Coupling is divided into rigid coupling and elastic coupling.Rigid coupling does not have buffering and the ability to compensate the relative displacement of two axes, requiring strict alignment of two axes, but this kind of coupling has simple structure and low manufacturing.Elastic coupling can be divided into inelastic component flexible coupling and flexible component elastic coupling, the former kind only has the ability to compensate the relative displacement of two axes, but can not cushion the vibration,the latter type contains elastic components, in addition to the ability to compensate the relative displacement of two axes, but also has a buffer and damping, but the torque transmitted is generally less than the flexible coupling of inelastic components. Because the structure design and manufacturing accuracy of desktop printers is not high enough, but the load is small,so flexible component flexible coupling is more suitable for desktop level 3d printers.The coupling is flexible coupling with elastic elements.