Pneumatic positioning system for precision assembly

Micro assembly is typically characterised by positioning tolerances below a few micrometers. In the case of a hybrid micro system assembly, such as optical glass fibres, micro ball lenses or micro probes for measurement tasks, even positioning accuracies in the sub-micrometer range have to be achieved. Due to the need for highly accurate assembly systems and extensive alignment procedures the assembly of hybrid microsystems is characterised by customised solutions. In this context the Fraunhofer IPT develops a concept on how to realise a highly flexible, fast and cost-efficient hybrid assembly system, consisting of a conventional assembly device and an active assembly head. The active assembly head will be pre-positioned by imprecise but dynamic conventional handling devices like an industrial robot. By means of its integrated 6-axes fine positioning system and its sensor system it will be able to first detect position and orientation deviations and second compensate the deviation and execute the final positioning and alignment of the micro part. In this context, a matchbox-sized air bearing stage with an integrated non contact interface for a transfer of pneumatic energy between stage and slides was conceived, allowing ultra precise and frictionless guidance for travel ranges up to 3 mm. In order to apply this distinct design to the whole system, even actuators and sensors must be wireless or pneumatically driven in order to ensure a friction free stage movement. In this context the requirements caused by a conventional pre-positioning device will be discussed. It will be shown that travel ranges of about I mm must be achieved in order to allow a reliable and safe use of the hybrid handling device. Based on that analysis, a design of a friction free, damped pneumatic actuator design as well as a concept of a pneumatic sensor will be presented. Both components will target a travel range of I mm combined with a resolution in the sub-micron range.