 My name is Nick Lee and I'm going to be talking about an overview of state-of-the-art 3D printing technologies for about the next 25 minutes. One caveat for all of this is just that this is an emerging field. There are tons of different technologies out there and I'm not going to be able to cover everything. So I'm sure that many of you have heard of other printing techniques that we won't be talking about today. This is just intended to give you an overview of common methods that are out there and some of the new things emerging in the field as well. So I'm a PhD candidate at the MIT Media Lab. My background is in biomedical engineering and neuroscience but for the past five to six years I've been focusing almost exclusively on additive manufacturing. And my specific focus in my studies is on additive manufacturing at an extremely large scale using sustainable materials and custom fabrication systems. Over that time I've 3D printed with just about every sort of commercial 3D printing method that's out there in the field right now. So we're going to go over a little bit of the introduction of 3D printing techniques starting with the history of how these sorts of technologies evolved with really early forms of additive manufacturing. And then we'll dive into three common methods in more detail and go through how these different methods of 3D printing work, how information is processed on these machines, and what to expect from the outputs of them as well. We're also going to take some time at the end to just do a lightning round of emerging technologies that might be coming up in the next five to ten years. That could be very promising. But first of all it might be good to back up and think about why we want to 3D print objects in the first place because understanding this basis makes it a little bit more clear how these technologies have evolved and what their limitations are. So some of the often cited reasons for why we may want to 3D print an object or justifications are first of all that the objects that can be created seem to be a very direct representation of what is in our CAD software. So you design something on your computer and what comes out on the other side looks and feels like this thing that was on your computer that that direct creation of a designed object isn't often found in a lot of other additive or in a lot of other manufacturing settings. Also 3D printing is relatively fast and easy to customize compared to other manufacturing methods. And there's comparably few geometric limitations which allows you to make extremely complex objects such as the multi-material print on the right there created by the mediated matter group. And even though there are many different ways to 3D print such as extruding melted plastics or using stereolithography to cure liquid resins all of these different sorts of methods have certain commonalities. So first of all in every system of 3D printing or I'm using that interchangeably with additive manufacturing in this case just any sort of a system like this. The object that we are building is going to be built in layers. So we take a three-dimensional object it's sliced into these different layers and then it's built one layer at a time. In all of these systems as well you have some kind of a material stock whether it's a thermoplastic or a photopolymer resin that undergoes a change of state either temporarily becoming liquid or being cured from liquid to a solid state. And then also in all these systems we have a positioning system that is coupled with a deposition or a curing system. So we have something that is moving around that is causing the deposition or curing system to add material in a selective manner. These are the commonalities that kind of exist between all different 3D printers and from this foundation we can build up an understanding of how the differences between them become important. If we think about what a general workflow looks like from the design of an object to the building of an object in 3D printing techniques we start with designing an object in CAD software. Now this could be something that is being designed either as a mesh object that has points connected by different lines to create a 3D boundary or a NURBS object that is more of a smooth mathematical representation of a shape and then when we want to 3D print that we convert it into a file type that can be read by commercial 3D printers. The most common ones that you would see would be an STL that's a stereolithography file that stores objects as a mesh or an OBJ file which does roughly the exact same thing. You may also see file types like PLY that also stores metadata related to the materials that should be assigned to every single point on that mesh object. Those are the external processes they're what typically happen on the designer's computer before information is fed to the 3D printer. Now within the 3D printer there's a lot of work that's done to actually turn that file type into the object that is going to be built. So first of all that object is processed through slicing as I mentioned earlier in order to layer to understand the layers that are going to be built by the machine. Those layers are then processed to be turned into machine code that will say how the machine is actually going to be able to build those layers and then finally we get a built object. Now one really important thing here that is a little bit contradictory to what I said before is that while there seems to be a very direct translation from the designed object on our computer to the built object on the other side, the built object is not the same as what was designed. Because of this layering process we inherently have differences between the monolithic entity that we see on our computers and the thing that comes out on the other end. This is going to impact the mechanical properties of the object. It's going to have implications for how it behaves over time. So it's