Metal 3D printing can support complex geometries like organic structures and hollow parts

For parts impossible to manufacture through any of the methods previously discussed, there’s the additive manufacturing process of direct metal laser sintering. DMLS boldly goes where other manufacturing processes can’t. Like its plastic counterpart selective laser sintering (SLS), which uses a laser to fuse nylon-based powder into almost any shape imaginable, DMLS achieves similar results in metals such as aluminum, cobalt chrome, Inconel, stainless steel, and titanium. Metal 3D printing machines at Protolabs A row of indsutrial-grade machines used for direct metal laser sintering at Protolabs. Like most additive processes, DMLS builds the parts from the bottom up, like layers of a cake. It begins with a 3D CAD model, which is sliced into layers roughly 0.001 in. thick. A laser then “draws” each tissue-thin slice of the CAD model on a bed of metal powder, one with the consistency of flour. As the laser passes, the metal particles are melted and fused to their neighbors, creating metal with the same mechanical properties as that emerging from the business end of a steel mill. As each layer is completed, a rubber blade pulls additional material across the in-process part and the laser goes back to work, successively fusing each level to its predecessor. Several hours later, a finished part emerges. Tolerances to +/- 0.003 in. are typically possible with DMLS, along with part features smaller than the period at the end of this sentence. Because very high temperatures are involved, small struts are often required to support the workpiece during the build process and to prevent warping—post processing is necessary to remove these supports. Also, since surface roughness is comparable to that of a casting, around 200-400 µin Ra, some sort of secondary polishing or machining operation may be necessary.