Osai Controllers fly through 3 and 5-axis machining at British Aerospace

A worldwide search for state-of-the-art three and five-axis machines for very high precision routing of small aircraft parts at British Aerospace, Brough, led to the selection of machining centres fitting with 10-Series controllers from Osai.

British Aerospace Military Aircraft and Aerostructures has a total capability to design, manufacture, test and support military systems and aircraft and to manufacture detailed assemblies, sub-assemblies and components for a range of civil aircraft. It is a world leader and, at its factory in Brough, Yorkshire, it makes parts for the Tornado, Hawk, Harrier, Gripen, Eurofighter, Nimrod MRA4, Airbus and the BA146 Regional Jet.

Manufacturing Development Engineer, Dean Broughton was tasked with the replacement of two 3-Axis machining centres that were nearing the end of their life. "Initially, we surveyed the market and saw several demonstrations, including a 5-axis machine, which we realised offered possibilities for machining stretch panels (wing sections). We put together a specification and approached several machine-tool suppliers. Each was given the same test piece to produce and provided with tools and data. The operator, engineer/programmer, maintenance engineer and myself all gave their views and the ratings were compiled."

All the results, including ease of operation and programming, accuracy and speed of cycle, were all assessed. The winning combination proved to be CMS machining centres fitted with 10-Series Osai controllers and two three-axis and one five-axis machines were ordered and installed last year.

"The operator particularly liked the Osai controller," adds Dean Broughton. "Whilst we were in Italy, he was talking to the programmer who was programming the three-axis machine. A little more than an hour later, our own operator pulled up the program and did the demonstration himself. He was very enthusiastic!"

The Osai 10-Series numerical control system provides state-of-the-art control with unbeatable flexibility, making the range ideal for specialised high-speed metal cutting machines.

The standard controller covers applications from 3-axis mono-process up to the simultaneous management of 24 processes and 32 axes - all in a single CNC. The management of such a high number of processes by a single CNC significantly simplifies many of the problems associated with multiple control integration in complex applications incorporating several machining heads.

With the optional integral PC and Windows compatibility, the 10-Series is designed to provide easy commissioning and programming. Sophisticated control algorithms ensure superb results, particularly where a high quality of finish is required. This is achieved by a block execution time in the order of 1msec and an axis sampling time of just 200 microseconds. A large dynamic RAM stores all of the data and programs necessary for the most complex components.

The five axis PF Series CMS machining centre has a fixed bridge, which provides the longitudinal 'X' and vertical 'Z' axes movements. The transverse movement 'Y' is carried out by the worktable itself, the final two axes being 'B', ± 110° inclination of the tool-head from vertical, and 'C', a full 360° rotation of the tool-head.

The machining centre is used solely for the production of stretch-form panels. Sheets are heat-treated by solution, quenched and held in chillers to elongate their 'plastic' state, required for working.

Using the Osai controller, the operator imports the required program from the British-Aerospace computer-network and selects the work-sheet for the component. This provides exact instructions on its mounting position, direct on the table or on blocks. Instructions also include any special notes, sometimes accompanied by digital pictures to assist in the process. Panels are mounted on the machining centre on a 'sandwich'-type jig for rigidity.

The operator then instigates the machining program, which, depending on the component, takes about 10 minutes. This compares with several hours taken previously to undertake the same job, with quality and accuracy being equally as good. The machine first drills all holes, which can vary from 2.5-6.35 mm, routs with a 10 mm cutter and then finishes with a 4 or 6 mm router.

Many of the panels, for leading edge wing sections or engine shrouds, are categorised as 'ICY' (interchangeable) and are produced to very tight tolerances. They are designed for rapid removal by ¼-turn fasteners and must provide a weather tight fit, without the need for additional sealing. Some finished parts are finally chemically etched to reduce weight.

"The Osai controller is very easy to use with its menu-driven operation," says Dean Broughton. "Operators have needed little training and we have found all three controllers exceptionally reliable," he says.

The three-axis CMS machines, originally designed for the woodworking industry, are perfectly suited to the production of small aluminium parts for aerospace applications. Stacks of aluminium sheets, up to 12 mm in depth, with individual sheets up to 3.2 mm thickness, although the norm is 1.2 - 1.6 mm, are placed on a wooden bed. The first part of any program is to provide an automatic screw-down, which ensures that two or three 5 mm screws fasten every finished part.

For each job, a nest design is produced and screw-down positions are defined. This is saved to the network, from where the operator can import it into the Osai 10-Series controller.

The sequence of operations starts with the drilling of 4.9 mm holes for the screw-down, following which the routing is carried out, usually with a 10 mm cutter, with any finishing being done with 3 or 6 mm routers to produce slots or radii. Finished parts are degreased, delugged, deburred, idented, heat-treated and formed if required.

"We are delighted with both our choice of machining centres and with the Osai controllers," concludes Dean Broughton. "We have had excellent support from Osai, who helped us with the linking of the machines to the network. The controllers work very well and are a good match to the high performance of the machining centres."

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