Linear servo motor for applications
with limited space

With this design, each individual pipette can be controlled easily and very precisely. Dynetics used the linear servo motor together with the FMAX compact controller, the hybrid module Commander and the Arcus CRX-8 driver for the design. The linear servo motor is a high-precision, direct-drive motor consisting of a shaft with rare earth iron-bore-neodymium permanent magnets and a runner with cylindrical coil windings. There is no iron in either the shaft or the motor driver ensuring high precision and a cogging-less function. The coils themselves form the core giving the motor the necessary stiffness. Linear servo motors are contactless. Since the coil completely encloses the magnets, the magnetic flux density is used effectively. This allows a large (0.5 to 5 mm) annular nominal air gap. This air gap is uncritical in the sense that there are no changes in force. Thanks to the cylindrical design and other design elements such as the shape and alignment of the coil and permanent magnets, the generated force operates to 100 percent only in the direction of travel with moderate heat dissipating. The iron core also provides large absorbing forces between the stator and the valve and leads to cogging in the linear motion.

No lubrication and adjustment maintenance required

The linear servo motor does not require lubrication and does not suffer any loss of performance due to wear or ageing. Thanks to its maintenance-free operation and long service life, this motor scores with low life-cycle costs. ▪ ds