Cold Working
Although the name might imply that materials are chilled, most of cold working is performed at ambient or room temperatures. Also known as
cold forming, this manufacturing method is widely used and provides many benefits over heated processes. The most obvious advantage is the energy savings as materials do not need to be heated to the re-crystallization temperatures for effective handling. In fact, it is imperative that materials be worked at temperatures lower than this in order to create parts and components with a more compact and efficient grain structure at the atomic level, which in turn results in improved material strength and hardness. This compaction provides further economic savings as there is limited waste material in cold processing. Additionally, cold working provides fast turn around of reproducible products with tight dimensional tolerances. Heated metal expands and contracts unpredictably; cold working eliminates this avenue for dimensional variance. For these reasons and more, cold forming processes are preferred in many industries, including construction, automotive, hardware, stamping, injection molding, aerospace, agriculture, recreation, furniture, electronics, pyrotechnics, packaging and upholstery.
There are several different cold working methods available to accommodate such diverse industrial applications.
Cold roll forming is among the most popular in the creation of strips and sheets of precise thickness and dimensions. Roll forming machines consist of a series of rollers or roller dies which compress the raw materials fed into them. Headers for
cold headed part production offer more complexity as they can create collars, necks, lugs, flats or fins at any point along the length of a stock shape or blank. A single die, two blow header is used for simpler
cold heading while multi-die, multi-blow headers are integral to the creation of more intricate parts. Cold drawing is also commonly available in cold working shops. A rod is filed or hammered to a point before being placed in and pulled through a die, in effect stretching the material.
Cold extrusion follows a similar order, though blanks are pushed rather than pulled through the machinery. As is evident, dies are an integral component of cold machining; they confine and direct material into the desired shape with pre-determined dimensions. Punches are another popular tool of cold working. Punches create the force needed to exceed the elastic limit of a given metal in order for the blank or raw materials to undergo plastic deformation. The use of punch and die technology can sometimes result in a part with heightened internal strain or stresses. To combat this, annealing may be used in conjunction with cold working processes to create a hard, strong and ductile product.
