Low cost sensor for the measurement of yarn input tension on knitting machines

The production of weft knitted fabric demands a continuous monitoring of the yarn forces directly involved in the knitting process. This monitoring prevents the occurrence of unthreaded yarns due to yarn break, and thus avoids the decrease on productivity. On the other hand, more information concerning the knitting process is desirable, because it allows the evaluation of possible future malfunctions and detection of faults. The classical device which is usually used to accomplish the first task does not have the necessary technology to accomplish the second task. The purpose of this paper is to present research that is being carried out to develop a different sensor device, capable of complying with both objectives and thus successfully replace the present system, which is used solely to detect lack or exceeding force applied to the yarn. Furthermore, the solution suggested is a low cost one, allowing its installation in every feeder as the present solution. Some considerations are made concerning the problems that this approach present and the dynamical behaviour for different configurations of the system is discussed.