Five-Axis Machining Center is optimized for accuracy.
October 20, 2008 -
Offered standard with 40-taper spindle rated 25 kW/14,000 rpm, D500 minimizes cumulative inaccuracy inherent upon increase of simultaneously interpolated axes. Rapid traverses of 48 m/min in X and 50 m/min in Y and Z axes can be achieved when supporting workpieces up to 350 kg on table or 300 kg on pallet of APC configurations, as can 50 rpm positioning of 360° C-axis table and +30°/-120° A-axis trunnion. Acceleration/deceleration during cutting is optimized via 3 direct-drive motors.
(Archive News Story - Products mentioned in this Archive News Story may or may not be available from the manufacturer.)
Makino Takes 5-Axis Machining Accuracy to a New Level
Renowned for supplying machining centres capable of very high levels of accuracy, the Japanese manufacturer, Makino, has announced a sequel to the V55-5XA vertical-spindle, 5-axis machining centre that it launched in 1999. Designated D500, the new machine overcomes limitations of similar models on the market in five key areas.
One is the minimisation of cumulative inaccuracy inherent when the number of simultaneously interpolated axes increases. Second is the provision of quicker movement in the linear and rotary axes when supporting heavy workpieces up to 350 kg on the table, or 300 kg on the pallet of APC configurations. Under these loads, rapid traverses of 48 m/min in X and 50 m/min in Y and Z are achieved, as are 50 rpm positioning of the 360 degree C-axis table and, surprisingly, of the +30 / -120 degree A-axis trunnion as well.
Higher levels of automation and better ergonomics are two further goals that have been met. The fifth objective was to increase acceleration and deceleration during cutting, which has been realised by upgrading the drive to the rotary axes, traditionally the weak links in full 5-axis machining. Faster motions are delivered by three high-torque, direct drive motors, one at each end of the trunnion and one on the table.
The machine is available in the UK through sole agent, NCMT, which says that the accuracy figures quoted by Makino for positioning and for repeatability are typically half those claimed by other manufacturers of similarly designed, 5-axis machines. In X, Y and Z, full stroke positioning on the D500 is ± 2.5 microns (± 1.5 microns if linear scales are used instead of rotary encoders) and repeatability figures are respectively ± 1.5 microns and ± 1.0 micron. In the rotary axes, positioning is within ± 3.0 seconds of arc and repeatability is ± 2.0 seconds of arc.
The cumulative effect of addressing these five key areas is the introduction of a machine that offers advantages for manufacturers of all types of component. Linking Makino's proven pallet handling and storage systems allows flexible, cost-effective machining of parts by the general engineering sector within a 650 mm diameter by 500 mm envelope, even in small batch sizes and even one-offs.
So that operator access to the front of the machine is not impeded, the pallet change mechanism is located to the rear, made possible by having the trunnion and table / pallet assembly effect X-axis movement under the spindle head, which traverses in Y and Z.
Manufacture of engine components for the motorsport industry is aided by the machine's extreme accuracy, while in the aerospace sector, the speed of the rotary axes helps reduce cycle times for simultaneous 5-axis profile milling of turbine blades. For the latter application, a 60 per cent reduction in cycle time has been achieved compared with machining the same part on a V55-5XA.
Die and mould machining is the other main application area for the D500. Its rigidity when in 3+2-axis machining mode with the rotary axes clamped minimises the mismatch when machining to the same line from two different directions, frequently avoiding the need for hand finishing. Surface finish is said to be 30 per cent better than on the superseded machining centre while improved rigidity, even in full 5-axis mode, cuts roughing times by about the same percentage.
The standard 40-taper spindle is rated at 25 kW / 14,000 rpm, although the user can opt for a 20,000 or 30,000 rpm version with patented cooling of the spindle and headstock. Temperature controlled oil is circulated initially through the centre of the rotating spindle and then passes to the outside of the spindle bearings, before being routed through the stator core and back to the cooler. A measure of the system's effectiveness is that the temperature gradient from oil input to output is around 16oC at full load.
The effect is to maintain the inner and outer races at almost the same temperature, ensuring that the preload remains constant and consequently allowing the same cutting force to be exerted throughout the spindle speed range without any variation in accuracy.
Linear roller guideways are one size larger than are usual on a machine of this size to ensure high rigidity and low friction. All axes have core cooled, large diameter ballscrews. Design of the chip management system is commensurate with the need to evacuate large quantities of chips quickly and efficiently. Software innovations within the SGI.4 control system include enhanced smoothing strategies for high speed profiling, a workpiece setting function and collision avoidance.
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