Six Degrees of Freedom (DOF) robotic manipulators can use non-planar layers to deposit materials in additive manufacturing. Conformal material deposition requires accurately positioning and orienting the deposition tool on non-planar surfaces. Using industrial manipulators to move the deposition tool enables 6 DOF motion and avoids collision between the tool and the pre-existing substrate. Regular articulated industrial robots have high repeatability but do not exhibit high accuracy. Therefore, performing printing that involves small features becomes challenging. In this paper, we present advances in non-planar surface registration with respect to the robot frame, deposition tool calibration, and gap compensation scheme to enable accurate positioning of the tool tip with respect to the non-planar substrate. This enables us to maintain an accurately controlled gap between the tool tip and the underlying surface to allow printing of mesoscale features on curved surfaces. We test the efficacy of the proposed approach by printing a single layer of ink patterns with approximately 130 μm line width on spherical (radius < 1 cm), cylindrical, and planar substrates. We also demonstrate the capability of changing tool orientation enabled by the 6 DOF robotic manipulator and show that adjusting tool orientation is critical in enabling conformal printing on highly curved surfaces. Finally, the gap variation is characterized and accurate control of the gap is demonstrated.

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