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Titanium Machining using Makinos T2, T2.5 and T4 Horizontal HMCs

Titanium Machining using Makinos T2, T2.5 and T4 Horizontal HMCs

Added to MTDCNC by MTDCNC on 14 May 2012

Staff from NCMT, the UK agent for Makino machine tools, will be present on the Japanese manufacturer's stand throughout the show to promote three distinct areas of production in the aerospace industry.

One is milling of aircraft structural parts in titanium alloys using Makino's T2, T2.5 and T4 horizontal machining centres. Another is machining of aluminium aerostructures on the latest Makino 5-axis MAG platform and the new -nx series machining centres, all of which are horizontal-spindle models. Thirdly, production of larger nickel alloy engine components using the VIPER grinding process will be highlighted.

Titanium machining

The show will mark the first anniversary of the launch of the T2 5/6-axis machining centre in Europe. The 2,000 mm x 2,000 mm x 1,800 mm capacity machine is able to hog up to 500 cm3 of Ti-6Al-4V per minute from workpieces weighing up to five tonnes. Despite having such impressive roughing performance, the machine is also capable of 5-axis simultaneous finishing to very high precision.

A significant technological advance is the use of three rotary CNC axes, a ±110-degree A-axis and a 360-degree C-axis on the spindle head, plus 360 degrees of continuous movement on the B-axis table. The user is able to choose A/C mode and position B for machining airframe parts, for example, or can A/B for efficiently machining engine casings and other circular components. In either case, the sixth CNC axis can be repeatedly repositioned during a machining cycle.

The machine has a very rigid structure able to withstand high feed forces good damping to resist vibration a dynamically stiff, high torque, high power spindle and copious coolant delivery for efficient cooling at the point of cutting and rapid evacuation of swarf.

To prevent collisions, Vericut simulation of the entire machining area including spindle, tool, component, fixture and table takes place in the machine control on the post-processed program, rather than off-line within the CAD/CAM environment. The virtual cycle runs almost in real time, lagging the actual cutting path by a few milliseconds, sufficient to stop the machine should a collision be predicted.

Aluminium machining

Makino offers its MAG series of 5-axis, horizontal machining centres for producing large aircraft structural components but at the smaller end of the scale, the recently introduced a51nx and a61nx models offer raised productivity, accuracy and reliability.

The 40-taper, horizontal machines feature improved casting designs as well as enhancements to the spindle and guideways. They impart rigidity, precision, lower vibration and improved tool life normally associated with 50-taper HMCs, while maintaining high speed machining capability. An HSK-A63 interface is optional.

The a51nx features a 560 mm X-axis and, compared with the a51, extended Y- and Z-axes of 640 mm, giving a 14 per cent larger working envelope than the previous equivalent model. The standard a61nx has 730 mm by 650 mm by 800 mm axis travels, whilst an optional tall column extends the Y-axis to 730 mm. Due to the larger Z-axis strokes on the a51nx and a61nx, maximum tool length is increased to 430 mm and 510 mm respectively.

More powerful standard and optional spindles are offered. The standard type is a 14,000 rpm design with 240 Nm of torque and 22 kW of continuous output &ndash a 19 per cent increase. A 300 Nm spindle for high metal removal rates in ferrous materials is available, as is a 20,000 rpm, core-cooled spindle.

Axis acceleration of 1g to 50 m/min cutting feeds and 60 m/min rapids minimise non-cutting time. Additionally, -nx models have a direct drive B-axis table that affords faster indexing than the previous worm gear drive, as well as reduced complexity, wear and backlash. The motor includes an inertia control system that adjusts table speed and acceleration based on pallet payload.

VIPER grinding

For producing aero engine parts from nickel alloys and other difficult-to-machine metals, VIPER (very impressive performance extreme removal) creep-feed grinding is capable of stock removal rates up to eight times those achievable when conventionally grinding nickel alloys using a plated CBN wheel. Broaching, milling and turning operations can also be eliminated using the VIPER superabrasive process. In all cases, consumable costs are reduced dramatically.

Latest development from Makino is the introduction of the 7-axis i-Grinder G7, which like other VIPER machines is based on a machining centre platform. This allows both grinding wheels and other metalcutting tools to be exchanged automatically between the tool magazine and the spindle, allowing a variety of machining operations to be carried out in the same cycle. Metal removal rate when VIPER grinding on the G7 is of the order of 80 cc/min.

The smaller Makino i-Grinder G5 accepts parts nominally up to 300 mm diameter, but with increasing aircraft engine size, some larger vanes were falling outside the machine's working envelope. The X: 730 mm by Y: 650 mm by Z: 730 mm capacity of the G7 addresses the problem. Increased space in the machining area also allows room to house two roll stacks to dress the grinding wheels, allowing flexibility to produce a greater variety of components without having to change the rolls.

Alternatively, in the case of some complex components like turbine vanes, more than three operations may be needed. Usually, three is the maximum number of grinding wheel profiles a dressing roll stack can hold. So on a G5, components requiring four or more operations have to be part-machined in batches to achieve economical manufacture and then returned to the machine for another set-up, with consequent work-in-progress, wasted time and potential for loss of accuracy. On the G7, such parts can be machined in one visit to the machine, so one-off production is economical.

Makino NCMT Grinding Division offers this technology across continental Europe and Scandinavia in addition to the UK and Ireland.

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