Motion System Design

Copasetic couplings: Flexible couplings

Flexible shaft couplings transmit torque from one shaft to another, and redress misalignment between them. The trick is that flexible couplings must act as springs — but maintain high stiffness, too.

In basic automation machines, coupling springiness is not noticeable. However, it can become problematic in high-performance applications if a system regularly comes to abrupt stops. Here, the average flexible coupling winds up, springs back, and eventually rings into position. Critical movements must be delayed until the ringing settles, to maintain accuracy.

A new NBK XGT series of shaft couplings eliminates ringing with a specialized injection-molded polymer between their two shaft hubs. The polymer is designed to adjust for misalignments, but in aggressive moves, it damps ringing and limits payload overshoot. Too, the molded part maintains the zero-backlash rotation required in high-performance motion applications.


On display: NBK XGT flexible coupling

Key features: Injected-molded polymer is flexible, but damps shock and impulse-induced vibration, and eliminates all measurable resonance — to 1,000 Hz.

What it means to you: Machines that respond faster, with reduced settling times — by 50% to 90% where it's primarily contributed by the coupling. Also helps damp other system resonances originating in the motor or load, so servo gains and overall system performance can be increased.

What else: Example times to stop and target rotation speed: 40 and 60 msec; bore diameters 3 to 28 mm, overshoot distance reduced up to 60%.

Innovator: NBK and The Precision Alliance, Fort Mill, S.C.

For more info: [email protected] • (803) 396-5544.

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