Sewing is one of the most commonly used manufacturing processes in the world. In the textile industry, development of sewing machines with optimal mechanical performance is very important. Obviously, the quality of sewing, increase of the needle transmission force and the optimal mechanical advantage are greatly dependent on the design criteria of the needle driving mechanism. Therefore, in this paper, first a newly developed needle driving mechanism of a sewing machine is introduced. Then, the

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... concepts of transmission angle and mechanical advantage are described. Next, the multiobjective constrained optimization of this mechanism using the genetic algorithm is explained. The objective functions of the optimization problem are considered in such a way to fulfil some of the most important design criteria such as reducing the needle generated heat, reducing undesirable vibrations and increasing the mechanical performance. The obtained results confirm improvement of the required design criteria of the newly developed mechanism in this study. It is also concluded that improving the mechanical advantage of about 14% causes an increase in the value of the needle jerk about 30%. This clearly states that higher mechanical advantage, is achieved by the cost of increasing the needle jerk.