JPH08309667A - Resin bond super abrasive grain wheel - Google Patents

Abstract

PURPOSE: To provide a resin bond super abrasive grain wheel with which electric discharge machining for a high accurate complicated shape can be performed. CONSTITUTION: In a resin bond, when contained 15 to 60% by volume ratio as a super abrasive grain and containing 10% or more by volume ratio dendritic or flake metal power as a conductivity giving substance, a resin bond super abrasive grain wheel, excellent in shape accuracy and shape maintainability, having complicated-shaped abrasive grain layer with a reduced cost, can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin-bonded superabrasive wheel capable of performing electric discharge machining of an abrasive grain layer into a complicated shape having ultraprecision accuracy.

[0002]

2. Description of the Related Art In order to form a superabrasive wheel for forming a superabrasive wheel with superprecision, an electric discharge machining is applied to form an abrasive grain layer into a complicated shape such as a concave shape for superprecision machining. The use itself has been widely known in the past. For example, in Japanese Patent Publication No. 46-31276, a surface of a metal-bonded diamond grindstone is made to face a discharge electrode surface of a required shape, and a gap is formed in the gap. It is disclosed that electric discharge is performed to dissolve and remove the bonding metal, expose diamond particles from the surface of the bonding material, and adjust the grinding shape.

On the other hand, in recent years, in place of the metal bond superabrasive grain wheel, there has been a demand for precision pattern machining of a resin bond superabrasive grain wheel which is excellent in sharpness. Regarding the processing of this resin bond superabrasive wheel, the Precision Engineering Society, Spring Lecture (1988-3) 50.
3. Suzuki, Autumn Meeting of Precision Engineering Society (1988-10) 45,
There is a report by Uematsu et al. That even in the case of a resin-bonded superabrasive wheel, it is possible to apply discharge truing if the resin bond contains a conductive substance.

However, since the resin bond is originally insufficient in conductivity, unevenness in processing occurs by simply adding a conductive substance to the bond, so that it is very difficult to perform high-precision processing by electric discharge machining. Is. In fact, regarding the machining accuracy of discharge-trued metal-bonded super-abrasive grain wheels, Yanase and Uematsu et al. Have described it in the Autumn Meeting of Precision Engineering (1989 10) 355. No processing accuracy has been reported.

Therefore, in order to form the abrasive grain layer of the resin-bond superabrasive grain wheel into a complicated shape, machining with a polishing grindstone, a metal bond wheel in which the abrasive grain layer is formed by electric discharge machining, Co-rubbing with the electrodeposited superabrasive wheel is performed.

However, since the resin bond abrasive grain layer has elasticity, when creating a complicated shape by machining or co-rubbing, it has a drawback that it is deformed by stress and precision is difficult to obtain, and the machining cost becomes high. Especially,
In the case of co-rubbing, the protrusion of the abrasive grains from the bond surface becomes small, and the sharpness of the abrasive grains deteriorates due to abrasion of the tips of the abrasive grains. This sharpening has a drawback in that the final shape accuracy is deteriorated.

Further, Japanese Patent Publication No. 48-15997 discloses that a so-called cluster of dendrite metal particle groups produced by electrolysis is interposed in an abrasive grain layer, which is used to retain superabrasive grains. It enhances the grinding efficiency by the abrasive grains together with the force, and there is no description about the contribution to the electric discharge machining for creating the shape of the resin bond abrasive grain layer.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to solve the problem of high precision complicated shape machining of a resin bond superabrasive grain wheel, and it is possible to apply precision machining of an abrasive grain layer by electric discharge machining. To provide a resin-bonded super-abrasive grain wheel.

[0009]

According to the present invention, the super-abrasive grains are contained in the resin bond in a volume ratio of 15 to 60%, and the average grain size is 3%.
It is characterized in that the shape of the abrasive grain layer can be created by precision electric discharge machining by containing powder particles of a conductive substance of 0 μm or less in an amount of 10% or more by volume ratio.

