White Paper: Motion Control
Small Actuator Selection Guide
SPONSORED BY: ![]()
From packaging to life science applications to office equipment to factory automation, smooth motion, fast accelerating and highly accurate are hallmarks of high quality linear movement actuators. Together with increasing needs for miniaturization, actuators must also be compact. One system that meets both requirements in its conversion of motor torque to linear thrust is the single axis ball screw actuator.
Typically, ball screw actuator systems come in at least five different stage sizes with several travel length options. Once an engineer identifies the optimum system, he or she then just needs the right motor.
However, to choose the right system for an application, actuator systems must be carefully analyzed. Comparisons of the design and sizing of components such as the slide block, raceway, bearing, guide rail, ball- screw, nut, and housing materials are critical as they all factor into actuator performance.
Don't have an account?
Overview
The "Small Actuator Selection Guide" by NB Corporation provides an in-depth overview of ball screw actuator systems, focusing on their application, design considerations, and performance factors—particularly for actuators with travel distances of four feet or less. Ball screw actuators convert rotary motion into precise linear motion through a combination of a ball screw and a slide block guided by recirculating steel balls rolling between the block and guide rails. These systems are favored in industries like packaging, life sciences, office equipment, and factory automation, where compact size, smooth motion, acceleration, and high accuracy are critical.
One major advantage highlighted is the availability of off-the-shelf system solutions that integrate components such as the ball screw, guide rail, and nut into a compact assembly. Compared to custom-built assemblies that combine separate components, pre-designed systems tend to be up to 30% smaller and offer better design cohesion.
Key factors in actuator selection include load capacity, travel speed, stroke length, environmental conditions, orientation, and positional accuracy. Load capacity depends not only on the size of the ball screw and guide rails but also on the number and size of the steel ball circuits within the block. Doubling ball circuits can significantly increase load capacity without enlarging the actuator size.
Precision and rigidity are influenced by the design of the guide rail and ball recirculation grooves. Rails with a U-shape profile positioned lower than the ball screw center enhance rigidity and allow for compact, one-end supported applications by reducing deformation under moment loads. Ball grooves designed for four-point contact (gothic arch design) eliminate clearance that results in deflection, thus maximizing positioning accuracy compared to two-point contact grooves.
Application speed also guides actuator lead length selection; longer leads enable faster travel but may reduce positional accuracy, whereas shorter leads support heavier loads with smaller motors but require higher motor speeds to maintain velocity.
Finally, environmental considerations such as exposure to liquids or particulate contaminants can impact actuator selection. Standard metal covers often have gaps that allow ingress, so custom protective bellows covers may be used to ensure system integrity in such conditions.
Overall, the guide emphasizes understanding component design differences and application requirements to select the optimum small ball screw actuator system, balancing speed, load capacity, precision, and environmental ruggedness for best performance.