What are the advantages and disadvantages of rigid couplings and semi-flexible couplings

Semi-flexible coupling: between the flexible join and the rigid join. It is required that the axial line of the axial line of the two axis will be more relaxed than the rigid join. The vibration is more than the rigid join because it is required to relax. Rigid coupling: the coaxial degree between the two shafts of the loading time is strict, the normal end face is not 0.04, the radial pulsation is not greater than 0.03, the axial core tilt is not more than 0.05/1000.