Cold forming
From Wikipedia, the free encyclopedia
Cold forming or cold forging, is a manufacturing process in which metal is shaped at ambient temperature to produce metal components to a close tolerance and net shape. Techniques include bending, cold drawing, cold heading, coining extrusion (forward or backward), thread rolling and others, all without removal of material, thus cold forming the component.
A blank of metal is placed within a die, and a punch is pressed into the blank to cold form the part. The blank then takes on the form of the punch and the die. Under extreme pressure, many metals can be formed into new shapes without heat or cutting. The process is low in energy consumption and produces little or no waste.
There are three main types of extrusion -
Forward Extrusion, where the stock piece or billet is pressed into the die by pressure from the punch. The geometries produced range from basic 'T' shapes to conical and stepped radius parts.
Backward Extrusion, where the billet is extruded through the cavity between the punch and die to create a cup or cylindrical shape. These can be single radius shapes or feature stepped or shouldered radii.
Combined Extrusion, a combination of forwards and backwards extrusion. The billet is extruded and forward formed into the die.
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[edit] Benefits of cold forming
In a conventional machine process, the part is turned or milled from an oversized stock bar. The scrap material is at best recyclable, at worst, wasted. In cold forming, the raw material is sheared from the stock bar or wire to exactly the required volume to produce the finished component, as opposed to saw cutting, which produces further waste. The difference between the two processes in terms of material saving becomes even more significant at larger volumes, and even more so when using expensive materials such as copper. The saving on raw material as a result of cold forming can be very significant, as is the saving in machining time.
Additionally, during cold forming the part undergoes work hardening and under the pressure of the cold forming process, the grain structure within the metal flow across each other and contour into the shape of the product. The grain structure of the metal is enhanced, making the component a stronger part and less prone to failure than conventional machined components.[1].
Another added benefit of cold forming is that the cosmetic finish of the components is brighter in appearance and formed to consistently high tolerances, often reducing the need for complex finishing and polishing.
[edit] Production cycle
Production cycle times when cold forming are very short. On multi-station machinery, production cycle times are even less. As the production run increases, the benefits become obvious. The savings of waste material and the improved throughput generate real cost advantages, especially over a long production run.
