JPH04300155A - Grinding wheel for polishing lens - Google Patents

Abstract

PURPOSE:To polish the surface of a lens made of optical glass with a high degree of accuracy with polishing speeds at the rotational center side and the rotational outer peripheral side of a surface to be polished being made to be uniform. CONSTITUTION:An electroplated abrasive grain layer 6 in which an ultra- abrasive grain is fixed in a metal plating phase is formed over a surface 1 to be plated on a grindstone base body 1. The averaged particle size of the ultra-abrasive grain is in a range of 3 to 30mum, the content rate of the abrasive grain on a side 6 near to the rotational axis of the grind stone is set to be higher than that on a side remote from the rotational axis.

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 a method for manufacturing the same, and in particular, the present invention relates to a lens grinding wheel for grinding the surface of an optical glass lens and a method for manufacturing the same. Regarding improvements for uniformity.

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,
Although it has been found that a suitable finished surface roughness can be obtained by using superabrasive grains having an average grain size of 3 to 30 μm, the following problems have also become apparent.

That is, when a lens material is ground by rotating a grindstone around the axis, the circumferential speed of the abrasive grain layer is necessarily higher on the outer peripheral side of the rotation than on the rotation center side of the grinding surface, and the grinding by individual abrasive grains is difficult. The portions are also large. For general work materials, even if there is a difference in the amount of grinding of this degree and even a difference in grinding speed,
The effect on the final shape accuracy is relatively small, so it is hardly a problem, but in the grinding process of optical lenses, the demands on the shape accuracy of the ground surface are extremely strict, so there is a risk that it will not fall within the tolerance range. We have it.

[0009]

[Means for Solving the Problems] The present invention has been made to solve the above problems.
An electrodeposited abrasive grain layer is formed in which superabrasive grains are fixed with a metal plating phase, and the average grain size of the superabrasive grains is 3 to 30 μm, and the electrodeposited abrasive grain layer is close to the grinding wheel rotation axis. The abrasive grain content on the side is set higher than the abrasive grain content on the side farther from the grindstone rotation axis.

0010

[Function] According to the lens grinding wheel of the present invention, since the abrasive grain exposure density on the grinding surface is higher on the inner circumferential side than on the outer circumferential side, the slowness of the peripheral speed on the inner circumferential side of the abrasive grain layer is compensated for. , the grinding speed on the rotation center side and the outer peripheral side of the abrasive grain layer can be made uniform, and the shape accuracy of the workpiece can be improved.

[0011]

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, and FIG. 2 is a bottom view thereof. 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 plated surface 1A is formed. The plated surface 1A may be either a spherical or aspherical surface, and is not limited to a concave curved surface as shown, but may be a convex curved surface for concave processing.

As for the material of the grinding wheel base 1, not only metals such as aluminum alloy, stainless steel alloy, and copper alloy, but also non-conductive materials such as ceramics can be used if the plated surface 1A is made of a conductive material. However, in order to increase the cooling efficiency of the grinding wheel base 1 and reduce deformation of the grinding surface due to temperature rise, a material with high thermal conductivity and a low coefficient of thermal expansion is preferable, and from this point of view, copper alloy is particularly suitable. ing.

An electrodeposited abrasive layer 6 having a constant thickness is formed over the entire surface 1A to be plated. This electrodeposited abrasive grain layer 6 is made by dispersing superabrasive grains such as diamond or CBN in a multilayered (or single layered) form within a metal plating phase, and the average grain size of the superabrasive grains is 3 to 30 μm. It is desirable to set this.

It has been confirmed through experiments by the present inventors that if the diameter is less than 3 μm, clogging and abrasive grain dropout will be severe when grinding optical glass, and sufficient grinding efficiency cannot be obtained. 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.

The features of the lens grinding wheel of the present invention are shown in FIG.
As shown in , the abrasive grain content on the inner circumferential side 6A of the electrodeposited abrasive layer 6 that is close to the whetstone rotation axis is set higher than the abrasive grain content on the outer circumferential side 6B that is far from the whetstone rotation axis. It is in. In this example, the abrasive grain content increases steplessly from the outer periphery of the outer periphery 6B toward the center of the inner periphery 6A (the center of rotation of the grindstone). Although it is preferable for the abrasive grain content to change steplessly in this way from the viewpoint of effectiveness, the abrasive grain content may be changed stepwise if necessary.

The abrasive grain content of each part 6A, 6B should be determined according to the dimensions of the grindstone and the rotational speed during use, and should be experimentally set so that the grinding speed in each part during use is approximately uniform. be done. This is because other influencing factors such as the ability to discharge chips and the ability to supply grinding fluid are different between the inner peripheral side 6A and the outer peripheral side 6B, and it is difficult to make a general theory.

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.

[0018] Furthermore, if a Ni--Co alloy is used, the metal plating phase may contain 0.005 to 1.0 wt% of Mn. In this case, the metal plating phase becomes even harder, and the above effect becomes more pronounced. Mn is 0.
If it is less than 0.005 wt%, no effect will be obtained, and if it exceeds 1.0 wt%, no further improvement will be observed.

According to the lens grinding wheel having the above structure, the abrasive grain exposure density on the grinding surface is higher on the inner circumferential side 6B than on the outer circumferential side 6B.
Since the grinding speed is high at A, it is possible to correct the slow circumferential speed at the inner circumferential side 6A of the abrasive grain layer and equalize the grinding speed at the inner circumferential side 6A and outer circumferential side 6B, and the final lens obtained shape accuracy is improved. In addition, this whetstone has an average particle size of super abrasive grains of 3 to 3
Since it is set to 0 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. 3 and 4, It may be changed to a non-symmetrical shape. Further, particles other than superabrasive grains may be dispersed in the abrasive grain layer, and in that case, chip pockets are formed by shedding of the particles, thereby improving chip discharge performance and grinding fluid supply performance.

[0021]

As explained above, in the lens grinding wheel of the present invention, the exposed density of abrasive grains on the grinding surface is higher on the inner circumferential side than on the outer circumferential side, so that the circumferential speed on the inner circumferential side of the abrasive layer increases. By correcting the slowness of grinding, it is possible to equalize the grinding speed on the center side and the outer circumferential side of the abrasive grain layer, and the shape accuracy of the finally obtained workpiece is improved. In addition, this whetstone has an average particle size of super abrasive grains of 3 to 30
Since it is set to 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 a bottom view of the same grindstone.

FIG. 3 is a plan view showing another embodiment of the present invention.

FIG. 4 is a sectional view taken along line AA of the same embodiment.

[Explanation of symbols]

1. Grinding wheel base 1A Plated surface 2 Rotation axis 4 Flange part 6 Electrodeposited abrasive layer

Claims (1)

[Claims] 1. A lens grinding wheel comprising an electrodeposited abrasive grain layer in which superabrasive grains are fixed with a metal plating phase on a surface to be plated of a whetstone base, wherein the average grain size of the superabrasive grains is 3 to 3. 30μm
A lens characterized in that the abrasive grain content on the side of the electrodeposited abrasive layer nearer to the grinding wheel rotation axis is set higher than the abrasive grain content on the side farther from the grinding wheel rotation axis. Grinding wheel.