If you haven’t done any frame building before, it is difficult to read between the lines with the work that others do. I haven’t done a lot, and I have very few tools. I have to rely on other frame builders for certain tools. It’s likely that any 3D printed metal part will require some treatment to work well with bearings, threads, etc.
THIS THREAD has a lot of information on 3D printing metal parts. Most frame builders will use services that print in Stainless Steel or Titanium, though there are other materials, these are just the easiest for smaller outfits like frame builders to use for bike frames.