Caged Ball LM Guide Actuator Model SKR

The Caged Ball LM Guide Actuator Model SKR is a compact actuator that has an inner block, which is a combination of an LM block and ball screw nut, inside a U-shaped outer rail.
In addition, by using ball cages in the LM Guide units and the ball screw unit, this model achieves high speeds, low noise, and long-term maintenance-free operation superior to the conventional Model KR. (A ball cage is used only for the LM Guide section of models SKR20 and SKR26 and the ball screw is fitted with a QZ lubricator.)

Four-Way Equal Load

Each row of balls is arranged at a contact angle of 45° so that the load rating on the inner block is uniform in the four directions (radial, reverse-radial, and lateral directions). As a result, model SKR can be used in any mounting orientation.

High Rigidity

Use of an outer rail with a U-shaped cross section increases the rigidity with respect to moment and torsion.

Table 1: Cross-Sectional Characteristics of the Outer Rail

Model No.	lX (mm4)	lY (mm4)	Mass (kg/m)
SKR20	6.0 × 103	6.14 × 104	2.6
SKR26	1.66 × 104	1.48 × 105	3.9
SKR33	5.35 × 104	3.52 × 105	6.1
SKR46	2.05 × 105	1.45 × 106	12.6
SKR55	2.07 × 105	2.09 × 106	13.2
SKR65	4.51 × 105	5.73 × 106	22.1

l_X = geometric moment of inertia around X axis
l_Y = geometric moment of inertia around Y axis

High Accuracy

Since the linear guide consists of four rows of circular-arc grooves that enable balls to move smoothly with two points of contact even under a preload, a highly rigid guide with no clearance is achieved. Additionally, variation in frictional resistance caused by load fluctuation is minimized, allowing highly accurate feeding. The system contributes significantly to increasing precision and quality by providing precision-grade positioning performance to all kinds of machines.

Space Saving

These highly rigid, highly accurate actuators take up minimal space thanks to an integrated structure that incorporates LM Guide units on both sides of an inner block with a ball screw in the center.

High Speed

Model SKR supports a state-of-the-art high-rotation servomotor (6,000 min^-1) by using a ball cage and is capable of operating at higher speed than the Full-Ball Model KR. In order to achieve higher speed operation, models SKR33/55/65 are available in more lead variations, including high leads which were not feasible with the Model KR.

High Lubricity

Model SKR uses ball cages to eliminate friction between balls and significantly improve torque characteristics. As a result, the torque fluctuation is reduced and superb lubricity is achieved.

Low Noise and Reduced Running Sound

In model SKR, the use of a ball cage in the LM Guide section and ball screw section (excluding models SKR20/26) has eliminated collision noise between the balls. As a result, low noise and reduced running sound are achieved.

Long-Term Maintenance-Free Operation

With Model SKR, the ball cage increases grease retention and achieves long-term maintenance-free operation.

Tripled Service Life

With Model SKR, both the LM Guide unit and the ball screw unit have larger basic dynamic load ratings than the Full-Ball Model KR, and therefore a longer service life is achieved. The rated service life is calculated from the following equation.

As indicated in the equation above, the greater the basic dynamic load rating, the longer the service life of both the LM Guide unit and the ball screw unit.

Note: On the SKR20/26, only the LM Guide units features a ball cage.

Seal

Model SKR is equipped with end seals and side seals for contamination protection as standard.

Table 3 shows the rolling resistance and seal resistance per inner block (guide section).