Most engineers are comfortable with the qualities of square rail bearing linear actuators and they use them regularly for motion support. Let's take a quick moment to discuss the pros and cons of roller wheel bearing linear actuators.
If you are familiar with our HPLA series of linear actuators, you know they utilize a roller bearing wheel design instead of a square rail or recirculating bearing design. This sealed bearing design features either a polyamide wheel or a steel wheel for higher payloads. These roller wheel designs are not limited to Parker's HPLA series belt driven linear actuators, but can also be seen in belt driven product designs by many other manufacturers.
Pros of roller bearing wheels in linear actuators
Why use a roller wheel? The benefits to a roller wheel design include:
- Much lighter weight systems - You simply have multiple wheels versus steel track and bearing blocks
- Lower cost systems versus square rail designs - You don't have stroke dependent parts like you do for a machined bearing design
- More "environmentally hardened" - With the sealed wheel design, the polyamide wheels or steel wheels roll through dirt and debris that may otherwise clog up a square rail bearing or other recirculating bearing design
- Customization - If you need additional moment or load support, you can simply adjust the wheel locations to increase as needed
- Less maintenance required - Many of these bearings are sealed and lubricated for life
- More forgiving of misalignment issues - The polyamide wheel will provide some degree of flexibility versus an over-constrained rail and bearing design
Cons of roller bearing wheels in linear actuators
With any alternate solution, there are negatives as well. Some of the downsides to roller wheel designs are:
- Need a fixed pre-load method to eliminate carriage slop - Without pre-loading the wheels onto the surface, you will have a degree of "play" in the carriage
- Shock loading can eliminate pre-load - High impact loads can loosen that pre-load and induce "play" in the carriage
- Travel straightness / flatness will not be as precise - Because you are not using a machined surface and matched bearing design, you will not receive that level of flatness or straightness accuracy.
These are just some of the pros and cons of a roller wheel bearing linear actuator design. When it's time for your next motion project, consider all options before deciding upon which linear actuator makes the most sense for your application.
Article contributed by Ben Furnish, Marketing Manager, Parker Hannifin Corporation, Electromechanical Division.
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