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What affects the life of a diamond grinding wheel?

It is said that the life of a diamond grinding wheel is superior to that of a conventional grinding wheel in terms of sharpness because diamond is used for the abrasive grains, but as long as it is a grinding wheel, it will be reduced by grinding and polishing.

The price of a diamond grinding wheel is more expensive than that of a conventional grinding wheel, so the "lifetime" of how long it can be used is an important point. Here, we will mainly describe the life of the type of diamond grinding wheel that is used by rotating.

Relationship between life and sharpness in diamond grinding wheel

When grinding and polishing a workpiece, the reason why it "cuts" with a grinding wheel and the "lifetime" are closely related. Grinding wheels, especially diamond grinding wheels, are roughly divided into "abrasive grains" and "bonds (binders, cementing matrix, bond materials)". Both are in the form of "powder" at the manufacturing stage, and these powders are molded and sintered to form a diamond grinding wheel.

The abrasive grains of diamond grind and polish the workpiece, but in order to "cut", the sharp diamond edge must come out from the surface of the grinding wheel.

Between the surface of the grinding wheel and the workpiece, in addition to the action of "the grinding wheel scrapes the workpiece" during grinding, the action of "the chips of the workpiece scrape the grinding wheel" also occurs. In order to keep the edge of the diamond abrasive grain always protruding from the surface of the grinding wheel, the bond material holding the abrasive grain must be properly scraped during grinding. It is also necessary to moderately crush the diamond itself (micro-crushing) to create a new sharp edge and replace it with the abrasive grains in the layer below the current abrasive grains.

A grinding wheel that can be cut generally has the characteristics that the bond material is soft, the grain size is coarse, which is also the size of the abrasive grains (cutting edge), and the abrasive grains are prone to micro-crushing. If the conditions are reversed, the life of the grinding wheel will be extended.

Parameters that affect the life of the grinding wheel

However, since the specifications of the grinding wheel and the grinding conditions are intricately intertwined to create the optimum sharpness and life, even if one element is changed, the sharpness may not be good and the grinding wheel may not have a long life. By looking at each combination of work, machining conditions, and grinding wheel specifications, you will find the best conditions for actual machining.

Factors that affect the life of the diamond grinding wheel [Specifications of the grinding wheel]

Abrasive grains

Diamonds and CBN also come in multiple grades and shapes, and each grade has different crushability (toughness) related to the degree of wear and sharpness.

Particle size

The coarser the particle size, the larger the chips, while cutting, and the more the grinding wheel wears. In the rough process, even changing the particle size in one step will significantly change the particle size.

Coupling

The hardness of the bond and the degree of bonding of the bond are also the holding forces that keep the abrasive grains. It is closely related to the phenomenon that the abrasive grains cause a moderate self-renewal action and regenerate.

Concentration

The amount of abrasive grains such as diamond. Depending on concentration, the load applied to one abrasive grain and the depth of cut of the abrasive grain also change.

Bond type

The life of the grinding wheel also changes depending on the properties of the bond material such as resin, metal, vitrified, and electroplated.

Factors that affect the life of the diamond grinding wheel [Grinding conditions]

Cutting depth

Most grinding conditions, too large or too small, cause inherent problems and may require fine tuning. In the case of the depth of cut in grinding, if it is too small, the abrasive grains protruding from the surface of the grinding wheel will not cut into the workpiece, and the surface will slip, leading to unnecessarily increasing the grinding heat. It also leads to the burning of the grinding wheel and the burning of the workpiece, and the sharpness of the grinding wheel decreases. On the other hand, if the amount of cut is too large, the damage to the grinding wheel will be great, and the abrasive grains will be uprooted and the cutting edges will be reduced at once.

Feed rate

The feed rate is similar to the above cutting depth, and if it is too fast, the load on the grinding wheel will be too high, leading to the falling of the abrasive grains and premature wear of the grinding wheel. On the other hand, if it is too slow, the abrasive grains will slide on the surface of the workpiece, which will cause the grinding wheel to burn or lose its sharpness due to heat.

Rotational speed (peripheral speed)

Increasing the peripheral speed increases the grinding heat, which may lead to wear of the abrasive grains. This mainly leads to a decrease in sharpness, but as a result, if the grinding wheel cannot cut, the number of dressings will increase and the life of the grinding wheel will also decrease.

Type and amount of grinding fluid

Grinding fluid and grinding oil have the effect of reducing the "grinding resistance" between the workpiece and the grinding wheel, and also reducing the grinding heat. Grinding oil and grinding liquid are sometimes called coolant, but this is the name when the viewpoint of cooling is taken into consideration. Since the life of the grinding wheel and the sharpness are closely related, it can be considered that the factors related to the sharpness are also related to the life. Grinding fluid is often seen mainly from the viewpoint of sharpness, but it is one of the factors that greatly affect the life of the grinding wheel in terms of reducing the wear of the abrasive grains and removing the grinding heat.