Drafting Waves and Periodic Faults
topic
Drafting waves are periodic mass variations with wavelength equal to roller spacing, caused by incorrect roller settings, worn rollers, or eccentricity. Detected on the spectrogram of a Uster Tester as chimneys (sharp spectral peaks). Back-roller eccentricity produces waves at wavelength = πd × draft ratio; middle-roller eccentricity produces shorter-period waves. Diagnosis requires correlating spectrogram peak wavelengths to machine geometry.
Role
Drafting wave diagnosis is the most important analytical skill in ring spinning quality management. Periodic faults produce visible striping in woven and knitted fabrics — called barre or streakiness — that causes entire fabric lots to be rejected. The ability to read a spectrogram and trace it back to a machine component is a core competency that distinguishes expert textile technologists.