A calibration method for overconstrained spatial translational parallel manipulators

•Replaced the redundant constraints of the overconstrained mechanism with forces.•Transformed the overconstrained mechanism to a non-overconstained mechanism.•Established a mechanical model to derive the deformation caused by inner forces.•The inner force-induced deformation was added into the total kinematic model.•The accuracy of the robot can be improved from 1.635 mm to 0.155 mm.