PRS / PRR
Component Roller Screws
Available in diameters from 8 to 80mm, 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
A roller screw is a mechanism for converting rotary torque into linear motion, in a similar manner as acme screws or balls screws. However, unlike acme or ball screws, roller screws are capable of carrying heavy loads for thousands of hours in the most arduous conditions. This makes roller screws the ideal choice for demanding, continuous-duty environments. Click here to see comparison chart.
PRS Series Standard Features
- Large static loads - up to 218,000 lbf.
- Available in two classes of screws (PRS, PRR)
- Up to 15 times longer life than comparably sized ball screws. Ideally suited for continuous duty applications.
- Non-recirculating rollers.
- Available tolerance classes G5 (PRS) and G9 (PRR)
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.
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.
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:
Food and Beverage
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|
|G5||23 µm/300 mm (0.00096 in/ft)|
200 µm/1000 mm (0.0024 in/ft)
Exlar roller screws can be used with either grease or oil 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.
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.
Immersion oil lubrication can also be used. In this case, the oil level must be such that the bottom-most roller is fully submerged in oil.
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 (0.0004 - 0.0001 inches).