Superior performance grinding wheels must have the characteristics of sharp grinding, good self-sharpening and high durability. The main considerations when manufacturing and selecting grinding wheels are binders, abrasives, grinding wheel concentration and grinding tool hardness.
1. Binder
Among the four binders of CBN grinding tools (resin, ceramic, metal, electroplating), CBN grinding tools with ceramic binders are the fastest growing. Worldwide, the proportion of ceramic CBN grinding tools has increased from 4% in the 1980s to more than 50% now, with a rapid growth rate. Since ceramic CBN abrasives have the advantages of high grinding efficiency, good shape retention, high durability, easy dressing, high abrasive utilization rate (more than 75%, other types of binders are 50-60%), and long grinding wheel service life, they have become the preferred abrasives for efficient and high-precision grinding. At present, all CBN grinding wheels used for camshaft grinding use ceramic binders.
2. Abrasive selection
In grinding, abrasives are the main body of abrasives, and their performance directly affects the grinding effect. Compared with corundum abrasives, CBN abrasives have higher hardness and strength, so they cut sharp and wear-resistant. In high-intensity grinding conditions such as camshaft processing, using CBN abrasives is the best choice. Different brands of CBN abrasives have different crystal forms and particle shapes due to different manufacturing processes, and each has different strength, thermal stability, chemical corrosion resistance and crushing characteristics. Different brands of abrasives should be selected according to the type of binder, grinding workpiece and grinding method. It should be pointed out that CBN abrasives are at high temperatures. It is easy to react chemically with water and alkaline oxides to destroy its structure. This is a factor that must be considered when selecting the type, pressure and flow rate of grinding fluid.
3. Concentration
The concentration of the grinding wheel indicates the number of abrasive grains participating in the grinding per unit area of the grinding wheel working surface during grinding. High concentration can bring a high grinding ratio. The life of the grinding wheel with a concentration of 200% is 45 times longer than that of the grinding wheel with a concentration of 100%. At present, high-speed and high-efficiency grinding adopts a higher grinding wheel concentration. For example, the concentration of the ceramic CBN grinding wheel equipped with the imported camshaft grinder is generally 200%.
4. Hardness
The hardness grade of the grinding tool indicates the holding force of the binder on the abrasive. It is an important indicator of the manufacturer's process control and the main parameter for users to select the performance of the grinding tool. The uniform and stable hardness of the grinding wheel and the reasonable selection of the hardness are important prerequisites for ensuring the grinding quality. Foreign ceramic CBN grinding wheels generally have 37 hardness grades to choose from. At present, there is no hardness inspection standard for CBN grinding wheels (including diamond grinding tools) in China. Manufacturers only control the formula hardness.
