What is best? Linear guides with balls or rollers?

Kulor vs Rullar_2There is a discussion about which solution is best in linear guides, whether balls or rollers give the best results. But the fact is that the question is wrongly posed.

Rail guides with balls or rollers

As always with linear motion, the answer to any question starts by looking at your application. It is the application and the goal you have with it that determines which solution is best. It is about what needs you have in terms of stiffness, precision, accuracy and load, among other things. In other words, the choice between balls and rollers depends on what you want to achieve.

Rollers suit applications with high demands

Linear guides with rollers work like ball rail guides but have rollers instead of balls in the slider's four raceways. This gives an increased contact surface between slider and rail. Originally, balls were used in all rail guides, but as the machine tools developed, the demands on precision increased. In the process to improve this, a new type of rail guide was developed where the balls were replaced with rollers. This increased both the load-carrying capacity and the stiffness.

Roller guides are therefore suitable for demanding machine applications that require high load-bearing capacity in combination with maximum rigidity or for applications with large loads.

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Balls are suitable for most applications

If your machine application does not have extremely high requirements, ball guides work great. The linear ball guide is today the most common type of rail guide and, in general, roller rails do not add anything for a common application. They are certainly both stronger and stiffer on paper, but in many cases of installation it can be problematic as, above all, the great rigidity means that the smallest installation error easily leads to increased friction and internal forces that can even result in a greatly shortened service life.

Linear roller guides are more expensive and rarely needed unless you have very high requirements for high load capacity and high stiffness. Linear ball guides also work for fairly large loads, as the rail guide is rarely worn by the loads, so there is nothing to be gained by using roller rails for that reason either.

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