German-based Harmonic Drive chose Victrex Peek for the bearing cages of its Harmonic Drive (HD) gear units because of the polymer's superior combination of properties.

German-based Harmonic Drive, a manufacturer of precision gears and drives, chose Victrex Peek for the bearing cages of its Harmonic Drive (HD) gear units because of the polymer's superior combination of properties. HD gears are engineered for highly demanding applications in aerospace and defense. Their extreme light weight and compact design sets them apart from traditional planetary and helical gears.

Depending on the design, HD gears have a transmission ratio of between 30:1 and 320:1 and a torque of 0.5 Nm to 9000 Nm with single-step gearing.

Backlash and maintenance free, they can be used over a wide temperature range and offer high repeatability and torque capacity.

According to Andrew Ragan, Victrex Global Leader Industrial, 'The gear's bearing cages have to withstand operating temperatures of -55C (-67degF) to 150C (302degF) and be non-corroding and lubricant-friendly'.

' Because of the way the gear operates, the bearing cages are not tightly guided, which means that very high sudden impact stress is generated'.

' The cage also suffers constant elliptical deformation during operation.' Victrex peek has a continuous service temperature of 260C (500degF), as well as excellent characteristics at sub-zero temperatures.

It has very good chemical resistance and is compatible with almost all the lubricants and fluids used in the aerospace industry.

In addition, its outstanding sliding friction properties as well as high strength significantly extend the life of the bearings cages.

Low outgassing is an important requirement for space applications'.

' 'Precipitation on the sensitive electronics and optics could have serious consequences,' explains Ragan'.

' 'Victrex peek has very low levels of ionic extractables, which is why it is often used in semiconductor production.' Aerospace applications include actuators for solar panels, antenna orientation systems, opening mechanisms and manipulator arms.

The drives for exploration robots (Lunar Rover, Mars Pathfinder, Odyssey, etc) are also based on HD gears.

HD gears are also used in passenger aircraft as sensors for reporting the position of the landing flaps and in active vibration dampers which reduce structural noise in the rear cabin section.