important to remember that what comes out of the machine is not this continuous monolithic object that we imagine and I'll come back to this over and over again. The designed object is not the same as the built object and understanding what the 3D printer is doing is going to allow us to understand how the design differs from the built object. What we are seeing is not what we are getting in the case of translating from the digital design to the manufactured object. So the other thing that's important about this is that what we are getting is a reflection of the 3D printer's capabilities, the material stocks, the way that it processes the information that we've given it. So even if I have the digital file for an object, that's not enough for me to be able to faithfully recreate a 3D print that I might have in archives or somebody else's part that they've given me. To really recreate that, I would need to 3D print it on the exact same machine using the exact same stock in the exact same settings. In those differences, anything that changes there, such as the resolution height or the 3D printing method is ultimately going to change the output artifact sometimes in pretty dramatic ways. So we just need to remember this, that these are not just different methods of accomplishing the same goal. They actually will dramatically impact the performance of the object that we are creating here. So to trace back the history of additive manufacturing and think about some of the earliest techniques that came out, one of the themes here that's really interesting is that 3D printing has been around for a long time, even in very advanced systems. So the first 3D printer that was capable of 3D printing live cells and do tissue bioprinting was actually created in the late 80s. And this was created through hacking an inkjet printer from HP. They filled the ink cartridges with cells and culture media, and then they hacked the print bed to be able to move down so that they could print in layers. And this actually really is similar to inkjet and polyjet printers that we see on the market today. So this technology has been around for a very long time. It wasn't until the early 90s that Stratasys patented the fused deposition modeling system, which became the basis for a lot of the commercial 3D printing that we see today. This is where we first start to see the proliferation of printers, as we would think of them, things that are extruding, melted plastic and building up layers more similar to our current machines. Now, an important thing to remember here is that this sort of system was evolving alongside early CAD software. And 3D printing is one of the only technologies that I can personally think of, where the hardware outpaced the software dramatically. So even though we had multi-material cell printers and experimental settings in the 80s, SolidWorks 1995 was the first time that people were really able to design a 3D object easily on a computer that they had access to. And even then it was really just a 2D representation of that three-dimensional object that they wanted to have. So 3D printers were actually able to create objects that people were not able to design up until very recently. These are multi-material prints created by the mediated matter group that have gradients of stiff and soft material that were created from a polyjet printer. This object, when you think about how we would design it, is not something that actually could have been designed on CAD software up until very recently. It doesn't have distinct parts with different materials. The materials kind of flow into each other and form this gradient. So while printers have been able to create objects like this for a relatively long period of time, only recently have we developed methods to actually design objects that leverage those capabilities. The point of all this is just thinking that in the coming five to ten years, a lot of the advancements that we might see in 3D printing may not actually come from hardware advancements, but might just come from software catching up to what the hardware can already do. So thinking about the current state of where we are in 3D printing right now, past five years especially have seen this broad proliferation of technology. We suddenly have 3D printers that can print entire boats at an extremely large scale. We have carbon 3D making thermostat resins that print extremely rapidly and can make production-ready parts. There was a line of shoes that they made where the soles were 3D printed. We have desktop filament extruders that are available for less than $100 allowing hobbyists and artists to 3D print objects and masks for the first time. And we have different companies making production-ready parts out of 3D printed metal that can go directly to industry. So all these technologies have kind of exploded across the field and penetrated all these different sorts of industries in the past five to ten years. And we have these highly fragmented systems that work with different materials using different processes all to ostensibly accomplish the same thing, which is taking some sort of an object we've designed on our computer and then manifesting it in the real world. Because of this high fragmentation of the systems, you also see lots of different niche file types and processes for creating them. So part of what we're going to try to do here is break down the unified processes that exist in all of these different systems because if we understand that, then we can start the interface with 3D printers and understand them in a more general sense. The first additive manufacturing method that we were going to talk about here is filament extrusion. So you might hear terms such as FDM, that's Fuse Deposition Modeling or FFF, which is Fuse Filament Application. All of this is largely the same thing. This is 3D printing techniques that are taking a thermoplastic stock and are melting it and dragging it in a line