by Mark Jennings, technical director at Dawson Shanahan
Cold forming – the extrusion of a part from a blank – is a fast and economical way to produce robust, complex components in a wide range of materials. Trouble is, people don’t often use it.
Cold forming originated in the 19th century as a method for producing simple, high volume, components such as fasteners. Today, the process is capable of delivering precision engineered parts with up to 80% less scrap than machine processes. If you add in the facts that cold forming can offer faster lead times, better surface finish and improved mechanical characteristics, it’s hard to believe that it isn’t a hot topic.
Yet many designers and engineers persist in using conventional material removal processes, typically milling, and fight shy of cold forming. Perhaps the most surprising thing is that the economic climate has not encouraged designers and engineers to exploit the savings on machine time and material costs that cold forming brings. Take copper, for example: prices dropped a little at the end of 2011 but still remained at almost treble the figure they stood at three years earlier. So how do you make savings if your business depends heavily on the use of copper? Copper can’t easily be substituted for another metal, so the best option to control costs is to cut waste. Cold forming could be the solution.
Here’s a typical example: a nozzle for use in plasma or laser welding with a finished weight of 36g needs a blank of copper weighing 213g from which it can be milled; that’s 177g of scrap copper that has to be recycled, with all the associated transport, energy and processing costs. While 177g may not sound much, even at today’s copper prices it adds at least 85 pence to each part produced.
Cold forming is a simple process that can produce metal components at low ambient temperatures without removing any material. The ambient temperature allows parts to be completed as much as 15 times faster than more conventional options and makes a significant reduction in energy consumption. Cold forming can also increase strength, producing a part that is 18% stronger than that of machined components.
It is also now possible to cold-form stainless steel, as well as other exotic metals such as titanium, thanks to a method developed at Dawson Shanahan. The capability to cold form steel offers tremendous opportunities to manufacturers of ultra-high precision parts, including laser applications, where cold formed nozzles significantly increase cutting accuracy; or diesel injectors, which are generally more reliable than conventionally manufactured parts when used with biofuels.
There are still times when machining is necessary and a degree of machining can sometimes be used to finish a primarily cold-formed part. However, as economic and environmental pressures drive manufacturers to find new ways to reduce material waste and energy consumption, cold forming provides an alternative solution.