PATENTED fixture for nuclear waste containers

Decommissioning legacy nuclear waste silos on the former UK power generating site at Sellafield requires the machining of large numbers of ‘bins’ to close geometrical tolerances, thus ensuring they can be stacked safely. These bins are three-metre-cube, double-walled, box fabrications that are highly resonant and, to make their production even more difficult, are made from 6 mm thick duplex stainless-steel plate that tends to induce vibrations during milling.

One of the firms leading the Sellafield decommissioning work, Stillington-based Darchem Engineering, had been taking delivery of machined bins from Newcastle-based contract machinist BEL Engineering since 2017.

CEO Jonathan Lamb says: “We wanted to increase productivity but realised that further improvements to the machining process were impossible using conventional machinery and fixturing. When we tried to raise the speed of machining, chatter resulted and it was difficult to hold tolerance. So we engaged with Kingsbury to develop an entirely new machining concept in respect of both work holding and metal cutting, to improve cycle time and hence increase production rate and reduce cost.”

It was not an exercise for the financially faint-hearted. The two companies invested £500,000 in researching and developing an optimal solution for machining two variants of waste bin, known as a PFCS (Pile Fuel Cladding Silo) and an MSSS (Magnox Swarf Storage Silo).

Richard Kingsbury, MD of Kingsbury, says: “Duplex will seek out any weakness in a machining system. We considered every conceivable source of vibration, from the machine bed to the column, guideways, spindle, spindle-tool interface and cutting tools, including their grade and geometry.

“We then turned our attention to a forensic analysis of how best to fixture the bins and it was here that we achieved a breakthrough,” he continues. “By inflating five airbags between the fixture and the box and five more inside the workpiece itself, we managed to muffle the entire unit so it could be milled at high speeds and feeds without vibration. A final piece of engineering involves hydraulically rotating the 12 swing clamps around the face of the fixture – one by one – out of the way of the approaching cutter so that at any time 11 are engaged to maximise rigidity.”

To understand the natural frequencies of the MSSS bin, the company performed modal analysis in 12 different but repeatable locations around the fabrication. A tap test on a fully fixtured bin, with 32 touch clamps and three push clamps engaged – in addition to the 12 swing clamps and with the internal and external airbags inflated – showed that the vibration amplitude fell to below 0.1 g in under 17 ms on average. That is much less time than the four hundredths of a second it takes successive inserts on an eight-tooth milling cutter rotating at 176 rpm to engage with the metal being machined.

The agitation induced in the material during the cutting process has therefore completely dissipated in the elapsed time between one tooth engaging with the workpiece and the next, an outcome that is impossible to achieve under conventional clamping conditions. This solution prevents any resonance occurring and avoids amplifying vibration, thus eliminating chatter and consequent dimensional inaccuracy and poor surface finish. In effect, the resonant frequencies of the bin are now altered to such an extent that the hollow workpiece has properties similar to those of a solid cube of metal.

The project started in March 2018. A Taurus 30 machining centre from one of Kingsbury’s principals, Waldrich Coburg, was the chosen machine-tool platform for the project, and final trials took place at the manufacturer’s factory in Germany in late 2019 and early 2020. Lamb witnessed these trials and was convinced it would save cost and help Sellafield hit its box production rate as legacy nuclear material extraction ramps up over the coming years.

In mid-2020, the UK’s Intellectual Property Office granted Kingsbury an industrial patent covering the design of the novel fixturing system, based on its ability to damp the structures during milling.

The machine has a cast-iron base and incorporates a static column and moving table, a configuration that lowers the centre of gravity and increases stability. The 400 x 400 mm cross section of the ram provides the rigidity needed when machining the lower part of the component at maximum extension.

A hydrostatic guideway with a film of oil between the slide and moving assembly supports each axis. Irrespective of speed and applied load, the distance between the faces remains constant, while the system distributes an unchanging volume of oil to further help suppress vibration. The spindle employs a large bearing pack and an HSK125-B tool interface, providing excellent rigidity and machining capability.

