Longer and stronger

Being that since the transformation of Voest-Alpine into WFL in 1993, the company has only ever developed mill/turning machines and its commitment to the technology allows it to push the boundaries in many aspects. Thus the centrepiece of its bi-annual technology meeting was its new generation M150, in which the vast majority of parts have been redesigned and tweaked to the point of complete redesign. Also on show were several difficult aerospace components that have been produced on its machines, common applications being landing gear, actuation levers and engine components.

Approximately 1,000 customers prospective and current descended upon the factory to examine the machines up close and tour the production area, which has the capacity to assemble 75 mill/turns at any one time. From the 1.8m centre distance M35 to the 8m M150, all are specified for complex components, many in the aerospace and energy industries.

Although the M150 was the only one of its kind on show, the new generation technology now applies to the company's M100, M120 and M150 ranges, for which at this size, each is built to specific customer specifications. The machine gets its official launch at EMO this October and the largest built so far has an 8m bed, though 10-12m variants are expected to follow in the next few years to meet customer demand.

So what makes an upgrade warrant the ‘new generation' tag? Well, the original designs have been stripped apart and the majority of components re-examined and redesigned with the ambition of a substantial increase in capacity, power and rigidity. A new 134HP (100kW) headstock, now situated on the floor can handle much higher workpiece weights of around 15 tonnes (testing to confirm 20 tonnes is still in progress) and cross slide stiffness has increased fourfold. The cast iron bed has become broader and more stable, taking up to 35 tonnes and with increased guide separations. The left hand headstock now has a longer housing with greater bearing separation and torsional rigidity in the new, patented, higher accuracy C axis, which itself incorporates two specially designed high ratio gears to eliminate backlash and is three times stronger than before. Torque in this axis has also been cranked up to 8,850lbf•ft (12,000Nm) in order to deal with larger parts and the inertia they produce.

The longitudinal upper cross slide has been thickened for extra strength while the cylindrical roller design of the X, Z and Y axis roller guides has six guide carriages. The turning, milling and drilling unit that forms the B axis also has an improved torque of 11,063lbf•ft (15,000Nm) to offer while the magazine can now take a weight of 77lb (35kg) for any given tool and offers more generous dimensions.

With the energy supply systems for the steady rests and tailstock now outside of the working area (a necessity due to its sheer size of the machine), energy chains in the working area and the access and service issues they can cause have been eliminated. The working area itself has also grown and now features flat access. Enlarged viewing windows and a height adjustable control desk also contribute to improved workspace ergonomics.

Assembling one of these machines is a large undertaking (bigger models taking over a year to complete), so the M100 and M120, which were producing aerospace specific components at the event were of the former generation, although they are still more than capable of most jobs required by customers.

The M100 was handling part of a heat resistant superalloy Inconel 718 jet engine shaft 86.6 inches (2,200mm) long and with a 7.9 inch (200mm) diameter. Prior to machining a rough boring operation throughout its length is performed, and the M100 does the rest. Tolerances required of the fine machining operation are achieved by the machine's ability to measure the part and correct the tool accordingly. Boring operations on these machines can reach a cutting depth of 98.4 inches (2.5m) in automatic mode, although manual modes can stretch further without affecting tolerances. Critically for such a component (especially jet engine shafts which also involve internal tapers), a CNC controlled feed-out boring bar is necessary. The insert cartridge is fed by adopting the milling motor into a U-axis drive motor and a gearbox. After machining, centric clamping and steady rest bands measure the actual centre line of the ID contour. The part is then turned around for machining the outside diameters centric to the inside contour. With a special gearbox and gearhead including an additional U-axis drive motor, off-centre bottle boring work can also be incorporated into the machining process.

On the M120 was part of an aluminium actuator used for landing gear flaps 47 inches (1,200mm) long with a swing of 45.3 inches (1,150mm). For reasons of cost-efficiency, the main component is aluminium but is reinforced by a tapered column of titanium which fits inside it. For extra stability the machine makes use of a swivelling B axis with two different clamping systems, reaching tolerances of two microns. In addition, as the customer has to switch regularly between titanium and aluminium, WFL was able to install two separate coolant systems (with titanium requiring an oil-based liquid, especially for the drilling process and aluminium using standard coolant).

Many aerospace parts such as these actuators incorporate a multitude of off-centre and complex contours and as such, the M120 was also chosen to exhibit WFL's proprietary Crash Guard software, which has recently been updated to include the ability to carry out analysis during the programming stage as well as during processing. Using data coming from the machine in realtime, a 3D reconstruction of the process, which is embedded on the control screen, ensures that tools never come within a specified distance of the machine or workpiece unless they are supposed to. This is especially useful when operations have to be interrupted or are reprogrammed on-the-fly. Contained within the Siemens CNC kernel, the customer is able to build their own models, which are then exported ready for use. What the new ‘Crash Guard Studio' software enables in addition to this through the preliminary visualisation of programming stages is improved error detection, efficiency, quality and safety with reduced set-up times, as most if not all problems are resolved at an earlier stage and the process is familiar by the time the operation begins.

As has been the norm for some time now, all WFL machines come with the Siemens Sinumerik 840D control due to its ability to offer up to 30 axis simultaneous control and straightforward scalability. For sales, installation, training, warranty and servicing in the UK, WFL is represented by Kyal Machine Tools.

www.wfl.at
www.kyalmachinetools.co.uk