Non-linear Friction Characterisation of the Unwinding Group in a Web Processing Machine

An experimental methodology is proposed to characterize the friction behaviour of the unwinding group in a web processing machine. The viscous friction effects from the gearbox are of primary focus in this work as they are dominant during the long and steady operating conditions of the web processing machine. The non-linear change in the viscous friction due to the increase in temperature of the gearbox lubricant is experimentally investigated and characterized. Apart from the viscous friction effects from the gearbox, the friction due to the bearings in the unwinding group is also characterised. The experimentally observed friction torque is represented as a 2D map w.r.t to the rotational speed of the motor and the gearbox lubricant temperature. From the obtained results, the non-linear behaviour of the friction is modelled through curve fit method. Also, a viscous friction coefficient derived from the obtained friction measurements is also presented in the work. The proposed methodology can be applied towards developing dynamic models for model-based design applications, control implementation, parameter identification and deployment of digital twins.