Thread motion ratio used to monitor sewing machines

A prototype system for detecting sewing defects through analysis of thread motion has been developed. A piezo‐electric transducer provides information on the time of motion of the top thread in a lockstitch sewing process. The ratio of this time of motion to the total single sewing cycle time is a measure termed the thread motion ratio. This measure offers consistency over variations in sewing machine speed. Research results are that the system yields reliable indication of thread consumption‐related faults, such as broken top or bobbin threads, misfed fabric, and thread tension imbalance, for several stitch types.