Edited by Mike Santora
In certain situations, such as a printing application for example, there might be an issue with banding. Vibration in the system can be caused by the coupling, causing the printer to band and creating errors in the printing. It’s important to note that not all couplings are balanced. There are couplings out there that do not have a balanced design. Again, printing is one of the applications that you can get into trouble just because you haven’t used the balanced design.
Inertia is another concern. Specifically, servo coupling inertia determined by mass and distribution about the axis. Too much coupling inertia, especially in systems with intermittent starts and stops, can introduce resistance into the system causing premature failure and or poor system performance.
The standard material in many flexible couplings for the hubs is aluminum, to keep the weight down, to keep the inertia low. A common scenario where engineers will get in trouble with inertia is on beam coupling applications, where they’ve done an application and then they’re using an aluminum beam coupling and the torque capacity is not what they need. It’s too low. They’re having issues with wind up because the aluminum beam coupling just isn’t strong enough and they ending up with positioning error.
Many times people say, “we’ll go to the stainless version, we don’t have enough room to put a bigger coupling in, we’re just going to go the stainless steel version of a beam coupling which does have higher torque capacity and that’s going to solve our problem.” Again, however, stainless steel beam couplings are much heavier than the aluminum versions and it wouldn’t be unusual at all to switch from an aluminum beam coupling, go to a stainless steel coupling, and now you’ve got issues with too much inertia. Your servo or stepper motors are tripping out and again this is an example of inertia causing issues and being a factor in your designs.
Many times if you’re using an aluminum beam coupling and it does not have enough torque capacity, many many times a better option is to go to a different type of coupling to solve the problem versus going to the much heavier stainless steel version of the coupling, there are better options that just switching to a stainless beam.
Ruland
www.ruland.com