| RADWASTE MANAGEMENT
Top: Close-up of machining in progress, showing the way in which the hydraulically actuated swing clamps sequentially rotate out of the path of the oncoming milling cutter
Centre: A graphic of the Taurus 30 twin-pallet machining centre
Bottom: Jonathan Lamb, CEO, BEL Engineering
That is much less time than the 40ms it takes successive inserts on an 8-tooth milling cutter rotating at 176rpm to engage with the metal being machined. So the agitation induced in the material during the
cutting process completely dissipates in the time between one tooth and the next engaging with the workpiece. That is impossible to achieve under conventional clamping conditions. Any resonance that would amplify vibration is thus prevented, eliminating chatter and consequent dimensional inaccuracy and poor surface finish. The resonant frequencies of the bin have been altered to such an extent that the hollow workpiece has properties similar to those of a solid cube of metal.
Automated machining cell A Taurus 30 machining centre from one of Kingsbury’s principals, Waldrich Coburg, was the chosen machine tool platform for the project. The project started in March 2018 and final trials took place at the factory in Germany in late 2019 and early 2020. They were witnessed by Jonathan Lamb, who was convinced it would save cost and assist Sellafield increase box production rate as it ramps up nuclear material extraction over the coming years. In mid-2020, an industrial patent was granted to
Kingsbury by the Intellectual Property Office of the United Kingdom covering the design of the novel fixturing system, based on its ability to damp the structures being milled. The machine has a cast iron base and incorporates a
static column and a moving table, a configuration that lowers the centre of gravity and increases stability. The 400mm x 400mm cross section of the ram provides the rigidity needed when machining the lower part of the component at maximum extension. Each axis is supported by a hydrostatic guideway with a film of oil between the slide and the moving assembly. Irrespective of speed and applied load, the distance between the faces remains constant as an unchanging volume of oil is distributed, suppressing vibration further. 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 to the
MSSS skip and the PFCS box, each of which is also held in its own fixture, complete with airbags. Two fixture assemblies have been designed, capable of holding six different part variants for both boxes. A complete set of parts needed for all MSSS and PFCS bins are fixtured across 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. ■
www.neimagazine.com | May 2021 | 35
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