JPH07290366A - Metal bond grinding wheel - Google Patents

Abstract

PURPOSE:To remarkably reduce the load fluctuation at the time of grinding, extremely reduce dressing, and improve the availability factor by flattening the tip sections of exposed abrasive grains, and specifying the concentration of the abrasive grains. CONSTITUTION:The content of abrasive grains in a grinding wheel, i.e., concentration specified by JIS-B 4131, is set to 1-20. The tip sections of the abrasive grains exposed on the surface of the grinding wheel are flattened. The flattened portion of the abrasive grains is preferably set to about 30% or more of the cumulative area. When the flattened portion is less than about 30% of the cumulative area, the roughness of the grinding surface of a work becomes too rough, the abrasive grains are abraded, and the frequency of dressing is nonpreferably increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal bond grindstone used for grinding hard and brittle materials such as glass and ceramics.

[0002]

2. Description of the Related Art Conventionally, a grindstone having diamond as an abrasive grain is generally used for grinding glass. This type of grindstone has an abrasive content, that is, JIS B
Concentration defined in 4131 is 50-1
It is about 00. Since this grindstone has a strong bonding force between the diamond and the bond, it has the advantage that the abrasive grains are hard to be detached, but has the drawback that the load gradually increases during grinding and eventually grinding becomes impossible. This is because the pointed part of the diamond protruding from the bond is worn and flattened, the contact area between the diamond and the work increases, and the amount of diamond abrasive particles protruding decreases and the bond directly contacts the work, etc. It is thought to be due to.

In order to recover the grinding performance of this grindstone, a treatment called dressing is generally applied. This dressing is made by grinding a sintered body of white alumina or green carborundum with a grindstone with poor grinding performance, shaving the bond to make the diamond stick out, making the diamond a pointed shape, and a diamond with a flattened tip. Is to be removed.

However, there is a problem in that work efficiency deterioration due to dressing and reduction in the life of the grindstone due to grinding of diamond and bonds are unavoidable.

Although it is conceivable to reduce the content of abrasive grains in order to reduce the load, this method also causes the load to increase with the grinding process, and by reducing the abrasive grains, the work piece There is also a problem that the surface roughness deteriorates.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art, to reduce the change in grinding load, to reduce the frequency of dressing, and to provide a grindstone with high grinding efficiency. .

[0007]

The present invention is characterized in that, in a metal-bonded grindstone in which diamond is used as abrasive grains, the exposed abrasive grains are flattened at their tips and the concentration of the abrasive grains is set to 1-20. It is a metal bond whetstone.

In the present invention, the abrasive grains, diamond, are fixed by metal bonds. As the bond, iron-based, cobalt-based, brass-based, etc. are used.
Of these, iron-based materials are particularly preferable as bonds because they have a strong bonding force with diamond.

Content of abrasive grains in the grindstone, that is, J
The concentration defined in IS B4131 is 1 to 20. If the concentration of the abrasive grains is less than 1, the amount of the abrasive grains becomes too small, the ground surface of the work becomes rough, and the grinding efficiency decreases. On the other hand, when the concentration of the abrasive grains exceeds 20, the cumulative area of the abrasive grains contacting the surface to be ground becomes too large, the grinding load becomes large, and a device having high rigidity is required, and the equipment becomes large.

The tips of the abrasive grains exposed on the surface are flattened. The flattened portion of the abrasive grains preferably has an accumulated area of 30% or more of the accumulated area of the maximum cross-sectional area of each abrasive grain exposed on the surface. If the accumulated area of the flattened portion is less than 30%, the roughness of the ground surface of the workpiece becomes too rough, and the abrasive grains wear and the frequency of dressing increases, which is not preferable.

As a method for flattening the tips of diamond abrasive grains, a dummy work which is not used as a product is repeatedly ground by flattening, a truing grindstone (white alumina General whetstones such as etc., diamond whetstones, etc. are attached and the target whetstone is pressed against this surface, rotated surface plate (cast iron, ceramics
For example, there is a method of pressing a grindstone against quartz glass or the like.

The method of removing the surface layer of the metal bond and projecting the diamond abrasive grains is to rotate the grindstone so that the runout is minimized, and discharge the oil while applying oil or water to the metal phase of the grindstone. There are a method of uniformly removing a certain depth of the surface layer portion, a method of electrolytically eluting by applying an anode potential while applying an electrolytic solution, and the like.

As the grain size of the abrasive grains, the grain size of diamond which is usually used is used. As the shape of the grindstone, various shapes are used including the shape defined by JIS B4131.

