Coupling Selection

Coupling Selection for Various Applications, Common to Complex

Whether you are dealing with a typical coupling situation, or a more challenging one, it’s important to select the correct design for your specific needs. This will help ensure integrity overtime, avoid a potential failure, and add to overall system efficiency. Let’s explore some of the scenarios and options:

Rigid or Flexible?

A shaft alignment coupling is used to connect two shafts together. Two general classes of couplings are available: rigid and flexible. If the two shafts are 100% in line, with no angular misalignment or lateral displacement, a rigid (aka solid) coupling will get the job done. If there is a height mismatch between the motor and shaft, or angular misalignment, you would need a flexible coupling. There are lots of them. Selection is generally based on several factors:

• Degree of misalignment
• Type of misalignment (angular, lateral, or radial)
• Torque (or power) that will be transferred through the coupling
• The inertia of the system

Selecting the Right Flexible Coupling                     

Flexible couplings come in many flavors, including spider, wafer spring, bellows or molded. Inertia is one determining aspect when choosing the best style for your application. For instance, let’s imagine your coupling weighs 10lbs, and you are spinning at 1,000RPM. That would take a while to stop rotating. Rotation would be imparted into the system while it was slowing down. The solution? Lightweight couplings, such as bellows or universal lateral. Inertia is minimized when the system is shut off.  Flexible zero-backlash couplings, also known as beam-style couplings, will isolate vibration and absorb shock loads.

In certain situations, you may have to reposition the motor driving a system. Let say the motor blows, and you want to quickly remove the coupling. In this scenario, a multi part coupling similar to a spider or a multi jaw coupling would fit the bill.  Spider couplings contain an integral clamp hub using socket head cap screws. Multi jaw couplings have interlocking teeth which permit precision coupling and decoupling.

If you are driving an encoder, you can reposition to reset your encoder or make required rotational adjustments. If you have two items that need to be timed, and they are a little out of phase, a multi jaw coupling can be separated, rotated and reengaged depending on the number of serrations. The multi jaw coupling makes it easier to rotate and reposition the element on the drivetrain.

Avoiding Static with Sensitive Electronics

If you are working with sensitive electronic equipment, you must avoid the enemy: static electricity generated by the motor.  For these applications, you would require an electrically insulated solution to isolate the energy. These include K-type, great for abrasive dust environments, or a molded Neoprene coupling. A miniature Oldham coupling with a nylon center member works particularly well for high torque, static sensitive applications. An electric charge can not be transmitted through any of these couplings.

Couplings are also available with pin hubs and split type clamp hubs similar to gear hubs. Pin hubs are available for permanent uses, while clamp types allow for removable or replaceable installation. (By the way… if this sounds familiar, it’s similar to what we discussed in our previous blog.)

As you can see, there are many coupling styles available - each designed to solve a set of particular challenges. Selection should be done on a case by case basis. To avoid long-term performance issues and maximize efficiency and utility, be certain to consider all of the options available, and match the features to your specific application.