Lockstitch sewing machine is one of the most common apparel industrial machines. The thread take-up lever mechanism of a sewing machine has an important role for proper stitch forming and smooth working of the machine. Acquiring a mechanism with optimized geometry is of great importance to reach this goal. Therefore, in this study the optimization of the thread take-up lever mechanism with respect to some important features such as the optimal path of the coupler point and variation of coupler point acceleration (jerk) is presented. Modification of the objective function with respect to the jerk is applied to assure smooth movement of the thread take-up lever during sewing process. For this purpose, the imperialistic competitive algorithm is used to find the optimal link lengths of the take-up lever mechanism. The analysis results present further verify that the coupler point jerk in the optimized mechanism in the horizontal direction has been decreased about 52 percent without any conflict in the consistent operation of different parts of the sewing machine.

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