The factors influencing self twists include two main categories: structural parameters and process parameters on the self-twist spinning machine. Firstly from the twist formula of in-phase self-twist yarn over a half cycle length, six structural parameters can be obtained i.e. the oscillating stroke D, cycle length X, the distance L1from the nip of the front rollers to the nip of the self-twist rollers, the perimeter of strand P, the feeding distance e of two strands, and the distance L2from the nip of the self-twist rollers to the convergence guide O. Among these six parameters, the effect of the oscillating stroke D and cycle length X on the self-twist is opposite; therefore, the oscillating stroke D and cycle length X should have a reasonable configuration in order to get more self twists. At the same time, the greater the distance from the nip of the front rollers to the nip of the self-twist rollers can achieve more twists of self-twist yarn in the case of limited space. Twists over the half cycle length decrease with an increase in the circumference of strand P, along with that in the feeding distance e and distance L2from the nip of the self-twist rollers to the convergence guide. The twists are also influenced by the processing parameters, such as the spinning speed, the pressure of the self-twist rollers, and the spinning tension E1and E2from the nip of the front rollers to the self-twist rollers and from the nip of the self-twist rollers to the convergence guide, respectively. The lower the spinning speed and the higher the pressure of the self-twist rollers, the more self-twists can be obtained. In the same way, the smaller the spinning tension E1and E2, the more twists can be achieved. However, the value of spinning tension E1and E2cannot be lower than 1.025 and 0.92, otherwise the normal spinning process cannot be obtained.