to construct a 3D printed object. So this is a Mark Forge printer. It is 3D printing chopped carbon fiber that is embedded in a nylon filament. If you could see the whole printer, you would see that there's basically a big spool of this nylon filament that's being fed through it. And then that nozzle that's moving across the different layers is melting that and then dragging it across sequential layers as the bed moves down in order to create this printed object. This is the kind of archetypal FDM printing method that we think of. What's actually going on when we design objects for this is that we start with some sort of a mesh object or some three-dimensional representation, like I mentioned before. And most commonly, this is being processed into an STL object for these sorts of prints. STL mesh file types, they store something that looks a lot like the Stanford Bunny year. So you have a three-dimensional boundary that is all these different points connected by lines in this triangular mesh. You might also see, like I mentioned, a .ply file type. There are now multi-material filament extruder printers that can have multiple colors of thermoplastic or multiple different materials. And so a .ply file type or something like an FBX file type would store metadata that specifies at every single point what material should be extruded there. When these objects are processed inside of the 3D printing system, one of the first things that happens is they have to be processed for their overhangs. So the FDM systems, they can't freeform print in thin air. They need to print on a layer that already exists below them. So any sorts of overhangs have to be analyzed. And then the system generates a network of supports that basically provide a foundation that the rest of the object can be printed on top of. For something like a Mark Force 3D printer, these supports look like kind of a thin accordion of material that you can remove later. In other sorts of systems, sometimes they look like small towers that get attached to it and you clip off to it later. But it's a secondary system that acts as a scaffold for the main print. These supports are sliced along with the main object that is being created. And then those slices are infilled with a single connected path that the thermoplastic is dragged along in order to create a three-dimensional object. This infill can be varied in density, according to how much material you want to use or how dense you want your part to be. But it's important to remember that what we are creating here is this long, basically line that turns into a 3D printed object. Now, the machine code for that is essentially just embedding where the extruder is going to travel to and how quickly it should go there. Oftentimes, this is in the form of what we call G code. G code looks a little bit like this as these string of numbers. And if you see there, there are these x, y, and z coordinates that are vectors that the nozzle has to travel to in sequence. Typically, this also contains some sort of data related to the speed that it should be moving at, the temperature for the extruder and then the extrusion rate itself. Oftentimes, the machine is handling all this automatically. It's very rare that designers would actually interface with this part of the system. But understanding this, this is what's going on on kind of inside of the machine in order to translate that processed object into some sort of a series of commands that can actually be constructed by the machine. And finally, we get our built object when the machine actually traces out that path and melts plastic in these layers in order to create something. Now, it's really clear here to emphasize what I'm talking about with this idea that what we see is not necessarily what we get. So this is the Stanford Bunny printed here and we can clearly see the resolution lines there. Objects like this, one of the main differences that we would know is that they are much weaker if they are sheared across those lines. So this affects the mechanical properties and also just the visual aesthetics of these objects. And it's determined by the resolution that they can print at. Now, FDM and FFF printers have become incredibly common for hobbyists in the field. They are typically very inexpensive. The materials are not particularly expensive either. So lots of hobbyists and artists have picked up this system, but it also enables extremely large scale 3D printing and also access to interesting new materials recently. So this is 3D printed glass constructed by the mediated matter group. And this was essentially an FDM printing system where melting glass was being dragged in very much the same method that we would have seen with the Mark Forge print earlier. To recap what I've been saying about these sorts of printing systems for FDM and FFF, these extrusion prints, they're common, they're extremely affordable and they can be scaled up to incredibly large sizes for industrial 3D printing. Typically, they involve some kind of a thermoplastic filament that is being melted, although there are certain new materials that are being incorporated into these kinds of systems. And oftentimes they have a limited resolution compared to other printers that might use lasers to cure their print layers. This is just a function of the fact that because you have to squeeze melted plastic through a nozzle, inherently that nozzle can only be so small while allowing the plastic to travel through it. So there are physical limitations to how these systems can print and what resolution they can achieve. But some of the interesting advances that are coming along right now in these systems have to do with people essentially embedding different materials inside of thermoplastics. So as I mentioned, Mark Forge puts chopped carbon fiber into their nylon printing system, which then aligns as the print is extruded. There's also wood filament printing. People using bamboo mixed