There are three types of extruded products' tailing:

1) hollow tail of extruded products. In the process of extrusion, due to the friction between the inner wall of the extrusion barrel and the die section, the metal flows unevenly, which makes the middle metal flow faster than the surrounding metal, resulting in the lack of metal in the middle part. In the later stage of extrusion, when the residual (residual) is thin, the middle metal flows out and can not be supplemented, forming hollow tail shrinkage of extruded products. Generally, when the diameter of extruded products is large, the extrusion ratio is small, and the remnant (residue) is very thin, it is easy to produce hollow shrinkage tail of products.

2) the subcutaneous shrinkage of the extruded product. The hypodermic tail appears in the epidermis of the product, most of which are discontinuous and arc-shaped. The reason is that in the later stage of extrusion, the metal is sheared and fractured due to the sharp sliding of the dead zone interface, and the dead zone metal is involved in the flow and coated on the extruded products, resulting in the layered shrinkage. In general, in the process of extrusion, there is enough residual pressure and the method of peeling extrusion is adopted to reduce the production of extruded products.

3) circular tail reduction of extruded products. This kind of tailing is a common one. When the extrusion reaches the final turbulent stage, the oil-bearing dirt metal accumulated near the junction corner of the extrusion gasket and the extrusion cylinder flows to the middle layer of the product along the interface of the hard deformation area at the rear end, forming the extrusion tailing. Generally, the circular tail shrinks gradually from the back to the front in the 200-1000 mm length of the rear end of the extruded product, and even disappears.

The basic measure to prevent and reduce the shrinkage of extrusion products is to improve the metal flow. All measures to reduce the uneven metal flow are conducive to reduce the formation of shrinkage of extrusion products.