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Emerald Group Publishing Limited
Copyright © 2008, Emerald Group Publishing Limited
Five-axis production solution for titanium and aluminium parts
Article Type: Aerospace technology From: Aircraft Engineering and Aerospace Technology: An International Journal, Volume 80, Issue 2.
The ability to machine larger aluminium and titanium aerospace components, using five-axis production technology, is high on deepadas the agenda for Bristol-based Oldland CNC Engineering, and has prompted the recent installation of its third Hedelius five-axis moving column vertical machining centre (VMC).
The key factor in the choice of this production platform for John Tucker, Managing Director, was the ability to machine in three-axis mode to say produce original reference or datum faces on one side of the machine and then, via a large programmable trunnion mounted rotary and tilting table, fitted to the other side of the machine base, produce true five-axis toolpaths in a single cycle on the remainder of the component.
Indeed, with the Hedelius RS 125-K supplied by C Dugard of Hove, Oldland has the best of both worlds because a single operator can prepare, manipulate, and load/unload, deburr or inspect a component on one side, while the machine continues its automated cycle on the other and thus maximises productivity and machine utilisation.
The Hedelius is not the first five-axis venture for this progressive 50-man company. In addition to two previous installations of the smaller capacity Hedelius RS 80 machines, also sourced from C Dugard, has been two large capacity Edel CyPort 4020 five-axis gantry machining centres the first installed in 2004, the second 18 months later. As a result, the first Edel machine took the company into Airbus A380 component machining providing the capability for structural parts such as wing skins, that is a particularly successful area of expertise for the Bristol company.
Explains John Tucker: “Following the first Edel we became more competitive and significantly increased our order book for large and more complex parts. That success led to the second machine with all the advantages of common tooling, fixturing and programming.”
The Edel has a capacity of 3,970 x 2,310 x 1,250mm and will accept tools up to 130mm diameter by 300mm long in the 18,000revs/min, 21kW spindle. The Heidenhain i TNC 530 controlled NC head that is carried on a Z-axis ram has direct drives to the ^2008 rotational C and ^1108 swivelling A-axes that can be positioned to an accuracy of ^0.0028. This level of accuracy has proven to be critical, in the type of components Oldland now produce.
Like the Hedelius machines, the Edel gave flexibility to cope with a wide range and challenging components and when required, multiple quantities of smaller parts can also be positioned around the table area to further improve machine utilisation while helping to reduce work in progress and cycle times.
Oldland was established in 1975 by brothers David, having a design background and John with that of a toolmaker. As the company's track record confirms, the business is almost entirely devoted to serving the aerospace sector that is very close to its doorstep in Barton Hill, Bristol. Customers rank as blue chip names in the industry including Airbus UK, GKN Aerospace Services, GE Aviation and GKN Aerostructures, Yeovil and in recent years has chalked up worthy creditations including “Supplier of the Year” awards.
Five-axis machining is viewed by many as an expensive and complex system to manage and support, especially in the subcontract arena. But here, Oldland has scored an important advantage by taking the technology on board. “We never really know what is around the corner,” says John Tucker, “but we have the flexibility and the capability to utilise high power at low speed for machining titanium and the high speed required for aluminium with all the advantages gained by applying the technology.
At both ends of the material spectrum, the ability to combine operations was important to guarantee to meet the geometry requirements of the customers' design engineers for feature to feature relationship achieved because of the capability to position within the same cycle. But John Tucker is not complacent. He maintains: “Five-axis working was new to us and it took a long time to get fully conversant and up to speed. You need a totally different approach to machine a part and by investing in Mastercam, Catia V5 and Vericut to write and modify toolpaths before sending programs to the machine tool made the transition more bearable. You really do not learn until you are on the shopfloor and the machine is in cut.”
He continues by reflecting the reaction to his investment by customers: “They have been very complimentary about the quality levels we have been able to achieve using this technology and especially the high levels of surface finish.” To this he adds: “Due to the tooling always being applied at the most beneficial position to achieve a cut, there is no compromise. This enables maximum metal removal and the maintenance of the benefits from the most effective tool geometry. We have found the cutter path and stepover can be difficult to detect and especially once the surface coating is applied to the parts because the surface finish is so good.”
He also maintains that probing critical dimensions on the machines prior to removal has resulted in only nominal differences of a few microns to when parts are later checked on the company's co-ordinate measuring machines. “That is an important endorsement to the repeatability of the process,” he qualifies.
The Edel has the advantage of the NC head using patented linear drive torque motors, two for the swivelling A-axis and one for the rotating C-axis. These permanently energised synchronous motors have zero backlash and high-dynamic movement. The outer rotor is in effect, an outer race around the stator that enables the magnetic force to create a significantly higher torque when compared with inner rotors of the same dimension. When the operational cycle requires A- and C-axes to be changed, as when taking roughing cuts, the high stall torque of the rotor acts as a brake in addition to the mechanical clamping of the axes giving maximum rigidity.
With a 10m/min maximum feed rate, as well as a 3608/s swivelling speed and 100revs/min rotational speed for the two axis NC head which has direct measuring scales, the Edel CyPort 4020 provides a fast simultaneous machining capability using five-axes of motion.
The capability of the new Hedelius RS Kombi machines to create pendulum machining cycles enables each of the six faces of a component or, two totally different parts, to be produced simultaneously by loading one side of the table whilst the other is machining. In effect, used properly this configuration enables productivity to be significantly improved.
The machines also employ ROTA SWING technology developed by Hedelius enabling both three- and five- axis simultaneous machining to be employed on the same machine bed. The machine also has the capability to hold right angle heads and special attachments in the spindle. Such is the area of the fixed table, in the latest RS 125-K, this equates to 1,250 x 2,500mm that additional indexing, rotary, swivelling and compound table units can easily be added to provide additional flexibility to the trunnion area.
Overall, the travelling column RS 125-K has an X-axis of 4,500mm, a Y-axis of 1,250mm and 770mm in Z. The machine has the optional 12,000revs/min spindle and the table a swivel angle of +108 to 2908 and a full 3608 rotation in the C-axis. The swing of the rotary table is up to 1,600mm diameter that allows Oldland's production engineers to pass larger components through the machining envelope and take maximum advantage of its 56 tool carrying capability.
Details available from: C Dugard Machine Tools, Tel: +44 (0) 1273 732286, web site: www.dugard.com