In this paper, five positions of a planar RPR serial chain are specified and the synthesis equations for two RR constraints are solved to obtain a six-bar linkage. Analysis of the resulting linkage determines if it moves the end-effector smoothly through the five task positions without a branch defect. The design procedure presented randomly selects variations to the positions of the RPR chain in order to obtain new six-bar linkages. This dimensional synthesis algorithm yields a set of six-bar linkages that move the end-effector near the original task positions. This synthesis procedure is applied to the design of a linkage that generates a square pattern. The procedure yielded 122 defect-free linkages for one million iterations. © Springer Science+Business Media Dordrecht 2013.