About Cold Heading
Cold heading, also known as cold forming, is a multiple step process used to form metal at room temperature using hammers and dies at a high speed. This is done all without heating the metal. It starts with reducing and cutting metal wire from a large coil into a blank through a drawing machine into a heading machine. In the heading machine, the blank is hit between the die and punch block at each station to push the material into the confides of the die producing the desired shape. Upsets and extrusions are the two techniques used to force material into the voided space.
- Upset- Metal in the die is forced out by the punch to produce a section larger than the initial blank. The blank’s height is reduced and the starting diameter increases.
- Extrusion- There are two types of extrusion, forward and backward. A forward extrusion is when the metal is forced into a cavity smaller than the diameter of the piece itself creating compression. A backward extrusion is when the metal in the die is forced backward around a punch to produce a hole or cavity inside a piece.
Gear teeth, holes, and other contours can be created in the blank by specialized tooling. Various and potentially complex pieces can be produced through very efficient means.
Advantages of Cold heading
Because the volume of the blank is being hammered into a die and there is no cutting required, the process has little or no scrap. Cold heading creates stronger pieces much more efficiently. In addition, because no heat is required, there is less environmental impact, and workers are provided with a safer environment.The production is fast with no cooling down process required and creates pieces with closer tolerances without secondary operations.
Disadvantages of Cold Heading
Without heat, the pieces must be created with more force. While dies may be cheaper, the machinery required is bigger and more expensive. The pieces cannot be as thick as they may in machining because hammers can only force so much metal into a space. Harder metals can require multiple blows to fill a die and certain materials cannot be used in a cold heading machine at all. More complex pieces will require secondary operations as cold heading machines cannot perform operations like rolling, stamping, or bending.
Cold Heading Applications
Cold heading has typically been used to create pieces like simple fasteners, though with technology always improving, cold heading can be used to create highly specialized fasteners and specialty pieces. This includes fasteners used in bridges, automotive manufacturing, electronics, and speciality bolts.