A 3-dimensional model of an industrial robot's manipulator is discussed here. The manipulator is built of two links. Each link is a bar of thin walls, with a box-shaped cross section. Harmonical forces and moments work on both ends of each bar. Lengthwisely and flexibly vibrating robot model is presented in the form of two-block hypergraph. On the base of the skeleton of this hypergraph, a matrix of dynamical flexibilities is developed for the system. The matrix allows us to determine amplitudes of the vibrations of the end of point of the robot's manipulator, separately along each of global axis X, Y, Z. The determined amplitudes anable us to predict the real trajectory of the manipulator and compare it with theoretical trajectory.