 12b formed at the bottom of the housing 12 to the polishing liquid tank 28 and stored in the polishing liquid tank 28 is supplied to the polishing liquid suction line 30b. Is sucked by the polishing liquid circulation pump 30 and supplied again into the housing 12 through the polishing liquid discharge conduit 30a. The polishing liquid circulation pump 30 preferably comprises a tubing pump.
[0014]
In this embodiment, the polishing liquid is made of a suspension in which carboxymethyl cellulose (CMC) is mixed with ion-exchanged water having a pH of 7 and alumina oxide abrasive grains having a mesh size of # 4000 are dispersed as free abrasive grains. In order to prevent the polishing liquid from scattering by centrifugal force and to disperse alumina abrasive grains having a relatively large particle size in the polishing liquid, a polishing liquid having a relatively high viscosity was used.
[0015]
Hereinafter, the operation of the embodiment of the present invention will be described.
In general, when alumina abrasive grains are dispersed in an aqueous solution in which CMC is dissolved, the hydrophilic groups of CMC release metal ions and become negatively charged, and the abrasive grains are adsorbed by the hydrophobic groups. When a voltage is applied between the positive electrode 18 and the negative electrode 20 to form an electric field in a minute gap between the positive electrode 18 and the negative electrode 20 in a polishing liquid composed of a suspension in which abrasive grains are dispersed in a CMC solution, the abrasive adsorbed hydrophobically on the CMC The particles are attracted to the surface of the positive electrode 18 by an electrophoresis phenomenon. Then, the CMC and abrasive grains sucked on the surface of the positive electrode 18 are hydrophobically adsorbed on the surface of the positive electrode 18 to form a gel-like film 38 having a high abrasive concentration as shown in FIG.
[0016]
When the ball grindstone 26 is rotated about the axis a2 and is moved in an arc as indicated by arrows A and A 'in FIG. 3, the surface of the positive electrode 18 on which the above-described film 38 is formed is pressed. The ball grindstone 26 is trued (formed) into a hemispherical shape. Further, the ball grindstone 26 is rotated about the axis a2 and the tip thereof is brought into contact with the coating 38 on the surface of the positive electrode 18 while being moved in an arc as indicated by arrows A and A 'in FIG. Thus, the tip of the ball grindstone 26 is dressed (sharpened) in a hemispherical shape. That is, by pressing the ball grindstone 26 in contact with the surface of the positive electrode 18, both the diamond abrasive grains of the ball grindstone 26 and the melamine resin as the binder are removed and truing, and the ball grindstone 26 is moved to the positive electrode. By positioning the ball grindstone 26 so as to be in contact with the gel-like film 38 formed on the surface 18, the gel-like film acts as a polisher, and only the melamine resin of the ball grindstone 26 is removed, and the ball grindstone 26. Is dressed. In this embodiment, while the tip of the ball grindstone 26 is brought into contact with the surface of the positive electrode 18 or the film 18a formed on the surface in this way, the spindle device 24 moves the ball grindstone 26 to arrows A and A 'in FIG. As shown in the figure, it is characterized by reciprocating in an arc shape.
[0017]
Next, the operation of the above-described embodiment will be described in more detail. In FIG. 3, a contact P between the positive electrode 18 and the ball grindstone 26 is considered. In practice, the above-described film 38 is formed between the outer surface of the positive electrode 18 and the surface of the ball grindstone 26. In a strict sense, the positive electrode 18 and the ball grindstone 26 are not in contact with each other. Although the two are sometimes spaced apart from each other at an interval of about 30 μm, the distance is so small that the coating 38 can be regarded as a part of the surface of the positive electrode 18. In this specification, it is considered that the positive electrode 18 and the ball grindstone 26 are in contact with each other as long as they are located inside.
[0018]
As shown in FIG. 3, the velocity vector of the surface of the positive electrode 18 at the contact P is represented by Rω1 when the radius of the positive electrode 18 is R and the rotational angular velocity is ω1. The velocity vector at the contact point P on the surface of the ball grindstone 26 is represented by rω2, where r is the radius between the central axis a2 and the contact point P, and ω2 is the rotational angular velocity of the ball grindstone 26. In FIG. 3, the direction of the vector rω2 is originally perpendicular to the paper surface of FIG. 3, but is shown in the direction of the center of the positive electrode 18 for illustration.
