Dawson Shanahan is a company that doesn't take no for an answer. No, that is, to being told something is technically impossible. The cold forming specialist, which backs that up with a precision machining capability, is not put off by such suggestions.
The two recent 'impossibilities' that the company has confounded are in the cold forming of a high accuracy needle-less injection medical device and the orbital forging of an exotic, expensive steel part for the aero engine market. In the first case, it was the cold-forming machine manufacturer that advised the company of the challenge, while, in the second, it was an area expert. In both instances, the company applied its extensive man-years of knowledge to succeed.
The orbital forging project is ongoing with a major UK aerospace engine maker, while the aluminium medical device is now entering high production, with the company having made substantial investment in bespoke, post-cold-forming grinding technology (see p28).
Set up in the 1920s, Dawson Shanahan is headed up by David Dawson, chairman and joint managing director – last surviving son of the founder, Edward Dawson – but the company is run by a management team led by Les Reeves, joint-managing director.
Today, Mr Dawson is mostly focused on technical manufacturing challenges in the cold forming area, process development and machine purchase – the latter takes him world-wide and also sees him bidding for kit over the Internet, with some interesting results, like buying an automated, two machine Kummer cell. He is knowledgeable and a passionate talker on the subject of machine technology and the benefits of cold forming, and, as regards the latter, can clearly become exasperated when confronted by alternative, inefficient production practices.
Image: David Dawson, left; Les Reeves, right
The company's material forming roots can be traced to WWII, but it was the 1970s that saw it take off, linked to that most modern of industries, semiconductor manufacture and where heat-sinks made of oxygen-free copper – one of the least machineable grades of copper - were required for power semiconductors. This was a business that saw the company produce ¼ million parts/month at its peak, but, over time, that business went abroad.
To be sure, cold forming is not a 'pretty' or delicate process – it is, after all, the squeezing of a blank of metal, using punches and dies, that takes force and grunt – the company has presses up to 600 tonnes. Neither are cold formers or presses the tidy boxes that modern CNC metalcutting machine tools tend to be, so they do not give the impression of being modern. But much more cold forming is 'green', as it uses far less raw material.
And that's the process's major hook. Indeed, it was material usage reduction that saw Dawson Shanahan first develop cold forming for its power semi-conductor heat-sink efforts in the 70s. And it is this strength that has seen the company make big inroads over recent years into the OEM equipment laser/plasma nozzle shield market. These consumable items are made of copper, and copper prices have risen from around £1,000/tonne 10 years ago to more than £6,000/tonne earlier last year, although it has fallen back below £5,000 of late. And while there are multiple process steps in a cold-formed part versus the potential one-hit machining approach, material cost savings more than offset this. The aero engine orbital forged part development is similarly material cost related.
As joint managing director Les Reeves explains of the nozzle shields: "The customer was making these from solid and would never have thought of making them by cold forming. They were starting off with 293 g and machining it to a finished weight of 55 g. We start with a slug weighing 85 g, before machining it to the finished dimensions."
Engineering director Mark Jennings amplifies the point, stressing the precision machining aspect: "A cold forming company would have looked at that, seen the thread as a finished item and said 'we can't do that'. Because we have cold forming, turning and threading under one roof, we are 'in the picture'."
The combination of cold forming and machining under one roof is a key differentiator for Dawson Shanahan, says Mr Reeves, which does set it apart from the cold forming-only brigade, as the nozzle shield example attests. And the combined offering is the major part of its business, he adds. "We're always looking for niche applications where we can be smart," interjects David Dawson.
In the case of the nozzle shields, the customers' in-house machined parts were made from free-machining tellurium copper. But this is less readily available and more expensive than oxygen-free copper, and there are only a few suppliers of tellurium, which is also a negative in the health sense. Savings for one company that changed from tellurium copper cutting to the cold-formed, oxygen-free material processing were in excess of $250,000/annum.
Dawson Shanahan now makes approaching one million plasma consumables a year and supplies six of the top 10 OEMs worldwide, but, importantly, agrees as a condition of this business not to supply the aftermarket. It is also talking to two more OEMs. But it can take time to change, due to the single source concerns and because a change from in-house machining to outsourced manufacture can eliminate large machine shops and associated personnel, Mr Dawson offers. In addition, there's the spares market worry, hence the OEM-only assurance given.
