High Precision Micro Positioning Systems Used in Uhv Applications

The advantages of miniaturisation, e.g. low masses, low power consumption and small dimensions open new fields of applications for powerful micro actuators in areas dealing with particular environmental conditions like ultra high vacuum or wide temperature ranges. In fact these kinds of applications are mostly challenging positioning tasks, such as the sensitive movement or exact adjustment of sensors, optical devices, probes and tools. In addition to their miniaturised dimensions and low weight the micro gears should offer a backlash-free and precise angular transmission behaviour for such applications. The Micro Harmonic Drive gear is the world ́s smallest zero-backlash gear system. Originally invented in 2001 by Micromotion GmbH this innovative gear design has successfully been transferred from a research environment into numerous industrial applications. The combination of high reduction ratio, excellent repeatability, high efficiency and high torque capacity offered by this gear principle make it highly suitable for precise positioning applications in semiconductor manufacturing equipment, medical devices, measuring equipment, optical devices as well as ultra high vacuum, aircraft and even spacecraft. This micro gear, with an outer diameter of down to 6 mm and an axial length of only 1 mm in the smallest currently available size, provides gear ratios between 160 : 1 and 1000 : 1 in a single stage [1]. These high ratios are necessary to convert the very high rotational speeds of up to 100,000 rpm and very low output torques in a range of some μNm provided by current micro motors [2], [3] into lower speeds and higher torques as required by real applications in industrial machines and equipment. The gear is manufactured by a special production process, called “Direct-LIG”, by which the individual gear components are formed galvanically in a 3-dimensional mould produced from a photoresist using X-ray lithography. However actuators for applications in areas like UHV, Cryo technics, aircraft and spacecraft have to deal with further requirements in addition to properties like zero backlash, high positioning accuracy and extreme demands to reduced mass and dimensions. Due to its unique functional principle the Micro Harmonic Drive gear offers the possibility to operate at extreme environmental conditions. To be able to use actuators reliably also at extreme environmental conditions, like UHV or wide temperature ranges, there have to be fulfilled special arrangements in relation to the built-up, the materials used and in particular to the lubrication system. The Micro Harmonic Drive gear provides the basics to be used in such applications. Important properties of the Micro Harmonic Drive gear are: • The possibility to use a dry lubrication system • The single components like housing, shafts, bearings up to the single gear wheels are made of high-strength and corrosion-resistant