This video examine the AM process called vat photopolymerization using the example of stereolithography (SLA). Review the SLA process using a video example, examine some SLA produced objects, and explore important applications, advantages, and disadvantages of the technology.
- Hi, welcome back and welcome to our first technology deep dive. This is the first segment in which we're going to explore one of the key processes that falls underneath the overall additive manufacturing umbrella. In this case, we're going to look at a process called vat photopolymerization, and in particular, at a technology called stereolithography. Now, in order to have these discussions, I'm delighted to say that we have Dr. Amy Elliott with us. Amy did her PhD at Virginia Tech University in mechanical engineering where she was a researcher on additive manufacturing and currently, Amy works at Oak Ridge National Lab where she continues that research.
So Amy, we are delighted to have you with us to share your expertise. - Thanks for having me. - Now, it's appropriate that we begin with stereolithography, because stereolithography is really the foundational technology of additive manufacturing. It was invented over 30 years ago by a man named Charles Hull who went on to found 3D Systems, which is one of the major providers of additive manufacturing equipment in the industry. So it's really the granddaddy of all additive manufacturing processes. Now, in this process, we use a photopolymer made of liquid, right, and it looks something like this.
So it's a liquid in a vat to which we apply an ultraviolet light and in applying that light, the liquid is cured and goes from a liquid state to a solid state layer by layer as in most or all additive processes until a final object is created. In this case, a replica of the human heart. Now, in order to understand this process fully, what we're going to do is look at a video that our friends at 3D Systems have provided us that's going to show us the process end-to-end and then we'll come back and Amy's going to share with us some of the key applications for this technology as well as some of its advantages and the disadvantages.
So let's go to the video. As in almost all additive manufacturing processes, we begin with a model created in a CAD system for computer-aided design. The software then slices that model and passes it to the machine. In this case, a stereolithography machine. In a stereolithography system, we've got, we begin with a vat of photopolymer, that's what we see at the bottom here, and then above we have an image projection module that shines down a UV light in a very precise pattern.
As each layer is processed, the build platform moves down and a roller moves across to smooth out the surface, and we repeat that process over and over and over again until we have a solid object like the heart we just illustrated. - [Amy] So you can see the part actually grows downward from that top surface of the vat. - [Mark] And when we're complete, the platform raises up and we pull the object out. Here we see some real parts that have just finished the process and what I want to note here is you can see both the item itself and you can see some less dense structures on which that item is sitting.
Those are support structures. Amy, what do the support structures exist? - [Amy] Well, if you didn't have the support structures, the part would just be floating in the vat, so you do need something to anchor it down to the build platform. - Okay, and so we see the blue light playing across this vat of photopolymer, curing that, turning it from liquid to solid, and then the final part rising up out of the vat, but that's not the end of the process, is it Amy? - No, actually after you remove the object from the vat, you do have to rinse the rest of that resin off and then do a post-cure which actually solidifies it to its final material property.
- Makes it more durable. - Exactly. - Terrific. What do we see as the big application for stereolithography? - Well, the number one application for stereolithography is prototyping. This was traditionally what we saw as rapid prototyping. That's kind of where that phrase came from, because we can get really high resolution and really great accuracy with this process. - So is that the biggest advantage that we see for stereolithography, high-resolution? - Right, high-resolution, we can do very complex parts, we can do some very complex geometries with this technology that you really wouldn't be able to do easily with other additive manufacturing technologies.
- Terrific, so when we look at this heart again, we see it's very smooth and lots of detail here. - Right, so we can get a great surface finish. This of course has been polished to get that glossy effect, but with these materials, we can achieve a water clear material. - Okay, what about disadvantages? - The number one disadvantage of this process is the material properties. Photopolymers are just inherently weak. They've gotten a lot better over the years, but we still see that they are the weakest among all the additive manufacturing materials. - Okay, so stereolithography, really the granddaddy of all additive manufacturing processes.
Simply by virtue of its age, it's foundational here right? It's kind of where the name, rapid prototyping, came from, and it's been around a long time. A big advantage is we get this clarity and we get this high precision, nice smoothness, so it's really good at showing what something looks like but boy, we wouldn't want to have to depend on it if this part had to last for a really long time. - Exactly.
- What is additive manufacturing?
- Working with light-activated polymers
- Resin printing
- Modeling and extruding materials
- Fusing, melting, and sintering
- Binder jetting
- Laminating sheets
- Developing a product
- Shaping the direction of tooling
- Evolving a supply chain
- Evolving a product
- Evolving a business model