The solution developed for the MSSS box applies equally to the MSSS skip and the PFCS box, each of which takes advantage of its own fixture, complete with airbags. Automation on the Taurus 30 sees two fixture assemblies capable of holding six different part variants for both boxes. It means that a complete ship set of parts needed for all MSSS and PFCS bins are fixtured across the two pallets. While one pallet is within the machining area, the operator has free access to unload and then reload to the fixture assemblies on the other pallet, so downtime is limited to the pallet changeover time.

Lamb concludes: “I’m certain that the combination of Kingsbury’s patented fixture solution and the Waldrich Coburg Taurus machining centre will provide Sellafield with a reliable and cost-effective long-term solution for the manufacture of the MSSS and PFCS boxes.”

For further information
www.kingsburyuk.com

Ficep boosts customer support

Ficep is increasing its customer support focus with a new service engineer appointment. Although the company says it already offers the highest ratio of service engineers to installations in the steel processing industry, Ficep has now appointed a dedicated service engineer to cover Scotland. The arrival of the new engineer takes the total number of service engineers in the business to nine, with coverage across the whole of the UK.

UK service manager Richard Clark says: “Our CNC machinery sits at the heart of the production line for many of our customers, and downtime would cause the entire manufacturing operation to suffer almost immediately. As such, we’re continually looking at ways of enhancing the support we offer.

“Our field team has extensive CNC experience and is highly trained on Ficep equipment,” continues Clark. “We aim to reduce the time engineers spend in the car and increase the amount of time they can spend on site. Adding to our network of service engineers is helping us achieve this, and means that our customers in Scotland can now have an experienced engineer on site even more quickly, if needed.”

Ficep’s focus on aftercare and customer support aims to meet a range of business needs, and the company offers flexible support packages, all designed with customers in mind. For instance, the company offers experienced technical support with its hotline engineers, who can diagnose issues without delay via an internet connection. Ficep also offers numerous service contracts. The standard package includes an annual machine service, a guaranteed 48-hour response time, two call-out days during the year, and discounts on spares. Bespoke support is also available.

For further information
www.ficep.co.uk/services

Record Lantek sales in 2020

In a year marked by the impact of the COVID-19 pandemic, sheet-metal software solutions expert, Lantek, achieved record sales of €21.3m, slightly higher than the figure recorded in the previous financial year. The company also achieved a record figure in terms of the number of active users. In 2020, Lantek gained 2247 new customers, bringing the total to 25,747 across more than 100 countries. The UK, in particular, achieved another year of continuous growth and adapted well to remote working for support, training and commercial presentations.

For further information
www.lantek.com

Virtual careers fair

Swiss Steel, Bevan Group and Alucast are among the UK manufacturers taking part in the Made Futures virtual careers fair (22-26 March), a free virtual event encouraging people to apply for jobs in manufacturing. The Made in Group, a trade association challenging the erosion of British industry, will host the week-long event via an interactive platform.

Manufacturers across the Midlands and Yorkshire will have a virtual stand where job seekers can speak directly with employers and learn more about their businesses.

For further information
https://is.gd/efilos

XYZ strengthens sales team

XYZ Machine Tools has made additions to its sales team with the appointments of Josh Adams and Lee Wilkinson, along with a change of role for John Aspinall. The most recent appointment is Adams (left), who will take on the area sales manager role covering Leicestershire, Oxfordshire and Coventry. He has extensive tool-making knowledge and experience in sales within the tooling and work-holding sector.

The second appointment is that of Wilkinson (centre), who will develop sales in the southeast of England, covering parts of Bedfordshire, Essex, London, Surrey and Kent. With an engineering background and broad experience in sales of high-quality tooling, work holding and machine tools, Wilkinson is looking forward to getting face-to-face with customers. A further new area sales manager is John Aspinall, who moves internally from education sales. Aspinall will cover South Yorkshire, Derbyshire, Staffordshire and into the Walsall and Telford postcode areas.

For further information www.xyzmachinetools.com