A comprehensive review of the geometry and mechanics of the spinning triangle

The spinning triangle is a critical transitional zone in the ring spinning process, wherein drafted fiber strands are progressively consolidated into a coherent yarn structure. The geometry (including triangle height, width, and symmetry) and the mechanics (including the distribution of fiber tension) of this zone play a decisive role in determining yarn properties such as strength, hairiness, and residual torque, as well as in influencing end breakage and process stability. This review provides a comprehensive analysis of the spinning triangle by examining its mechanical behavior, geometric characteristics, and their interaction with process factors such as spinning tension, yarn count, twist level, etc. The study systematically reviews and compares a wide range of theoretical models, numerical simulations, and experimental investigations. It critically analyzes the similarities and contradictions among these studies to provide a clearer understanding of how the geometry and mechanics of the spinning triangle are influenced under varying spinning conditions. In doing so, this work identifies and introduces key research directions aimed at improving both yarn quality and spinning process performance. The review offers an integrated framework that links the structural behavior of the spinning triangle to process optimization, and it lays the foundation for future innovations in spinning system design and control.