The SKR-type LM guide actuator with Caged Ball Technology is a compact actuator that places a nut block(s) that integrates an LM block and ball screw nut onto the inside of the LM rail of a U-shaped cross-sectional form. Moreover, the addition of the LM guide and ball screw sections with Caged Ball Technology allows the SKR-type LM guide actuator to achieve higher speed, lower noise, longer maintenance-free operation, and other features in comparison with the conventional KR-type.

Construction and Features

1. Four-way Equal Load Rating
Each row of balls is arranged at a contact angle of 45° so that loads acting on the nut block in the four directions (radial, reverse-radial, and two lateral directions) show the same rated load. Thus, the SKR-type LM guide actuators can be used in any position.

2. High Rigidity
The adoption of the LM rail of a U-shaped cross-sectional form allows improved rigidity against moment.

3. High Precision
The linear motion guide raceway has four rows of circular arc grooves that provide smooth motion by mere pre-load; clearance-free, highly rigid guidance is obtained. In addition, changes in frictional resistance resulting from load variations are minimized, allowing the SKR-type to achieve high-precision feed.

4. Space Saving
The integration of a LM guide raceway on both side faces of a nut block and the integration of a ball screw nut at the center of the nut block allow the SKR-type to achieve high rigidity and high precision in a minimal space.

5. Long Life Span and Long-term Maintenance-free Operation
Thanks to the effectiveness of its ball retainers, the SKR has improved grease retention capability, allowing it to achieve a long life span and long-term maintenance-free operation. The SKR achieves a longer life span because its basic dynamic rated load at the LM guide and ball screw sections is greater than that of the conventional KR models (in the case of the KR3310, three times greater). The rated life span can be calculated by the following equation.

6. High Speed
Through the use of Caged Ball Technology, the SKR-type is compatible with the latest high-speed rotational AC servo-motors (6000 min-1), achieving higher speeds than the conventional KR-type. The ball screw lead settings of the conventional KR33 type were 6 mm and 10 mm. To achieve a higher feed rate, a 20 mm ball screw lead has been added to the new SKR 33 series.

7. Excellent Sliding Capability
Caged Ball Technology also helps the SKR-type eliminate ball-to-ball friction, significantly improving the torque characteristics. It minimizes torque variations, allowing excellent sliding capability.

8. Low Noise
The use of Caged Ball Technology in the LM guide and ball screw allows the SKR-type to eliminate the noise caused by the balls colliding. This lets the SKR-type achieve low noise emission and a pleasing sound quality.

Courtesy of  THK