When the piercing aluminum mirror frame extrusions machine is in reverse extrusion, the direction of metal discharge is opposite to the direction of the extrusion rod, and there is no relative movement between the extrusion cylinder and the billet.
Advantages of using reverse extrusion:
1、 Because there is no friction between the billet and the extrusion cylinder, the extrusion pressure is much lower than that of the forward extrusion. During the reverse extrusion, the extrusion pressure is constant in the whole range of the extrusion rod. It can be used to extrude refractory materials with higher extrusion index at lower temperature.
2、 The microstructure and mechanical properties of the extruded products are almost the same.
3、 Compared with the positive extrusion, the waste material is obviously reduced and the output is higher; larger ingot can be used, which is conducive to strengthening the facility efficiency and the continuous production.
Compared with the forward extrusion method, the reverse extrusion method also has the following disadvantages:
1、 The extrusion tube of the piercing aluminum mirror frame extrusions machine must be able to move to ensure the production efficiency during reverse extrusion. The process of the extrusion tube should be slightly larger than the size of the extrusion tube. Therefore, it is not suitable for any kind of piercing mirror aluminum extruder to reverse extrude.
2、 The surface quality of extruded mirror frame aluminum is low.
3、 The period of extrusion is usually longer than that of forward extrusion. But because it can enlarge the size and quality of ingot, reduce the surplus loss, and increase the extrusion speed, the auxiliary time is increased to a certain extent, and then the reverse extrusion has higher production efficiency.
4、 The maximum circumscribed diameter of extruded mirror frame aluminum is limited by the strength of hollow extrusion rod.