As the conductive substance powder particles, nickel,
A semi-conductive substance such as iron, zinc, copper, silver, an alloy thereof, or graphite can be used, and the particle has a specific surface area of 1000 cm ² rather than a spherical shape.
/ G or more, preferably 3000 cm ² / g or more of a dendritic or flaky metal powder is preferable.

The particles of the conductive substance powder need not only have conductivity in the resin bond but also fully exhibit the function as a resin bond superabrasive grain wheel, and therefore, need to have excellent abrasive grain retention. is there. From this point of view, the filler used is preferably a metal powder such as copper, iron or nickel. Particularly, as the shape of the metal powder, the specific surface area, that is, the total surface area of the particles per unit weight of the powder is 3000.
Most preferably, it is a resin or piece having a size of cm ² / g or more. The size of the dendritic or flaky copper powder at that time is
It is desirable that the average particle size is 30 μm or less. The use of dendritic, flaky, porous, or fibrous metal powder having a large specific surface area increases the resin bond strength, reduces the degree of wear, and improves the shape retention of the abrasive layer.

Further, the uniform dispersion of the conductive material particles throughout and the large specific surface area of the dispersed conductive material particles are indispensable requirements for uniform electric discharge machining of the abrasive grain layer. . From this point of view, it is necessary that the average particle diameter of the conductive material is 30 μm or less, preferably 10 μm or less. In particular, when the shape of the abrasive grain layer is processed with high precision, the average particle diameter of the conductivity imparting substance needs to be 10 μm or less.

Further, in the case where the abrasive grain layer is required to have particularly elasticity in order to reduce the occurrence of cracking and chipping of the work material, and when a large amount of superabrasive grains is contained, the content ratio of the conductivity-imparting substance is It is desirable that the volume ratio is 10 to 20% and the average particle diameter is 10 μm or less.

Further, in order to improve the shape-maintaining property of the abrasive grain layer, which is particularly important in forming the resin-bonded superabrasive grain wheel, a resin such as phenol, epoxy, melamine or polyester for forming the abrasive grain layer is used. One of the effective means is to increase the strength of the resin bond used and to improve the wear resistance. Furthermore, it is necessary to have heat resistance, and considering the influence of sparks in electric discharge machining, it is particularly preferable to use a polyimide resin having heat resistance.

As a method for improving the dispersibility of the conductive substance, it is preferable to reduce the average particle size of the resin powder in the raw material. Increasing the volume ratio of superabrasive grains in the abrasive grain layer is effective as a means for improving the shape retention of the abrasive grain layer, and at least 15% or more of the superabrasive grains is preferable in terms of volume ratio. In order to make the increased superabrasive grains work effectively, it is necessary to increase the holding force of the superabrasive grains. In this case, it is preferable to use coated superabrasive particles known per se. However, if the total content of the coated superabrasive grains and the conductive substance exceeds about 70% by volume, the formability by resin bond deteriorates, and it is impossible to obtain the physical properties that match the required grinding performance. Considering these various factors, it is desirable that the amount of superabrasive grains is 15 to 60% by volume in the resin bond. In order to improve the shape retention of the abrasive grain layer, it is effective to increase the grain size of the superabrasive grains, but the precision of the finished surface due to electrical discharge machining becomes rough, which also affects the machining precision. Therefore, it is preferable to select the grain size of the abrasive grains in consideration of the processing purpose and finishing accuracy.

[0016]

The conductive substance necessary for electric discharge machining of the abrasive grain layer by containing 10% or more by volume of a conductive substance having an average particle size of 30 μm or less as a filler in the resin bond A uniform dispersed state is ensured during the resin bond. Further, by using the dendritic or flaky metal powder as the filler satisfying the above conditions, the specific surface area is improved, the sparks are sufficiently dispersed in the electric discharge machining, and the machining with high accuracy is performed. Similarly, due to the shape thereof, the metal powder or the resin can be intimately entangled with each other when the abrasive grain layer is molded, and a high-strength resin bond is formed.

