Stop marks are defects caused by machine stops during the knitting process. In general, sudden stops and starts, as well as restarting after long downtime, produce such defects. Stop marks appear as banded stripes across the fabric width, where the spacing between course rows changes. Fabrics with stop marks are unacceptable and must be downgraded.
For a long time, efforts to reduce such stop marks had not succeeded, mainly due to the complexity of the problem — and as knitting speeds increased, the probability of such defects also rose.
The ITV (Institut für Textiltechnik der RWTH Aachen) developed a stop-mark detection system for warp-knitted fabrics. The project started by studying starting marks of woven fabrics, and the developed system enables objective, reproducible analysis of stop marks. The whole process is based on image processing. Features are extracted from samples using punch cards and tape, whose size can vary depending on the knitting area and the size of the stop mark. During feature extraction, the defect region is not deformed and knitting tension is unaffected.
Research also covers preventing needle holes with finishing agents, and the relationship between tricot fabric structure and needle holes. When needle holes occur during sewing of tricot fabrics, work efficiency drops and seconds increase. The problem is complex because it involves the sewing machine, needles, knit type, yarn properties and sewing method. Factories adopt preventive measures such as reducing sewing speed, selecting better needles and lubricating the thread. This study focuses on the mechanical properties of knit fabrics that experience has shown to affect needle holes, and researches methods and effects of prevention.