When metal is formed using a cold working process, the finished stock is referred to as cold headed parts. Cold heading is a more specialized technique that falls within the broader category of manufacturing known as cold forming. Rather than using heat, the metals are formed at approximately room temperature.
Among the many different cold working methods are cold extrusion, cold roll forming, cold drawing, orbital forming, and impact extrusion. Typically, the products that are manufactured using these operations are small items like fasteners. Bolts, pins, and screws are in high demand in many different industries. Many fasteners are manufactured in a cold working process that begins with a stock form of metal like wire, plate, or sheet.
Larger items can be made using cold forming, but for more complex products it is a less practical manufacturing solution. Cold forming usually refers to steel, but other metals like aluminum, iron, brass, copper, and titanium can all be made into small parts using the same techniques. The exact manufacturing methods may vary, but almost all cold forming processes make use of extreme pressure. This is necessary to cause the deformation of the materials so that the right characteristics are shaped into the metal. Read More…
There are many different machines that cold working metal fabricators can use. A roll forming machine is built with a series of heavy rolls that can be used to smooth strips of metal to a precise thickness. A cold header allows workers to create more complex metal forms with squares, offsets, and more. Multiple dies on the cold header are used to gradually reduce the size of the metal for added strength. This is how lugs, flats, fins, and other shapes are formed. Another process, cold drawing, uses a rod that is filed or hammered to a point and then placed in a die. The metal is pulled through the die so that it is stretched. Cold extrusion uses a similar process, but the metals are pushed through the die rather than pulled.
As you can see, dies are important components in basically every type of cold forming machinery. That’s because they make it possible to confine the metal in order to change its dimensions. To transfer force from the machine to the part being manufactured, a punch is used. The force of the punch needs to be greater than the metal’s maximum elastic limit so that deformation occurs and the metal is permanently in the shape of the punch.
There are many benefits for consumers and manufacturers alike when a cold working process is used. Hot forming process usually require a lot of energy to create extreme temperatures, so cold forming is generally much cheaper and more efficient. Less material is wasted in a cold forming process, which represents another significant reduction in cost. Unlike welding, cutting, and drilling; no scraps are created when metal is deformed using a cold working process. Of course, scraps can be recycled but that is also time consuming and costly.
Because cold formed parts are so solid and durable, they may not even require any secondary finishing operations during manufacturing. The hardening that a metal part experiences due to repeated pressure during cold forming increases tensile strength. Unlike a hot forming process that can change the dimensions of a material with expansion caused by heat, cold forming is exact since the temperature is constant.
A potential downside of cold forming is that it can increase the internal stress of an object or piece of metal. This is why manufacturers use annealing which allows them to soften the metal and reduce the strain. Sometimes manufacturers will alternate between cold forming and annealing during the manufacturing process to get the right balance for stock forms and fasteners.
Technological advances in cold forming operations have allowed manufacturers to produce more complex parts like spark plugs and axles at a faster rate than ever before. Further advances in metallurgy have increased the number of alloys that can be processed without heat treatment. From aerospace to hardware to injection molding and agriculture; cold forming is now an important process for many different industries. The endless variations that exist mean that fabricators who offer cold working usually perform operations like piercing, sizing, trimming, pointing and thread rolling. Some typical secondary operations include: patching, tapping, milling, shaving, bending, drilling, and knurling.