JPS6211989B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a dressing method for a resinoid grindstone. Resinoid grinding wheels, which use thermosetting synthetic resin as the binder for the abrasive grains, are trued (reshaped) to give the outer surface of the grinding wheel a predetermined shape before starting the grinding process. As shown, abrasive grains 11 on the outer surface of resinoid grinding wheel 13
- 11 are buried inside the binder 12 and have few protruding parts, making it difficult to act as a cutting edge suitable for grinding. However, trued resinoid grinding wheels are usually used for grinding with few protruding parts where the abrasive grains are buried on the outer surface, and as the abrasive grains protrude while being used, the grinding performance improves, but in the initial stage of use It has a bad flaw. After truing, the resinoid grinding wheel with embedded abrasive grains may be dressed (retouched) to make the abrasive grains protrude as necessary, but conventional processing operations are troublesome, and the abrasive grains are It is difficult to adjust the amount of protrusion, and depending on the type of abrasive grains, the abrasive grains may not easily protrude. Additionally, since resinoid grindstones generally have elasticity, they have the disadvantage of lowering the machining accuracy of the material to be ground. Therefore, in order to improve machining accuracy, it is necessary to use a grinding wheel with low porosity and high hardness, but it has been difficult to apply conventional dressing methods to such a grinding wheel with low porosity. Furthermore, since the binder of the resinoid grindstone is organic, the binder is carbonized by the heat generated during dressing, resulting in a reduction in the holding power of the abrasive grains. On the other hand, resinoid whetstones have the advantage of being softer against the workpiece during grinding and have greater impact resistance, compared to whetstones that use an inorganic binder such as vitrified whetstones, but do not have the above-mentioned drawbacks. Despite this, demand has been increasing recently.
Therefore, in view of the high demand for resinoid grindstones, the present inventors tried to eliminate the above-mentioned drawbacks, and as a result of research, they obtained good results and completed the present invention. That is, an object of the present invention is to provide a dressing method for a resinoid grindstone that allows abrasive grains buried in a binder to easily protrude during truing, thereby improving the grindability of the resinoid grindstone.
Another object of the present invention is to use
To provide a dressing method capable of efficiently dressing a resinoid grindstone without truing. The present invention is a method for dressing the outer surface of a resinoid grindstone using a flexible abrasive material formed by bonding abrasive grains with an organic binder. As the abrasive grains for dressing, abrasive grains normally used for resinoid grindstones, such as alumina and silicon carbide, can be used. The size of the abrasive grains for dressing is suitably the same as the abrasive grains of the resinoid abrasive wheel to be dressed, or 2 to 3 grades larger. If the size of the abrasive grains for dressing is too small or too large, the efficiency of dressing will deteriorate. As the organic binder, materials such as foamed polyurethane, soft synthetic resin such as PVA resin, rubber, and shellac can be used. The ratio of organic binder to abrasive grains in flexible abrasive materials varies depending on the type of organic binder, the type of abrasive grains, and the grain size. It is formed by mixing 70-80 parts by weight of PVA resin with 30-20 parts by weight of PVA resin and firing the mixture. The shape of the flexible base material is not limited to a three-dimensional shape such as a disk or a rectangular parallelepiped, but may also be a flat shape such as a belt shape, circle, or rectangle. The flexible abrasive material having the following configuration can be used. That is, for example, (a) a flexible bond in which abrasive grains are distributed three-dimensionally, such as in a grinding wheel for dressing, and bonded and supported by an organic binder such as rubber, ceramic, synthetic fiber, or foamed polyurethane. abrasive materials, (b) coated abrasive materials in which abrasive grains are two-dimensionally distributed and bonded to a flexible substrate, such as coated abrasive paper, abrasive belts, or (c)
A flexible material such as a buff made of cloth, leather, etc. can be used. The flexible base material is paper,
