Manufacturers of large, heavy components are increasingly demanding the capability to machine them in a single set-up to achieve short lead times, improve accuracy and reduce work-in-progress.  Aimed at these users is the new Okuma VTM-1200YB from UK agent, NCMT.

The 30-tonne, double column machine has been designed as a cross between a heavy duty vertical turning and boring facility and a fully-featured, 5-axis machining centre.  Structurally it is configured as a bed-type machining centre but instead of a conventional table, it has a 30 kW / 500 rpm / 6,000 Nm torque turning spindle with 360,000-increment C-axis positioning.

The table has a pair of large cross section X-axis slideways carrying a substantial column with vertical Z-axis slides.  These in turn locate a saddle with Y-axis cross slides to support a 37 kW / 10,000 rpm / 505 Nm milling spindle (B-axis) with HSK-A 100 taper. By locking it using a Curvic coupling, turning operations on components up to 1,200 mm diameter by 1,080 mm long can be carried out without risk of damaging the bearings.

150-degree B-axis positioning allows standard tooling to be used in situations where specials might otherwise have to be considered.  In addition, it is possible to improve milling efficiency when using ball nose cutters by using the tool at an angle to avoid zero surface speed cutting at the tip.  Similarly, angled holes can be produced without the need for special fixtures using a three-dimensional co-ordinate conversion facility within the control software.

The standard tool magazine houses 60 cutters and a common taper standard is used for both milling and turning. Through-tool coolant rated at 150 bar ensures efficient cooling and chip control, especially when working with tough materials such as titanium and Inconel.

Axis travels are 1,270 mm in X, 1,080 mm in Z (vertical), and 1,000 mm in Y.  Absoscale linear encoders guarantee 0.1µm feedback. Rapid traverse rate is 32 m/min in all linear axes, 20 rpm for the 360-degree C-axis and 19.5 rpm on the B-axis.  Control is by Okuma's own OSP-P200 CNC system.

During simultaneous 5 axis milling, tool center point control and Super-NURBS ensures high contour accuracy and surface finish. In combination with the Okuma's Thermo-Friendly Concept, even if the ambient temperature changes, a user can achieve accuracies better than 10 microns. 

Options include a pallet change system, allowing the machine to be configured as a semi-automated, stand-alone machining cell.