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.
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.
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