Page 22 - february

METALWORKING EQUIPMENT AND TOOLS

FRICTION IN LINEAR ROLLING GUIDES
The static friction (initial friction) of linear rolling guides is much less than that of
conventional sliding guides. In addition, there is less difference between static and dynamic
friction, and friction changes little with speed. These are the unrivaled properties of linear rolling
guides, allowing them to reduce power consumption, increase operating temperatures and
increase travel speeds. Since the frictional resistance and its variations are small, fast response
to movement commands and high positioning accuracy can be achieved.
FRICTION COEFFICIENT
The frictional resistance in rolling guides depends on their type, load, travel speed and
lubricant used. Typically, lubrication and seals are the primary factors in frictional resistance in
low-pressure applications. Loads and high speed, and the magnitude of the load determines the
frictional resistance in high load and low speed applications. In fact, the frictional resistance in
rolling guides depends on many factors, but in practice, the following formula is used.

F=μP........................(1,10)
Ball without preload
Ball diameter 10 mm Roller diameter and length F: frictional resistance, N
10x10 mm
Preload ball
μ: dynamic coefficient of friction
P: load, N
Effective preload: equivalent to 0.05 Co
Elastic deformation Roller without preload

Preloaded roller
For guides with seals, the seal
Load N resistance is added to the value shown
above, but this resistance is highly
Fig. 2. Relationship between load and coefficient of friction.
dependent on the rubbing seal lip and the
condition of the lubricant. With correct
lubrication and installation methods and
moderate loads, the friction coefficients at Linear Roller Guide Operations are in the range
shown in Table 1. Typically, the coefficient of friction increases with light load. In fig. 2 shows
typical examples of such dependence.

Vasily Maksymiv, Linear Technician

22 Stanochniy park