In the manufacturing field, normally a product is expected to be beautiful, not so heavy, small size, easy to move and more important, as much cheap as possible. But how about producing a mechanical product, a shaft or a gear in a gearbox for example? It is clear that the requirement for the product will not be like that. In fact, our mechanical product must be high in precision and can work effectively in harsh environment. Which decides this expectation? The answer is so many, namely the material, the geometry (or technical design), the working regime, the way the part has been fabricated….If from a available design, but the part is produced by different process, then final quality will be very different like, surface roughness, the precision level….So, it is really important to design a good manufacturing process just to ensure that our mechanical product will work correctly, effectively and long life time.