With the continuous emergence of new materials and new technologies, and the technological progress of the processing industry, for large-volume, high-precision grinding, the hardness of the processed parts is greater than HRC45, and CBN grinding wheels are basically selected for grinding. However, the CBN grinding wheel needs to be trimmed after a period of use. Since CBN is currently the superhard material second only to diamond, general tools cannot be trimmed. At this time, the emergence of CVD Diamond dressing wheel makes the CBN grinding wheel well trimmed. And to make it widely used in various industries, the following is a brief introduction to the classification of CBN grinding wheels and CVD Diamond dressing wheel, and how CVD Diamond dressing wheel dress CBN grinding wheels.

1. Classification of CBN grinding wheels

CBN grinding wheel is made of CBN (cubic boron nitride) abrasive as raw material, and metal powder, resin powder, ceramics and electroplated metal are used as binders to make products of various shapes, which are used for grinding and grinding tools, called For CBN grinding wheel. CBN grinding wheels are divided into four categories, namely electroplated CBN grinding wheels, sintered CBN grinding wheels, resin CBN grinding wheels and vitrified bond CBN grinding wheels.

Electroplated CBN grinding wheel: The molding process of the grinding wheel is simple and the production cost is low. The molding is simple but there is only one layer of coating, which cannot be corrected. During the processing, it is difficult to know when the wear layer is damaged. It is suitable for small-batch machining and complex geometric shape grinding and as a dressing roller.

Sintered CBN grinding wheel: high hardness and high density, processed into a high-precision dressing roller, the cost is high. It is mainly used for dressing rollers of grinding wheels and processing of large quantities of superhard materials.

Resin CBN grinding wheel: The production process of the grinding wheel is simple and the production cost is low. The molding is simple but not easy to correct and shape. It is used for the processing of multi-shape and small batches.

Vitrified bonded CBN grinding wheel: The vitrified bonded CBN grinding wheel has the advantages of strong grinding force, high-speed processing without burning the workpiece, correctable and durable, and is currently the most ideal high-speed, high-efficiency and high-precision grinding tool

2. Application of CBN grinding wheel

With the continuous emergence of new materials and new technologies, and with the technological progress of the processing industry, the application range of CBN grinding wheels continues to expand, and the consumption continues to increase. In developed industrial countries, for large-volume, high-precision grinding, the hardness of the workpiece is greater than HRC45, and ceramic CBN grinding wheels are basically used for grinding. It is widely used in the main parts of automobiles, such as camshafts, crankshafts, gear shafts and gears of gearboxes, bearings and brake pads. Used in precision machined parts of machine tools, such as grinding of guide rails, lead screws and motor shafts, and printing machine parts. At the same time, for some difficult-to-machine materials and some tough materials (stainless steel, titanium alloy, etc.), CBN grinding wheels are ideal for grinding processes. CBN grinding wheels are also used in rolls, aviation, aerospace and military industries.

3. Classification of diamond dressing wheel

diamond dressing wheel are divided into HNT electroplated diamond dressing wheel (as shown in Figure 1), HNT sintered diamond dressing wheel (as shown in Figure 2) and CVD diamond dressing wheel, of which HNT electroplated diamond dressing wheel and HNT sintered diamond dressing wheel are mainly used for dressing resin and ceramic grinding wheels, CVD diamond dressing wheel are mainly used for dressing high hardness CBN grinding wheels. The domestic market mainly uses HNT sintered diamond dressing wheel, which have longer service life and more stable grinding, while overseas mainly use electroplated diamond dressing wheel.

The manufacturing process of HNT sintered diamond dressing wheel is as follows: process a mold according to the requirements of the drawings, then artificially implant large-grain diamonds into the mold according to a certain density in an orderly manner, and then use sintering furnace and powder metallurgy technology to sinter, and then Remove the mold, process the hole and the end face with the diamond profile as the benchmark, and then dress the grinding wheel on the grinding machine, calculate the appropriate dressing allowance, and go through repeated grinding and testing on the professional grinding machine until it conforms to the finished product drawing Require.

The production process of the HNT electroplating method is: according to the technical requirements of the produced part section, a mold is made, the artificial diamond is electroplated, the steel core is bonded with a binder (low melting point alloy), and the abrasive tool is removed by gold cutting (reference conversion) Carcass, so that the diamond is evenly exposed, the grinding wheel is trimmed on the grinding machine, a workpiece is replicated, and all technical requirements of the workpiece surface are measured in the testing center, and the finished product is qualified.

4. Application of CVD diamond dressing wheel

CVD diamond dressing wheel are mainly used for dressing CBN grinding wheels. CBN grinding wheels are currently the hardest grinding wheel. If you want to dress them, you can only choose materials harder than CBN. In the early days, diamond pens were mainly used to dress them, which belongs to the original dressing process. , With the emergence of CVD diamond dressing wheel, castings replace diamond pens to dress CBN grinding wheels.

CVD (Chemical Vapor Deposition) diamond is a mixture of carbon-containing gas and hydrogen that is excited and decomposed at high temperature and pressure below standard atmospheric pressure to form active diamond carbon atoms, and deposit inter-growth polycrystalline diamond on the substrate . Since CVD diamond does not contain any metal catalyst, its thermal stability is close to that of natural diamond, and it is an ideal tool for dressing CBN grinding wheels.

5. Mechanism of dressing CBN grinding wheel with CVD diamond dressing wheel

The dressing mechanism is to realize the grinding wheel shaping through the relative motion generated between the diamond dressing wheel and the rotary motion of the CBN grinding wheel. Dressing feed ar and dressing speed ratio q (q=vr/vs, vr is the linear speed of diamond dressing wheel, vs is the linear speed of CBN grinding wheel) have an important influence on the grinding performance of the dressed CBN grinding wheel. The larger dressing speed ratio q = the trimmed CBN grinding wheel has less grinding force, but the surface roughness of the workpiece is larger. The grinding wheel is sharper after dressing with a larger dressing feed ar. S.Malkin  et al believe that the dressing mechanism of the diamond dressing wheel shaping method and the grinding performance of the dressing wheel are mainly controlled by the angle (interference angle d) between the abrasive grain trajectory of the CBN grinding wheel and the diamond abrasive trajectory (interference angle d). , the dressing force is smaller, but the surface of the grinding wheel after dressing is rougher. The selection range of the medium speed ratio is q=0.4～0.7. The speed ratio q<-1.0 should be selected for precision grinding. The specific value should be determined according to the grinding roughness requirements and the characteristics of the grinding wheel. For example, it can be used when grinding precision zirconia parts. Speed ratio q<-1.0  Dressing CBN ceramic grinding wheel, so that lower roughness (Ra=0.06µm) and higher roundness (0.6µm) can be obtained.