JPH04300156A - Grinding wheel for polishing lens - Google Patents

Abstract

PURPOSE:To increase the contact pressure between abrasive and a workpiece to be polished so as to enhance the polishing efficiency and to enhance the discharge ability of chips and the lubricity at a surface to be polished in order to reduce the polishing resistance during polishing of a lens. CONSTITUTION:There are provided a grindstone base body 1 having a curved surface 1A corresponding to the shape of an optical lens article and an abrasive layer 6 formed over the curved surface 1A. Several convexities having a uniform degree of projection and made of at least graphite are formed on the curved surface 1A, and the abrasive layer 6 is formed by fixing ultra-abrasive grain having an averaged particle size of 3 to 30mum, onto the curved surface formed thereon with the convexities in a metal plating phase.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a lens grinding wheel for grinding the surface of an optical glass lens, and in particular, it improves grinding efficiency by increasing the contact pressure between individual abrasive grains and the work material. This invention relates to improvements for improving chip discharge and lubricity on the grinding surface and reducing grinding resistance.

0002

[Prior Art] Conventionally, optical lenses have been manufactured by roughly forming molten glass, then rough grinding using a grindstone such as a curve generator, then lapping with free abrasive grains, and then A method of finishing by polishing has been used for a long time.

[0003] This processing method has the advantage that high-precision optical lenses can be manufactured using processing equipment with a simple configuration.
On the other hand, it has the problem of being highly dependent on the skill of the worker and having low productivity. In addition, when manufacturing aspherical lenses, it is impossible to perform shear-like lapping when the lens and polishing body are moved relative to each other, as in spherical grinding and surface grinding, so surface accuracy is required at the grinding stage. It is important to increase the amount of processing and minimize the amount of processing in post-processes.

For this reason, recently, in order to reduce the dependence on skill and achieve automation and labor-saving, as well as to make it possible to process aspherical lenses, precision grinding has been used instead of the rough grinding described above to improve the quality of optical glass. A method that provides a precise shape, eliminates lapping, and performs direct polishing is becoming popular. Some attempts have already been made to precisely grind lenses using resin bonded grindstones or vitrified bonded grindstones containing diamond abrasive grains.

[0005]

[Problems to be Solved by the Invention] However, in the resin bonded grindstone or vitrified bond grindstone described above, the hardness of the bonding phase is low and it is easily worn, resulting in large changes in the shape of the grinding surface, and it is necessary to frequently correct the shape. There was a problem that high precision grinding accuracy could not be maintained.

[0006] Therefore, the present inventors devised a method for precision grinding of optical lenses using an electroplated grindstone using a highly wear-resistant metal plating phase as a bonding phase, and actually produced various grindstones. We conducted an experiment.

As a result, in this type of electrodeposited grindstone, the metal plating phase that supports the superabrasive grains is extremely hard, so the average grain size of the superabrasive grains can be made smaller than when other bonding materials are used. It has been found that if this is not done, deep scratches and the like will occur on the machined surface, making it impossible to obtain the desired finished surface roughness. For example, in a resin-bonded grindstone, the bonding phase itself has some elasticity, so the cuts of individual abrasive grains are slightly evened out, and 7 to 10μ
m superabrasive grains are used, while electrodeposited grindstones use 3 to 3 m superabrasive grains.
Unless superabrasive grains of 0 μm are used, it is difficult to obtain the desired surface roughness.

[0008] However, in the electrodeposited grinding wheel using such fine superabrasive grains, the surface of the metal plating phase is dense and the grain size of the superabrasive grains is small, so the grinding surface has poor undulations and the grinding surface is rough. The efficiency of supplying the grinding fluid to the grinding fluid and the ability to discharge chips from the grinding fluid are low. Therefore, it has the disadvantage that it gets clogged early and the contact pressure between the individual abrasive grains and the workpiece decreases, resulting in a decrease in grinding efficiency.

[0009]

[Means for Solving the Problems] A grindstone base having a curved surface corresponding to the product shape of an optical lens, and an abrasive grain layer formed on the curved surface, the curved surface of the grindstone base having a constant protrusion amount. A large number of convex portions are formed, at least these convex portions are formed of a soft material such as graphite, and the abrasive grain layer has an average grain size of 3 to 30 μm on the curved surface including the surface of these convex portions. It is characterized by an electrodeposited abrasive layer formed by fixing superabrasive grains with a metal plating phase.

