igus evolves trapezoidal thread

Trapezoidal threads have been an essential component of mechanical engineering for decades, converting rotational movement into linear motion in applications such as window or door drives, in adjustments within production plants or in laboratory technology machines. But there is always room to improve and reinvent. "Working at igus means daring to take an industry standard component and say: It can be even better," emphasises Robert Day, dryspin product manager at igus in Northampton. 

The motion plastics specialist has optimised the interaction between the leadscrew and polymer threaded nut, achieving a 30% longer service life and 82% efficiency.

Compared to standard trapezoidal threads, igus has enlarged the thread surface of the nut, and increased the distance between the thread pitches of the screw. This small adjustment has a considerable impact, because the increase in the thread area means more high-performance plastic is used for power transmission which is tribologically optimised to handle friction and wear. 

"Due to this asymmetry, we have managed to extend the service life by around 30%compared to symmetrical trapezoidal threads," says Day.

Optimising the thread angle also increases the efficiency of the energy supplied. By flattening the thread angles of the nut and screw, they were able to achieve an exceptional efficiency of up to 82% with high pitch threads.

Low vibration and near silent operation

dryspin leadscrew technology is not only durable and efficient, but also quieter than most conventional trapezoidal threads. This is because the teeth are rounded rather than square, so the contact surface between the threaded nut and the screw is reduced. This leads to fewer vibrations, therefore minimising rattling, or squeaking. 

"Due to these rounded threads, the motion is free from vibration and almost silent. The tighter manufacturing tolerance of the lead screws compared to DIN 103 7e also ensures more precise running behaviour and significantly higher speeds in the application" says Day.

igus developed and patented its dryspin thread technology in 1996, initially as an alternative to high helix pitch threads. Over 50 sizes are now available including matched screws and threaded nuts, as well as dimensions with low pitches for quick one-to-one replacement of old trapezoidal threads. The screws are made of stainless steel or aluminium and the nuts are injection moulded as standard in seven high-performance plastics in several designs – from cylindrical structures with a collar or keyed surface to versions with spring preload. There is also the option to machine the nuts from plastic bar or to SLS print parts for rapid prototyping.

Seamless operation in railways

Lead screw technology is widely used across various industries, including the rail sector, where ensuring passenger safety and operational efficiency are paramount. Sliding steps on trains bridge the gap between the train and the platform, providing safe boarding and alighting for passengers. However, traditional sliding step mechanisms often face problems such as sticking, misalignment, and high maintenance costs. A leading rail operator needed a solution that would eliminate these issues while reducing weight, minimising components, and ensuring reliability despite the high temperature fluctuations and exposure to dirt and moisture.

The use of dryspin lead screw drives gave the perfect solution. Made from stainless steel, paired with iglidur J nuts, they offered several advantages and exceeded expectations. The system functioned without fault despite high temperature fluctuations and exposure to dirt and moisture, ensuring reliable performance in all environmental conditions. The simplified guidance system eliminated sticking, and the maintenance-free design reduced life cycle costs. Additionally, the system's ability to withstand and offset heavy loads, along with manual retraction capability during power failures, ensured enhanced safety and convenience for passengers. 

Read more about dryspin® lead screw drives in railway technology at:

www.igus.co.uk/info/lead-screw-rail-technology