Joint project AReS

 

Actively controlled weft braking system for air-jet weaving machines

 

Motivation

During air-jet weaving, a weft thread is accelerated with the help of compressed air and inserted into the reed channel. The quality of the fabric is significantly influenced by the required retaining force and the deceleration of the thread during insertion. In modern textile machines, a predefined braking profile is typically followed. This profile is controlled by the machine angle and does not respond to variations in the flight behavior of the weft thread. An improperly adjusted thread brake results in the yarn moving backward and fabric defects. Therefore, the use of a controlled weft thread braking system is essential to ensure fabric quality and prevent weft errors in the fabric.

 

Project goals and methods

The aim of the project is to increase the reproducibility of weft insertion by using a controlled thread brake. This reduces the stabilization time of the yarn during weft insertion, lowers energy consumption and improves the quality of the fabric.

The position and velocity of the thread tip can be captured by high-speed cameras. With the help of image processing algorithms, these data can be evaluated in real-time and thus enabled to a controller. Model-based control strategies can predict the future system behavior based on the model of the weft insertion, enabling the controller to determine an optimal controller output. A highly dynamic thread brake is controlled to selectively brake the weft thread. This ensures a smooth yarn velocity profile during weft insertion, without any negative velocities (no backward movement). The system is validated both on a laboratory weaving machine and in an industrial environment.

 

Innovations and Perspectives

To improve fabric quality, the movement of a weft thread during the insertion process will be considered. In comparison to a conventionally controlled brake, there is great potential in a highly dynamic thread braking system that precisely decelerates the weft thread by regulating its position. A model-based control is capable of limiting the backward movement of the weft thread, thus avoiding weft errors. By implementing an actively controlled weft thread braking system, the quality of the fabric is enhanced, the productivity of the weaving machine is increased and energy consumption is reduced.

 

Project partner
RWTH Aachen University, ITA - Institut für Textiltechnik