Draft Zones and Roller Settings
topic
A three-over-three drafting system has two draft zones: back zone (between back and middle rollers, break draft 1.1–1.5) and main zone (between middle and front rollers, main draft 10–40). Roller settings are the distances between roller nip lines, set slightly greater than the upper quartile fibre length (typically staple length + 6–12 mm) to prevent fibre rupture while maintaining control. Incorrect settings cause drafting waves with periodicity equal to the roller spacing.
Role
Precise roller settings are the foundation of yarn evenness. Engineers who understand the relationship between fibre length distribution and roller spacing can systematically eliminate periodic faults, reducing fabric defects by 30–50% and improving weaving efficiency.