Machining centres for aerospace

Citation

(1999), "Machining centres for aerospace", Aircraft Engineering and Aerospace Technology, Vol. 71 No. 4. https://doi.org/10.1108/aeat.1999.12771dab.003

Machining centres for aerospace

Machining centres for aerospace

Keywords: Marwin, Aerospace industry, Machining

First seen at EMO Paris '99 was the Automax II high speed, five-axis machining centre designed specifically to produce structural members from solid aluminium for the aircraft and aerospace industries. The machine on show has 2.1m by 1.2m twin pallet system and is the smallest in a range manufactured for world markets by Marwin Production Systems at its Wolverhampton factory in the UK.

According to Marwin it is designed and manufactured to be between five and ten times more productive for this type of work than conventional machining centres; the machine can produce more than 60 percent of all structural parts used in the construction of commercial and military aircraft and helicopters.

The horizontal, inverter-driven spindle fitted to the machine at EMO was rated at 75 kW/27,000rev/min and it is believed that this is the first time that this specification has been seen. The high-speed, high-power formula enables fast rates of metal removal. Coupled with rapid machine dynamics they are thought to make Automax II very suitable for the economic machining of distortion-free, thin wall components with a wall thickness down to 0.5mm whilst still maintaining high quality surface finishes.

As befits a machine whose use is highly specific to the customer, a wide range of options and additional equipment may be selected to the point where the configuration supplied is virtually a tailored system or multi-machine flexible manufacturing cell based on standard modules.

Instead of tilting the table to provide the fourth and fifth CNC axes, as on conventional machines, the Automax spindle is mounted in a twist and tilt unit giving <$>\pm<$> 45 degrees horizontal and vertical movement. Rapid rotation of the spindle in the A and B axes is 1,500deg/min. Rapid linear feed is in excess of 20m/min and acceleration/deceleration is also fast at 2.5m/s2.

The 24-station, disc-type tool storage magazine for ISO 40 tools weighing up to 10kg can be replaced by increased quantity disc-type units, multi-station chain-type tool magazines or by Marwin's crate system with unlimited capacity and robotic tool handling. For high volume production, a separate load/unload station can be added to the Automax base machine to accommodate a third pallet.

Control system is the Fanuc 160i with tool life management and an integrated PC with Ethernet card capable of accepting part program data via a DNC link. High speed contouring (HPCC), Marwin's post processor and remote machine monitoring are options. Completing the configuration and enhancement options are chip and coolant management systems; spindle bearing condition monitoring; vacuum component clamping; and table and spindle probes for setting-up and calibrating the machine, component, pallet, fixture and laser tool measurement.

Marwin Production Systems has also launched a new, high speed, horizontal machining centre at the top end of its Automax range. Similar models are used in several British Aerospace factories whilst in the USA the machines are operated by Boeing Helicopters and aerospace subcontractor, Tolo, now part of B F Goodrich Aerospace Division.

Called Automax VI, the five-axis CNC profile milling machine may be fitted with pallets up to five metres by 2.5 metres, giving more than 40 per cent extra area for clamping aluminium alloy workpieces than the machine at Boeing, hitherto the largest Automax built (Plate 6). If equipped with a fixed pallet, the new machine may be constructed on a modular principle to any length.

Market research carried out by Marwin has showed that there are many components, especially those with complicated forms and critical tolerance requirements, which cannot be processed economically on large, horizontal bed machines. To address this need, the Automax design utilises a vertical table or multi-pallet system to clamp the billet coupled with efficient swarf management. Additionally, the machine employs very high speeds and rates of acceleration for spindle and axis movements.

Plate 6 The new Automax VI horizontal machining centre is manufactured by Marwin Production Systems, Wolverhampton, for producing large airframe components

The figures quoted are impressive. Up to 75kW is available from the cartridge spindle and maximum speed options are 24,000 or 40,000rev/min. Rapid traverse rates are 40m/min whilst acc/dec is 5m/s2 to minimise non-cutting times, especially when the spindle is traversing over short distances. Tooling with HSK F 63 or 80 taper is used for rigidity consistent with heavy metal removal rates. Laser-based, automatic tool length setting is available, as is full tool management software.

To suit customer requirements, high precision contour control may be specified as well as adaptive control and production data acquisition. CNC system options are Fanuc and Siemens.

Details from Marwin Production Systems Ltd. Tel: +44 (0)1902 366633; Fax: +44 (0)1902 366573.