Dynamic Characterisation of Variable Lead Screw Weft-Guiding Mechanism with Screw Pair Clearance

This study aims to investigate the dynamic characteristics of a variable lead screw weft-guiding mechanism considering screw pair clearance. Modeling the clearance collision of screw pairs is inherently challenging, let alone when the screw lead is variable. The motion law of the follower is predetermined, and the variable lead screw is designed using a planar analysis method. A hybrid contact force model together with the improved Gonthier model is adopted to characterize the collision force within the clearance. The Newton-Euler equations are employed to establish the dynamic model of the variable lead screw weft-guiding mechanism with screw pair clearance, which is accomplished for the first time. The effects of clearance value, rotational speed, and spiral working profile on the dynamic responses of the mechanism are systematically investigated. Results indicate that screw pair clearance significantly affects the stability and accuracy of the rapier. Moreover, the dynamic responses of the mechanism vary under different clearance values, rotational speeds, and spiral working profiles. These findings provide a theoretical basis for the optimal design of weft-guiding mechanisms.