Selecting the right wave washer involves a careful assessment of several critical application parameters to ensure optimal performance, proper preload, and extended component life.
Wave washers, also known as wave springs, are coiled components that provide a compensating spring force in a compact axial space. They are typically used to take up axial end play, provide preload in bearing assemblies, or compensate for dimensional variations within an assembly, ensuring consistent contact and preventing rattling or looseness.
Key Factors for Wave Washer Selection
To accurately choose a wave washer, consider the following essential criteria:
1. Load Requirements
Determine the axial load requirements of your bearing assembly. This is paramount. The wave washer must generate the specific preload needed to properly seat bearings, eliminate vibration, or maintain consistent pressure on components without causing excessive friction or damage. Different wave washer designs and materials have varying load capacities. Ensure that the chosen wave washer can provide the necessary preload without overloading the bearing. Calculate the target spring force at the desired working height or deflection.
- Preload Force: The specific force required to take up end play or keep components in contact.
- Operating Load: The maximum or minimum force the washer will experience during operation.
2. Deflection and Working Height
Understand the amount of axial compression (deflection) the wave washer will undergo from its free state to its installed height, and its compressed height in operation.
- Free Height: The height of the washer when no load is applied.
- Work Height: The height of the washer under the desired operating load.
- Deflection: The difference between the free height and the work height. Ensure the washer can provide the required load within the available deflection range without going solid.
3. Space Constraints
Wave washers are often chosen for their compact nature. Carefully measure the available space in your application:
- Radial Space: The maximum outer diameter (OD) and minimum inner diameter (ID) that the washer can fit into.
- Axial Space: The maximum height available for the washer in its compressed state.
4. Material Selection
The operating environment and required performance dictate the material choice:
- Standard Materials: Carbon steel (often pre-hardened and tempered), stainless steel (e.g., 17-7 PH, 302, 316) for corrosion resistance.
- High-Temperature Applications: Inconel, Elgiloy, or other exotic alloys for extreme heat.
- Corrosive Environments: Stainless steel, bronze, or specialized coatings.
- Magnetic Properties: Non-magnetic alloys where magnetic interference is a concern.
- Fatigue Life: Material properties influence how many compression cycles the washer can withstand without failure.
5. Operating Environment
Consider any factors that might affect the washer's performance:
- Temperature: High or low temperatures can affect material properties, spring rate, and fatigue life.
- Chemical Exposure: Presence of oils, solvents, acids, or other chemicals.
- Vibration and Shock: The washer's ability to withstand dynamic loads.
- Cleanliness: Requirements for medical or food-grade applications.
6. Spring Rate
The spring rate, or stiffness, determines how much force is generated per unit of deflection.
- A higher spring rate means more force for a given deflection.
- A lower spring rate provides more flexibility and a smoother force curve.
7. Shaft and Bore Diameter
The wave washer must fit correctly around a shaft and/or within a bore:
- Shaft Diameter: The inner diameter (ID) of the washer must be slightly larger than the shaft.
- Bore Diameter: The outer diameter (OD) of the washer must be slightly smaller than the bore.
Step-by-Step Selection Process
- Identify Load Requirements: Determine the precise axial force (preload) needed for your application, especially for bearing assemblies.
- Measure Available Space: Record the maximum radial (OD/ID) and axial (work height) dimensions.
- Calculate Deflection: Based on your free height and work height, calculate the required deflection.
- Consider Environmental Factors: Note operating temperature range, chemical exposure, and any other relevant conditions.
- Choose Material: Select a material that meets the load, temperature, and corrosion resistance requirements.
- Determine Spring Type: Decide if a single-turn, multi-turn, or nested wave washer is most appropriate based on force-to-deflection needs and space.
- Consult Manufacturer Data: Refer to manufacturer catalogs or engineering tools (e.g., Smalley Spring & Wave Washer Resources) that provide load-deflection curves, material specifications, and standard sizes.
- Verify Fit and Performance: Ensure the selected washer's dimensions, load capacity, and spring rate match your application's needs. Prototype testing is often recommended.
Types of Wave Washers
| Type | Description | Common Use Cases |
|---|---|---|
| Single Turn | A simple, single-coil design, often with gaps. | Basic preload applications, small loads, simple axial take-up. |
| Multi-Turn | Two or more turns, providing greater deflection and often a more consistent force. | Moderate loads, improved force consistency over longer deflections, bearing preload. |
| Nested | Multiple waves stacked in parallel, offering significantly higher force. | High-force applications in compact spaces where standard springs are too large. |
For example, if you are designing a miniature gearbox and need to eliminate end play in a bearing, you would first determine the axial preload required for that bearing (e.g., 5-10 lbs). Next, you would measure the axial space available between the bearing and its housing, and the shaft/bore diameters. If the space is very limited axially but you need a moderate load, a multi-turn wave washer made of 17-7 PH stainless steel (for good strength and corrosion resistance) would likely be a suitable choice, ensuring its spring rate provides the desired preload within the available deflection.
By meticulously evaluating these factors, you can select a wave washer that precisely meets the demands of your application, ensuring reliable and long-lasting performance.
