TPA mold Pressing is what our company adopts in the production of cemented carbide. But why?
Pressing Principle:
The mixture is loaded into the mold cavity, and under the action of the pressure exerted by the press punch or other pressure-transmitting medium, the pressure penetrates the powder in the mold cavity, and the powder is displaced and deformed. The distance between them becomes smaller, mechanical meshing occurs between the powder particles, and the porosity is greatly reduced. At the same time, under the action of the molding agent, the mixture is compacted into a compact with a certain shape, size, density, and strength.
On the basis of ensuring that the press, mold, and compound meet the pressing requirements, effective means are used to control various influencing factors in the process, and finally, a compact with high precision size is obtained.
Due to the friction between the powder particles and the mold wall, the pressure is attenuated in the direction of the height of the green compact, causing the weight change per unit height of the green compact, which reflects the change in the density of the green compact.
Advantages of TPA Mold Pressing
Green compact density is a key factor affecting product quality. Practice has proved that the density of the green compact is not only affected by the powder composition and properties, compact shape, and mold surface quality but also mainly related to the characteristics of the powder body moving after being stressed during the pressing process: A, the difference between the powder body and the mold wall. The friction between the two will cause uneven distribution of the density of the compact; B, when the powder in the cavity is compressed, the powder body hardly moves laterally. The powder was aliquoted into five equal weight layers with metal foil and placed in a compression die, which was pressed in one direction and two directions, respectively.
It can be seen from the unidirectionally pressed compacts that the thickness and shape of each layer are different, and the average density of each layer decreases from top to bottom along the height direction, with the fifth layer being the lowest. There is a "neutral layer" in the compact. This layer of powder hardly moves during the pressing process and is the low-density part of the compact. During unidirectional pressing, the "neutral layer" is located in the lower layer of the green compact, and is only compressed in one direction on it, so the density distribution is very uneven. During bidirectional pressing, the "neutral layer" is in the middle of the green compact, and both sides are equally compressed, so the density is relatively uniform. The location of the "neutral layer" in the compact indicates the uniformity of the density distribution, which is clearly affected by the way of pressing.
The traditional hydraulic press (using a round steel die) is a one-way pressing, while the TPA press (using a TPA die) is a two-way pressing. It can be seen from the above that TPA mold pressing has obvious advantages. Therefore, in production practice, TPA molds have been widely used.
In our company's actual practices, different product molds are produced by our state-of-art CNC machining center. It is very important to specifically design the models of the product molds since each product has its unique shape and size. And in the next passage, we'll discuss the design of the mold of the carbide button for mining.
