Why Cold Heading
Cold Heading is a process where a length of wire is cut off of a coil and then placed into a die. A hammer will then either UPSET the material (Place a head on it) or EXTRUDE the material (force the wire into a smaller die).
The material will simply be rearranged and therefore there is no loss of material, and typically no scrap .
- Because the material is moved, instead of cut, Cold Heading improves the finished part’s grain structure. This unbroken grain flow gives the part greater strength to weight ratio. Conversely, the grain structure is weakened by cutting operations (as with screw machined parts).
- Net / Near net shape can be achieved to eliminate or reduce secondary operations and greatly reduce scrap.
- Product Consistency | Dimensional accuracy | Quality | Surface finish
Upsetting is generally used to create a head on a fastener. There is a limit to the amount of material that can be upset in one blow; therefore forming a more complex part in which more metal is moved farther is better accomplished in multiple stages, or blows, which is why multi-die machines are used.
The head on a standard indented hex washer screw is an example of upsetting on a single die, 2-blow header.
The cut off on top is used to make the hex head to the left.
Backward extrusion uses an angular punch. Because the metal has no place to go, it literally flows along the outer perimeter of the punch, backwards.
This is useful in forming a variety of cylindrical shapes such as nuts, sleeves and tubular rivets.
The tubes on the right are made from the cutoff on the left. 100% of the material is used.
This is an example of Near Net shape after Cold Heading.
The part on the LEFT is the cut-off from the wire coil.
The part in the CENTER is after a 4-die cold header progression.
The part on the RIGHT has been completed on the CNC.
Very minimal scrap is generated.