Applying Constrained Experimental Designs for Optimizing Draft Distributions

Abstract
Due to higher computation in the spinning industry continuous improvement has to be carried out on the production line of the factory, without disturbing both quality and productivity, to attain the best working conditions, taking into consideration the higher number of factors as possible. The quality and productivity of cotton yarns depends to great extent on machine setting and fiber types, while labor performance and environmental condition had lesser effect. Drafting theories confirm that the amount of draft has the greatest impact on the yarn quality. Previous studies focused on studying factors affecting the quality and yarn specifications on for obtaining yarn with specified quality. There are also studies that achieved a specific product using experimental design in many sectors of yarn manufacturing. But most of these researches did not examine more than five factors.
The purpose of research is to study the largest possible number of factors affecting the quality of yarns in the spinning mill, without affecting the productivity and the yarn properties, in order to reach the best operating conditions using the dependent and interdependent factors experimental design. Drafts are considered as dependent factors while settings, speeds, and twist as independent factors. These factors consist of: total draft in card; total and break draft, front and back setting in first and second drawing; total draft, spindle speed and twist factor at roving frame. Thirty six trials for twelve factors were studied at normal operating conditions, to obtain carded yarns of 19.67 Tex. Levels of factors were selected so as not to affect the quality of the factory. Yarn with 5% Uster level was achieved for all properties except elongation. This leads to the best operating conditions for the required product, which are better than the company specifications.