Which type of actuator to choose; ball screw or belt drive? Both actuators feature antifriction linear bearing guidance systems that provides for predictable long, reliable travel life - even at 100% duty cycle and excellent moment-load capacity. Each type can be coupled to high performance servo systems to ensure precise positioning. Both feature magnetically sealed stainless covers to ensure against the egress of contamination. They also share convenient t-slot mounting, limit switches, encoders, and motor/gearbox mounting flanges and multiple carriages.

Selecting the right drive technology comes down to Speed and Travel Length with a consideration toward Accuracy, Rigidity and Repeatability.

Ball screw driven units  often exhibit a stiffer system and are generally more accurate, based on the type of ball screw employed. Typically PBC actuators employ a class 10 screw (.0004/ft accumulative) and class 5 screws are available with a non preloaded ball nut. Optional preloaded ball nuts are available. The limitation to ball screw powered units is travel length and speed. Ball screw driven units succumb to phenomena called critical speed which is a wave harmonic that distorts the screw when the screw rotates too fast in relation to its travel length. PBC provides critical speed charts that should be adhered to when selecting the actuator. Ball screws like to run in a straight line and it is important to monitor the distance between mounting surfaces with regard to load, especially in a horizontal application. Too much droop will affect the critical speed and column strength ratings and will cause damage to the unit. Consequently, it is important to ensure the travel length accommodates the column loading on the screw. Lead screw (Acme/Trapezoidal) units are available. They are a quiet self-braking (low lead) alternative to ball screws, however, their life is not predictable and their natural wear may affect future system accuracy.

Belt driven actuators  provide more flexibility in the mounting surfaces and are available up to four meters of continuous length and may be but-jointed for longer lengths. To obtain the optimum load/speed performance they often have to be inertia matched by an external gearbox coupled before the motor. They also should employ a brake in vertical applications! In any vertical application including ball screws it is a best practice to include a brake. Belt drive units go fast up to 6 m/sec and due to the steel reinforced belt are very repeatable and are less likely to be affected by actuator droop or twist. The low carriage mass coupled to a steel-reinforced timing belt provides high acceleration with sustained velocity. Acceleration at 20 m/s2 and speeds up to 6 m/s, can achieve performance comparable to linear motors at a fraction of the cost. .

Both units coupled with servo motors and controls can provide a compact high-performance accurate linear motion solution at a competitive cost. Electric linear actuators are quickly finding their place in replacing pneumatic and hydraulic actuators in applications that require control, accuracy and high performance. Industries such as packaging, pharmaceutical, food & beverage, semiconductor, and factory automation, are ideal candidates.