If you’ve ever installed a rotary encoder on a piece of machinery, you may be tempted to connect the shafts first and then mount the encoder body. This approach makes a lot of sense intuitively—it also happens to be wrong.
Connecting the shafts first increases the chance that the encoder and shaft will be misaligned, which will increase bearing wear and reduce service life. In severe cases of misalignment, the encoder may even fail soon after you start it up.
An Easy Fix. Fortunately, there’s a very easy way to avoid this type of misalignment. Just make sure you double check encoder and shaft alignment and secure the encoder body before you fully tighten the shaft connections. It’s that simple.
This installation order holds true for both shafted and hollow shaft applications:
- For a shaft-to-shaft connection, you’ll first check for axial, angular and radial alignment between the drive and encoder shafts. Once the shafts are lined up and the encoder body is secured, you can then tighten the flexible coupling that connects the two shafts—and it’s important to use a flexible coupling. (See Figure 1.)
- For hollow shaft installation, you should first mount the encoder and coupling loosely on the shaft. Then bolt the coupling to the drive flange. Only then should you tighten the clamping hub that locks the drive shaft in the encoder hollow shaft receptacle. (See Figure 2.)
And while it may sound obvious: Never use a hammer or other blunt object to bring shafts and encoders into alignment.
Avoid Misalignment. Ask any of our field service engineers about encoder misalignment, and they’ll tell you improper installation procedures cause most of the issues that they encounter. Following this simple mounting procedure will go a long way toward keeping your encoder running for its intended lifespan.
And keep in mind that not all misalignment is rooted in the installation procedures. Rotating machines tend to drift out of perfect alignment as they operate, in part due to their susceptibility to vibration. Proper installation alone won’t eliminate the potential for misalignment as the machine runs. So it’s important to pick encoders with a mechanical design that explicitly minimizes the stresses on the bearings.