Flexible materials such as cloth, leather, and rubber are suitable. The flexible abrasive material is formed by adhering a predetermined amount of dressing abrasive grains to a flexible base material of a predetermined size using an organic binder. In addition, when using these, a resinoid grindstone whose size of abrasive grains is equal to or several grades larger than that of the resinoid grindstone to be used for dressing is selected and used. By bringing the grinding surface of the flexible abrasive material into contact with the outer surface of the resinoid grinding wheel that has been trued, and then grinding and dressing the outer surface of the resinoid grinding wheel, the abrasive grains of the resinoid grinding wheel are not damaged and the abrasive Intergranular binder (thermosetting synthetic resin)
can be effectively controlled and removed. In this way, as shown in FIG. 1, a resinoid grindstone 3 is obtained in which the abrasive grains 1 to 1 on the outer surface sharply protrude outward from the bonding agent 2 surface. This resinoid whetstone 3
exhibits high precision grinding performance even in the early stages of grinding. Since the present invention is a method of dressing the outer surface of a resinoid grinding wheel with a flexible abrasive material to make the abrasive grains on the outer surface of the resinoid grinding wheel protrude, it is not limited to true-dressed resinoid grinding wheels. It can be easily applied to resinoid grinding wheels that do not have truing.
The abrasive grains on the outer surface can be made to protrude sharply. In addition, resinoid grinding wheels for grinding are usually
A high porosity grinding wheel containing about 30 to 40% micropores in the binder is used, but because solenoid grinding wheels generally have elasticity, they have the disadvantage of lowering the machining accuracy of the workpiece. However, in order to improve the machining accuracy, it is necessary to use a grinding wheel with low porosity and high hardness. It has been difficult to apply conventional dressing methods to grinding wheels with such low porosity. According to the present invention, even those with a porosity of about 10% or less (10 to 0%) can be easily dressed, so a resinoid grindstone with a low porosity, which has not been used in the past, can be used for precision grinding. . Furthermore, the resinoid grindstone generates heat due to contact between the grindstone and the workpiece during grinding, but at this time, the organic binder is carbonized and the holding power of the abrasive grains is reduced. Therefore, by mixing highly thermally conductive metal powder such as Al, Cu, or Ni, or carbon powder into the binder, it is possible to dissipate frictional heat, prevent carbonization, and improve grindability and durability. That is, metal powder or carbon powder having high thermal conductivity can be appropriately mixed into the binder in an amount of about 5 to 40% by volume based on the binder. The metal powder or carbon powder used has a diameter of 100 microns or less, which is smaller than the abrasive grains of the whetstone, since it does not adversely affect the grindability of the whetstone. Resinoid grindstones mixed with highly thermally conductive metal powder or carbon powder do not accumulate heat near the abrasive cutting edge during grinding, are less likely to carbonize the binder, and do not reduce abrasive retention.
On the other hand, the workpiece that is ground with this resinoid grindstone has the advantage of being less susceptible to thermal damage such as grinding burns and cracks. Next, an experimental example of the present invention will be explained. Experimental example 1 According to the display standard for grinding wheels, the resinoid grinding wheel of GA80X7B, that is, the alumina abrasive grain (GA)
A circular whetstone made of 80 mesh bonded with phenolic resin (outer diameter 405 mm, thickness 25 mm, center hole diameter
152.4mm) Prepare two sheets of A1 and B1. And the whetstone
Both A1 and B1 have an abrasive grain rate of 49% and a porosity of 5.
%, and truing was similarly performed using a diamond tool. Next, alumina abrasive grains (WA80) of the same size as the abrasive grains of whetstone B1 were bonded to whetstone B1 using PVA resin, and the bonded portion was dressed with a grinding wheel having flexibility to make the abrasive grains protrude. Next, use the grindstone A1 or B1 to grind to an outer diameter of 90 mm thickness.
A 10mm circular high-speed steel (hardness H _R C 62) was cut at a grinding wheel circumferential speed of 2500m/min. and a cutting speed of 0.5mm/min.
Grinding was carried out under conditions of min. The results of measuring the grinding resistance, which represents the grindstone shaft resistance during grinding in terms of power consumption, and the roundness of the high-speed steel after grinding are shown in Table 1 below.

