A measurement method for temporary fastener and its preload force
The thin-walled parts generally need to be positioned and clamped by the temporary fasteners before formal assem-bly.The quality of positioning and clamping directly affects the subsequent process quality of the thin-walled parts,and even the quality of the final assembled products.The temporary fasteners'clamping force and preload force are key to the assembly quality.In this article,a method of measuring the temporary fastener's preload force is proposed.The deformation is expanded when the temporary fastener is subjected to a preload force by inserting a group of the Belleville springs.The deformation is sensed by the compression spring leaning on the hexagonal wrench,and then by the force sensor adjacent to the compression spring.Therefore,the preload force exerted to the temporary fastener is finally inferred by the relationship between the force and the deformation of the Belleville spring.The other end of the hexagonal wrench is connected to the motor through a sleeve coupling,and the axial displacement of the hexagonal wrench is compensated inside the sleeve coupling.As a result,the automated assembly of the tem-porary fasteners is simultaneous with the measurement of the preload force.Finally,efforts are made to work out the parameters and the combination method of the Belleville springs used with the M4 temporary fastener,as well as the deformation range of the disc springs(Belleville spring washers)when monitoring the preload.
thin-walled parttemporary fastenermeasurement of preload forceautomated assemblydisc spring