Leamington Spa-based Mills CNC Ltd (
www.millscnc.co.uk), the exclusive distributor of Doosan machine tools in the UK and Ireland, recently launched its new VCF 850 series of five-axis vertical machining centres. These large-capacity machines feature a B-axis head that can tilt 110deg either side of vertical and a 500 or 800mm-diameter rotary table (depending on table configuration), allowing them to machine large and complex parts in a single set-up.
The VCF 850 machines have a substantial one-piece Meehanite bed with heavy ribbing to reduce vibration and deformation during heavy cutting operations, thereby improving accuracy, surface finish and tool life. Moreover, the travelling-column design means that the table — and therefore the workpiece — remains ‘locked’ during machining, thereby ensuring a uniform load on the guideways, ballscrews and drive motors. All axes use roller-type linear-motion guideways, and the double-nut ballscrews for each axis are cooled by circulated, refrigerated oil (as are other critical components including the ball nut, support bearings and motor housing). Furthermore, the X, Y, and Z axes use absolute-type linear glass scales for high levels of positional accuracy.
The machines are equipped with a Doosan rotary table (either embedded or top-mounted), and the dual-contact Big Plus high-torque spindle (204Nm) is rated at 18.5/22kW 12,000rev/min; this features high-precision, permanently lubricated, ceramic ball bearings, as well as a system that circulates refrigerated cooling oil around the spindle in order to maintain a constant operating temperature regardless of the ambient temperature. In addition, a spindle encoder allows rigid tapping for greater productivity.
As standard, a 30-position drum-type tool magazine is fitted; a 60-tool chain-type double-arm ATC is available as an option. Tool-to-tool change-over time is 1.5sec. A separate pick-up magazine holds five tools up to 80mm long and 130mm in diameter. The 3m X axis allows table partitioning for pendulum-type machining.