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Planetary roller screws
Planetary roller screws for high axial loads – where a ball screw reaches its limits.
Planetary roller screws from ELTMAR
In a planetary roller screw, threaded rollers arranged planetarily around the screw shaft carry the load instead of balls. More contact points mean higher load capacity, stiffness and service life within the same envelope.
The solution for electromechanical actuators replacing hydraulics: no oil, precise force and position control and lower energy consumption.
Availability
Made to order, manufactured to drawing
Consulting
+48 790 280 320
[email protected]
High load capacity, stiffness and precision
Roller screw drives are used in applications that require high rotational speed limits (high travel speeds), high axial rigidity, and high load capacities. Furthermore, they offer excellent positioning and repeatability accuracy, reaching the micrometer (µm) range.
Due to the number of contact points, roller screw drives possess a high load-carrying capacity and are characterized by a long service life. For instance, a roller screw drive with a nominal diameter d0 of 12 mm and a lead Pz of 4 mm features approximately 140 effective contact points for power transmission.
- High rotational speed limits and high travel speeds
- High axial load-carrying capacity
- High axial rigidity
- High positioning and repeatability accuracy
Roller screw vs. ball screw
In ball screw drives, applied loads are transferred from the screw to the nut via the balls. According to the principles of Hertzian contact stress, the load-carrying capacity of the balls depends on their diameter. However, the diameter of the rolling elements cannot exceed the lead of the thread; in fact, it is typically about 30% to 40% smaller. Additionally, the number of effective contact points influences the load-carrying capacity.
Roller screw drives offer a significantly higher load-carrying capacity than comparable ball screw drives. This high capacity is achieved through the use of threaded rollers as rolling elements, which results in a large number of contact surfaces. Ball screw drives with small leads, in particular, have a much lower load-carrying capacity compared to roller screw drives. Moreover, the necessary ball-guiding mechanisms can negatively affect smooth operation. In the case of two-piece preloaded nuts, the load-carrying capacity is lower than that of one-piece preloaded nuts due to the effective load-bearing length of the threaded rollers.
Fields of use
- Electric presses and servo presses
- Actuators replacing hydraulics
- Injection moulding machines
- Welding and riveting
- Test benches
Selection parameters
- Static and dynamic axial load
- Lead and speed
- Required stiffness and accuracy
- Duty cycle and service life
- Mounting and bearing arrangement
Comparison
Indicative overview – the final choice depends on the application parameters.
| Feature | Ball screw | Planetary roller screw |
|---|---|---|
| Load capacity | high | very high |
| Stiffness | good | very high |
| Shock resistance | limited | high |
| Small lead | limited | possible |
Variants and versions
- RGT – standard
- RGTR – with roller recirculation
- RGTI – inverted
- Special versions to drawing
How we select
Enquiry
You send us the application parameters, a drawing or the part number.
Analysis and selection
We check loads, service life and operating conditions and propose options.
Quotation
A concrete offer with price and delivery date.
Delivery and support
We deliver the complete set and stay in touch during installation and commissioning.
Frequently asked questions
Can’t find your answer? Call us: +48 790 280 320
When should I choose a roller screw instead of a ball screw?
For high forces, shock loads and long required service life in a compact design.
Can a roller screw actuator replace hydraulics?
In many applications, yes: no oil, with precise force and position control. This requires an analysis of the duty cycle.
What is the lead time?
4 to 8 working weeks.
Enquiry: planetary roller screws
Give us the parameters you know – we will clarify the rest by phone. You can also send a drawing to [email protected].
+48 790 280 320
Company headquarters
- ul. Strzelców Bytomskich 13B lok. 7
- 44-109 Gliwice, Poland
Contact details
Elements of Linear Technique for Machinery Automation Robotics
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