Extrusion Butt

In extrusion production processing, a portion of the aluminum billet remains inside the extrusion container rather than being extruded out; this residual metal is commonly referred to as the “extrusion butt” or simply the “butt.”

Retaining the butt serves to save extrusion time and energy, ensure the safety of the extrusion press, and prevent direct impact between the dummy block and the extrusion die. The size of the extrusion butt varies depending on the extrusion method and process conditions. The butt thickness is greater in direct extrusion than in indirect extrusion, and greater for soft alloys than for hard alloys; it is also larger when the extrusion container diameter is larger.

To comprehensively save on extrusion time and energy during production, a method involving a thicker butt and a reduced tail-cut length—known as “thick-butt extrusion”—is sometimes employed.

The butt thickness generally ranges from 0.1 to 0.25 times the inner diameter of the extrusion container, with the lower limit selected for large presses and the upper limit for small presses. In any case, the minimum butt thickness should not be less than 15 mm.