The dry powder stamper is a stamper and a press. The key to the stamper design is to consider the elastic expansion of the compact volume due to the relaxation of the internal stress after the pressure is removed or the film is removed. The three principles of stamping design are good mold size, small surface roughness and uniform density, so as to give full play to the process characteristics of powder metallurgy without cutting and less cutting. At the same time, it is necessary to reasonably select the mold material and the die structure and processing requirements.
The presses for dry powder stamping are divided into mechanical presses and hydraulic presses. Both types of presses can produce the same product. In theory, the required pressing energy is almost the same, but each has its own characteristics. The mechanical press has a high productivity of 1.5 to 5 times that of a hydraulic press.
There is internal friction between the powder particles and external friction between the powder particles and the wall of the die, resulting in uneven density distribution of the compact, which is manifested in the higher density of the part closer to the die pressing die when using unidirectional pressing (Fig. 1a). The density of the farther part is lower. When the height and diameter of the compact are large, the difference between the upper and lower densities is very large, and the same product can be produced by the two-way press. Theoretically, the required pressing energy is almost the same, but each has its own characteristics. The mechanical press has a high productivity and is 1.5 to 5 times that of the hydraulic press, which is not suitable for pressing large and long products.