Innovative Concept for Additive Manufacturing of Compliant Mechanisms
The new geometric possibilities offered by additive manufacturing have allowed us to develop, build, and test compliant mechanisms with almost no support structure under the fixture blades.
Bringing together CSEM’s experience in the design and development of high-performance flexural elements and mechanisms for more than thirty years has opened the doors to new opportunities. The entire process of acquiring in-depth knowledge and practical experience of a new production method, for example, for metallic additive manufacturing, with its new design freedom and associated limitation will be presented.
All this work, done at CSEM, determined the limits related to the manufacturing of thin, flexible structures used in compliant mechanisms. In this particular context, usual weakness attributed to AM processes such as surface roughness, material porosity and mechanical anisotropy, which may become major showstoppers, have been taken into account with the development of new strategies to overcome these drawbacks. First, the feasibility of producing AM-based compliant structures was proven by elaborating an SLM-based manufacturing strategy and produced functional monolithic demonstrators made of high strength stainless steel 17-4PH. In addition, flexure test samples and tensile test samples were produced and submitted respectively to alternate bending fatigue tests and tensile tests in order to validate the material performances. Fatigue test and tensile test data were completed by fractographic analysis, characterization of roughness and porosity, as well as microstructural examinations.
The results of these investigations will be presented and compared to those of the reference material and process used at CSEM for similar applications manufactured by wire electro-discharge machining. These steps allow CSEM to re-design, produce, and test complete compliant mechanisms built by additive manufacturing to validate the entire processing chain. The complete redesign for the AM of compliant mechanism structures enables CSEM to develop innovative concepts, patent pending, to drastically reduce the need for machining after additive manufacturing. Support structures under flexure blades can thus be minimized, and the overall process can be more streamlined.
Moreover, this concept allows the researchers to easily design and produce monolithic cross-flexure pivots with interlocked flexible blades. Thanks to this concept, CSEM is now developing architectures of compliant mechanisms based on additive manufacturing (COMAM) for the European Space Agency (ESA) in the frame of a GSTP research project. The past and current work of design, 3D printing, and testing on several compliant mechanisms will be presented in this talk. These demonstrators will be used as a use-case for future high-precision and harsh environment applications such as cryogenic and space.