Principle and characteristics of extrusion molding process

It is generally under normal temperature conditions

The principle of extrusion molding: After adding a certain amount of organic plasticizer to metal powder and mixing it evenly, it can be extruded at a certain temperature (usually within the range of 40-200 ℃). This method is called "cold extrusion method" or "plasticized powder extrusion method". It is generally extruded under normal temperature conditions. The ceramic powder used for extrusion must be mixed evenly with water and Plasticizer before it can be used for extrusion. Vacuuming during the extrusion process is beneficial for the discharge of air from the billet, thereby increasing the green density of the formed billet.

In the extrusion process of ceramic materials, the forward movement of the blank under extrusion pressure requires overcoming a certain amount of resistance, which mainly comes from the friction force generated by the relative movement of the blank and the mold wall parts.

When the billet is squeezed into the extrusion nozzle, the flow rate of the billet increases due to a significant reduction in the extrusion cross-section. The flow rate of the billet in the center part that is not subject to mold wall friction is significantly faster than that in the part near the mold wall, which causes shear tension in the extruded part, which is called "additional internal stress". The presence of additional internal stress can easily cause delamination or cracking of the product. In order to reduce additional internal stress, the roughness of the inner wall of the extrusion nozzle can be reduced to reduce the friction force between the blank and the mold wall. Therefore, designing the angle of the extrusion nozzle reasonably can prevent the flow rate of the billet from changing too quickly when entering the extrusion nozzle, thereby reducing its additional internal stress.

The characteristics of extrusion molding: Extrusion molding is suitable for forming tubular and cross-sectional parts with consistent shape. The length of the extruded parts is almost unlimited, and the shape of the extrusion can be controlled by changing the extrusion nozzle. The wall thickness of the workpiece prepared by this method can be very thin, as listed in Table 3-4. The honeycomb ceramic products widely used in recent years are manufactured by extrusion molding method. In addition, the extrusion molding method can also prepare thin sheets with a thickness less than Imm, and then prepare parts of different shapes through methods such as cutting or stamping

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