Dynamic modelling of the latch needle cam system of weft knitting machines

Abstract

Knitted textile fabrics are usually produced on weft knitting machines. The basic mechanism of the machines to convert textile yarn into knitted fabric is called a latch needle cam system. A rigid-body model with five bodies is set up to analyse the motion of the needle of the latch needle cam system. The force element is modelled as a spring damper element between the needle butt and each virtual body on the cam curves. The spring constant is obtained from the cam angle, the friction coefficient and the stiffness of the needle. Numerical examples are given to show the path of the needle butt and the forces between the needle and the cams. For various rotational speeds of the cylinder, the maximum vertical and horizontal forces are obtained.