This is nothing new. I had very precise, laser sintered, steel objects in my hands during exhibitions, at least 5 years ago. I never understood though, there s

This is nothing new. I had very precise, laser sintered, steel objects in my hands during exhibitions, at least 5 years ago. I never understood though, there seems to be no laser sinter aluminum. The most common answer is oxidation. But how hard can it be to do it in a vacum?