[0017]

EXAMPLE An example in which copper powder is used as the conductivity-imparting substance to be contained in the abrasive grain layer of the resin-bonded superabrasive grain wheel will be described.

Example 1 Changes in electrical discharge machinability, shape accuracy, and physical properties due to changes in the shape of copper powder as a conductivity-imparting substance were examined.
As a superabrasive grain layer, 100 (superabrasive grain volume content of 25%) was used as an outlet, and the volume ratio of the abrasive grains having a Ni coat of 55% with respect to the mesh size # 600 of superabrasive grains was 3% by volume.
9.1% was used, and a thermosetting polyimide resin was used as a resin for bonding.

As the copper powder as the conductivity-imparting substance,
FIG. 1A shows that the specific surface area produced by the electrolysis method is 450.
0-5000 cm ² / g of dendritic material is shown, (b)
Has a specific surface area of 350 to 40 produced by the melt pulverization method.
0 c ² / g of spherical particles is shown, and (c) has a specific surface area of 4000 to 5000 cm ² produced by a mechanical milling method.
/ G of flaky particles, and (d) shows granular particles having a specific surface area of 1000 to 1200 cm ² / g produced by the molten metal powdering method. In each case, 30.0% by volume of copper powder having an average particle diameter of 30 μm was used.

As shown in FIG. 2, while the resin-bonded superabrasive wheel consisting of the abrasive grain layer 1 attached to the outer peripheral surface of the aluminum base 2 is fixed to the holder 3, the graphite electrode 4 is rotated. Electric discharge machining was carried out using this to machine into a shape corresponding to the shape of this graphite electrode 4.

Table 1 shows the bending strength index in each case,
The surface roughness of the abrasive layer and the processing accuracy of the abrasive layer are shown. The shape accuracy shown in the table was confirmed by transferring the shape from the wheel to the carbon plate after electric discharge machining and measuring the shape of the carbon plate.

[0022]

[Table 1]

In each case, a shape that can be created only by conventional co-polishing and wheel overlapping was obtained by electric discharge machining. However, when the shape of the metal powder is spherical or granular powder, it looks like black burn on the grinding surface after electric discharge machining. Unusual discharge marks were confirmed. The machining shape accuracy due to the difference in the shape of the metal powder is as shown in Table 1 at each of A, B, C, and D shown in FIG. 3, and it can be seen that all of them are finished with high accuracy. . Further, it can be seen that the shape powder having a large specific surface area is processed with high accuracy and the surface roughness of the abrasive grain layer is small in correspondence with the specific surface area.

Further, the bending strength of the resin bond abrasive grain layer is set to J
The result of measurement according to IS K 5911 is shown as an index with the bending strength when dendritic powder is used as 100. It can be seen that the bending strength varies depending on the shape of the metal powder. The dendritic and flaky powders have almost the same bending strength, and can be molded with higher strength than other powders.

In summary of these results, it has been found that by using the specified amount of the conductivity-imparting substance, it is possible to form a precise shape by electric discharge machining in any case. Also, when dendritic or flaky powder is used, the surface quality of the abrasive grain layer is better than other powders, it is highly accurate, wear at the time of grinding is relatively small, and shape retention is high. It becomes a resin bond superabrasive wheel. Also, due to both effects, the shape correction interval becomes longer.

The average particle size in the above examples is
Microtrac Particle Size Analyzer Mode
It is the value which showed the average of three measurements using 1 7995-10 SRA.

