The project team at Tectra Automation devised a solution for Elimen Engineering to replace the hydraulic system in a vulcanising press. The solution, which had to guarantee an accurate pressing cycle that distributes a 130-ton press load evenly, consisted of four Bosch Rexroth size 75 flanged nut planetary screw assemblies (PLSAs), also called roller screws.
Compared with its hydraulic predecessor, these PLSAs offer improved speed, simplicity and energy efficiency, and provide an effective drive solution for applications requiring up to 29 500 kgf. The roller screws attain very high positioning and repeat accuracy, even when minimal travel distances are involved. In addition, the compact design means they are easily 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 also ensures that PLSAs can be electrically controlled, offering accuracy and high repeatability.
The Elinem Engineering project was awarded to Tectra Automation in April 2019 with completion in June, only three months later. “We have the product range to provide the most appropriate solution and the technical capabilities to see them through,” says Julie Van den Berg, Product Manager, Tectra Automation.
“Combining a roller screw with a servo motor produces a mechatronic unit with the nominal force of a hydraulic cylinder,” explains Jaco de Beer, Projects Manager, Tectra Automation. “Ultra-high accuracy, positioning and flexibility, as well as low energy consumption make the design perfect for use as a feed axis in modern servo presses, machine tools and injection molding machines.”
De Beer adds that the planetary design, with planets positioned axially parallel around a rolled threaded screw, ensures smooth running characteristics and noticeably lower noise emissions compared to ball screws. “The numerous contact surfaces inherent in the design lead to a high load-bearing capacity and long service life.” Another advantage is the roller screw’s innovative sealing system, which provides for long lubrication intervals. This reduces maintenance costs and helps protect the environment by keeping lubricant consumption to a minimum.
There is a standard 12-month warranty on the PLSAs, dependent on their use within the agreed project parameters. “However, the estimated lifetime calculation completed on the PLSAs reveals that they should reach a theoretical lifetime of five years,” Van den Berg points out in conclusion.