0010

[Function] According to the lens grinding wheel of the present invention, many convex portions are formed in the abrasive grain layer corresponding to the convex portions formed on the curved surface, so even if the total grinding area is large, the workpiece material The contact area with the abrasive grain layer is kept small, and the contact pressure of the abrasive grains located on the convex portion is increased to improve the cutting efficiency and obtain high grinding efficiency.

Further, as the grinding progresses, the abrasive grain layer formed on the convex portion is worn away, and the convex portion below is exposed. Since these protrusions are made of a soft material such as graphite, they gradually wear out as the grinding progresses and are supplied to the grinding surface, acting as a lubricant. At the same time, even if the tip of the convex part wears out, the abrasive grain layer around the worn part takes over the grinding process, so the contact pressure of the abrasive grains is always maintained high, making it possible to maintain good grinding efficiency for a long time. It is.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a longitudinal sectional view showing an embodiment of a lens grinding wheel according to the present invention. Reference numeral 1 in the figure is a disk-shaped grindstone base, and the flange part 4 of the rotating shaft 2 is coaxially fixed to the center of the upper surface, while the lower surface of the grindstone base 1 corresponds to the curved shape of the lens to be machined. A curved surface 1A is formed. This curved surface 1A may be either spherical or aspherical,
Further, the curved surface 1A is not limited to a concave curved surface as shown in the drawings, but may be a convex curved surface for concave surface processing.

A large number of convex portions 8 having a constant protrusion amount are formed on the curved surface 1A, and in this example, the entire grindstone base 1 is molded from a soft material such as graphite or fluororesin. However, the entire grindstone base 1 does not necessarily have to be made of a soft material, and it is sufficient that at least these protrusions 8 are made of a soft material. For example, the grindstone base 1 may be constructed of a base body and a graphite layer of a constant thickness formed on the curved surface of the base body, and the graphite layer may be provided with convex portions 8, or portions corresponding to the convex portions 8 may be formed. It is also possible to embed graphite material only in the convex portion.

In this embodiment, each convex portion 8 is formed into a gentle hemispherical shape (disk shape). However, the convex portion 8 is not limited to this shape, and may have any shape such as an elliptical disk shape, a square shape, a honeycomb shape, etc., or by forming a large number of concave portions on the curved surface 1A, the other portions may be relatively It may also be a convex portion.

Regardless of the shape of the convex portion 8, the curved surface 1
It is desirable that the total area of the convex portion 8 at A and the total area of the other portions of the curved surface 1A are set approximately equal. If the areas of both are approximately equal and the surface of the convex part 8 is a curved surface that is gently continuous with other parts within the curved surface 1A, the convex part 8
Even in the process of wear, the total area of the abrasive layer 6 in contact with the workpiece material changes little, which has the advantage of minimizing fluctuations in grinding efficiency.

[0016] However, if necessary, the total area of the two may be significantly different. The dimensions and protrusion amount of the convex portion 8 in plan view should be appropriately set according to the dimensions of the grindstone base 1.

An electrodeposited abrasive grain layer 6 is formed to a constant thickness over the entire surface of the curved surface 1A including the surface of each convex portion 8. This electrodeposited abrasive layer 6 is made of diamond or CBN.
Multi-layered super abrasive grains (single layer is also possible) within the metal plating phase
It is dispersed in

It is desirable that the average particle diameter of the superabrasive grains be set to 3 to 30 μm; if it is less than 3 μm, clogging and abrasive grain dropout will be severe when grinding optical glass, and sufficient grinding efficiency cannot be obtained. This has been confirmed through experiments conducted by the inventors. Furthermore, if the average grain size is larger than 30 μm, the striations formed on the surface to be cut by the superabrasive grains become deep, and the finished surface roughness required for lens grinding (for example, Rz: about 0.7 μm) cannot be obtained.

On the other hand, the metal plating phase is composed of Ni, Co, Ni--Co alloy, or the like. When using a Ni-Co alloy, the Co content is 10 to 60 w.
It is desirable to set it as t%. An alloy having this composition has improved fatigue resistance and rigidity compared to the case of a simple Ni plating phase. If the Co content is less than 10 wt%, sufficient heat resistance and fatigue resistance effects cannot be obtained. Moreover, if Co is 60 wt % or more, Co is expensive, leading to an increase in the manufacturing cost.

