S . K . Gupta and H . A . Bruck

In-mold assembly process has been used for manufacturing articulated structures at the macro scale. But the in-mold assembly process at the mesoscale behaves differently and poses new challenges due to reduced structural rigidity of the mesoscale premolded component. One of the major challenges that need to be addressed is that of the plastic deformation of the premolded component during the second stage injection. This paper reports a mold design strategy and a detailed modeling approach to characterize and control this deformation. The following new results are reported in this paper. First, a mesoscale mold design with varying cavity shape is described to perform in-mold assembly of the mesoscale revolute joint. Secondly a transient flow based modeling approach to determine the forces experienced by the mesoscale parts due to injection molding is described. These forces are of particular interest in the in-mold assembly perspective since they are forces applied on the premolded component due to flow of the second stage melt. Finally, a mechanics-based model developed using experimental data and numerical CFD and FEA simulations is presented for the determination of critical mold design parameters that are necessary for repeatable fabrication of articulating mesoscale revolute joints. Using the advances reported in this paper a mesoscale revolute joint has been successfully molded. To the best of our knowledge, this is the first demonstration of in-mold assembly process using a varying cavity shape mold to create an articulating mesoscale revolute joint.