Machine Design

Linear motors drive all axes

The new VL 50 from Mitsui Seiki USA is said to be the first vertical machining center using linear motors on the X, Y, and Z axes.

The VL 50 machining center uses linear-motor drives on all axes.

The new VL 50 from Mitsui Seiki USA, Franklin Lakes, N.J. (, is said to be the first vertical machining center using linear motors on the X, Y, and Z axes. The unit reportedly outperforms conventional drives at high-speed point milling in multiaxis contouring applications. Linear technology also provides high geometric and positioning accuracies, offering consistently high precision even on long job runs. The company uses low-heat, counteracting, permanent-magnet linear motors that eliminate mechanical backlash, vibration, and noise normally associated with ball screws and other types of drives.

The machine is especially suited for mold and die, aerospace, and precision-parts industries for high-speed machining of high-temperature alloys and hardened tool-steel components. These applications typically face severe requirements for 3D contouring, tight tolerances, and fine surface finishes. But the technology is expected to eventually find use in other areas, such as semiconductor, micromachining, and graphite EDM parts, according to Scott Walker, the company president.

The VL 50 has a 16 X 12 X 8-in. work area, and its toolchanger holds 16 tools. Rapid traverse and cutting feed rates in all axes is 1,574 ipm. Acceleration rate is 1g, and spindle speeds range from 300 to 30,000 rpm. The control system is a Fanuc 15i MB.

A custom alloy used on the sliding components - column, spindle head, and carriage - contribute to overall speed and accuracy. It reduces weight while maintaining stiffness and thermal stability. A three-point, heavily ribbed cast-iron bed weighs over 14,300 lb and fully supports the high machining speeds. A precision glass-scale feedback system detects 0.1 µm increments and has a bidirectional accuracy of <2 µm.

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