Cold Forming
Cold forming is the process of changing the shape of a material by plastic deformation at low temperatures. The shaping of components that are unable to be produced through the traditional hot forming process can be accomplished through cold forming. This is often the case with components that require complex shapes or a very accurate tight tolerance. As a result of the low processing temperatures for cold forming, the heat affected zone that arises from hot forming temperatures is minimized. This feature makes cold forming very practical for creating thin-wall components from materials that have a tendency to fracture.
Types of Cold Forming
The main types of cold forming are extrusion and drawing. In the extrusion process, an applied force is used to create dimensional change as a force moves a material through a shaped die. The material is moved at a relatively slow rate allowing the material grain structure to re-orient during the forming process. On the other hand, in sheet metal drawing the applied pressure is used to reshape the material during a quick forming process. As a result of this very rapid forming method the grain structure of the material is mainly unaltered. This process relies heavily on lubrication.
In addition to extrusion and drawing, there are many other forms of cold forming. Roll forming, where a material passes between two rolls with the applied pressure forming the material into a desired profile, is an example of cold forming. Another example is forging, where a material is formed into a desired shape through a combination of plastic deformation and mechanical work. Cold heading is a process used to form a head on specific parts and components. Punching and perforating are also categorized as cold forming processes.
Advantages and Disadvantages
There are numerous advantages for cold forming a material instead of hot forming. Among these are that the process requires minimal material wastage, increased tool life, good surface finish and tight dimensional tolerances. In addition, it requires less energy to form the material at low temperatures. Cold forming is also preferred when working with brittle materials that are not suitable for hot forming, like brass and aluminum alloys.
On the other hand, cold forming has its own limitations. Since the techniques rely heavily on manipulation of the grain structure, forming complex parts with tight tolerances can be difficult. In addition, cold forming processes require the use of small punches, dies and tools that can be costly depending on application. For consistent results, close monitoring of tools and process parameters is also necessary.
Conclusion
Cold forming is the process of reshaping a material by plastic deformation at a low temperature. There are numerous processes that fall within the cold forming category, including extrusion, drawing, roll forming and forging. Cold forming delivers many advantages such as minimal material wastage and good surface finish, but it does require the use of costly tools for complex components and close monitoring for consistent results.
