Factors Affecting The Performance Of Resin-bonded Diamond Tools

Resin diamond tools are made of resin binders, fillers and diamond abrasives mixed and then cured by hot pressing. Its performance is also directly affected by resin binders, fillers and diamond abrasives.

1 The influence of binders mainly includes the influence of binder type and content, etc.

(1) The common feature of all kinds of resin bonded diamond tools is poor heat resistance. During the process of processing work piece, the heat generated between the diamond tools and the workpiece is easy to cause the local temperature to be too high. Once the critical value is reached, the control of the resin bonded diamond will be ineffective, and the diamond will fall off without full grinding and bluntness, thus greatly increasing the processing cost. At present, the main way to improve the heat resistance is to modify the resin binder. Gao Liangxuan [3] Modified phenolic resin with square alkyl ether, its heat resistance can reach over 180C. Du Yang et al. [4] A new borosilicate-containing phenolic resin BSP was synthesized from organosilicon prepolymer, boric acid, phenol and formaldehyde. Due to the introduction of B-O bond and organic silicon chain in the structure of phenolic resin, BSP resin has excellent heat resistance and toughness, and also improves the water resistance and storage stability of the resin. Xiao Dongzheng et al. [5] modified phenolic resin with BMI (bismaleimide) obtained phenolic resin with good heat resistance.
(2) The influence of resin binder content. The resin binder content has a great influence on the processing performance of diamond tools. Literature [24] introduced that in the single crystal silicon wafer thin grinding wheel, the content of resin binder increases, the hardness and compressive strength of the grinding wheel increases gradually. When the content of resin binder increases to a certain extent, the increase of grinding wheel wear ratio tends to be slow. At the same time, the surface of grinding wheel is prone to blockage. The higher the content, the more serious the blockage is.
(3) The influence of particle size of resin binder. Resin powder produced in China as diamond abrasives mostly has particle size between 80 and 180 mesh. There are two defects in this grain size range, one is that it affects the compaction formability of abrasives, the other is that it may affect the properties of binders. During pressing, although the resin powder can be softened by heat and has certain fluidity to achieve the purpose of coating abrasive particles, during pressing, the binder is pressed in the die with limited space and the flow range of the resin is limited. When the particle size of the resin powder is coarse, some abrasive bonds are not strong and fall off too quickly. Some studies have shown that when the resin granularity is refined, it can improve the fluidity of the forming material and facilitate the hot-pressing of the abrasive tool.

2 The influence of filler mainly includes the effect of filler type and content, etc.

Filler is an important part of diamond grinding tool. Adding proper amount of filler can not only reduce cost greatly, but also improve mechanical strength and extend service life of the grinding tool.
(1) There are many kinds of fillers, and different kinds of fillers have different effects on abrasive tools. It can be divided into four categories according to its nature and use:
1. Inactive filler. Used in plasticizable processes to reduce abrasive cost;
(2) Active filler. The plasticizing and adsorbing effect enhances the bonding ability of abrasive particles and binders.
3. Reinforcement filler. For example, glass fibers, carbon fibers, etc., with the aim of increasing the strength of the binder;
4. Reduce the strength of the binder filler. Make grinding tools suitable for finishing tools.
In the resin abrasive tools of super hard material, its function is mainly to improve the heat resistance, hardness and strength of the binder, with the ultimate purpose of improving its durability. There are many kinds of fillers. For diamond resin abrasives and phenolic resin binders, Cr2O3, ZnO and Cu powder are common fillers in China. In addition to Cu powder, fillers for polyimide binder are used abroad for dry grinding with Zr, Co, CaCO3, etc. and for wet grinding with ceramic materials such as SiO2 and Al2O3.

3 The influence of abrasive diamond mainly includes the influence of diamond coating, type and grain size.

(1) After the diamond surface is coated with metal, the compressive strength of single particle is increased and the wear ratio is reduced, which means the service life is prolonged. Compared with non-coated diamond, the specific functions include the following aspects: 1) the coating slows down the thermal pulse to the resin binder and the thermal conductivity of the diamond coating is smaller than that of the diamond, so the instantaneous high temperature generated when the diamond abrasive contacts the tool is transferred to the resin after the coating, thus protecting the resin close to the abrasive from high temperature damage; 2. The plating improves the bonding strength between diamond and binder; the metal plating is coated with diamond in the inner layer and the outer layer bonds well with the resin binder; 3. The plating improves the crushing strength of diamond particles, and the defects of diamond particles are compensated after metal plating, which plays a reinforcing role. Moreover, the plating contains tough metals, which is conducive to improving the crushing strength of diamond particles; The plating acts as an isolation and protection against abrasive particles, oxygen and other harmful media. At the same time, at high grinding temperature, the plating can inhibit the graphitization of diamond crystals.
(2) Ultra-hard abrasives are classified in detail by domestic and foreign super-hard material manufacturers, in which low-quality diamond abrasives or diamond abrasives with high self-sharpness and micro-breakability treated by special processes are mainly used for the preparation of resin-bonded diamond tools. For example, the diamonds of PDA433, PDA321, PDA311 and PDA211 brands provided by E6 Company have high self-sharpness and micro-breakability. At present, RVD diamond abrasive is widely used in domestic resin molds, with needle-like particles, irregular crystal shape, low strength, brittleness, rough surface but sharp grinding, and good combination with resin binder. In recent years, polycrystalline CSD diamond abrasive has been developed in China for resin bonded abrasive tools, which significantly improves the sharpness of resin diamond tools.

4 Effect of finishing on resin bonded diamond grinding wheel

The dressing process is an indispensable factor in the preparation of grinding wheels. Resin diamond grinding wheels of various shapes can be obtained through dressing. Resin bonded diamond grinding wheel surface diamond is cut by grinding wheel sharpening. Proper dressing directly affects the service performance of grinding wheel. Zou Dacheng designed a new resin-bonded diamond wheel dressing method, and carried out wheel dressing experiments with white corundum, silicon carbide, boron carbide, molybdenum and ferromolybdenum alloys. By comparing and analyzing the dressing force, surface morphology accuracy, wheel sharpening effect and grinding performance of each method, the dressing effects of different dressing methods on resin-bonded diamond wheel were compared. Choosing a suitable repair technology for practical application will help to improve the service performance of resin diamond grinding wheels.