The Dynamics of Roller Drafting

Abstract

A description is given of the design and operation of a drafting force tester, with emphasis on the material and process variables which influence test results. Visual observations are reported of sliver contraction, fiber straightening, and fiber snap back. Comparison is made between the force-deformation behavior of a sliver in steady-state drafting, in an arrested-back-roller drafting test and in a conventional Instron tensile test. The deformation behavior is characterized by fiber extension, sliver consolidation, and force buildup, followed by fiber slippage and force decline. The effect of surface roughness is investigated for various test configurations. Other specific variables studied were roller separation, draft ratio, fiber crimp, and sliver processing history.