In 2004, Machining Techniques was one of the first subcontractors on Tyneside to wholeheartedly adopt 5-axis machining. It allowed the family-run firm in South Shields to carve out a niche for itself, one that still exists today. To begin with, founder and managing director, Dave Ditchburn, bought second-hand machines which he programmed in 3+2 mode for 5-sided machining, but has recently progressed to buying new plant from Hurco.
Savings in floor-to-floor time are dramatic compared with using 3-axis and 4-axis machines. A typical job put on Machining Techniques' Hurco VMX42U 5-axis machine is a knee prosthetic made from 60 mm diameter aluminium bar. Mr Ditchburn previously manufactured the part on a 3-axis machining centre in six separate operations. Now, using the fourth and fifth axes on the Hurco to position the prosthetic, the number of set-ups has been reduced to two, resulting in a floor-to-floor time saving of around one-third.
Total machining time is approximately similar, but there is a big reduction in handling time. This not only speeds production but also translates into better accuracy, as fewer refixturings result in less accumulative error and there is reduced potential for human error.
Another 5-sided component frequently put on the subcontractor's smaller Hurco VMX30U, installed in January 2013, is an aluminium manifold for a hydraulic leg prosthetic. Seven set-ups have been reduced to two and tolerances held are considerably better, to within ± 10 microns dimensionally and ± 2 seconds of arc perpendicularity.
A large proportion of jobs for the medical and scientific sectors fall within the machine's 762 x 508 x 520 mm working volume, leaving the 1,067 x 610 x 520 mm VMX42U free to produce bigger parts for the oil and gas industry and general engineering sector.
Both Hurcos are fitted with 40-station tool magazines instead of the standard 20 so that sufficient tools are always available to complete even the most complex of jobs. Renishaw tool setting and part probing was pre-installed on both machines to speed setting and minimise spindle downtime between batch runs.
Around 60 per cent of components are machined from solid aluminium by the Tyneside subcontractor, although it regularly produces parts in materials ranging from plastics and brass to high tensile steel (eg 4140), stainless steel and tough nickel alloys. Medical work, from prosthetic limb components to structural parts for X-ray machines, accounts for about half of the subcontractors business.
Mr Ditchburn said, 'Although 5-axis machining centres cost a little more to buy, which means you have to charge a higher hourly rate, you can produce parts more quickly.
'We are able to quote customers lower prices and win more business, as jobs do not take so long, yet at the same time make better margins.
'So we like to stand back and look at every new job, as well as those currently being made on our other machines, to see if we can put it on one of our 5-axis centres.'
The larger VXM42U was delivered from the Hurco stand at MACH 2010. Mr Ditchburn reviewed 5-axis machines from five potential suppliers but decided on the Hurco for two reasons.
First, it was keenly priced for a true 5-axis machine, ie one designed and built as such, rather than as a 3-axis machine with a bolt-on compound table. He cited problems of trailing cables and swarf traps with the latter configuration.
Second, the twin-screen control powered by Windows-based WinMax software allows him and the other setter-operators to program 3+2-axis work at the machine, which is the norm at the South Shields factory, leaving the company’s CAD/CAM system free to concentrate on preparing cutting cycles for more complex work.
He mentioned a feature in the control that is especially useful in simplifying and speeding the conversational programming of 3+2-axis / 5-sided cycles, namely 'transform plane'. It is necessary to define a datum only once and the software automatically determines all datums in the other planes. In essence, it changes 5-axis programming back to 2.5D programming on a 3-axis mill, eliminating the requirement to factor in the tilting and rotating motions.
Among other features of WinMax that Mr Ditchburn likes is ‘Conversational NC Merge’, which allows parts of a cycle written conversationally to be combined with G-code elements produced off-line.
Additionally, the latest version of Hurco's software includes 'Industry Standard NC', which allows the controls to run programs prepared for Machining Techniques' 3-axis and 4-axis machining centres equipped with other manufacturers' CNC systems. It is useful if no complex jobs need to be machined at any given time, bearing in mind that currently 40 per cent of throughput at South Shields does not involve 5-axis cycles.
Mr Ditchburn continued, 'WinMax saves a lot of time, up to an hour on some set-ups. With batch sizes small, from 50-off down to ones and twos, it is common for us to put three or four different jobs on a machine per day, so the benefit to us in terms of maximising spindle uptime is huge.
'People tend to be put off by the apparent complexity of 5-axis programming, but with Hurco's WinMax control it is the easiest thing in the world. Even our CNC lathe operators and apprentice, Andrew Gray, were quickly able to learn how to use it.
'It is very difficult to find experienced setter / operators locally, so we plan to grow our own skills base by taking on another apprentice during the first half of 2014. We expect that he too will become self-sufficient faster than if he were using another manufacturers' control.'