Joint project YarnSelector
Development of an automatic yarn sorting unit to reduce fabric defects during air-jet weaving
- 01.10.2020 to 30.09.2022
- Production Systems
During air-jet weaving, a weft yarn is accelerated using compressed air and inserted into the reed channel. During the weft insertion, weaving defects can occur, such as yarn breakage or incomplete weft insertion. This leads to machine stoppages or fabric defects, which reduce both the productivity of the system and the fabric quality.
So far, the yarn has been considered a predetermined and unchangeable parameter in the investigation of weft defects. However, an analysis of the initial yarn for defects (such as thick and thin spots) offers the potential to detect a large portion of fabric defects early on. In order to improve fabric quality and avoid machine stoppages, a yarn removal system is being developed as part of the research project that evaluates the yarn immediately before weft insertion and removes it if defects are detected.
Project goals and methods
The yarn removal system evaluates the yarn before it is inserted into the weaving shed, automatically detects defects in the yarn and segregates the damaged section in real-time. The goal is to improve fabric quality, reduce material costs and avoid efficiency-reducing machine stoppages.
For real-time detection of yarn defects, an optical sensor is integrated between the yarn package and the creel. Using a model-based observer, the position profile of detected defects is subsequently calculated. This allows the subsequent removal process to be limited to the faulty windings only. The yarn removal unit to be designed guarantees a sufficiently high level of dynamics to remove the defective section during manufacturing. Synchronization of the removal operation with the weaving process is achieved through event-based control, which coordinates the active weft channels and ensures that the weaving machine can continue to operate at high speed. To achieve this, machine parameters such as the yarn unwinding speed or the machine speed will be adjusted using model-based optimal control. Weft-related machine stoppages should be largely prevented.
Innovations and Perspectives
Material-related causes of weft defects are rarely considered in industrial and research works. Approaches for online yarn analysis and selection currently do not exist. In the scope of this project, yarn defects are regarded as the primary cause of weft defects and machine stoppages. Thus the defects are automatically segregated in real-time using a novel yarn removal unit. The automation solution (segregation unit and integrated optimal process control) has significant potential for increased efficiency compared to established process controls due to reduced machine stoppages. Furthermore, the implementation of the automated yarn removal system promises improved fabric quality as sections of lower quality yarn can be segregated depending on the set threshold.