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NUM has supplied a custom spindle motor and application-specific CNC system to OMAG to create a five-axis machining centre that combines former and lathe functions for processing stone materials.

The Blade5 machine offers flexibility for processing stone workpieces by supporting capabilities including sawing, milling, routing, turning, sculpting and polishing.

One of the machine’s key features is a high-performance spindle motor with a large peak torque capability of 400Nm.

The spindle motor accelerates all aspects of stone processing, according to the manufacturer.

The machine – with a working area of 5 x 5m – is also able to create a wide range of shapes and profiles direct from CAD/CAM files, making it suited to the creation of one-off pieces or volume production.

It also features a laser scanning option, which allows digitisation and subsequent replication of finely featured work, such as stone artwork.

The spindle motor and the CNC system for the machine’s five positioning axes, which are fully interpolated, were supplied by OMAG’s technology partner NUM.

OMAG’s Blade5 machine is based on a large overhead gantry-style structure, supporting a multi-axis machine head.

The gantry’s main horizontal X and Y axes are based on linear guides that employ ball screw drives and guide blocks fitted with re-circulating ball bearings.

These combine high load-bearing capabilities with smooth, backlash-free positioning.

In the largest configuration of Blade5, both axes have a stroke length of up to 5m, giving machine operators a 25m2 of working area.

The vertical Z-axis, which carries the machine head, employs the same type of technology and can raise the head 3m above the base of the system, enabling huge stone workpieces to be accommodated.

The stone being processed can either be held in a fixed position on a 3.5 x 2m worktop, or rotated by a lathe attachment for turning purposes.

The machine head spindle can accommodate a variety of cutting and forming tools, including a diamond cutting blade up to 1.6m in diameter.

The head contains two positioning axes, which enable the spindle to be inclined by up to 145deg to the vertical and rotated laterally by as much as 380deg.

The gantry’s X, Y and Z axes, as well as the dynamic inclination and lateral rotation of the machine head, are controlled by NUMdrive C servo drives and NUM BPX brushless motors; all five axes are capable of fully interpolated motion, under overall control of a NUM Axium Power CNC system.

This all-digital approach helps ensure accurate and repeatable processing of the workpiece – the cutting co-ordinates are downloaded as ISO files from the machine’s host PC to the Axium Power CNC system.

An optional laser-scanning system enables accurate three-dimensional measurements to be retrieved from a finished piece of work – such as a statue – and automatically converted into an appropriate ISO file, allowing precise replication of the work.

To achieve a high standard of finishing, OMAG has also developed a macro, which evaluates the dynamic motion control commands from the Axium Power CNC system in real time to correct for tool wear, ensuring optimum contact with the workpiece at all times.

The machine head spindle is driven by a liquid-cooled synchronous motor developed by NUM specifically for this application.

NUM supplies the motor’s rotor and stator as separate components, and OMAG then integrates them in the machine head, including bonding the rotor directly to the spindle to maximise rigidity.

The motor, which is driven by a NUMdrive C unit and an MDLL power supply, has a continuous power rating of 25kW at 2,000rev/min, a maximum speed of 8,000rev/min and a peak torque capability of 400Nm.

OMAG’s PC-based CAD/CAM software includes a library of machine tools, which can be requested by the operator; the physical tools are maintained in a rack to the side of the work area.

Typically, these will include milling and turning tools, as well as one or more cutting blades.

Tool changeover is handled automatically; when requested by the operator, the Blade5 machine automatically parks one tool and then places another on the spindle, which uses the industry-standard ISO 50 taper.

The machine’s intuitive human machine interface (HMI) comprises a large touch-sensitive monitor, keyboard and dual joysticks for manually controlling movement when required.

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