Powder metallurgy press molding method is introduced?
With the development of powder metallurgy technology, the performance requirements of powder metallurgy products are also increasing, and a variety of different molding methods are produced. At present, the traditional pressing methods are: one-way pressing and two-way pressing. The pressing equipment is a hydraulic press (also calledpowder metallurgy press). The two-way pressing is divided into female mold floating pressing and female mold pull-down pressing.
Molding method:
1. One-way pressing One-way pressing Working principle: The positions of the female model cavity and the lower die punch are fixed. The upper die punch is driven by the press cam to enter the female model cavity downward, and pressurize the powder in the female model cavity, so that the powder is pressed into blanks with a certain density and strength.
One cycle of one-way pressing has the following steps: A powder filling: powder is fed manually or by a powder feeder, and the powder is filled in the cavity of the female model by gravity. B one-way pressing: after the powder is filled, the position of the female model cavity and the lower die punch is fixed, and the upper die punch is driven by the press cam to enter the female model cavity downward, so that the powder is pressed into blanks with a certain density and strength. C holding pressure: in order to effectively transmit the pressure and make the density distribution of the blank uniform, the upper die punch should be kept motionless for a period of time under the 180-degree forming and pressing position, so that the air in the blank has enough time to escape. D demoulding: after the pressure holding is completed, the upper die punch is driven upward from the female model cavity by the cam reset of the press, while the lower die punch pushes the blank out of the female model cavity under the action of the lower cylinder of the powder metallurgy press. E reset: the upper die is punched back to a high point, the powder feeder pushes out the pressed blank, while the lower die is punched back to a fixed position, and the powder is filled in the cavity of the female model under the action of gravity.
2. Two-way pressing Two-way pressing is generally divided into female mold floating pressing and female mold pull-down pressing. 2.1 female mold floating pressing female mold floating pressing working principle: the female mold is supported by a spring and is in a floating state, the lower mold is fixed, and the upper mold is driven by the cam to enter the female mold cavity downward to exert downward pressure on the powder. At the beginning of pressurization, because the friction between the powder and the cavity wall of the female model is less than the spring supporting force, only the upper die punch moves downward. As the pressure increases, the friction between the powder and the cavity wall of the female model is greater than the spring supporting force. When the spring supporting force is dry, the cavity of the female model moves downward together with the upper die punch, and moves relative to the lower die punch, thus achieving the effect of two-way pressing.
A cycle of negative die float pressing has the following steps. A loading: manually or by the automatic powder feeder powder evenly into the female model cavity. B upper punch and lower pressure: after the powder is filled, the female mold spring supports the lower mold punch position to be fixed. the upper mold punch is driven by the press cam to enter the female model cavity downward to apply downward pressure to the powder in the female model cavity. C female die floating: as the pressure exerted by the upper die punch increases, the friction force between the powder and the wall of the female model cavity also increases. when the friction force is greater than the spring support force of the dry female model cavity, the female model cavity and the upper die punch move downward together until the blank is formed.