This article reports a mold design strategy and a detailed mechanics-based modeling approach to characterize and control the plastic deformation of premolded components during in-mold assembly of mesoscale revolute joints. The following new results are reported in this article. First, a mesoscale mold design with varying cavity shape is described to perform in-mold assembly of the mesoscale revolute joint. Second, a transient computational fluid dynamics (CFD) modeling approach to determine the forces experienced by the mesoscale parts due to injection molding is described. Finally, a mechanics-based model approach developed using a combination of experimental materials property data and the CFD results as input to a finite element simulation of the deformation response of the mesoscale part 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 article 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. POLYM. ENG. SCI., 49:293304, 2009. (C) 2008 Society of Plastics Engineers