I'm a huge additive manufacturing fan and would really like to see how this turns out. I'm not sure however if 3D printing is going to be the way to go. Most 3D printers are using plastic or gypsum and it being a grill means it might take a beating not sure how it would hold up. You can try the 3D metal printing but the end product is often pretty rough. Is this not something you could take a local fab shop? Either way it sounds like an interesting project.