Image: The automated Kummer cell, purchased over the Internet by David Dawson
The latest project in the plasma industry is nozzles themselves. More difficult than shields, due to the number of small diameter holes, challenging profiles and second op workholding issues, but progress has been made in developing the process over a few months, Mr Dawson reveals. Volumes top 2 million/annum for one company alone.
There is still a large opportunity in general for the £9.5 million turnover company, which has ambitions to grow to £20 million by 2020, says Mr Reeves. "Some of this will be organic, but some will come through acquisition, either in the UK or abroad," he adds.
However, Dawson Shanahan's biggest challenge is to convince designers that "cold forming can be used to make something other than nuts and bolts". So, if after qualification they're not in the nuts and bolts industry, they don't see it as a possible candidate, he explains. But, once convinced, "they buy from us in volume", he points out, while Mr Jennings adds that he sees parts that could be cold formed "every day ", adding "it drives me crazy".
But it's slow progress. Says Mr Jennings: "At the moment, we have focused on the plasma industry, because we have had success and can demonstrate that to others in the industry. Going into completely new industries, you have to get that first success."
Recent other orders include copper power switch gear parts (1 kg from solid compared to 400 g raw material usage when cold-forming), while new parts currently in progress include the plasma nozzle and aerospace engine part already mentioned. Laser nozzle manufacture for turbine blade cooling hole drilling is another project underway.
The company is also pushing plasma and laser nozzle designs, using the so-called 'Holy Grail' de laval profile, which can be more easily achieved by cold forming than by machining – a de laval profile is a tube that is 'pinched' in the middle, making an asymmetric hourglass-shape. "We have worked with the University of Cambridge on next-generation laser nozzle designs that they can't machine, but which we can form," says Mr Dawson.
For a manufacturing technology with a 'nuts and bolts' image, Dawson Shanahan is clear demonstration that there aren't old processes, just old thinking.
Box item 1
Company in profile
There are three companies in the group. The main Dawson Shanahan site at Potters Bar (55 employees), which is complemented by two other divisions, a medical one (Dawson Medical, 11 employees), also at Potters Bar, and a manufacturing unit in Wales, previously Floform, which was acquired in 2009 (cold-forming and machining specialist, 31 employees).
Dawson Wales focuses on heavy duty diesel engine components for global companies such as the Volvo Group, including Renault Trucks and Mack Trucks. It boasts TS16949 and ISO 14001, in addition to ISO 9001.
This division employs over 30 people and has recently secured a $1 million order to supply an American-owned plant in Morocco with copper power diode bases, an example of a part made in the 60s that has returned to UK shores, having done the low-cost country tour. These require cold forming, brazing then machining.
Box item 2
Dawson Shanahan has been key in the development of a revolutionary needle-free syringe which requires precision manufacturing to work effectively. It is the first US FDA-approved needless injection device – an anti-migraine application is the launch application.
The components made by Dawson Shanahan are an aluminium chamber and a steel ram. The success of the design is partly due to the high quality finish and intricate production of the cold formed parts, which make it possible for the administration mechanism to work. The chamber is 6 mm outside diameter and 5 mm inside, with a 7 micron bore tolerance. The bore depth is 11x length, achieved in 5 blows.
Image: The medical device, parts for which are manufactured in the company's specialist cell
The cold forming tooling employed for the aluminium chamber was designed by Mr Dawson, with the Italian cold forming machine maker advising him that the process was not possible.
The ram, which has two o-ring seal grooves, has a groove ground across the diameter that, in combination with a latch, maintains the ram in its axial position until release under gas pressure. Special creep-feed grinding machines and process were again developed by Dawson Shanahan to produce these features.
The company worked with Asahi Diamond Industrial on grinding wheels and specialist machine builder E-Tech to deliver a solution that gives results believed to be far better than anything currently achievable in a commercial environment.
Dawson Shanahan claims that the process is capable of producing parts with exceptionally accurate, highly polished surface finishes, with tolerances of less than 1.0 micron when measured over each square millimetre of surface area. Similarly, for components with angled faces, the company quotes levels of deviation that are less than 0.25 degrees across surfaces measuring just a few millimetres in size. Machine cycle times are typically around 2.5 seconds, with no need for further polishing or de-burring of components. Current production is over 1 million sets/year.
The Potters Bar firm is one of very few UK companies able to boast the medical device ISO 13485 accreditation and works to US cGMP standards (cGMP = current good manufacturing processes).
First published in Machinery, March 2012