Wave Springs Beat the Heat

Thermal expansion is a common problem in applications that are exposed to high temperatures or that use materials sensitive to temperature changes. The usual problem is that internal components, such as sensors, become loose after external components expand due to an increase in operating temperatures causing unwanted movement, vibration, and noise within the application. Design engineers plan to avoid this situation by pre-loading components with spring elements that compensate for thermal expansion and fix the components tight in place, avoiding unwanted movement within the application.

However, not all spring elements are suited to easily compensate for a wider range of axial endplay caused by thermal expansion.

This was the case when Rotor Clip was asked to find a solution to preload a sensor used in an automotive exhaust gas system. During regular operation the exhaust system would heat up and cool down in different intervals. Some parts of the application would expand more than other components which resulted in a possible loose fit of the sensor in its housing.

In the original design the sensor case was preloaded by a conventional disc spring in order to prevent movement of the sensor and, ultimately, the unwanted noise and vibration described earlier along with the possibility of the unwanted movement leading to a defective sensor. After several tests it was discovered that the disc spring could not offer the required levels of work height needed to keep the sensor seated tight in the application.

Rotor Clip solved this problem with a single-turn wave spring made from A286 stainless steel conform to DIN Material No. 1.4980. The wave spring solution Rotor Clip provided solves three application challenges at once:

1. It offers sufficient travel to compensate for the maximum thermal expansion within the application.
2. Due to the material choice (A286 stainless steel) the spring is less prone to fatigue due the application’s operating temperatures and, therefore, prolongs total application life.
3. It simplifies the assembly process by eliminating a secondary assembly step. (The original design required that the disc spring element be held in place before the sensor was seated inside the application housing. In contrast the wave spring “clings” to the inside of the housing in which the sensor sits, eliminating the necessity for this secondary step).

In summary, wave springs deliver a high degree of versatility to the designer seeking to solve a particular application problem, like the one described above. The flexibility afforded by the wave spring regarding materials, configurations and styles, makes it a critical “go to” component for the engineer searching for viable alternatives to traditional ways of accomplishing effective component pre-load.