Planetary Roller Screws

June 22, 2011
Exlar’s component planetary roller screw line has been expanded to include two performance capacities, available in PRS and PRR models.
The PRS models, with G5 lead accuracy, are available in screw diameters ranging from 8- to 80-mm, and deliver static load ratings up to 218,000-lbf. Exlar’s PRR models, with G9 lead accuracy, are available in screw diameters of 12- to 27-mm and offer static loads up to 18,000-lbf. Exlar’s roller screws are a superior mechanism for converting rotary torque into linear motion. They function in a similar manner as acme screws or ball screws, with a nut traveling on a threaded shaft. However, unlike acme or ball screws, Exlar roller screws are capable of carrying heavy loads—at high speeds—with high duty cycles for thousands of hours in the most arduous conditions. This makes them an optimal choice for demanding, continuous-duty applications. Exlar roller screws are also an ideal replacement for ball screws, due to their longer travel life in the same compact size.Roller Screw vs. Hydraulic & Pneumatic Solutions
In applications where high loads are anticipated, or faster cycling is desired, Exlar roller screw actuators provide a superior alternative to hydraulic or pneumatic solutions. Electromechanical systems using roller screws offer major advantages, as they do not require a complex support system of valves, pumps, filters and sensors. Thus, roller screw based systems require much less space and deliver significantly long working lives with minimal maintenance. Further, these systems eliminate hydraulic fluid leaks and significantly reduce noise levels, resulting in highly efficient operation. Electromechanical systems also offer increased flexibility, making them suitable for diverse applications.Roller vs. Ball Screw Performance
Loads and Stiffness: Due to design factors, the number of contact points in a ball screw is limited by the ball size. Alternatively, Exlar's planetary roller screw designs have significantly more contact points on comparably sized ball screws. Increased contact points enable roller screws to provide higher load carrying capacities, plus improved stiffness. This results in minimal space requirements to sufficiently meet the specified load rating.Exlar’s planetary roller screws are ideal for the following applications:
  Medical Assembly – artificial hearts, patient positioning tables, automated high force syringes   Machine Tool – presses, broaching, grinding, dressing, cutting   Plastics, Glass and Textile – mold closing, toggle drives, eject axes, transfers, shifting   Military – weapons positioning, door control, artillery handling   Assembly – riveting, fastening, joining, clamping, part positioning, weld guns   Food and Beverage – volumetric filling, palletizing, cartooning, sealing Exlar Corporation -

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