Using high drafting on a sliver-to-yarn ring spinning frame requires. some critical conditions. In order to understand what occurs during this process, an experimental design is used, and the most influential parameters and their interactions are determined. This approach is applied to spinning of thick and medium cotton yarns for denim fabrics, revealing that a well chosen configuration of the high drafting device leads to a very regular yarn. Some complementary experiments under critical conditions highlight the importance of condensers in such systems. Statistical and mechanical explanations are in good agreement with previous theoretical and experimental work.