Searching optimum problem is very important in engineering field. There are many methods to solve this problem but no one can assure that the optimum found is the global optimum. We can only have a conclusion that one method can find a better optimum solution than another method. One conventional approach to find optimum is Taguchi method which was applied very widely and successfully in many disciplines. Another approach is Neurogenetic method which includes artificial neural network and genetic algorithm. This method has emerged as a very effective and powerful method to search optimum solution. The purpose of this study is to compare the conventional method with the new method in finding optimum design and calculating contribution of each factor. Thus, these two methods were applied for finding optimal solution of the lag screw which plays a very important role in curing patients. Because the lag screw needs bending strength which resists breakage and pullout strength which resists loosening, the two methods were exploited to find optimal solution for each bending case and pullout case separately.
From the results, the optimum found by Neurogentic method is better than the optimum found by Taguchi method, especially in the bending case which is the more complex case compared to pullout case. It means that the more complicated relationship between factors and response the better optimum solution can be found by Neurogenetic method compared to Taguchi method. Besides, using artificial neural network, the contribution of each factor could be calculated by Modified Profile method and the results were similar to the contribution calculated by analysis of variance in Taguchi method.
This study is an objective suggestion for engineers in choosing method to find the optimum solution. The Taguchi method should be applied if the case is simple because the Taguchi method is systematic, simple and easy to achieve the result. The Neurogenetic method should be applied if the case is complex because using Neurogenentic method can obtain better optimum solutions. It is a notice that if the artificial neural network is well-trained, the Neurogenetic can be very powerful and can be applied in many situations, like: multi-objective optimization.

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