We often get asked for a replacement coupling when a customer’s rotary encoder keeps giving noisy or intermittent signals, even though the encoder itself tests fine on the bench. In actual application, the root cause is very often not the encoder at all – it’s the mechanical connection between the encoder shaft and the driven shaft.
Shaft encoders must be protected against excessive mechanical stress, which happens whenever there is angular, axial, or radial misalignment between the machine shaft and the encoder shaft. Even a small amount of misalignment, run continuously, will eventually damage the encoder’s internal bearings or shaft seal.
This looks simple, but choosing the right coupling means matching a few things: the bore size on both the motor/machine side and the encoder side, the torque the coupling needs to transmit, and how much misalignment it needs to absorb. Our flexible couplings (based on the Dynapar FCPL series, a three-beam helical design with clamp-style attachment – no setscrews digging into the shaft) are available in both metric and inch sizes, with bore sizes from about 1/8″ up to 1-1/8″ (or 4-10 mm on the metric side) and peak torque ratings from 16 up to 300 depending on the model.
From our experience, before we quote a coupling, we would normally check the exact shaft diameters on both sides, the mounting distance, and roughly how much misalignment we’re compensating for. Send us these details and we can match you to the correct coupling size. Hope this helps.
