Introduction to the Caged Ball Concept
When rotary ball bearings were originally introduced over 150 years ago, they were not equipped with a cage. This
design resulted in high noise levels, short service life and low maximum rotating speed. Consequently, the cage was
introduced into the bearing design resulting in low noise levels and high rotating speeds. In addition, the bearings
equipped with the cage demonstrated long service life despite the reduced number of balls vs. the full complement type.
Rotary ball bearings with the cage evolved significantly over the years, thus allowing for a wide range of applications.
The same cage concept would clearly work in linear ball bearings, except for elliptical path of the balls inside the
linear bearings being different from the circular path of the balls inside rotary bearings. Thus, the metal cage
employed by the rotary bearings could not have worked for the LM Guides.
THK, the first manufacturer in the world to develop the LM Guide, is also the first to introduce the LM Guide that
incorporates Caged Ball Technology. This revolutionary LM Guide is able to achieve a dramatic improvement in
performance over conventional products. It delivers long service life and excellent high-speed performance in the
same manner as rotary bearings equipped with cage, while eliminating maintenance for prolonged periods of time.
Evolution of Rotary Bearings
Initial Stage of Development
(Full Complement of Balls)
Reduction of grease life
Short service life
Excessive heat generation
Ball collision noise
Current Design (with Cage)
Excellent grease retention inside the
Extended service life
Low heat generation
Elimination of noise caused by metal-
to-metal contact between the balls
Smooth operation due to orderly ball
1. Excellent High-Speed Performance
The use of ball cage eliminates generation
of heat caused by friction between balls
resulting in excellent high-speed
Advantages of Caged Ball