PRS Series Roller Screw Overview

PRS Series Roller Screw Overview
Available in diameters from 3.5 to 150mm, Exlar PRS Series roller screws provide solutions to a wide range of applications - from the most compact and precise to the largest and extremely high load requirements. Roller Screw Advantages Roller screw design provides high speeds, stiffness and shock load resistance compared to other technologies. Click here to see comparison chart. Large static loads - up to 779,000 lbf. High screw speeds - 5,000 rpm and above Up to 15 times longer life than comparably sized ball screws. Ideally suited for continuous duty applications. Preloaded nut options for zero backlash. Variety of flange designs
Unique Design This robust roller screw design is composed of rollers that are manufactured with precisely the same thread angle as the nut. This construction is particularly well-suited to applications that require very high loads and high speeds. This is possible because Exlar's planetary roller screw designs provide many more contact points than possible on comparably sized ball screws. The result is higher stiffness, higher load capacity and 15 times the travel life of similarly sized ball screws. The diagram at right shows the number of contact points in a ball screw compared to the number of contact points in a roller screw.
Typical Applications Planetary roller screws are used in the most critical, demanding and precise applications requiring linear motion. Roller screws offer a perfect replacement for hydraulics because of the load and cycle capability. Examples of industries and other applications for planetary roller screws include:

Medical
-Artificial Hearts
-Patient Positioning Tables
-Automated, High Force Syringes

Machine Tool
-Presses, Broaching
-Grinding, Dressing, Cutting

Military
-Weapons Positioning
-Door Control, Artillery Handling

Assembly
-Riveting, Fastening, Joining,
-Clamping, Part Positioning, Weld Guns

Plastics, Glass and Textile
-Mold Closing, Toggle Drives,
-Eject Axes, Transfers, Shifting

Food and Beverage
-Volumetreic Filling, Paletizing,
-Cartoning, Sealing

PRS Series Standard Features Ground screw for high-precision application Non-recirculating rollers Available to tolerance classes G1, G3, G4 and G5 Single, split (preloaded) and double nuts are available Three standard nut flanges (no flange, end flange, center flange) are available
In addition to the standard features listed above, and the sizes listed in the dimensions tables link below, Exlar can design a custom roller screw specifically tailored to your application. Please contact us for more information. Lead Accuracy Exlar roller screws are grouped in tolerance classes according to DIN 69051, part 3. These manufacturing tolerances are expressed as lead errors per distance of linear travel, as shown below.
Tolerance Class	Lead Accuracy
G1	0.006 mm/300 mm (0.00024 in/ft)
G3	0.012 mm/300 mm (0.00048 in/ft)
G4	0.020 mm/300 mm (0.00080 in/ft)
G5	0.024 mm/300 mm (0.00096 in/ft)
Lubrication Exlar roller screws can be used with either grease or oil lubrication. Grease Lubrication Bearing greases of KP (DIN 51825, part 3) consistency factor of 2 should be used. Optional wipers can be installed on each end of the nut to protect it from contamination in dirty environments. Grease lubrication intervals depend on screw size and operating conditions. Exlar's Applications Engineering Department can provide grease lubrication recommendations for any application conditions. Oil Lubrication If oil lubrication is desired, a high performance gear oil with an EP additive is recommended The oil lubrication rate is dependent on the screw diameter, number of rollers, and the amount of heat dissipated; oil consumption will generally range from about 1 to 30 ml/hr. Nut and Flange Types Exlar roller screws are available with three standard nut types, as described below: Single Nuts Exlar single nut roller screws are ideal for applications where maximum life and minimal backlash are required. The single nuts have backlash limits of 0.01 - 0.03 mm (0004 - 0.001 inches). Split (preloaded) Nuts Split nuts are designed to eliminate backlash entirely. The split nuts are preloaded by clamping the two halves of the nut together, spaced by a precision ground washer. They are preloaded at the factory to 5% of dynamic load rating, unless otherwise specified by the customer. Double Nuts Double nuts provide the high load rating and lifetime advantages of single nuts along with the zero-backlash attributes of split nuts. A double nut consists of two single nuts preloaded against each other, clamped together and spaced by a precision ground washer. The two single nuts are also preloaded to 5% of the dynamic load rating. Exlar standard roller screw flange designs are shown next page. Custom configurations can also be designed. Specifications and details on the PRS Series Roller Screws can be found in the following areas: PRS Series Dimension Drawings (dwg file) PRS Series Flange Options (dwg file) Dimension Tables Specifications Ordering Information Roller Screw Basics Design Guidelines - Download .pdf file of PRS Series brochure (274k)

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