A retrofitted CNC has transformed an ageing, 'difficult-to-operate' manual lathe into a user-friendly, fully-functional CNC turning machine
By retrofitting an Anilam 4200T CNC to an ageing lathe, the UK Astronomy Technology Centre (ATC) has transformed what was 'a difficult-to-operate piece of equipment that technicians were hesitant to use' into a user-friendly, fully-functional CNC turning machine. As a result, CNC turning with the Anilam control is now the preferred route for two-axis turning at the centre.
Reflecting on the problems caused by the old controller Ewan Marshall, project technician at the Royal Observatory, Edinburgh ATC, says 'Despite the fact that all the turning work is fairly straightforward two-axis machining, the old control was difficult to program, therefore it was not the most cost-effective method to manufacture the components, resulting in the machine not being used to its full potential.' Today, however, after Anilam's local agent, Inscot, retrofitted the 4200T, ATC engineers have at their disposal a powerful yet user-friendly (full-screen editing and conversational help menu) CNC system featuring G code input with full text editor for cut, paste, search and replace, for example, plus interactive conversational G code help graphics and CAM programming.
Program utilities on the 4200T include create, delete/undelete, list, copy, rename and print, and the system also features constant surface speed as standard, to help guarantee consistent surface finish and extended tool life.
Also, the control can run in several operational modes - including teach mode achieved via single or dual handwheel operation with dual axis interpolation.
Being well-versed in G code programming, the ATC operators describe the Anilam as a vast improvement compared to the former control, as technician George Davidson confirms: 'In comparison to the previous CNC, which was a real nightmare, the Anilam guides us through everything.
We have extensive G code experience, so we tend to code in the job as we see it, rather than drawing it on the screen first.
'The Anilam CNC is really easy-to-use, so much so that the machine is now in more frequent use across a range of parts - which wasn't the case previously.' One example of the work being put through the new-look lathe is the beam steering mirror blanks required for the spectrometer focal plane unit within SPIRE (Spectral and Photometric Imaging Receiver), one of three instruments that will be carried on the European Space Agency's Herschel Space Observatory (formerly the Far Infra-Red and Sub-millimetre Telescope) scheduled for launch in 2007.
With its 3.5m primary mirror, it will be the biggest space telescope yet flown.
Designed for spectral and photometric observations at far infra-red and sub-millimetre wavelengths, SPIRE will investigate the statistics and physics of galaxy and structure formation in the early universe, and study the earliest stages of star formation.
SPIRE's focal plane unit - and therefore the mirror blanks - are critical components, and the blanks are rough and finish turned from 60mm diameter 6061 aluminium billets 90mm long before being switched to one of several milling machines-manual/DRO lathes for a variety of profile boring and milling, as well as part-off operations before being outsourced for diamond machining.
Machining includes the creation of a 'spectacle' feature and an opposing 'clamp' feature, as well as the production of a cavity face, various slots and the mirror face to an intermediate thickness of 10.55mm before diamond machining to create the mirror finish of 2 microns.
The turning and milling sequences are interspersed with two thermal cycling routines to stabilise the material structure for low temperature use.
With its mission 'to help keep the UK at the forefront of world astronomy by providing a UK focus for the design, production and promotion of state-of-the-art astronomical technology', the ATC shares the old Royal Observatory Edinburgh site at Blackford Hill with the Edinburgh University Institute for Astronomy, and with 11 employees the machine shop plays a key role in the manufacture of the various spectrometers, telescopes and infra-red cameras produced for customers the world over, including the Isaac Newton Group, UKIRT and Gemini telescopes.
No two projects are the same, so batch sizes through the machine shop are small - often one-offs - and Ewan Marshall says ATC is like every other manufacturing organisation in that each contract has to be competitively priced, produced on time and delivered to specification (even though ATC operates with Government funding and in a non-profitmaking mode).
As well as the impressive machine shop, ATC maintains its centre of excellence mantle via expert teams covering project science, project management, applied optics, and electronic and software engineering, and it invariably acts as the turnkey player in developing the specific solutions and designs (often in conjunction with universities at home and abroad) then determining and managing the appropriate manufacturing processes and lead time schedules.
Including administration, around 100 people are employed in the centre's CAD/CAM and electronic CAD, optical design, optical test laboratory, detector test facility and cleanroom, software development, machine shop, cryogenic and vacuum facilities, as well as the telescope simulator and fixture testing areas.
Many of the components produced are tested at -260deg and 25G before final commissioning on site by ATC staff.
The machine shop traditionally handles the production of all components within a 500mm3 envelope; anything larger that needs to be either machined or fabricated is outsourced along with specialist tasks such as gold plating and mirror-finish machining.
However, within the next few years the completion of a GBP 4 rebuilding project to create new workshops, laboratories and office space will enable ATC to handle larger projects, say up to 2 m3.
'There are no plans to extend our machining capacity,' says Ewan Marshall, 'rather, the expansion will enable us to cope more easily with the assembly and test of larger projects, through the construction of buildings with high-ceilings and heavy overhead cranes.' Most of the material processed by the machine shop is aluminium (in addition to lightness it exhibits good thermal characteristics at low temperatures), with stainless steel and copper processed in lesser quantities and, interestingly, each operator is held totally responsible for the complete machining and resulting quality of the components he produces.
Every technician can work across either the CNC milling machines (which all feature Heidenhain CNCs) or the manual/DRO and CNC lathes in addition to handling a myriad of inspection routines as well as operating the co-ordinate measuring machine and assimilating the resultant QC data.
Also, each technician will plan and manage the production route of 'his' components to align with the master production schedule.
Machining work is evenly split between turning and milling.
'So,' says Ewan Marshall in conclusion, 'the updating of the lathe with the Anilam CNC was met with a huge sigh of relief by everyone.
Nobody had wanted to use the machine, but after Anilam's recommended training session, we were all conversant and comfortable with the control.
We now confidently use the machine whenever we can.'
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