Causes of formation of shrinkage in aluminum extrusion process and preventive measures

On the China Aluminum Network, tailing refers to a specific type of waste material that occurs during the extrusion process of aluminum alloys. It typically manifests in two forms: hollow shrinking tail and ring shrinking tail. A hollow shrinking tail is caused by oil or residue from the extrusion gasket, leading to insufficient material left at the end, which results in a lack of metal supply and creates a funnel-like shape. On the other hand, a ring shrinkage occurs when the metal supply in the deformation area becomes inadequate toward the end of the extrusion process. This forces the metal to flow laterally around the extrusion gasket, causing turbulence. The cold and oily material on the edges and sides gets re-circulated into the final product. Ring shrinkage usually appears on the cross-section of the product's end and can be either continuous or intermittent.

To prevent these types of shrinkage, several key measures can be implemented:

1) Minimize the temperature difference between the aluminum billet and the tool, or consider using low-temperature extrusion techniques. 2) Ensure that the surface of the billet is clean and heated uniformly to avoid uneven material flow. 3) Avoid greasing the squeegee or using tarpaulin to wipe the pad, as this can introduce contaminants. 4) Improve the surface finish of the die and extrusion container, and regularly clean the extrusion tube to maintain efficiency. 5) Slow down the extrusion speed during the final stages of the process to reduce stress on the material. 6) Use proper lubrication or employ reverse extrusion methods to enhance material flow. 7) Leave an appropriate amount of residual material at the end and cut off the tail as needed, possibly increasing the residual thickness if necessary.

By implementing these strategies, manufacturers can significantly reduce the occurrence of tailing and improve the quality and consistency of extruded aluminum products. Understanding the root causes of these defects and taking proactive steps to address them is essential for maintaining high standards in the extrusion industry.

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