# Miniature Profile Ball Rail Technical Information

## ACCURACY

NMR Miniature Linear Guide series have three accuracy classes: P, H, and N.  The NMR Miniature Linear Guide series have three degrees of preload: V0, Vs and V1 (as described in the Table of Preload below). Preload can enhance stiffness, precision, and torsion resistance, but will negatively affect life and friction. ## SPEED

The maximum speed for the standard NMR-SS/ZZ type is: Maximum acceleration: (if the preload V0, capable of reaching 40 m/s2)

The maximum speed for the standard NMR-EE/EZ type is: Maximum acceleration: (if the preload V0, capable of reaching 60 m/s2) ## LIFE

For the static load traveling along the acting direction, the maximum calculated stress at the rolling elements and the raceway, by a curvature radius ? 0.52, is 4200MPa and, by a curvature radius ? 0.6, is 4600MPa.

To convert 100kl of life to 50kl of live, use the following formula: Note: Under such stress, a permanent total deformation is generated at this contact point corresponding to about 0.0001 times the rolling element diameter (ISO 14728-2).

## Static Moment Ratings M

For C, Co, M of each model refer to dimensional table. Nook Precision Profile Rails have the same dynamic load capacity in four directions: radial, reverse-radial and bi-lateral. ## Static Safety Factor

Generally, the maximum permitted static load on the runner block is equivalent to static load ratings C0. However, in repeated linear motion applications, unexpected load is caused by the inertia when the system starts or stops. Therefore, the safety factor fs should be calculated in order to determine the allowable load.  When the dynamic loads are applied to normal load zones with constant magnitude and direction, theoretically, the rate life of a linear guide can reach 100 km of travel distance (ISO 14728-1).

## Rating Life L

The dynamic rating is based on 100km of life. When the standard of 50km travel distance is used, the dynamic load rating will exceed the value based on the standard ISO 14728-1 by 20% or more. Where the stroke (m) and the number of cycles per minute n1 (cpm) are constant, the rated fatigue life Lh (hr) is calculated by the following formula. ## EQUIVALENT DYNAMIC LOAD AND SPEED

If the load and speed are not constant, each actual load and speed must be taken into account and both will influence the life.

If there is a change in load only, the equivalent dynamic load can be calculated according to the following formula: If the linear guide takes on load from an arbitrary angle, itâ€™s equivalent dynamic load rating is calculated using the following formula: ## Equivalent Speed

If there is a change in speed only, the equivalent speed can be calculated using the following formula: If there are changes in both load and speed, the equivalent dynamic load can be calculated using the following formula: ## Combining Linear Forces with Moment Loads

If both load and moment act on the linear guide, the equivalent dynamic load can be calculated by the formula. ## FRICTION

The NMR miniature linear guide series is characterized with light starting friction and low, stable and consistent friction during operation. ## Source of friction

• Resistance of the sealing system
• Resistance of the collision between the balls during operation
• Resistance from the collision between the balls and the returnpath
• Rolling resistance of the balls in the gothic arch load zone
• Resistance from the churning of the lubricant in the runner block
• Resistance from the penetrated contaminant Figure 1