Determining reaction abilities of sewing machine operators in joining curved seams

In accordance with his/her psycho‐physical abilities and degree of skill, regulating system in the operator's brain will match the speed of sewing operations, e.g. actual machine stitching speed, using a simple movement of the foot, to adapt it to his/her sensory and motoric reaction abilities. Workpiece in sewing is fed employing three degrees of freedom movement, i.e. using three independent regulating circuits: position of the seam, edges and workpiece layer length. Cybernetic bases of the regulating system man‐machine‐workpiece are presented, as well as the development of the necessary and maximum possible sewing machine operator's reactions in joining curved seams. The procedure is explained by constructing a mathematical model and obtaining the equations used in calculating necessary and maximum operator's reaction abilities. Measurements necessary were performed in the Department of Clothing Technology, Faculty of Textile Technology, University of Zagreb, using modern measuring equipment while garment‐sewing processes were recorded under actual in‐plant conditions. The results obtained were computer‐processed and a 3D graphic representation was obtained together with a mathematical model appropriate to calculate interdependence of the mentioned parameters. Appropriate software package was developed, which allows a quick, accurate and continuous determination of normal machine‐hand times, as dependent on all the influential parameters.