Reliable lead screw technology for a precise and sensitive joystick control system

Profile

• What was needed: a zero-backlash lead screw nut with matching lead screw from dryspin 
• Requirements: quiet travel, minimal nut and lead screw clearance, quiet and vibration-free operation even under load, freedom from lubrication and maintenance
• Industry: aerospace
• Success for the customer: "The use of dryspin lead screw technology has significantly improved the entire behaviour of the drive, from the feel and noise level to the extremely clean and quiet operating behaviour," says Thomas Brunner, Head of Mechanical Engineering at BRUNNER Elektronik. 

Problem

"We use metal recirculating ball screws for our joystick. They were relatively expensive, noisy and the behaviour of the lead screw was never 100% satisfactory for us. We have been working successfully with igus for over 20 years and when Axel Ebert visited us again, he presented a new igus lead screw with a new type of lead screw nut. He positively raved about the many advantages of the system at the time, so we tested it shortly afterwards - and what can I say, we were thrilled from the start!", recalls the Head of Mechanical Engineering. The dryspin lead screw technology was specially developed by igus in 2015 and is based on the principle of lubrication-free and maintenance-free linear technology. The specifications and geometries of the lead screw technology, which are matched to the plastic nut and lead screw, guarantee efficiency levels of up to 82% and a service life that is up to 30% longer than that of conventional lead screw drives. Axel Ebert, Key Account Manager for Bearing Technology at igus Switzerland, explains: "The rounded tooth flank geometry reduces the contact surface between the lead screw and lead screw nut, which means that the threaded systems run almost noiselessly and without vibration under load." Hence, the decision in favour of dryspin was quickly made. However, the special requirement of reducing the clearance of the nut still had to be solved. But here, too, igus was able to provide a remedy.

Solution

The solution: the zero-backlash lead screw nut. A preload mechanism has proven to be an effective measure for reducing unwanted axial clearance. The zero-backlash lead screw nut proposed by Axel Ebert is also used here. It is specially designed for fast and efficient applications and consists of a support nut, a fixing collar with torsion spring, a friction disc and the axial element. The torsion spring brings the pretension into the thread system. "The joystick uses two lead screws. With the ball screw used in the past, the two bearing sides had to be exactly aligned to guarantee smooth operation of the lead screw. Not so with the igus lead screw, which is fixed at the bottom and has a plain bearing with some clearance at the top thanks to an iglidur plain bearing. As a result, we achieve a much higher degree of efficiency and a significantly better feel during the movements," states BRUNNER and Ebert adds: "The zero-backlash nuts used are an igus standard catalogue item. All dimensions are available from stock. We manufacture the lead screws ourselves according to BRUNNER's requirements and drawings." In addition to the lead screw and the nut, BRUNNER also uses iglidur plain bearings and drylin R linear plain bearings from igus for the moving applications.