Design and fabrication of miniature compliant hinges for multi-material compliant mechanisms (Englisch)

This paper presents the approach for the design and the fabrication of miniature compliant hinges in multi-material compliant mechanisms. The methodology described in this paper allows for the concurrent design of the part and the manufacturing process. The following new results were reported in this paper. First, we presented a method to design miniature hinges in multi-material structures, subjected to demanding loading conditions and large deflections. The shape synthesis of the hinge geometry involved the incorporation of MMM process-specific features. These included the hinge geometry itself, the hinge-link interface geometry, including the embedded length and interlocking features, and hinge positioning geometries for the second stage molding. Second, we presented an optimization model of the hinge, involving functional and manufacturing constrains. Third, we described a new manufacturing method for creating multi-material compliant structures using injection molding processes. This included the MMM process sequence, the mold cavity design, gate selection, and runner system development. Finally, we presented a case study of a multimaterial compliant mechanism used as the drive mechanism in a MAV prototype. We have demonstrated the technical feasibility of our mechanism design through successful test flights of our MAV. The MAV was capable of repeatable flights with a 31-g payload, which represents 75 % of the total unloaded MAV weight. While airborne, the MAV was highly stable and controllable in both indoor and outdoor flights. The miniature hinges utilized to achieve selective, localized compliance in the multi-material structure resulted in an efficient and compact design of the MAV drive mechanism. Additionally, the multi-material compliant mechanism resulted in a reduced number of parts in the drive assembly by eliminating several rigid body articulating joints. The methods described in this paper are applicable to any lightweight, loadbearing compliant mechanism manufactured using multimaterial injection molding.