Example 2 EDM machinability due to changes in volume ratio and average particle size of metal powder in electric discharge machining of a resin bond superabrasive wheel,
We also investigated the influence of processing shape accuracy and superabrasive grain mesh size on shape accuracy. The resin bond superabrasive grain wheel was molded for various compositions such that the volume ratio of the copper powder in the resin bond was 0 to 40% and the average grain size was 10 to 70 μm, and the abrasive grain layer was the same as in Example 1 above. Electric discharge machining was performed on the shape. As the copper powder, a dendritic copper powder which could obtain good results in Example 1 was used. The super-abrasive grains were 100 (a super-abrasive grain volume content of 25%) at the outlet, and the Ni coat weight ratio was 55% and the mesh size was # 230/270. The electrical discharge machining procedure was the same as in the case of Example 1. After that, the surface of the abrasive grain layer of the resin bond superabrasive grain wheel was observed. The observation results are shown in Table 2.

[0028]

[Table 2]

In the observation of the electric discharge machining state, when the copper powder average particle diameter is 30 μm, the volume ratio is 20% or more, and when it is 10 μm, the volume ratio is 10% or more, stable electric discharge machining can be performed, and black which is considered to be an abnormal discharge mark No burning was confirmed. This is indicated by a double circle. Copper powder average particle size is 10
When the volume ratio is 5% in the case of μm and the volume ratio is 30% in the case of 50 μm, it is confirmed that the abrasive grain layer has several abnormal discharge marks such as black burn with a diameter of 0.2 mm or more. Was done. This is indicated by a circle. Further, when the average particle diameter of the copper powder is 50 μm or more, stable electric discharge machining cannot be performed even if the volume ratio is 20% or more, or there are 10 or more abnormal electric discharge marks such as black burn with a diameter of 0.2 mm or more in the abrasive grain layer. occured. This is indicated by the Δ and X marks.
And for any of the average particle sizes, the copper volume ratio is 40%.
In the above cases, molding defects have occurred. This is indicated by the-mark.

Next, from the results of observation of the abrasive grain layer surface of the resin-bonded superabrasive grain wheel in Table 2, stable electrical discharge machining is possible, and abnormal electrical discharge marks such as black burn with a diameter of 0.2 mm or more are not confirmed, or The shape accuracy was measured for the cases where ⊚ and ◯ were added in the electrical discharge machining state observation list of Table 2 which was confirmed several times. This abrasive grain layer shape measurement is omitted this time because there is a high possibility that stable and precise die forming cannot be performed if the abrasive grain layer has 10 or more abnormal discharge marks with a diameter of 0.2 mm or more. . The shape accuracy was confirmed by transferring the shape from a wheel after electric discharge machining to a carbon plate and measuring the shape of the carbon plate. At the same time, the surface roughness of the abrasive layer was also measured. The results are shown in Table 3.

[0031]

[Table 3]

From the table, the average grain size of the copper powder is 30 μm.
In the case of m, the volume ratio is 20, 30%, and in the case of 10 μm, the volume ratio of the abrasive grain layer is 10, 20, 30%.
It is confirmed that any of the points A, B, C, and D shown in (3) is finished with high precision processing. When the surface roughness of the abrasive layer is also the above composition, the average particle diameter of the copper powder is 10 μm.
In the case of, the volume ratio was 5%, and in the case of 50 μm, the body bond ratio was less than 30%. From these results, if the composition range of the effective electric discharge machining in the resin-bonded superabrasive wheel is limited, the volume ratio of the copper powder is preferably 20 to 30% or more, and correspondingly, the average particle size is preferably 30 μm or less.
And when the elasticity which is the feature of the resin-bonded superabrasive grain wheel is required or when a large amount of superabrasive grains are contained, and when the volume ratio of the copper powder is 10 to 20% is small, 10 μm or less is particularly preferable. Was confirmed.

