Many projects require a repeating linear motion, and selecting the best system to facilitate that motion can be challenging. There are several solutions available, all with advantages and disadvantages between load capacity, accuracy, maintainability, and cost.
Plain Bushings: Simple and Dependable
Plain Bushing image from Doppelmayr
The simplest, easiest, and lowest maintenance option is the plain bushing. Its easy maintainability comes from the following reasons:
- Bushing directly supports loads
- No moving parts
- Bushing does not require lubrication in most cases, which can eliminate any environmental concerns
Unfortunately, while a high load capacity and easy maintainability are great, the direct contact creates a high friction coefficient. This will require larger actuation forces (the amount of force required to complete the contact switching action), usually through air or hydraulic cylinders, and all that friction will generate a good bit of heat- not great for high speed, frequent motion applications. Guide accuracy and repeatability are also lower for plain bushings. However, if you have a heavy load, or a high environmental concern, you can’t beat the dependability and simplicity.
Linear Bushings: Low Cost, High Speed
What if you have a high-speed application that requires good accuracy and low actuation force? Then a linear bushing is probably your answer. The linear bushing offers the following functions:
- Rolls on parallel shafts, which allow accuracy and repeatability while providing a low coefficient of friction
- Loads can be driven with pneumatics or an electric motor coupled with a worm gear or a belt.
While the linear bushing is relatively cheaper than other options, the load rating is also lower. The rails have to support the load throughout the travel distance and the roller balls only have a point contact. Of course, if your motion is vertical, then this is not an issue.
One thing to remember is that lubrication maintenance is needed to keep friction low, and moving parts will eventually need replacement. But if you are looking for a low cost, dependable solution for a high-speed application, linear bushings are a great solution.
Compact Linear Bushing image from MISUMI
If you need help finding the right solution, call us at 800-681-7475 or check out our Linear Bushings Guide.