Planetary screw assemblies (PLSAs), or roller screws, were recently used as part of a solution to replace the hydraulic system in a vulcanising press. The solution, which had to guarantee an accurate pressing cycle that distributes a 130 t press load evenly, consisted of four size 75 flanged nut PLSAs.
Compared with its hydraulic predecessor, the PLSAs are said to offer improved speed, simplicity and energy efficiency, as well as provide an effective drive solution for applications requiring up to 29 500 kgf. The roller screws have the potential to attain high positioning and repeat accuracy, even when minimal travel distances are involved. In addition, the compact design means they can be integrated into applications that require high load capability, precision and low environmental impact.
Unlike hydraulics, PLSAs are driven directly by electrical motors, which require less heat and experience reduced electrical and mechanical energy loss. The direct drive allows PLSAs to be electrically controlled, offering accuracy and high repeatability.
The Elinem Engineering project was awarded to Tectra Automation in April 2019 and took three months to complete.
The company explains that the planetary design, with planets positioned axially parallel around a rolled threaded screw, ensures smooth running and lower noise emissions compared to ball screws. Additional advantages are said to include a high load-bearing capacity, long service life and a sealing system, which provides for long lubrication intervals.