Moyola Utilises DST Six-Axis Machining Centres

Moyola Precision Engineering has invested in three high-speed, six-axis machining centres from Dorries Scharmann Technologie (DST) for its aerospace division. Mark Semple, managing director at Moyola, said having an extra CNC axis in addition to the more usual five axes results in productivity and cost benefits when machining aircraft structural parts. An advantage is that deep recesses and other awkward areas on components can be accessed and machined at high speed by short cutters.

If the same parts were machined on conventional five-axis machines, longer tools would be needed for clearance. There would be a consequent risk of chatter adversely affecting surface finish. The likelihood, therefore, is that cutting speeds and feeds would have to be reduced, compromising productivity. The kinematically-driven Sprint Z3 head on the two DST Ecospeed F2035 machining centres tilts through +/- 40 degrees in both the vertical A-axis and horizontal B-axis. This is said to be suitable for the majority of machining tasks.

However, the ability to automatically replace the in-line spindle with a right-angle milling head in less than three minutes allows steep angles up to 130-degrees to be achieved. By interpolating the 360-degree C-axis rotation of the head with the X-, Y-, Z-, A- and B-axis, difficult-to-reach areas on aircraft parts can be machined easily with short, rigid tooling. The angle head is used to machine 50 per cent of the parts that go through the Ecospeed F2035s at Moyola. Irrespective of whether the in-line or right-angle head is in use, full advantage can be taken of the 120kW/30,000 rev/min spindle on the latest F2035 and of the 80kW/30,000 rev/min spindle on an otherwise almost identical machine installed in 2005.

Unlike on many high-speed machining centres, it is not necessary to be operating at maximum rev/min to achieve full power, which is available at speeds as low as 13,800rev/min - less than half of full speed. This flexibility enables cutting speeds, feeds and depths of cut to be optimised to achieve maximum performance for each cutting tool assembly. The use of oil mist lubrication rather than coolant through the predominantly solid carbide tools allows the area where metal is being cut to be seen clearly. Good visibility facilitates editing to shave further seconds off cycle times more effectively than if the milling operations were obscured by coolant.

It is also more environmentally friendly, DST said. Design features of the F2035, such as vertical pallet orientation and an absence of swarf traps, allow the machines to remain free from swarf in the working area despite not having flood coolant. Minimum lubrication mist also saves money annually in coolant costs and improves the working environment. All of the DST machines are equipped with twin pallets, including a six-axis Ecospeed F HT installed in 2007 for producing smaller aircraft parts. Even so, cutting cycles are often so fast that, using conventional fixturing, the next component cannot be set up on the second pallet quickly enough to avoid spindle idle time.

Consequently, Zero Point location has been added to all the pallets to speed set-up, a facility more commonly associated with single-pallet machines. Aluminium has a high co-efficient of expansion and features have to be machined to tight positional tolerances, typically 25 microns total, to ensure accurate assembly across different temperatures in a range of environments. The DST machines are said to be able to deliver this level of accuracy without any problem. As the cost of machining goes down, the value added by metal-cutting is often less than the cost of the material. It is important, therefore, to minimise billet wastage, or put another way, maximise material utilisation by producing as many parts as possible from each billet.

This is done by Moyola engineers programming in Catia. It highlights another benefit of the Ecospeed 2035s - namely the 2.5m Y-axis, larger than on any other machining centre on the shop floor at Castledawson. More components can therefore be nested into each billet, which can be up to 2 x 3.5m. The additional width is said to be useful when machining batches of curved fuselage ribs, with smaller parts placed in unused areas close to the billet edges. Reduced frequency of set-up is a further benefit of using larger billets, as it maximises spindle uptime and productivity.

Powermill Aids Move To Five-Axis Machining

Messier-Bugatti is using Delcam's Powermill CAM system to support its move into five-axis machining. Previously the company only had equipment with up to four axes. However, with the move to continuous five-axis machines, it felt it needed a more efficient CAM system to make the most of its new capabilities. Messier-Bugatti specialises in aeronautical braking systems and carbon brakes and has equipped more than 3,500 commercial aircraft.

The Powermill seats have been installed in the company's Molsheim works in eastern France, which is now the production plant for wheels and brakes, hydraulic systems and equipment, as well as handling carbon-disk refurbishment. The most important factors in the decision to select Powermill were flexibility and the efficiency of the resulting programs. In addition, even though most of its parts are made of aluminium, Messier-Bugatti also machines titanium - a demanding material that requires high-quality toolpaths. Stephane Schneider, manufacturing process engineer, said: 'We find it easy to import Catia parts into Powermill, thanks to Delcam's Exchange translation software.

'Then we create the programs within Powermill. 'Finally, we check the toolpaths in Vericut. 'If needed, we can modify any sections of the toolpaths quickly before machining the parts. Among the advantages that Powermill bring to his work, Schneider said he appreciates the control over the different high-speed machining strategies, the smoothness of the toolpaths and the reduction in the vibration of the parts during machining. As well as helping to maintain accuracy, this protects the tooling and the machines.

Controller Simplifies Multi-Axis Motion Setup

Parker Hannifin has launched the Compax3F electrohydraulic controller, designed to help engineers increase productivity and machine performance. The control features optimised force/pressure control, controller pre-setting for closed-loop position control, an updated valve library with the latest Parker valves, and a multi-axis tool supported by a comprehensive database of multi-axis applications. Compax3F is particularly suitable for applications such as die casting, metal forming, blow moulding and tube bending.

Up to 31 motion profiles can be selected including absolute/relative position, force/pressure control, positioning or electronic gearing, with the controller providing synchronous running for up to two hydraulic axes, including replacement for NC 100 axis in new projects. With absolute/relative positioning, for example, a motion set defines a complete group of motions by target position, travel speed, maximum acceleration, maximum deceleration and maximum jerk.

In the case of dynamic positioning, a new profile can be selected during a positioning sequence. All motion parameters will be set valid, with a smooth transition taking place from one profile to the next. Electronic gearing allows synchronous operation of a second hydraulic axis with a transmission ratio 1:1 from a single Compax3F, or synchronous operation of a master axis with any transmission ratio from multiple Compax3F units. Each Compax3F also offers reg-related positioning where two motions are defined: Regsearch, which involves the search of an external signal such as a registration mark on a product; and Regmove, where the external signal interrupts the search movement.

No programming skills are required as the controller uses a simplified configuration setup menu, enabling engineers to select program sequences from profile tables that are easy to parameterise. Common closed-loop controls, such as position, force/pressure or velocity, can be chosen as well as synchronous run or electronic gearing. An extensive tool box containing numerous functions also help to reduce commissioning times to a minimum. Compax3F offers higher product quality due to optimised processes, simplified commissioning by means of menu-driven software and quick installation.

A new force/pressure controller allows force control with control valves or variable displacement pump, and speed feedback for moving systems such as cylinders. Additional Ethernet fieldbus functionality is provided with an Ethercat interface for technology functions T30 and T40. Technology function T30 provides programmable motion control complying with IEC 61131-3, while function T40 adds electronic cam functions including a cam switching mechanism, cam profiles, cam memory and Camdesigner.