In cold extrusion forming, the cracking of the sleeve is caused by transverse tearing. It can be avoided by the following methods:

1. Reduce friction to decrease the additional tensile stress on the metal surface. This can be achieved by improving extrusion lubrication conditions or using smoother die surfaces.

2. Control the extrusion temperature to prevent excessive temperature from reducing the tensile strength of the metal surface. This can be achieved by selecting appropriate extrusion temperatures or improving the cooling system.

3. Control the extrusion speed to avoid excessive additional tensile stress on the metal surface. This can be achieved by adjusting the operating parameters of the extrusion machine or using more suitable extrusion speeds.

In summary, in order to prevent cracking during cold extrusion forming, it is important to strictly control process parameters and take appropriate measures to reduce friction, control extrusion temperature and speed. This can effectively prevent the formation of cracks.