DMLS and SLM are awesome for making complex shapes, but the parts straight out of the printer aren’t always completely waterproof. That’s because the sintered metal can have super tiny pores that let liquid sneak through. Even when the part is really dense (like 99%+), those little gaps can still be there, which might lead to leaks when pressure is applied.

To make sure everything is totally sealed and waterproof, you usually need to do a bit of extra work after making the part. One way is Hot Isostatic Pressing (HIP)—basically, squeezing it evenly to get rid of tiny air pockets and make it denser. Another trick is surface sealing, like using epoxy or PVD coatings, which help fill in little gaps and keep rust away. And finally, polishing or machining smooths things out, especially where gaskets go, so you get a nice, tight seal.

HIP does a great job of making the part denser, but if you want it to be completely waterproof, you’ll probably still need a surface treatment like electropolishing or sealing. A nice, smooth finish also helps gaskets do their job better. If the case needs to handle deep water, the safest bet is to combine HIP with a PVD or epoxy coating for extra protection.

Have a look at Tritone Technologies they can print to a very high standard. But not sure it will be waterproof without a second process.