Impact Extrusion is a press forming process used to fabricate aluminum and other non-ferrous metals into "net" or "near net" shapes.
A material blank called a "slug" is cut from bar stock to a pre-engineered weight. The slug is heat treated to a "soft" condition, lubricated and then placed in a die cavity mounted in a vertical or horizontal press. The press is cycled to drive a punch into the slug material causing metal to flow within the die cavity and around the punch to form the impact extrusion final shape. The punch and die configurations determine the inside and outside part dimensions
Impact extrusion may occur as a reverse extrusion where metal flows in the opposite direction to the travel of the punch, forward extrusion where the metal flows in the same direction as the travel of the punch, or both as reverse and forward extrusions where the metal flows in both directions simultaneously. Reverse extrusion is the most common method for impact extrusion and is typically used to form cups and other closed end vessels. Forward extrusion is used to make longer shapes where extruded material is normally smaller in diameter or size than the starting slug size. Reverse and forward extrusion are used together to create more complex shapes.
Impact extrusion is normally performed on cold slugs, although heat may be applied in some instances to reduce the press tonnage during extrusion. The amount of press tonnage required to impact extrude material is a function of both the properties of the slug material and alloy as well as the percentage of area reduction occurring during the impacting process.
The impact extrusion process is a very cost effective method of metal fabrication as both less material and less processing labor are required to produce an impact extrusion than would be required to machine the same part from solid blanks. Also, superior mechanical properties are often achieved as a result of the cold work performed during the impact process.
