Compression Principle: Compression Principle of Cold Compression Molding of Metal Diamond Grinding Wheel: Powder particles of moulding material displace and deform under the action of pressing pressure, contact area increases and pore decreases, thus forming a green body with a certain geometry, size, density and strength. In the process of compaction, a series of changes will take place in the density of green body.

With the increase of forming pressure, the change of green body density can be roughly divided into three stages.

Stage 1: With the increase of forming pressure, the density of green body increases rapidly. At this stage, the metal powder particles are displaced in the direction that is beneficial to them under the forming pressure, filling the voids, and the displacement phenomenon is obvious.

Stage 2: With the increase of forming pressure, the density of green body increases slightly. At this stage, the density of the green body has reached a certain value, the pressure continues to increase, the displacement of the powder particles decreases, and the compressive resistance in the powder body occurs, but the deformation has not yet begun.

Stage 3: With the increase of forming pressure, the density of green body continues to increase. At this stage, the forming pressure exceeds the critical pressure of the powder particles, and the powder particles begin to undergo elastic deformation, plastic deformation, brittle fracture and other phenomena, so that the density of the green body continues to increase. However, when the moulding pressure increases to a certain extent, and then continues to increase the pressure, the friction force of powder particles on the die increases, and the grinding wheel body density also reaches a certain value, which will produce a great compression phenomenon, the density will no longer change significantly, in a gentle state.

The compaction process has an important influence on the density of green body. High density and uniform green body requires high surface finish, high hardness and rigidity of moulding die; bi-directional pressing has higher density and uniformity than unidirectional pressing; low-speed pressing and long holding time are conducive to improving density and uniformity of green body.

A series of changes will also take place in the strength of the green body during the pressing process. There are mechanical meshing forces between the powder particles in the grinding wheel body and the gravitational force between the atoms on the powder surface, which make the grinding wheel body have certain strength. In the process of grinding wheel forming and pressing, with the increase of pressure, the porosity between powder particles decreases and the green body becomes denser gradually. Because of the displacement and deformation of powder particles, the interconnection between particles is strengthened and the mechanical meshing effect is strengthened. Moreover, due to the increase of pressure, when the powder particles are close to each other and the surface atoms enter the gravitational range, the interconnection effect will also be strengthened. The strength of green body has been improved continuously.

Powder properties have an important influence on compacting properties. Powder with high hardness, small plasticity and high friction has poor compacting performance; powder with low purity and high oxygen content has poor compacting performance; powder with single particle size and regular shape has poor compacting performance. In practical application, the compacting properties of green bodies can be improved by adding forming agent or lubricant, reducing raw materials, using coarse and fine powder mixtures and powder with complex particle shapes.