Strictly periodic faults are only related to mechanical defects of the spinning and preparation machines. Nearly periodic faults are drafting waves, which are related to drafting zones that are not set according to the processed fiber length. The consequence are fibers which are not under control and thus will cause periodic or nearly periodic faults in the yarn. These mechanical deficiencies will cause distinctive patterns in the fabric, also known as moiré faults. Depending on the fabric width, they are clearly visible and will cause a fabric to be down-graded as second quality.
Based on the YARNMAP mass diagram the spectrogram is calculated and shown in the report. If one or more of the 160 channels is showing high variations, it will be marked red. The experienced user of laboratory instruments will know which mechanical part of the spinning or preparation machines is causing the periodic fault. Then, the maintenance team has to check the machine part, clean or exchange it if needed or re-adjust the settings.