Powder bed fusion machines consist of three core parts: The build platform, a material source & recoater, and a source of thermal energy.

During operation, a thin layer of powder is spread by the recoater blade across the build platform. Then the heat source — either a laser or an electron beam — scans across the build platform, melting powder selectively as it goes. Where the metal is melted, it fuses to the metal around it, creating a solid part. After one layer is scanned, the recoater blade spreads another layer of powder and the process repeats.

Printing things this way is slow; a part the size of a juice glass might take ten hours. The recoater takes a few seconds to spread each layer, and although the laser is moving incredibly fast, it takes some time to scan the cross section of a part line by line. Add to that the fact that each layer is about eight ten-thousands of an inch thick, and you see how anything larger than a thimble would take a long time to complete.

Although powder bed fusion can be done by both lasers and electron beams, lasers are far more common. Electron beam melting (EBM) is notoriously difficult to control, and although it has some advantages, EBM parts tend to have very coarse surfaces and require more post processing as a result. EBM also suffers from relatively low market penetration; by my count, there are fewer than five service providers for EBM in the US.

By comparison, laser sintering (which I’ll refer to as DMLS, for direct metal laser sintering, though that is technically an EOS trade name) is almost ubiquitous. I’m aware of about seventy US shops offering metal laser sintering in-house, and even consumer-facing providers like iMaterialse offer DMLS. And although EOS sells far more metal laser sintering machines than any of their competitors, the market is still competitive — and that competition is beneficial to the industry as a whole.

Within the aerospace industry, DMLS has a high adoption rate — at least in an R&D context. In fact, my collaborators and primary tour guides to the industry (Dave Bartosik and Dustin Lindley) both began their careers in additive at Morris Technologies, the aerospace DMLS giant that was acquired by GE Aviation in 2012. Between the two of them there’s about as much experience printing titanium parts as anyone else in the world.

But for all the work that has gone into understanding the properties of additively manufactured parts, the process is still very much in its infancy. It is not in any sense a mature technology, and the result is that each new part you design for DMLS — and, indeed, each new copy of the part that you print — is very much an experiment. Small variations in geometry and orientation can have huge effects on the way that a part prints. The laser’s scanning path is a closely studied subject, but much is not yet understood about it. Even keeping those variables constant, it’s often the case that building the same part on a different machine will produce very different results.

All of which is to say that DMLS is anything but plug-and-play. Even when a design has been optimized specifically for the process, it often takes dozens of tries before a functional part comes out of the printer. And the process of troubleshooting a failed build — even at the most advanced DMLS shops in the world — still involves a lot of trial and error.