The problems and preventive measures of layer formation when fine-grained abrasive tools are pressed Molding pressure is an important process factor, which affects the strength, hardness, porosity and distribution of the part. In general documents, hardness and porosity are regarded as synonymous, which does not exist in actual situations. The hardness is constant, the content of Al2O3 in the corundum is high, or the melting degree of corundum in the binder is small, the porosity will decrease. Fusible, small particle size, and high-boron binders all increase the hardness of soft products and reduce the porosity of hard products. High molding pressure increases the hardness, but there is a certain range. If the pressure is too high, the coarse particles will be crushed and the strength will decrease. Because there is no bonding agent on the newly created section If the hardness of the parts is the same but the material is different, the pressure of the parts of white corundum is high. Increasing the pressure can reduce the porosity and make it more dispersed. According to the compact packing of the same size sphere, the porosity rate of the products with single size and various size should be certain. But the actual particles are not spheres but are angular. The porosity varies with the pressure due to the damage of the edges and the movement of the contact surface. At the same time, the single particle size is actually a particle size range, but the relative size and proportion of the particle size range of various particle size are different, so the change of stomatal rate also occurs. Fine particle products are composed of fine particles, fine particles have a larger surface, particles contact more, so the hardness is higher. When the hardness is the same, the porosity is larger. The large contact surface also increases the forming pressure relatively. Large particles have larger pores, while fine particles have smaller pores. It is best to use mixed particle sizes for the abrasives for manufacturing high-density products, so that the proportion of different particles can be made into products with high packing density and low porosity. To manufacture products with low porosity, stricter control of the particle size range can be considered. Reasons for delamination of fine-grained products 1. Fast pressure during molding: The gas in the molding material does not escape, the two sides have been compacted and concentrated in the middle to form an air layer. After the external pressure is removed, the gas expands into a middle layer. 2. Elastic aftereffect: When the pressure is very high, the blank has a higher elasticity. The smaller the particle size, the closer the contact between the particles, and the smaller the change in this stress transfer. In the pressing, double-sided pressure is used, and the middle layer of the product is the weakest, the friction is different from the upper, the middle and the lower, and the elasticity is different, so layer cracks are generated under the action of elastic stress. 3. Water concentration: Moisture moves downwards from the pressure surface. Double-sided pressure causes moisture concentration in the middle and lower parts and lowers the strength. This also causes layer scraps. Even if no cracks appear after molding, cracks may occur during firing. Therefore, it is more reasonable if the board can be turned and dried during drying. 4. The die sleeve becomes larger when subjected to high pressure, When it is not pressurized, it shrinks, causing the middle layer to crack and bulge up and down. Fine-grained products almost inevitably produce layered waste under high pressure. Therefore, it is particularly necessary to avoid delamination and find a new molding method. Avoidance measures 1. Slowly pressurize to make the gas escape fully. 2. It is added to the specified pressure and maintained for a certain time, so that the molding material can be fully moved, so that the density is uniform, the strength is uniform, and the elastic stress is relaxed, and the stress aftereffect is eliminated. 3. Use vacuum forming. Or use vibration, pressure reduction and other methods. 4. Using pouring or plastic molding. 5. When forming semi-dry material, reduce pressure and increase maintenance time. 6. Use dry materials for molding, use adhesive as the binder, and after the combination is loosened, the particle surface is covered with a layer of glue film. Under normal circumstances, the particles will not be agglomerated in contact with each other, but when pressure is applied, the film and the film are in close contact and cemented. Or use a thermoplastic material to form a wrapper film, and then shape it. Hot air is introduced during the molding process to produce plastic cementation such as paraffin wax and asphalt. Dry material molding can make the non-mechanical weighing process adopt fixed-volume weighing. The dry material is easy to disperse, has good fluidity, and is also beneficial to eliminate imbalance.