The packing densification of binary cylindrical particle mixtures under 3D mechanical vibrations was systematically studied in physical experiments. The influences of vibration time, frequency, amplitude, vibration acceleration (vibration intensity), particle size ratio of large versus small particles, composition of the binary mixtures (volume fraction of large particles), and container size (wall effects) on the packing density of the binary cylindrical particles were discussed and analyzed. The results indicate that for each fixed composition and size ratio, high packing density can be obtained by properly controlling the vibration conditions. Appropriate composition (e.g. 72 vol.%, volume fraction of large cylinders in current work) with large size ratio can contribute to the high packing density. Increasing the container size can reduce the container wall effects and obtain dense packing. Through extrapolation, the maximum packing density of binary cylindrical particles without container wall effects can reach about 0.8822, which agrees well with the proposed analytical model in literature. (C) 2016 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.