A 3-D Printed Ti-6Al-4V 3-DOF Compliant Parallel Mechanism for High Precision Manipulation
This paper presents the synthesis and evaluation of a 3-D printed three degrees-of-freedom (DOF) spatial-motion compliant parallel mechanism (CPM). The CPM was synthesized by the beam-based structural optimization method and a prototype was fabricated by the electron beam melting (EBM) technology with Ti6Al4V material. The mechanical characteristics of 3-D printed compliant mechanism for precision applications, i.e., stiffness property, dynamic response, and large elastic deformation, were experimentally evaluated. Most importantly, a coefficient factor of 1.27 was proposed to determine the effective thickness for 3-D printed compliant mechanisms with 0.5 mm thick flexures. Using the effective thickness, the characteristics of the 3-D printed CPM have shown to agree with the prediction, with a maximum deviation of 10.5%. The Ti6Al4V CPM is able to achieve the large work range up to 4 mm of linear displacement, 6 degrees of angular displacements, fast dynamic response of 119 Hz, good decoupled motions, and high non-actuating stiffness. A 3-DOF manipulator was built based on the 3-D printed CPM and actuated by three voice-coil motors. Experimental results have shown that the 3-DOF manipulator could achieve repeatable motions with resolution of 20 nm for the translation along the Z-axis, 0.14 arcsecond for the rotation about the X-axis, and 0.12 arcsecond for the rotation about the Y-axis. In conclusion, EBM technology is suitable for fabricating compliant mechanisms in precision manipulator systems; the mechanical characteristics of 3-D printed compliant mechanisms are predictable when an effective thickness is used.