Ultra-precise linear shaft motors with high performance and small footprint

The linear shaft motor is a direct drive consisting of a shaft with rare earth permanent magnets (iron-boron neodymium alloy) and a runner made of cylindrical coil windings. The shaft provides the magnetic fields on which the runner acts. The driver assembly, in combination with the amplifier and control electronics, generates the power for the motor. A small current generates a great force. In this article, the mechatronics specialist Dynetics describes the further advantages of linear shaft motors.
Drive technology
The tubular coils completely enclose the magnets and thus use the entire magnetic flux of the permanent magnets
Linear shaft motor servos are somewhat unknown in the mechanical engineering market. They have typically been deeply embedded in high-precision OEM systems that handle lithography, wafer scanning and optical inspection applications. However, in the semiconductor automation sector, their ultra-precision capabilities make them the engine of choice. What are their advantages?

No Cogging

Applications that require precision in the nanometer range require a latch-free motor. The cogging torque occurs in flat linear motors where the iron core of the motor coil (forcer) reacts with the permanent magnets of the magnetic path or track. This pulling into the preferred position of the motor (latching) causes both power and speed ripple during movement.
This is highly undesirable in applications where an absolutely uniform, ripple-free speed or force is required by the motion profile. Neither in the shaft nor in the driver of the NPM motor is iron present, which ensures high precision and latch-free behavior. The coils themselves form the core and thus give the motor the stiffness.
The linear servo motors are contactless. Since the coil wraps completely around the magnets, the magnetic flux density is used effectively. This allows a large (0.5 to 5 mm) ring-shaped nominal air gap. This air gap is not critical, in the sense that there are no changes in force in this area. In conventional linear motors with iron cores, this ensures large absorption forces between the stator and the fitting and leads to cogging moments in linear movement. U-shaped linear motors, on the other hand, use an epoxy core that does not generate eddy currents or receiving forces.
The linear servo motor is designed for motor stiffness that is 100 times higher than that of a U-shaped motor with four times greater heat dissipation than similarly sized flat linear motors.
The linear shaft motor can be much more than a replacement for pneumatic cylinders
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