Resin Bond Diamond And CBN Grinding Wheels

1. Introduction of Resin Bond Diamond And CBN Grinding Wheels

Resin bonded superhard material tools are mainly made of Diamond or CBN as abrasive, tree fat powder as adhesive, adding appropriate filling materials, through the process of formula design, weighing mixing, hot pressing, secondary curing, follow-up processing and other processes, which are suitable for different grinding requirements of superhard tools. Compared with ceramic binder or metal binder superhard abrasives, it has the characteristics of simple manufacturing process, easy access to raw materials, low cost, and can be widely applied to low-quality superhard abrasives, and a wide range of processing objects, such as a variety of difficult to process steel, cemented carbide, glass, ceramics, stone and so on. Because the resin superhard grinding tool has good self-sharpness in the grinding process, it is not easy to plug, the grinding workpiece has good surface quality, and the grinding wheel is easy to dress.

The resin binder used in resin diamond tools is mainly divided into phenolic resin and polyimide resin two categories, the actual working temperature of phenolic resin diamond tools does not exceed 120 ° C, polyimide resin heat resistance is slightly better, can be used at 260 ° C for a long time. Because the price of polyimide resin is relatively expensive, especially in recent years, scientists have modified the phenolic resin so that its actual working temperature can reach more than 200℃.

2.Purpose of different shape:

Parallel grinding wheel: mainly used for cylindrical grinding of cemented carbide and blade processing

Parallel belt arc grinding wheel: mainly used for carbide forming grinding and circular arc surface forming grinding

Double-sided concave grinding wheel: mainly used for grinding measuring tools and coreless grinding machines

Double bevelled grinding wheel: mainly used for carbide gear hob, thread cutter forming grinding

Bowl wheel: mainly used for carbide cutting tools, high-speed steel cutting tools grinding, can also be used for milling.

3.The influence of abrasive diamond mainly includes the influence of diamond plating, type and particle size.

3-1 After the diamond surface is coated with metal, the single particle compressive strength is increased, and the wear ratio is reduced, that is, the service life is extended. Compared with uncoated diamond, the specific effect also includes the following aspects:

3-1-1 the coating slows down the thermal pulse of the resin bond, the thermal conductivity of the diamond coating is smaller than that of the diamond, so when the diamond abrasive touches the tool, the instantaneous high temperature generated by the coating is transmitted to the resin, thus protecting the resin immediately connected to the abrasive part from high temperature damage; 

3-2-2 The coating improves the bonding strength of diamond and binder, the metal coating contains diamond inside, and the external bond with the resin binder can be well bonded; 

3-3-3 The coating improves the crushing strength of diamond particles, the defects of diamond particles are compensated after metal-plated, and the coating contains ductile metal, which is conducive to improving the crushing strength of particles; 

3-3-4 The coating has an isolated protective effect on the wear particles, isolating the role of external oxygen and other harmful media, and at the same time, at high grinding temperature, the coating can inhibit the graphitization of diamond crystals.

3-2 Superhard material manufacturers at home and abroad have carried out a more detailed classification of superhard abrasives, of which low-quality diamond abrasives or diamond abrasives with high self-sharpness and micro-crushing treated by special processes are mainly used for the preparation of resin binder diamond tools. Such as E6 company provides PDA433, PDA321, PDA311, PDA211 and other grades of diamond, with high self-sharpness and micro-crushing. At present, RVD type diamond abrasive is widely used in resin molds in China. Its particles are mostly needle flake, irregular crystal shape, low strength, large brittleness, rough surface but sharp grinding, and good combination with resin binder. In recent years, polycrystalline CSD diamond abrasives developed in China have been used in resin bonding abrasives, which significantly improve the sharpness of resin diamond tools.

4.Effect of dressing on resin-bonded diamond / cbn grinding wheel

The dressing process is an indispensable factor in the preparation of grinding wheel. Resin diamond grinding wheels of various shapes can be obtained through dressing, and the surface of resin bonded diamond grinding wheel can be edged out through grinding wheel sharpening. Proper dressing processing directly affects the performance of grinding wheel. White corundum, silicon carbide, boron carbide, molybdenum, ferro molybdenum alloy and other methods can be used to dress the grinding wheel, the selection of dressing technology suitable for practical application will help to improve the performance of resin diamond grinding wheel

5.How to choose and use resin diamond grinding wheel

Resin diamond / cbn grinding wheel is widely used to process high hardness materials. When choosing to use resin diamond grinding wheel, the following points should be noted:

5-1 Performance match between abrasives, bonded and workpieces: Whether the performance of abrasives is excellent depends largely on whether the performance of abrasives, binders and workpieces are matched or not.   For specific processing objects, after the selection of abrasives, the choice of binder formulation is particularly critical.

At present, resin grinding wheels are mainly used for grinding thermal spray materials.   Because this grinding wheel has the characteristics of good self-sharpness, not easy to plug, high grinding efficiency, low surface roughness value of the workpiece, low grinding temperature, easy dressing, etc., it has a wide range of applications.

5-2 Selection of grinding wheel granularity: the lower the general surface roughness requirements, the finer the granularity.   In the process of processing, the grinding wheel level should be reasonably selected according to the grinding allowance.   When the grinding wheel size is less than W20, the cleanliness of the grinding environment is required to prevent process pollution from affecting the surface roughness Ra value of the machined workpiece.

5-3 Concentration selection: concentration is a special technical term for superhard grinding wheel, that is, the content of diamond or CBN per unit volume in the working layer of the grinding wheel;   Generally, the grinding wheel concentration of resin bond is 75-100.   If the concentration is increased, it is meaningless, because the holding power of the resin binder itself is weak;

5-4 Selection of grinding system parameters: Grinding system includes grinding machine equipment, grinding wheel, process parameters, etc.   The stiffness of the main shaft, the shockproof measures, the inherent performance of the grinding wheel, the balance and the machining accuracy all have an influence on the selection of grinding parameters.   Grinding parameters include grinding speed (grinding wheel line speed, working reciprocating feed speed),Feed speed, etc.   It should be selected and adjusted according to the grinding allowance of the workpiece, the grinding method and the specific conditions of the grinder.

5-5 Selection of grinding fluid: The purpose of using grinding fluid is to quickly derive the grinding heat generated in the grinding process and wash away the grinding debris in time.  There are many kinds of grinding fluids, which should be reasonably selected according to the type of workpiece materials and processing characteristics.

6. Drawing and Grit size