Zero backlash Oldham couplings are similar to the jaw coupling; there are two types. There are standard industrial grade Oldham couplings where there is some play or there is some slop between the disk and the hub. On our coupling, for example, it’s zero backlash so there is no slop. It’s a slight press fit on that disk to engage it in the hub so that there’s no error. These are the most forgiving, for parallel misalignment, of all the types of motion control couplings. That disk actually moves back and forth to accommodate the misalignment and is quite forgiving for parallel, which typically tends to be the misalignment problem people are dealing with.
The benefits. First, a note on RPM. If the max RPM is 4,500 whereas your bellows is 10,000, you do have to watch your RPM to make sure you don’t exceed that 4,500. It does not have the 8,000 and 10,000 RPM capabilities that some of the others do. The benefit is a three-piece design that allows for a highly customizable coupling. Mix and match, metric to inch, so forth, no problem. They also accommodate large amounts of parallel misalignment and are electrically isolating when the disk is in place. This again, is like the jaw coupling in that it is electrically isolating because you’re not going metal to metal on the hubs but again, this is only for very low voltage, signal type voltage. This type of coupling also produces low bearing loads so when this coupling is handling parallel misalignment, the disk is moving back and forth. It is not throwing a bearing load or a heavy bearing load at your motor bearing or your actuator input bearing. It’s very kind to your bearings.
Some drawbacks. Small angular misalignment capability is an issue they have when compared to most of the other couplings. Types of very small angular misalignment capability, although that’s typically not the issue with alignment in systems, typically it’s parallel. The fact that it has small angular misalignment capability usually isn’t an issue. Not suitable for push/pull applications. Again, you want to push/pull on one of these, obviously, couplings just going to fall apart. Most shafts must be fully supported. This is true of all the motion control couplings except the rigid, the Oldham, the jaw. Every type will go through except the rigid. There needs to be a bearing support on both shafts and close by within reasonable proximity of the coupling. This is a wear element and requires some maintenance. One of the drawbacks of this coupling is that over time, clearance is worn into that disk as it’s in service. At a certain point, it varies application to application. You’re going to get play in there. That disk is going to be worn and you’re going to get error.
Again, the downfall is potentially you could be making bad product, you’ve got an error in your system and you’re making bad product at that point. It’s good to try to get a general idea of how long your oldham couplings will last in the system and have a maintenance plan in place where you go in and you put a new disk in every six months, every year, and so forth. Every application will be a little bit different and we could give you some guidance on that as well. It might not be a bad idea for a time interval to change the disks. We see this type of coupling in industries like packaging, printing, semiconductor, solar, medical, automation and other applications in general.
Ruland
www.ruland.com