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Condition and parameter control of dry pressure bullet-proof die in dry press forming process

Oct 16, 2017

There are many methods of forming the product, which is made by dry pressing process, although the whole process is relatively simple operation, but also need to use a special dry pressure bullet-proof die, and need to control a variety of technical parameters, so as to ensure that Product molding quality to meet the standard.


Dry pressure bullet-proof die is used to directly load the powder into the mold, and then apply a certain force to its compression, the force applied to the dry pressure bullet-proof die is usually a one-way pressure, so blank gap Of the gas will be part of the discharge, particle displacement, and gradually move closer to each other tightly bite, and ultimately the formation of cross-section and the same mold section, the upper and lower sides of the shape of the mold by the upper and lower indenter to determine the body.


In practice can be found, into the Dry pressure bullet-proof die powder also have to meet certain conditions in order to contribute to dry pressure forming the order to complete. If the powder is very fine barren powder German, because of its poor mobility and arch bridge effect, will make the dry pressure bullet-proof diecavity of the uniform filling affected, and easy to make the density of the body is uneven or spallation.


In addition to the nature of the powder will affect the use of dry pressure bullet-proof die effect, there are many other factors will also affect the dry pressing performance, including the way to suppress, suppress the pressure and pressure time. The internal friction between the particles and the external friction between the particles and the mold wall can cause the pressure loss. Therefore, it is easy to produce the density unevenness in the height direction and the cross section of the compact pressure, so it is recommended to use the bidirectional Pressurized or twice pressurized to reduce this phenomenon.


When the cross-sectional area and shape of the billet are constant, the increase of the pressure is beneficial to the increase of the billet density in a certain range. However, when the limit value close to the density is increased, the pressing pressure does not further increase the density and is easy to occur Split or damage dry pressure bullet-proof die, so to control the size of the pressure. The same is true for the holding time, and there must be sufficient packing time to facilitate the uniform distribution of the density in the compact and the discharge of more gases.

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