Design and performance analysis of a composite flexure hinge based on micro-ultrasonic powder molding

This paper presents a new type of flexure hinge and its fabrication method based on micro-ultrasonic powder molding (micro-UPM). A right-circular notch-type flexure hinge (RFR-RC hinge) comprising an aluminum alloy 7075 (Al 7075) rigid structure and a polypropylene (PP) flexible structure was designed and fabricated. This composite RFR-RC hinge was experimentally studied, and the results helped confirm that the hinge could be considered a complete single structure; the flexible structure had a good forming quality, and the interlocking performance met normal use requirements. The RFR-RC hinge was evaluated in terms of its motion range, stiffness, and stiffness ratio through finite element analysis (FEA) and then compared with a single-material right-circular flexure hinge (RC hinge). The RFR-RC hinge provided a significantly wider operation range with a lower actuation force than the Al 7075-RC hinge and a higher motion pureness and accuracy than the PP-RC hinge. The motion stiffness obtained from the FEA was in agreement with the bending test results, thus validating the FEA results to some extent. From the bending tests, the elastic and total motion ranges of the RFR-RC hinge were found to be 0.068 rad and 0.202 rad, respectively. Finally, the fabrication of a 3-RRR compliant parallel mechanism and four typical applications were taken as examples to demonstrate that the RFR-RC hinge and its fabrication method have a wide range of applications.