[0020] Furthermore, if a Ni-Co alloy is used, 0.005 to 1.0 wt% of M is added to the metal plating phase 12.
n may be included. In this case, the metal plating phase 12 becomes even harder, and the above effect becomes more pronounced. Mn
If it is less than 0.005 wt%, no effect will be obtained, and 1.0
Even if it exceeds wt%, no further improvement is seen.

According to the lens grinding wheel having the above structure, as shown in FIG. 2, a large number of convex portions 6A are formed in the abrasive grain layer 6 corresponding to the convex portions 8 formed on the curved surface 1A. Therefore, even if the total grinding area is large, the contact area between the workpiece and the abrasive grain layer 6 is kept small, and the contact pressure of the abrasive grains located at the convex portions 6A with the workpiece is increased to increase cutting efficiency. High grinding efficiency can be obtained.

Further, as the grinding progresses, the convex portion 6A is worn away, and the convex portion 8 below it is exposed. Since these protrusions 8 are made of a soft material such as graphite, they gradually wear out as the grinding progresses and are supplied to the grinding surface, acting as a lubricant.

At the same time, as shown in FIG. 3, even if the tip of the convex portion 8 is worn, the abrasive grain layer 6A at the periphery of this worn part 8A takes over the grinding process, so the contact pressure of the abrasive grains is always maintained high. It is possible to maintain good grinding efficiency for a long time.

[0024] Furthermore, in this grindstone, the average particle diameter of the superabrasive grains 8 is 3.
Since it is set to ~30 μm, the grinding accuracy and finished surface roughness required for optical lens grinding can be obtained.

Although the grinding wheel base 1 was disk-shaped in the above embodiment, the present invention is not limited to the disk shape. For example, as shown in FIGS. 4 and 5, It may be changed to a non-symmetrical shape.

[0026]

[Effects of the Invention] As explained above, in the lens grinding wheel of the present invention, a large number of convex portions are formed in the abrasive grain layer corresponding to the convex portions formed on the curved surface, so that the total grinding area is reduced. At most, the contact area between the workpiece and the abrasive layer can be kept small,
By increasing the contact pressure of the abrasive grains located on this convex portion, the cutting efficiency is increased, and high grinding efficiency can be obtained.

Further, as the grinding progresses, the abrasive grain layer formed on the convex portion is worn away, and the convex portion below is exposed. Since these protrusions are made of a soft material such as graphite, they gradually wear out as the grinding progresses and are supplied to the grinding surface, acting as a lubricant. At the same time, even if the tip of the convex part wears out, the abrasive grain layer around the worn part takes over the grinding process, so the contact pressure of the abrasive grains is always maintained high, making it possible to maintain good grinding efficiency for a long time. It is.

[0028] Also, in this grindstone, the average particle size of the superabrasive grains 8 is 3
Since it is set to ~30 μm, the grinding accuracy and finished surface roughness required for optical lens grinding can be obtained.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of a lens grinding wheel according to the present invention.

FIG. 2 is an enlarged cross-sectional view of the abrasive grain layer of the same grindstone.

FIG. 3 is an enlarged cross-sectional view of an abrasive grain layer showing the effect of the present invention.

FIG. 4 is a plan view showing another embodiment of the present invention.

FIG. 5 is a sectional view taken along the line V-V of the same embodiment.

[Explanation of symbols]

1. Grinding wheel base 1A curved surface 2 Rotation axis 4 Flange part 6 Abrasive grain layer 6A Abrasive grain layer around the worn part 8 Convex part 8A　Convex worn part

Claims (2)

[Claims] 1. A grindstone for lens grinding, comprising a grindstone base having a curved surface corresponding to the product shape of an optical lens, and an abrasive grain layer formed on the curved surface, wherein the curved surface of the grindstone base has a protruding surface. A large number of convex portions with a constant amount are formed,
At least these convex portions are formed of a soft material, and
The abrasive grain layer is an electrodeposited abrasive grain layer formed by fixing superabrasive grains having an average grain size of 3 to 30 μm on the curved surface including the surfaces of these convex portions with a metal plating phase. Grinding wheel for lens grinding. 2. The lens grinding wheel according to claim 1, wherein the soft material is graphite.