The purpose of bearings is to act as sacrificial element used between two moving surfaces to absorb loads, provide low wear characteristics, and prevent scoring and galling of metallic surfaces by eliminating the possibility of metal-to-metal contact. The actuator hardware design often influences the available axial and radial envelope space for a bearing system. Just as with optimum seal size selection, there is a suitable size bearing proportion, in terms of the selected radial cross-section for a given diameter. Likewise, there is a suitable axial width for the given radial cross-section and/or projected bearing area criteria. In some cases, adjacent seals are not present, which would then allow for more flexibility in the bearing hardware design. Note that when polymeric bearings are used, the diametral hardware clearance (K) should be increased to ensure that the bearing will function under worst-case tolerance situations (i.e., no metal-to-metal contact). This increase in the working clearance should be applied through the entire axial plane of the actuator, including associated seals in series along this same working plane, to avoid the running hardware surface from contacting one or more metallic land areas before the bearing surface. Additional safety factors are often added to the clearance to account for compression of the bearing material, particularly underside loading. To determine the width of the bearing and the groove width, one must calculate the bearing load. CDI Products recommends following the bearing calculations as outlined in SAE ARP7024 “Polymeric Bearings for Linear Actuators.”
Features and Benefits
- Prevent metal-to-metal contact.
- Low friction
- Absorbs side load
- Weight savings potential compared to metal bearings (depending upon polymer material selection)
- High load bearing capacity, both static and dynamic operation
- Eliminates the risk of local stress concentrations.
- Eliminate the risk of hydrodynamic problems in the sealing system.
- Long service life
- Eliminate galling damage between components.
- Good friction characteristics
- Damp mechanical vibrations
- Easy installation