Binder jetting: Powder bed and inkjet head printing

- Hi, welcome back. In this process technology segment, we're going to look at something called binder jetting. Now, that's a technology that'll look a lot like powder bed fusion and a lot like material jetting, but it's different. In powder bed fusion, we're laying down a layer of material and we're actually applying an energy source to fuse it in place and make a solid object. In material jetting, we're laying down a layer of material and we're applying UV light again to create a solid object in place. For binder jetting, yes, we're laying down that material, plastic or metal in this case, but we're essentially gluing it together by adding a binder, and that's going to have implications for how we treat that object on the other end. This is another one of those technologies that we can really think of as 3D printing in the sense that it has that classic printhead that's applying the binding agent, and we're going to take a look at that for plastics at least with a little video that we have. So this is a process called color jet printing. As before, we're creating a 3D model using CAD and then our software's going to slice it up in order to feed it to the machine. The machine has important elements including a printhead that's actually spraying the binder down as well as a roller that's laying down layer after layer of the powder that's being fused together. That printhead moves across the powder bed just like an inkjet printer does, laying down that binder and creating the solid object. The unbound powder is what supports the overall object. Now we're going to see that in action. Note here that they're putting in a cartridge that actually contains colored binding agent. So we're going to get a colored product out. And in fact, as this printhead moves across the powder bed, we see those colors start to form up, layer after layer as the powder's drawn out of the system and fed into the object until we finally have a solid object that, in this case, is coated with powder. So we have to blow it off. And what we see come through here is a fully colored plastic object. Now, in this example, we're adding an infiltrant that actually fills in the microscopic pores of the object because there's lots of porosity, there's lots of voids in this object. And we finish with a fully colored, in this case, prototype. Now, we happen to have an example of one of these objects here in plastics, and I think it's interesting to note a couple things about this. One is it's complexity. It's really a beautiful object with lots of contours, lots of detail. The other thing that you can notice is all the color that's involved here, and that's a function of the binding agent itself. The powder is the same, is uniform, but the binding agent is what adds the color. And you can actually see that because if you look at the edges here, you can see that it's all white in there. That's the material itself. Now, the other thing to note is that this is very fragile. I want to be careful not to drop it because if I do, it's going to break. And that's an attribute, not just of plastics but of metals, where you've done done extensive work. - Right, yeah, so when the metals come out of the printer, they're really fragile. - [Mark] So why don't you take us through that process? - Sure, absolutely. So we start with the printer. This is a very small one for this technology, but it's great for experimental or very small builds. And we deposit the binder, the liquid binder into the powder bed, and that's how we glue the part together. We then take that powder bed and cure it in the curing oven. Then we center and infiltrate. So this is actually kind of where the magic happens. So here is an example of a part that has been cured but not centered. So this is just glued together, and it's very fragile. So this is what happens when you actually aren't careful with your part. It will break apart. - So I could literally take that part and snap it in half if I wanted to in this state. - Absolutely. It's very fragile in this state. But after that, you surround it with this thermal support, you add the infiltrant, and you actually fill up those voids that are within the part that make it very weak. And the finished product is almost fully dense part like this. - Okay, so how does this infiltration actually work? We're adding metal to the metal? - Right, so we just... We have our part and we put some infiltrate below it and then when we heat everything up to center the part, the infiltrate just wicks right up into the part. It's kind of like magic. (laughs) - Terrific. Interesting. What are the big advantages and disadvantages of this process? - I would say the biggest advantage of this process is that it's pretty simple. There are a lot of steps to take, but after you get the hang of it, it's not a very complex process, and it's pretty reliable. It's also very inexpensive. This is a very inexpensive way to do metals. It's also very scalable. So you can do very large pieces of metals with this technology, and it doesn't cost that much more. If you were to use SLS or electron beam melting, it would cost a lot more to do large pieces. We can also do ceramics, we can do sand, we can actually make sand cast molds. So instead of having to make an investment mold and then break it away and put it back together and cast, we can just print the mold directly. So there's a lot of things we can do with this process. - Okay, so big applications and tooling, right, big variety of materials, whether I want to use polymers, plastics, or whether I want to use metals or ceramics, easy to use, relatively inexpensive, but fragile parts, and if we're doing metal, we've got lots of steps that we have to consider.