Powder bed fusion II: Selective laser sintering

- Hi, welcome back. In this segment, we're going to talk about another powder bed fusion technology called selective laser centering. This technology, like other powder bed fusion technologies, takes a layer of powder. In this case, that powder can be polymer or metal, and applies an energy source, in this case, a laser in order to fuse that material into a solid object, layer by layer. Now, we're happy to have Kevin here with us from America Makes, and Kevin's going to help us understand both the applications and some of the advantages and disadvantages of this technology. What I'd like to do to begin is to look at a video of this process from end-to-end so we can get a good picture of how it functions. Like other additive processes, of course, we begin by creating a 3D model of the product, and then the software slices it into layers and feeds it to the machine. Now, the machine itself has several key elements, right? A piston and platform that raises the build platform up and down as we build the object, a roller assembly that smooths the powder so that we have a flat surface for the image projection module to work with. And it's from that point that the laser is actually projected down onto the powder bed. - [Kevin] That's an infrared laser you just saw. - [Mark] And of course, that roller moves back and forth, over and over while the part is built. And during that time, the build platform is lowered incrementally. And here, we can actually see the laser at work tracing out the pattern, and then applying another layer. Now it's important to note that part comes out covered in powder, and so there's a significant amount of cleanup, at least knocking the powder off. - [Kevin] And the powder can be recycled with different ratios depending upon how you want your end parts to look like. - Terrific and so this is the powder that we're actually looking at, at least for a plastic powder. This is the powder that we're looking at, right? - [Kevin] This powder you have here is called DuraForm PA. The PA stands for polyamide. - Okay, a common material for us? - Yes. Very common. It's a thermoplastic. - Terrific. What do we think of as the key applications for this type of technology? - Well, up until a few years ago, aerospace and automotive was, it was huge in both of those, those business segments. But here in the last two, three, or four years, the medical applications have just gone through the roof. - [Mark] So in particular, what kinds of medical applications are you seeing? - [Kevin] A lot of tooling for the doctors to use. Another application quite recently, there was a cranial patient over in Europe where they actually did a 3D scan, a CT scan of the individual, and they actually created a DuraForm material. They printed out for the doctor to put on the desk to prepare for the upcoming surgery. - [Mark] So to practice the surgery itself? - Yes, days before the actual surgery. Another application, they actually created segments of a skull. They implanted those segments on the skull of another patient in the Europe area. - Okay, terrific. All of the pieces that we're looking at here are made of plastic. What about other materials? What about metal? - There is one metal material, it's called A6. It's an encapsulated material that goes through the the build process, again, layer to layer. - What do we think of as the big advantages and disadvantages of selective laser centering? - One of the largest advantages is a speed. This is a very fast unit. Matter of fact, the machine that I have at the factory here, it scans at 12 meters per second, which is very, very fast. - Put that in context for me. How fast is that in terms of building a piece? - [Kevin] Well, I've actually had a part cake of about 380 pieces and about six inches of powder, and I've built that in 12 hours. - [Mark] What about the support structures? Support material? - That's a very key advantage. There are no supports. The material is the supports. Again, my machine here in the factory, I've got a 13 by 15 by 18 build volume, and I can place parts anywhere in that build volume as long as I have material in my feeds. - [Mark] Terrific. Disadvantages for SLS? - It's a bit rough. The surface is a bit rough. So even though you will b-blast it in what's called the post-processing piece of this, it can be a little rough. - Okay. What about color? - It gets a choice of two. You've got black and you've got white. - [Mark] So SLS, a powder bed fusion process. Relatively common. Lots of options in polymers. Not so many options in metals, but you get a good part quality. Disadvantages essentially being that we don't have a lot of color and grain sizes can lead to some surface roughness. Can I machine that? - Absolutely, you can machine it. You can get this down. You won't get a very, very, like a, the surface area of the table here, but you can get it down close to it.