Abstract: Aimed at enhancing the product quality of STL rapid prototype equipment, a series of experiments in manufacturing a part were made upon the equipment. Corresponding experiment scheme was designed. The experimental data were processed with the Taguchi method, and the best machining parameters were found. The aim to improve the dimensional precision and geometrical error was reached using these machining parameters. Some new concepts of the Taguchi method such as mono-contribution ratio, error contribution ratio are put forward. These new concepts improved the Taguchi method.