[Table] From Table 1, whetstone B1, which corresponds to the whetstone treated by the method of the present invention, is whetstone A1, which is treated by the conventional treatment method.
It can be seen that the sharpness and finishing accuracy of the whetstone are superior compared to the above. Experimental Example 2 Resinoid grinding wheels A2 and B2 having the specifications, abrasive grain ratio, and porosity shown in Table 2 below were prepared, and truing was performed on both grinding wheels A2 and B2 using a diamond tool. And the whetstone B2 is a whetstone.
Alumina abrasive grains of the same size as the B2 abrasive grains were bonded with PVA resin, and the bonded portion was dressed with a flexible grinding wheel to make the abrasive grains protrude.

[Table] The sizes of grinding wheels A2 and B2 are both the outer diameter.
It is 405mm thick, 25mm thick, and has a center hole diameter of 152.4mm. Next, a bearing steel (hardness H _R C62) with an outer diameter of 50 mm and a thickness of 20 mm was prepared using the grinding wheel A2 or B2 under conditions of a grinding wheel circumferential speed of 2500 m/min, a cutting speed of 2 mm/min, and a spark out of 2 sec. Each was ground. The amount of uncut portion of the bearing steel was smaller with grinding wheel B2, which was closer to the set dimensions, and the finishing accuracy was higher.

[Table] Experimental Example 3 Prepare resinoid grinding wheels A3 and B3 having the specifications, abrasive grain ratio, and porosity shown in Table 4 below, and
Both A3 and B3 were trued using a diamond tool. Grinding wheel B3 has 100~ in the binder.
200 mesh Al powder is mixed in at 20% of the binder, and 36 mesh alumina abrasive grains are mixed in.
They were bonded using PVA resin and the bonded portion was dressed with a flexible grinding wheel to make the abrasive grains protrude.

[Table] Note that the abrasive grains A3 and B3 were of the same size as in Example 2 above. However, the outer diameter is 50mm
A circular cast iron (hardness H _R C30) with a thickness of 20 mm was ground using the grinding wheel A3 or B3 at a circumferential speed of 2500 m/s.
Grinding was performed at a cutting speed of 6 mm/min. The results of this grinding were as shown in Table 5.

[Table] The grinding ratio in the table is (grinding volume of workpiece)/(wearing volume of grindstone).
As can be seen from Table 5, grindstone B3 has a higher grinding ratio than grindstone A3, and has greater durability. Additionally, grindstone B3 has the advantage of not causing grinding burn on cast iron.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the state of abrasive grains on the outer surface of a resinoid grindstone when treated by the method of the present invention;
FIG. 2 is an explanatory diagram showing the state of the abrasive grains on the outer surface of the resinoid grindstone when only truing is performed. 1,11...abrasive grain, 2,12...binder, 3,
13...Resinoid whetstone.

Claims (1)

[Claims] 1. When dressing a resinoid grindstone in which abrasive grains such as alumina are bonded with a thermosetting synthetic resin, the size of the abrasive grains is approximately equal to or several grades larger than that of the dressing resinoid grindstone. A method for dressing a resinoid grindstone, characterized in that the grinding surface portion of the resinoid grindstone is ground with a flexible abrasive material made by bonding abrasive grains for dressing with an organic binder such as a synthetic resin. 2 The resinoid grinding wheel contains about 10% (by volume) of the grinding wheel in its binder, which is a thermosetting synthetic resin.
The method for dressing a resinoid grindstone according to claim 1, wherein the resinoid grindstone contains micropores in the following amounts: 3 The resinoid grinding wheel contains about 5 to 40% (by volume) of the binder in the thermosetting synthetic resin that is the binder.
2. A method for dressing a resinoid grindstone according to claim 1, wherein the resinoid grindstone is mixed with a quantity of a highly thermally conductive metal powder such as Al. 4 The resinoid grinding wheel contains about 5 to 40% (by volume) of the binder in the thermosetting synthetic resin that is the binder.
A dressing method for a resinoid grindstone according to claim 1, wherein a certain amount of C powder is mixed therein.