The grindstone according to the present invention is particularly suitable for grinding a flat surface, but can also be used for grinding a curved surface.

[0015]

Since the grindstone of the present invention is in a state of being worn from the start of use, the fluctuation of the grinding load can be suppressed to a small level. In addition, since the contact area of the abrasive grains of diamond acting on the work is larger than that of the case of using sharp diamond, surface roughness comparable to normal concentration can be obtained despite the small concentration.

[0016]

Example An iron-based metal bond diamond whetstone with a grain size of 325 and concentration 10 was used as a grinding whetstone. Outer diameter 200 mm, thickness 10 mm, JIS B41
31 has a 1H1 shape. The apparatus used was a horizontal axis surface grinder, a spindle motor of 2.2 kW, and a table size of 500 mm × 200 mm.

The tip of the abrasive grains of this grindstone was flattened as follows. The alumina substrate was repeatedly ground. Grinding conditions are: grinding wheel rotation speed 3600 rpm, table speed 2 m / min, cross feed 50 mm / min,
Depth of cut is 5 μm step and work size is 15
It is 0 mm square. The grinding time was 20 minutes.

Next, in order to cause the abrasive grains to protrude from the bond phase, a discharge electrode made of carbon was set at a certain distance from the tip of the grindstone, and after connecting the positive electrode of the discharge power source to the carbon electrode and the negative electrode to the grindstone shaft, While rotating the grindstone at 30 rpm, a pulse current was applied to the electrodes to uniformly remove the bond phase without damaging the diamond. As a result,
The protrusion amount of diamond from the bond phase is 15 to 20
It was in the μm range.

As a result of observing the surface of this grindstone with a microscope,
About 90% of the diamond abrasive grains exposed on the surface of the grindstone are flattened, and the cumulative area of the flattened portion in an arbitrary field of view is calculated as the number of exposed abrasive grains and the maximum cutoff of each abrasive grain. The value obtained by dividing the product of the area and the cumulative value is 75%
I confirmed that it was before and after.

Using this grindstone, the surface of a synthetic quartz glass substrate having a diameter of 150 mm and a thickness of 6.3 mm was ground. The processing machine used is a horizontal rotary surface grinder. The grinding conditions are: a wheel rotation speed of 2400 rpm, a cross feed of 150 mm / min, and a cut amount of 50 μm steps.

The increase in the grinding load was only 5% after the first surface was ground after 100 surfaces were ground. The surface of the obtained synthetic quartz glass substrate was measured by a stylus type surface roughness meter, and as a result, the surface roughness was _Ra of 0.25 to 0.30 on average.
It was m. In addition, even if 100 surfaces were ground, the variation in roughness was very small and within ± 10%.

[0022]

[Comparative Example] As a grinding wheel, a metal bond diamond wheel using a brass bond having a grain size of 325 and a concentration of 75 was prepared. The outer diameter of the grindstone is 200
mm, grindstone width 10 mm, shape is 1H1 type specified in JIS B4131. The apparatus used is the same horizontal axis rotary surface grinder as in the example.

A grindstone was attached to the apparatus, dressing was performed using a white alumina grindstone, and then the same grinding as in the example was carried out. Grinding conditions and workpieces are the same as in the example.

In this case, the load increased as the grinding was performed, and the load for grinding the 22nd surface increased by about 50% with respect to the load for grinding the 1st surface. The surface roughness of the obtained workpiece was measured by a stylus type surface roughness meter as in the example. In the grinding of the first surface, _Ra was 0.35 μm on average, and in the grinding of the 28th surface, _Ra was 0.29 μm on average.

[0025]

The metal bond grindstone of the present invention has the following effects. (1) Surface roughness similar to that of a normal diamond grindstone can be obtained. (2) The load fluctuation during grinding is remarkably small, and therefore dressing can be extremely reduced and the operating rate can be greatly improved.
Further, by extremely reducing the number of dressings, the consumption of the grindstone is extremely small, and the grindstone cost can be significantly reduced. (3) The number of diamonds is small, and the cost of the grindstone can be reduced. (4) Since the load during grinding is not so different from that of the conventional grindstone, a normal grinding machine can be used.

Claims (2)

[Claims] 1. A metal bond grindstone in which diamond is used as an abrasive grain, wherein the exposed abrasive grain is flattened at the tip and the concentration of the abrasive grain is set to 1 to 20. 2. The metal bond grindstone according to claim 1, wherein the bond is mainly composed of iron.