Linear Motion

Linear Motion Slides

A linear motion slide is a type of bearing that is designed to be load-bearing and move in one linear direction. This is achieved by having a linear rail track that incorporates a rails system that has internal raceways and roller bearing sliders. They can be used as machine slides and can either be motor-driven or non-motorised.

Linear motion slides are used with various types of automated machinery in industry. Assembly robots in a manufacturing factory, such as the automotive industry, is one example. The slides allow attached tools to slide in a particular direction, back and forth, and if incorporated with another table that slides in a direction that is 90 to the first, as in an X-Y table, then considerable flexibility is introduced and great precision and accuracy of positioning becomes possible.

A linear motion bearing generally falls into one of four groups:

  1. Linear motion bearings with sliding contact
  2. Linear motion bearings with rolling element
  3. Linear motion bearings with hydrostatic or aerostatic properties
  4. Linear motion bearings with magnetic properties

The sliding contact type has the longest history, is very flexible, and is the least expensive method. However, these type of bearing have a greater friction coefficient than the other three basic types. Where precise positioning is required, this type of bearing lacks the superior precision of the other basic types.

The rolling element linear motion bearings type has a rolling element of either ball bearings or roller bearings, thereby decreasing friction and enhancing movement. The rolling elements are between the two moving parts. This provides a superior linear motion slide with significantly increased precision positioning, over the sliding contact type of linear motion bearing.

The hydrostatic or aerostatic linear motion bearing the very best precision positioning possible. This is achieved because the guide has no physical contact between its elements. Pressurised fluid is forcibly introduced between the two relatively moving parts, which maintains one of the parts in a floating condition. This method can be expensive, though it is also capable of high precision.

The magnetic linear moving bearing also has one of the two relatively moving parts floating, and not in mechanical contact with the other part. This is achieved by means of magnetic attraction or repulsion. However, this method is also expensive, consumes a relatively high amount of energy in order to work properly, and it has limited applications in practical use.

Rolling element linear motion slides are now taking over from sliding contact types. This is mainly because a rolling element creates less friction, it is easier to control for precise positioning and accuracy, it performs better at low and high speeds, and it requires a reduced level of maintenance.

Roller element bearings require hardened steel raceways, but sliding contact linear motion bearings can be made from materials that are not as hard, such as cold rolled steel, galvanized steel and even aluminium. While linear motion slides have a slightly greater friction coefficient than other types, a lubricant forcibly introduced between the two moving parts is pulled in by their relative action against one another. This produces a thin film which is more than adequate to maintain an efficient working system.Contact or call us at 01213660601