How a tolerance ring works is fairly simple, but in practice the design and specification of tolerance rings is much more involved. In a simple application such as RENCOL® Bearing Mount, it can be relatively easy to specify a tolerance ring. However, in more challenging applications or conditions, they are normally designed in collaboration with the user. For a tolerance ring to work, it’s important to specify the other two components correctly.
The RENCOL® Tolerance Ring design process in these cases is a collaborative one at an engineer-to-engineer level. For best results, the design should be initiated as early on in the overall system design stage as possible, as often customers need to adapt their components to fit a tolerance ring in (see the section below). The performance that a system using a tolerance ring can generate is dependent upon the following three elements:
As you move away from the early stages of the design process, and elements of the system are locked down, the flexibility and ease of introducing a tolerance ring into the system become more complex, as the flexibility to change key parameters are reduced.
The typical design process stages for are:
This 60 second video explains how a RENCOL® Tolerance Ring can be designed into your application, to meet your performance requirements and overall project timings.
There are a few things need to be considered when designing a tolerance rings – some of which may not be immediately obvious if you have never had experience of using tolerance rings before. The following are some items that we need to consider:
There needs to be some space between the components (normally around 0.4-1.2mm radially) to fit the tolerance rings in. Sometimes it’s not possible to change the dimensions (for instance the OD of a ball bearing to mount), and it is essential that the RENCOL® Tolerance Ring designer knows this.
It helps to determine the overall range in radial tolerances that are seen and as a result the forces being applied. It is also needed to make sure the minimum (or sometimes maximum) forces are achieved in worse case conditions.
This has the same effect as component tolerances (changes the force applied), if the components are different materials; so, thermal expansion also needs to be taken into consideration to make sure that always the right force is achieved.
The width of the tolerance ring will affect how the waves are designed. With a narrower tolerance ring, each wave will provide a smaller amount of radial force than if the tolerance ring was wider. Knowing the space constraints is important to see if a tolerance ring can give the desired performance.
Loads being applied to the system are very important when designing a tolerance ring and getting it wrong can lead to failure. The types of information that is needed are:
These applications tend to be more challenging and additional information are required.
In such systems the requirement is that the components move relative to each other when a certain torque value is exceeded. This is to provide protection to other components or external users.
The features needed depend on the requirements and normally it is down to the balance between how much radial load the tolerance ring has to withstand and the strength of the components. Below are the 3 most common arrangements of tolerance rings with their benefits and drawbacks.
This is the most cost effective component arrangement as no additional locating features are required on the mating components. The challenge with this arrangement is that the tolerance ring will take the full extent of any radial loading applied to the system, and sometimes may need tooling to keep the tolerance ring in place while assembling.
The addition of a step to the shaft or housing serves as a locating feature to help hold the tolerance ring during the assembly process. It also brings the additional benefits of improving the assembled concentricity, or helping increase the radial load capacity of the system.
Creating a groove to seat, or locate, the tolerance ring provides the best axial constraint for the assembly process. This feature can also bring additional benefits including; further improved assembled concentricity, improved assembly alignment and improved radial load capacity.
This video covers the three main assembly arrangement types: Free, Piloted and Centered arrangements to integrate a RENCOL® Tolerance Ring into your system.
If you are interested in seeing if a tolerance ring is the right part for you, or if you need help with the information you need to provide, contact us to find out!