Plastic Linear motion


Plastic Linear motion


Linear bearings are most widely used in printing and textile industries, also called linear guide systems.


Used to be metal ball bearings, now we have more options: plastic bearings and ceramic bearings. The precision and performance of plastic bearings have improved significantly during last two decades. It makes plastic bearings now withstand applications as well as standards of metal ball bearing system.

 


The plastic linear guide system works by using sliding elements. These components provide higher acceleration speeds than recirculating ball bearing systems. What is the physical reason behind this? Since there are no moving parts in the linear guide system, no mechanical failures will occur. Once the plastic sliding element starts to move, it is on the road. Instead, the ball bearings must accelerate and then push against each other to start moving. The same is true for deceleration: the balls must slow down slowly, otherwise there is a danger of skidding, bumping them together and eventually flattening the balls and damaging the shaft.

 

In theory, the speed of a linear guide system with plastic sliding elements is infinite. The upper limit depends on the machine itself: what the drive can handle, the operating speed of the motor. For these systems, the coefficient of static friction μ is about 0.16, while the coefficient of dynamic friction is about 0.13. On average, they can run four meters per second, although applications with speeds up to ten meters per second have been successful. This makes plastic bearings ideal for quick start and stop applications.

 

Sliding linear bearings are usually self-lubricating; the tribological design of these bearings includes basic materials, reinforcing fibers and dry lubricants. The movement of the bearing causes the dry lubricant to be transferred to the shaft, making it self-lubricating. In fact, it is recommended to use a rough shaft instead of a polished shaft for lubrication.