Specialist machine tool company Electron Engineering Services Ltd (EES), Halifax (www.electron-services.co.uk), recently completed a project to design and manufacture a CNC gantry machine for one of the UK’s leading manufacturers of aero-structure components.

EES initially approached the customer with the concept of a specially designed machine back in 2009, following its successful refurbishment and retrofit of a number of long-bed Marwin gantry machines, which are used for machining aircraft wing stringers and spars.

A pending restructuring of the customer’s manufacturing facilities in 2013/2014 left it with the choice of either re-locating several existing machines or contracting EES to manufacture the new gantry machine. The re-location would be costly and would result in a massive loss of production, so the second option was chosen.

The machine is of fixed-bed travelling-gantry construction, with a bed length of 31,500mm and an X-axis travel of 30,000mm. The component is clamped in vices mounted on cross-members that effectively form the table area of the bed; wide apertures between the cross-members allow the swarf to fall into the middle of the base, directly into the centre-mounted swarf conveyor.

Three independently programmable spindles are mounted on the front and rear of the gantry; the primary 45kW 2,000rev/min spindle on the front of the gantry is designed to carry a 315mm-wide face mill for the roughing and finishing of wing stringers; the two 15kW 9,000rev/min auxiliary spindles mounted on independent saddles on the rear of the gantry (pictured) are used for the machining of clamping slots and the profiling of any details on the back of the stringers.

The machine is fitted with the latest Fanuc 31i multi-channel CNC system, which allows three separate part programs (one for each spindle) to run simultaneously.

EES sales director Richard Vogel says: “We sat down with the client’s production engineers to discuss the challenges of machining this particular type of component and — just as important — the shortfalls of existing off-the-shelf machine tools. From there, we adapted our machine concept into a detailed design solution tailored to meet the client’s individual manufacturing requirements.

“Cycle times have been reduced significantly by the new machine due to the unique gantry design, which enables two machining operations to be performed simultaneously.

Furthermore, this has all been achieved in under 12 months, from concept design to commissioning at the client’s site — exactly to the quoted delivery date and at a fraction of the cost of any recognised commercially available gantry machine.”