[0019]
When the ball grindstone 26 is moved as described above, the direction of the vector Rω1 does not change but the direction changes. The direction and magnitude of the vector rω2 changes. Accordingly, the combined vector V of the two velocity vectors also changes its direction and size due to the movement of the ball grindstone 26, and does not have a constant direction and size in a specific area as in the prior art described above. .
[0020]
The velocity vector that rubs the surface of the ball grindstone 26 at the contact P is the combined vector V of the velocity vectors Rω1 and rω2, as described above. The ball grindstone 26 is reciprocated several times along the arc locus AA ′ to perform truing or dressing. However, in order to change the magnitude and direction of the combined vector every time it passes through the contact point P, in this embodiment, it is further reduced to 0. The rotation speed of the positive electrode 18 is varied in the range of 10 to 1000 rpm with a period of 5 Hz. As a result, the surface of the ball grindstone 26 is trued or dressed with the magnitude and direction of the combined vector V changing randomly at any position. Therefore, the problem that scratches are formed on the surface of the ball grindstone 26 during truing or dressing as in the prior art is solved.
[0021]
【The invention's effect】
According to the present invention, a positive electrode and an electric field are formed in a polishing liquid in which free abrasive grains are dispersed to cause electrophoresis of the abrasive grains, thereby forming a gel-like film containing abrasive grains on the surface of the positive electrode, The grinding tool was trued by bringing the grinding tool into contact with the surface of the positive electrode so that the velocity vector at the contact point between them changed while rotating the grinding tool and the positive electrode relatively. It is possible to dress the grinding tool by bringing it into contact with the film of loose abrasive grains. Therefore, the grinding tool can be formed and sharpened with high accuracy. In particular, the dressing can be a so-called soft dressing in which only the bond is scraped without causing the abrasive grains of the grinding tool to fall off as much as possible.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a dressing device according to an embodiment of the present invention.
2 is a cross-sectional view taken along line II-II in FIG.
FIG. 3 is an enlarged schematic view of a grinding tool and a positive electrode for explaining the operation of the present invention.
FIG. 4 is a prior art dressing device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Dressing apparatus 12 ... Housing 14 ... Motor 18 ... Positive electrode 20 ... Negative electrode 22 ... Negative electrode holder 26 ... Ball grindstone 30 ... Polishing liquid circulation pump 32 ... Power supply

Claims (3)

In truing and dressing equipment for grinding tools,
A hemispherical grinding tool rotatably supported;
A cylindrical positive electrode immersed in a polishing liquid in a processing tank and supported rotatably around an axis provided at the position of the axis and twist of the grinding tool;
A negative electrode having a cylindrical inner surface fixed and opposed to the positive electrode at a predetermined interval;
An electric field is formed between the positive electrode and the negative electrode to cause an electrophoretic phenomenon of free abrasive grains dispersed in the polishing liquid therebetween, and the grinding tool and the positive electrode are relatively rotated. A truing and dressing apparatus for a grinding tool, wherein the grinding tool is subjected to relative arc movement along a cylindrical outer peripheral surface of the positive electrode to perform truing and dressing of the grinding tool. 2. The truing and dressing device for a grinding tool according to claim 1, wherein the positive electrode is configured to be capable of changing a rotation speed at a predetermined cycle. The truing and dressing apparatus for a grinding tool according to claim 1 or 2, further comprising a polishing liquid circulating means for circulating the polishing liquid in the processing tank.

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