Are you facing the challenge of choosing between a plain bearing or a roller bearing?
Plain bearings contain no roller elements and rely on a sliding motion between the bearing components.
Roller bearings, on the other hand, have mechanical components like balls or cylinders that move between the bearing surfaces, creating rolling friction.
Find out which bearing technology best suits your needs in this blog article.
Specifically in hydrodynamic plain bearings, the lubricant forms a pressure film under the influence of relative motion between the bearing and the shaft. It separates the two surfaces and minimizes friction and wear. As a result, higher loads and speeds can be achieved.
Find out more about plain bearings on our axial and radial plain bearings product pages.
In contrast to plain bearings, roller bearings support the entire load with a series of rolling elements. As the shaft rotates, balls or rollers move between an outer and an inner ring. This rolling motion is a combination of rolling and sliding. The service life of the rolling elements inside is limited by material fatigue.
To select the right bearing for your application, it is important to understand its specific requirements. The following factors are key considerations for making a good decision:
Plain Bearings | Roller Bearings | |
Load Capacity | Hydrodynamic Plain bearings have a larger contact area between the two bearing surfaces compared to roller bearings, allowing them to withstand higher loads. The lubricant film in these bearings enables effective separation. Therefore, they are particularly well-suited for both high loads and high speeds. | In roller bearings, the load is distributed across fewer contact points. They are suitable for medium to high loads but can be overstrained and fail prematurely under extreme loads. |
Noise Generation and Friction | Since a lubricant is present between plain bearing and shaft, there is no metallic contact. This makes these bearings nearly silent. At optimal operating speeds, the hydrodynamic lubricant film results in minimal friction. The viscosity behavior of the oil significantly affects the friction losses. As speed increases, the friction losses are proportional to both speed and viscosity. | The direct, concentrated metallic contact in rolling bearings has lower noise-damping properties compared to hydrodynamic plain bearings. Due to the rolling contact, friction is usually low at operating conditions near standstill, approaching zero as speed decreases. However, as speed increases, additional effects such as cage friction can occur due to the more complex design, significantly increasing friction and potentially exceeding the sliding friction of plain bearings. |
Space Requirements | If space is limited or there are strict weight requirements in your application, a hydrodynamic plain bearing is the perfect solution. With wall thicknesses of just a few millimeters, these plain bearings require less space than roller bearings. This leads to weight savings that streamline the overall system, increase power density, and reduce raw material costs. | In most applications, the roller bearing itself determines the available space for the entire system. Therefore, the selection of the appropriate bearing significantly influences the dimensions of the available space. |
Vibration Behavior | In these plain bearings, the lubricant film inside dampens vibrations, resulting in good vibration behavior. Thus, hydrodynamic plain bearings are ideal for applications with dynamic loading. | In contrast, roller bearings transmit vibrations directly. These vibrations must be dampened to avoid noise. |
Maintenance and Service Life | In hydrodynamic operation and under proper lubrication conditions, there is no wear in hydrodynamic plain bearings because a constant layer of lubricant is maintained inside the bearing. However, the service life of this plain bearing depends on the quality of lubrication and operating conditions. Therefore, regular checks of the lubrication are necessary, but otherwise, these plain bearings are relatively low maintenance. | In contrast to plain bearings, the service life of roller bearings can be precisely calculated under normal operating conditions. Material fatigue limits their lifespan. When considering the total cost over the entire service life, the decision for plain bearings often proves to be more advantageous, as they tend to be more durable. |
Replacing traditional roller bearings with hydrodynamic plain bearings can provide both technological and competitive advantages in many applications. With these plain bearings, you can save weight and space while also handling greater loads. Reduced maintenance requirements and effective vibration damping make plain bearings a more attractive option. For example, engineers have already replaced roller bearings in pumps, compressors, and transmissions with these plain bearings.
In the following application areas, Miba’s hydrodynamic plain bearings have already proven themselves over rolling bearings:
Do you want to learn more about hydrodynamic plain bearings in relation to your application? Talk to us about a flexible solution for your industry.