Here is a faithful recreation of the Fallout 4 Mechanist Helmet This is a full scale replica so it approximaitly 310mm x 570mm x 313mm when printed.

Its broken into 20 individual parts so it can be printed in a 200mm x 200mm x 200mm print volume. This also makes printing, painting and assembly easier as well.

3D printing settings The material you use depends on your climate and how you plan to use it but I would suggest 3-4 perimeters and 40% infill.