1, Positive/Negative/Composite Extrusion

Positive extrusion refers to the extrusion method in which the direction of metal flow is the same as the direction of punch movement. During the positive extrusion process, the metal billet is placed inside the concave mold, and the convex mold advances forward, applying pressure to the metal billet to produce plastic flow and fill the mold cavity. The positive extrusion process has the advantages of simple operation, simple mold structure, and high production efficiency, and is suitable for producing profiles and bars with simple shapes and uniform cross-sections. However, the unevenness of metal flow during the forward extrusion process may lead to uneven stress distribution inside the product, affecting product quality.
Reverse extrusion refers to the extrusion method in which the direction of metal flow is opposite to the direction of punch movement. During the reverse extrusion process, the punch moves backwards and applies pressure to the metal billet, causing it to undergo reverse plastic flow. The reverse extrusion process is suitable for producing profiles and pipes with complex shapes and uneven cross-sections. Due to the more uniform metal flow during the reverse extrusion process, the internal stress distribution of the product is more reasonable, resulting in higher product quality. But the reverse extrusion process has higher requirements for mold design and manufacturing, and the production efficiency is relatively low.
Composite extrusion refers to an extrusion method where the direction of metal flow is both the same as and opposite to the direction of punch movement. During the composite extrusion process, a portion of the metal billet is subjected to positive extrusion, while the other portion is subjected to negative extrusion. The composite extrusion process combines the advantages of forward and backward extrusion, and can produce products with more complex shapes and uneven cross-sections. However, the composite extrusion process has higher requirements for mold design and manufacturing, and the production difficulty and cost are relatively high.
2, Hot/Cold/Warm Extrusion