By comparing the results of Table 1 of Example 1 and Table 3 of Example 2 above, the influence of the superabrasive grain mesh size on the shape accuracy was also observed as follows. That is, the superabrasive grain mesh size is from # 600 to # 230/2.
When it is changed to 70, the dimensional accuracy of the abrasive grain layer shape changes from + 0 ° 15 ′ to + 0 ° 20 ′ at the position A, 0.005 mm to −0.008 mm at the position C, and +0.005 mm at the position D. From + 0.008mm
Was getting worse. The surface roughness of the abrasive layer is 22 μm
To 39 μm, which is about double. From this comparison, it was confirmed that the shape accuracy and the surface roughness of the abrasive layer were affected by the superabrasive mesh size.

Example 3 In Examples 1 and 2, the results of investigating the grinding performance with respect to the hard-to-machine material cemented carbide with respect to the resin bond composition capable of high-precision electrical discharge machining are shown below. As the grinding test method, three kinds of tests were performed: one that was electric discharge machined with a resin-bonded superabrasive wheel of the same composition, one that was sharpened with a WA grindstone, and one that was conspicuous with a WA wheel of a metal-bonded superabrasive wheel. . Detailed wheel specifications and compositions are shown in Tables 4 and 5. The electric discharge machining method and conditions were the same as in Example 1, but no shape was created in the abrasive grain layer because a grinding test was performed. Further, the volume ratio and mesh size of the superabrasive grains of the metal bond superabrasive grain wheel and the resin bond superabrasive grain wheel were the same. Table 6 shows the grinding test conditions.

[0035]

[Table 4]

[0036]

[Table 5]

[0037]

[Table 6]

In Tables 7 and 8, the above electric discharge machining wheels are W
The grinding ratio and work surface roughness were slightly better than those of the A grindstone setting. The metal-bonded super-abrasive wheel had the largest grinding ratio, but the test was canceled due to abnormal grinding noise. In addition, FIG. 4 shows the power consumption transition status. As shown in the figure, both the electric discharge machining wheel and the WA grinding stone dressing wheel show the same power consumption value.

[0039]

[Table 7]

[0040]

[Table 8]

Based on these results, the electric discharge machining wheel having a resin bond composition capable of high precision electric discharge machining has a grinding performance equal to or higher than that of the WA grinding stone dressing wheel, and is extremely difficult to machine with a metal bond such as cemented carbide. It was confirmed that it was possible to process the cutting material.

[0042]

EFFECT OF THE INVENTION (l) A resin-bonded superabrasive wheel having a complicated shape such as a concave shape and high precision can be manufactured at low cost.
Metal bond super-abrasive grain wheel makes it difficult to process carbide and hard-to-cut materials such as cermet.By using the resin bond super-abrasive grain wheel, it is possible to perform high-efficiency and high-precision machining. Become. (2) Since the dressing process is performed at the same time as the shape creation by the electric discharge machining, the dressing process is unnecessary, and the deterioration of the shape accuracy due to the dressing of the resin bond superabrasive wheel is eliminated. (3) In the general machining of the difficult-to-cut material of the resin-bonded superabrasive grain wheel, the shape retention of the abrasive grain layer is improved, and the interval of shape correction is increased accordingly, and the work efficiency is improved.

[Brief description of drawings]

FIG. 1 is a micrograph showing a particle structure of a metal powder used as a conductivity imparting substance.

FIG. 2 shows an outline of an applied electric discharge machine.

FIG. 3 shows a cross-sectional shape of a processed abrasive grain layer.

FIG. 4 shows a transition of power consumption required for electric discharge machining.

[Explanation of symbols]

1 Abrasive layer 2 Aluminum base 3
Holding machine 4 Graphite electrode

Claims (2)

[Claims] 1. Super-abrasive grains in a volume ratio of 1 in a resin bond.
Resin containing 5 to 60% of conductive material powder particles having an average particle diameter of 30 μm or less in a volume ratio of 10% or more enables highly accurate shape creation of an abrasive layer by electric discharge machining. Bond super abrasive wheel. 2. The resin-bonded superabrasive wheel according to claim 1, comprising a metal powder having a specific surface area of 1000 cm ² / g or more.