Sunday, February 17, 2008

Retrofit CNC adds life

Rather than replace an older, but very useful CNC horizontal machining centre, a vintage car restorer opted to retrofit an up-to-date CNC and so saved on machine tool replacement costs

The opportunity to turn a hobby into a business doesn't arise every day, but this is exactly what happened to Will Fiennes, a lifelong fan of Riley motor cars, 30 years ago he hung up his physicist boots to follow his passion of restoring vintage motor cars. Leaving behind his role with Smiths Industries - where he applied his degree in tribology, electrical engineering and physics - and upon establishing Fiennes Restoration because he 'preferred to get his hands dirty', he focused on the supply of new spare parts for, and the restoration of, pre-war Derby Bentley and Rolls-Royce cars.

Such is the success of the operation that today he works for customers the world over.

'It was clear then that not many people knew too much about these cars,' said Fiennes, 'And that the supply of appropriate spares was dwindling.

So, having identified that demand, I set about satisfying it.' To give some idea of the scale of the operation, at any one time around 20 cars are at various stages of restoration, and the spares inventory now extends to an amazing 7,000 different line items, all computerised and 'accessible' online (www.fiennes.co.uk) via the company's website.

'The business hasn't changed that much during the past decades,' he reflected, 'Though CNC machines have helped us considerably to achieve consistently accurate and more cost-effective batches of machined parts.' He said: 'In this respect, CNC brings a new dimension to the word 'efficiency' even for a company like this (where a large batch may be just five-off components) though our manual machines do remain very effective for the production of suitable, relatively simple jobs.' He explained that the company havd a very old Britan capstan lathe, which it had bought secondhand with a new CNC lathe, and this wonderfully designed machine continues to reliably and accurately produce bushes and other small parts.

Fiennes said: 'I discovered during the early days of Fiennes Restoration that nothing is impossible; everything can be made if you have the right tools and attitude.

But over the years it has become clear that the nation's craft skills have dwindled rapidly, though we've been lucky in being able to maintain a high skills base, even though we're based in the wilds of Oxfordshire.' This is certainly evident among the company's 23 employees, and particularly in the mechanical restoration, coachwork and spare parts machining activities, where a very high standard of manual dexterity combines perfectly with high-technology equipment, tools and materials to enable the workforce to achieve finished results that the original car manufacturers would envy.

CNC was introduced 18 years ago, following a contract to machine cylinder head castings.

But lead times were extended to 40 hours per head when machining these parts on a DRO-driven vertical milling machine, and then sub-contracting the thread milling content as well as combustion chamber machining.

One option was to invest in CNC machinery.

However, to some extent this required a leap of faith, machining components designed 60 or 70 years ago using modern technology.

'I was sure that the way to shorten such an extensive lead time was to machine as much as possible in-house by CNC; ideally by using a horizontal machining centre where all faces of the castings could be machined in a single set-up,' said Fiennes.

'But a horizontal would have cost us at least six times more than the route we adopted - a CNC Avon turret mill, fitted with Anilam GXM control.

The versatility of the Avon allowed us to machine all faces of the 28in long casting with appropriate fixtures, albeit with a sacrifice of rigidity.' He said: 'This served us well for 15 years, when we found that increasing demand could not be met by the now elderly Avon.

We then invested in a new VMC with full fourth axis, but did not dispose of the Avon.

In fact, the VMC could not do everything that the Avon did, and in particular the end faces of the cylinder head castings continued to be machined on the Avon.

It has to be said that the horizontal option, with a substantially greater investment, would have allowed all the machining to be achieved on the one machine.' However, while the Avon has remained mechanically sound (ballscrews and motors, for example, were fine), the G and M code programming routines via the original GXM control were, he says, obviously suffering from age and were proving tiresome.

But rather than invest in another new vertical mill or machining centre, Will Fiennes decided that an Anilam 3000 Series CNC upgrade from ACI (UK) would be an ideal solution - and at least 70% cheaper than investing in an equivalent new machine.

ACI (UK) simply replaced the control and wiring, and the machine - which suffered a downtime of no more than 48h - 'Has been given a new lease of life', Fiennes said.

With the switch to the three-axis Anilam 3000M CNC, and after suitable onsite training, the ease of use of Anilam's renowned Machinist's Language quickly came to the fore.

Of particular merit, said Fiennes, was the control's wide range of standard cycles such as 'peck' drilling, pocket milling and face milling, as well as its advanced cycles that include ellipse, spiral, helical, tapping, irregular pocket milling and profile milling.

The special cycles such as counterboring are also highlighted as being especially useful.

Illustrating the system's ease of use, he says, is the standard cycle for bolt hole patterns that enables patterns of any configuration to be quickly produced by answering five simple questions.

Likewise, after answering a few questions, the drill cycle takes users through simple drill, peck drill and boring routines.

'In addition to the continuation of the cylinder head work, the revitalised Avon is used for producing a myriad of parts including the machining of small castings and various moulds and tool steel components that utilise the machine/control combination's three-axis capabilities.' Fiennes said: 'I set up Fiennes Restoration with no formal business training, which is just as well, because we continue to this day to break every rule in the business book, particularly in terms of best practice work-in-progress and stock levels.' He concluded: 'But I'd like to think that I've learned a thing or two over the years, and the financial sense of adopting the ACI (UK) rebuild is one example.

It's a business I wouldn't change for the world - and when I do find time to retire, I've still got a Riley waiting at home for me to restore.'

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