Improvement on workpiece manipulation

The reduced work piece dimensions, feature sizes and/or surface roughness requirements in micro-manufacturing processes introduce some new challenges, which are not so critical in macro-manufacturing. Regarding the workpiece manipulation and clamping, they must ensure stiffness, damping, accuracy and possibility of automation (as in macro-manufacturing), but ensuring that the micro-features are not damaged. In the case of the metrology, it must be taken into account that measuring workpiece features with micrometre range geometries and (sub)-nanometre range surface roughness is very close to the limits of existing measurement principles. The machines used for micro-manufacturing technologies differ drastically from state of the art macro-machining systems. Aerostatic or hydrostatic guide ways and spindles, optical encoders or even interferometers and thermally stabilised direct drives allow for a positioning precision down to the lower sub-micron scale. Opposite to the highly sophisticated machinery, the manipulation, alignment and clamping of workpieces as well as tools are mostly carried out manually with only little technical support. The necessary accuracy in the submicron range cannot be achieved by conventional workpiece handling and metrology systems used in the macro technology In order to face some of the difficulties related to workpiece clamping and re-positioning for the micro-manufacturing of complex 3D geometries, the University of Leuven has developed a novel part fixing concept. On the one hand, it allows for clamping the parts by adhesive means in order not to damage micro sized geometrical features or optical surfaces and, due to the nature of the used adhesive, introduces additional damping capabilities (~30%) in comparison to the usual mechanical clamping devices. Besides, the system allows for the modification of the part fixing position, ensuring the re-positioning of the part with a location uncertainty lower than 1 µm. Brunel University has worked on the development of a smart clamping system capable of monitoring the forces acting on different sections of the part. This way, it is possible to control the clamping forces in order to avoid possible geometrical distortions on the manufactured part. Also, it can work as an in-line dynamometer, providing the possibility for a detailed process state monitoring without the need to include an additional measuring element on the manufacturing equipment.