Machining centres in action - space and medical technology

(includes links to recent product launches) Parts for instrumentation used in space observation, both terrestrial and satellite-based, are machined to tight tolerances on two Hurco vertical machining centres (VMCs) at Rutherford Appleton Laboratory (RAL), near Didcot. The machines (01494 442222) are a 5-axis Hurco VM10U and a Hurco 3-axis VM30. High accuracy is essential, as radio telescopes, for which parts are being made, including the ALMA instrument in northern Chile, have to detect high frequency signals in the 95 GHz to 2.5 THz range. Wavelengths are consequently very short and sensitive to dimensional variation in sensing devices. The latest machining centre in the Millimetre Technology Group's Precision Development Facility (PDF) within RAL Space, as the department is known, is the 5-axis Hurco model VM10U, which was installed in April 2011. Fitted with Renishaw tool setting, the machine was purchased jointly with another department on the RAL campus, ISIS, which conducts research into atomic scale properties of materials, using a suite of neutron and muon instruments. Components required for its beamline accelerators also have to be very accurate and are made on the Hurcos. Image: Space-age machining at RAL is undertaken on Hurco machining centres LIGHT AS POSSIBLE An example of RAL Space hardware machined on the 5-axis VM10U are components that, when assembled, form parts for the Broadband Radiometer, destined for launch into space in 2012. The component, machined in 3+2-axis mode from solid aluminium to dimensional tolerances at the micron level, has to be as light as possible. To this end, the core is removed by wire-cutting after milling to leave a 0.8 mm wall all round. Mat Beardsley, manager of the PDF, explains: "Generally, subcontractors do not like making parts such as this, as the machining strategies take a long time to develop for novel bespoke components. "Due to the high machining accuracies associated with this type of componentry, it was difficult to find outside suppliers to take on the work, which was a driver for investing in our own 5-axis machine." Typical ISIS components produced on the Hurco 3-axis VMC, a VM30 installed in the summer of 2010, are tantalum parts for a beamline target, machined using coated solid carbide cutters to accuracies down to 10 microns. A high surface finish is required, but is not easy to achieve, due to the material's tendency to tear. Machining strategies, as well as feeds and speeds for the tooling, have consequently been modified within the CADCAM system used in RAL Space. More complicated components for the ISIS target are put onto the 5-axis machine, such as the tantalum flange and cross-flow guide that are subsequently pressed isostatically around a tungsten core. The introduction of 5-axis machining has also made huge savings in the manufacturing time of several integral parts for space flight hardware. Mr Beardsley comments: "Before investing in the Hurco machines, we had used other makes of VMC for more than 10 years and they are still in service. "When the ISIS beamline work came along, however, we needed a bigger capacity machine, but we have limited floor space. So we were looking for maximum working volume in the smallest possible footprint and the Hurco VM30 was ideal [1,270 by 508 by 508 mm axis travels/2,830 by 2,770 mm floor area]. "The same goes for the VM10U, which also offers a generous machining cube for the space it occupies. So, in view of our good experience with the previous 3-axis Hurco VMC, it was the logical choice when we needed a 5-axis machine." FACTORY SURGERY In America, Rochester Medical Implants is using Haas machining technology (01603 760539) to support its operations. Today, about 80% of RMI's work involves producing high precision orthopaedic implants, mainly for spinal surgery, and about 20% involves making the instruments used in that surgery. James Evans, the firm's president and general manager, joined RMI in 2007 after a career that included time at Corning as a divisional VP, responsible for marketing and product development. He explains: "RMI has roots dating back to 1996, but my partners Marv Selge and Dr Michael Method only bought into it in 2005. They quickly realised that it wasn't a passive investment and asked me to help. The firm was a supplier of surgical implants and instruments to a large OEM. But, though the outgoing quality was good, the internal processes weren't. It was a small operation, but it lacked discipline and the scrap rate was immeasurable." It took Mr Evans just five days to realise that he would have to wield his own scalpel. "It wasn't pleasant," he admits, "but we had to work fast to save the company. There were 24 employees and I only wanted 16 of them. So we terminated everybody on my fifth day and asked them to reapply for their jobs on the following Monday. We got back 15 of the people we wanted and we set about rebuilding the company. Thankfully, we already had some good machinery, including a number of Haas machines and lathes but no one was really working them to their full potential." The company's local Haas Factory Outlet (HFO) helped the company out, not only providing more machines, but new staff and partners, including good tool suppliers. One of the challenges was to efficiently machine PEEK-OPTIMA, a biocompatible polymer. The Haas outlet put the company in touch with tooling suppliers, who showed RMI how it should be done, prompting Mr Evans to make his first big purchase: a new 30,000 rpm Haas mill. "That was the only machine we bought in 2007, but, with its very sharp tooling and high spindle speeds, it significantly improved our ability to achieve excellent surface finishes with PEEK." In upgrading its CADCAM skills, the local Haas HFO helped out again, pointing the company at the nearby University of Vincennes, which has a Haas Technical Education Centre that runs a manufacturing technology course for third-year engineering students. During that year they perform 800 hours of Mastercam machining, modelling and Haas vertical milling. Mr Evans hired one of its graduates plus another Mastercam programmer – the company has three Mastercam seats. The company went through an equipment upgrade in 2008, buying eight new Haas machines: two additional 30,000 rpm mills for its dedicated PEEK cutting room and six 15,000 rpm mills for the metalcutting area. "We have continued to invest in people and machines since then and now have a good team: currently 32 employees and 15 Haas vertical mills (almost all 5-axis)," Mr Evans explains. "Those machines run five days a week (double shifts) and are available on Saturdays. They play an important part in our ability to respond positively and flexibly to our customers' needs, which means we are once again able to offer great service." Image: Rochester Medical Instruments likes Haas technology For example, he offers this example. "One client came to us on a Thursday evening needing parts for surgery the following week. They didn't even have a 3D model. We pulled a couple of late nighters, worked the weekend and the parts were implanted in the patient on the Tuesday! You don't get that sort of service everywhere; that's why companies come to us." Box item Further product information [] VTC-560/25 joins Mazak travelling-column VMC series [] Brother S2DN mill/drill/tap machining centre offers BT40 challenging 92 Nm of torque [] MAP HDC 150 5-axis machining centre from 2D CNC Machinery has linear axes; micron accuracy [] Doosan machine tools now have Renishaw GUI for probing (video) [] Mazak Vertical Centre Smart 530C machining centre fit for larger workpieces (video) [] Mori Seiki/DMG launch compact high performance MillTap 700 First published in Machinery, January 2012