Impact extrusion is a

manufacturing Manufacturing is the creation or production of goods with the help of equipment, labor, machines, tools, and chemical or biological processing or formulation. It is the essence of secondary sector of the economy. The term may refer to ...

process similar to

extrusion Extrusion is a process used to create objects of a fixed cross-sectional profile by pushing material through a die of the desired cross-section. Its two main advantages over other manufacturing processes are its ability to create very complex ...

and drawing by which products are made with a metal slug. The slug is pressed at a high velocity with extreme force into a die or

mold A mold () or mould () is one of the structures certain fungi can form. The dust-like, colored appearance of molds is due to the formation of spores containing fungal secondary metabolites. The spores are the dispersal units of the fungi. Not ...

by a

punch Punch commonly refers to: * Punch (combat), a strike made using the hand closed into a fist * Punch (drink), a wide assortment of drinks, non-alcoholic or alcoholic, generally containing fruit or fruit juice Punch may also refer to: Places * Pun ...

Process

The punch is attached to a mechanical or

hydraulic press A hydraulic press is a machine press using a hydraulic cylinder to generate a compressive force. It uses the hydraulic equivalent of a mechanical lever, and was also known as a Bramah press after the inventor, Joseph Bramah, of England. He ...

. These machines reciprocate in a cycle 20 to 60 times per minute. A cold slug is placed below the punch and over the die. The punch makes contact with the slug forcing it around the circumference of the punch and into the die. The metal slug deforms to fit the punch on the inside and the die on the outside. Lubricants are added to aid the machine for an easier punch-out. It only takes one impact for the finished shape to form from the slug. Once the slug has been contoured to the desired shape, a counter-punch ejector removes the work piece from within the die.

Some Characteristics of the Process

The wall thickness of the work piece is directly correlated with the clearance between the punch and die. The thinner the wall of the work piece the tighter its tolerances are. The end product has a better surface finish than the starting piece and the grain of the material is reformed to its new shape. This adds strength to the new form compared to cutting into the grain like in a machining process.

Effects on Work Material Properties

After going through this process the properties of the material used are altered. Its hardness and yield strength are increased, cross-sectional area is decreased, some residual surface stresses will be present and micro cracks may appear. Physical and chemical properties are only influenced slightly.

Die Style

Four major types of dies (tools) can be used. They are: forward, backward/reverse, combined, and hydrostatic extrusion. Forward extrusion pushes the slug into the die. Backward/reverse extrusion pushes the slug around the punch. Combined extrusion forces the slug both into the die and around the punch. Hydrostatic extrusion is used on brittle materials (i.e. molybdenum, beryllium, and tungsten) by applying pressure gradually to force the brittle material through the die. This is generally accomplished by the same method as forward extrusion.

Typical Workpiece Materials

Typical materials for this process are:

aluminium Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. I ...

brass Brass is an alloy of copper (Cu) and zinc (Zn), in proportions which can be varied to achieve different mechanical, electrical, and chemical properties. It is a substitutional alloy: atoms of the two constituents may replace each other wit ...

tin Tin is a chemical element with the symbol Sn (from la, stannum) and atomic number 50. Tin is a silvery-coloured metal. Tin is soft enough to be cut with little force and a bar of tin can be bent by hand with little effort. When bent, t ...

, mild steel, stainless steel,

magnesium Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ta ...

titanium Titanium is a chemical element with the Symbol (chemistry), symbol Ti and atomic number 22. Found in nature only as an oxide, it can be reduced to produce a lustrous transition metal with a silver color, low density, and high strength, resista ...

, and

zinc Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodi ...

Tool Materials

Typical tool steels used in extruding aluminum:

Tool Geometry

When using the technique of backward impact extrusion, putting an angle on the punch in the press is used to decrease the amount of pressure applied to the punch. This decreases the chance of creating a dead zone, which is an area of no pressure. On the opposite end of things, forward impact extrusion uses a radius on punch to keep the course in the workpiece material moving.

Example products made from impact extrusion

* Metal

toothpaste tube A tube, squeeze tube, or collapsible tube is a collapsible package which can be used for viscous liquids such as toothpaste, artist's paint, adhesive, caulk, & ointments. Basically, a tube is a cylindrical, hollow piece with a round or oval ...

Aluminium bottle Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It ...

* CO₂ cartridge * Aluminum

baseball bat A baseball bat is a smooth wooden or metal club used in the sport of baseball to hit the ball after it is thrown by the pitcher. By regulation it may be no more than in diameter at the thickest part and no more than in length. Although histor ...

* Permanent marker pen bodies * Ammunition cartridges

References

*Manufacturing Processes Reference Guide. Industrial Press, 1st edition, 1994. Robert H. Todd, Dell K. Allen, and Leo Alting * "Refined impact extrusion technologies are more material-efficient and give the polished aluminum enclosure its incredible shape and finish." https://www.apple.com/uk/mac-pro/ *Information and images provided
Extrusion Process & Extrusion Dies
(Public Document) *How Its Made - Impact extrusion of tube

{{DEFAULTSORT:Impact Extrusion Metal forming