with PLA in order to print objects that seem to be made similar to 3D printed wood. And also there's extremely large-scale additive manufacturing that uses systems like this, even at architectural scale. And many low-cost desktop products that can now be bought for less than $100. So this is one of these rapidly proliferating systems that's kind of going into all these different sectors and starting to become really common. The next really common system for 3D printing are SLA or DLS printers. These are VAT resin printers. What they all have in common is that they are using some pool of uncured resin. And then typically they're using a laser in order to cure that resin and layers as the printer sequentially builds up different layers of the object. So this is a resin printer that is using this method, is using a laser that you can't see that's underneath the resin. And that laser is tracing along the resin. And when it hits resin, it cures it into a solid object. This is of course sped up, but you can see that essentially the solid object rises out of a liquid resin, usually over the course of two to three hours to print an object of this size. And you can see the supports very clearly here in order to create this object. Now going back to the workflow for the 3D printer here, it is very similar to what we had before. You start with some sort of a solid representation of an object and we're often working with STL and OBJ file types for this kind of printing as well. But if we look at the way that the object is processed here, oftentimes these sorts of VAT resin printers can deal with more aggressive overhangs than an FDM system simply because they are curing smaller layers. Your resolution here is limited by the size of your laser that you're using in order to cure the path rather than actually extruding material, which means that you can build up something like a more complex overhang with more ease and supports don't need to be generated quite as much. When the objects are sliced and then infilled, oftentimes these sorts of printers have a much denser infill again because of that higher resolution. Now there is another method that has become increasingly popular here and this happens with DLS printers or what we would see in there's a commercial group Carbon 3D that does this to achieve extremely fast high resolution printing and this is essentially using an image that is projected onto the resin instead of a laser that traces the path. In this case you basically get an animation that is going to cure sequential layers all at once instead of being traced out by the laser's path. In the case of the laser tracing though our machine code looks very similar to how it looks for the extrusion. You are going from point to point and then telling the machine to cure in those specific points and trace out that path. In the case of doing a DLS or projection printing the machine code doesn't actually have any moving parts it would just be projecting these images that cure the resin directly. So that would actually look something more like this an animation where the white parts are being cured and the black parts are being left uncured. Now our built objects that come out on the other side of these printers tend to have much higher resolution than we see in FDM systems. Oftentimes you can't even see the resolution lines however they are still there. The mechanical properties of these objects are still impacted by the way that they are built so they will be weaker if they're sheared along those resolution lines. And oftentimes because we're dealing with resins in this and liquid resins that aren't safe to touch and also can't be exposed to light there is a good deal more post-processing with these systems sometimes they have to be washed or put into a bed of UV light that cures any sort of uncured resin that's still left on them so they can tend to be a little bit messier a little bit more expensive to working with these materials but they do have incredible capabilities. To give a recap of that these sorts of that resin printers they are incredibly fast and they can produce an incredibly high resolution object generally that require a deal of post-processing especially in some of these desktop systems and the resins have to be protected from light however you do get access to a large amount of functional materials and increasingly some of these desktop printers have allowed people to be 3d printing with things like ceramic resins which wouldn't have been available in the past or even biocompatible dental resins I saw that form labs offers recently you can print flexible materials using these systems really there's a huge array of different resins which is exciting for both hobbyists and people in industry right now and as I mentioned before carbon 3d is actually able to create production quality thermoset resins so what comes out of the printer instead of being a prototype could go directly into being a production part which is really interesting advancement that could allow them to push into industry a little bit more the last method that I'm going to go over today is sls selective laser centering or powder bed fusion what all of these sorts of methods have in common is that you have one big bed filled with a powdered material and the laser is tracing out and melting that material in order to create a solid as you see here now the processing for this sort of a system is fairly similar we start with this three-dimensional representation of an object but we don't need to generate any supports because the object already rests inside of a bed of this powdered material so the interesting thing about this is that we can essentially print a freeform object without any sort of supports at all the infill can be incredibly dense as well because we are using a laser to trace out the solid objects so oftentimes you'll just see a fully solid object with no real infill pattern as we might see in an fdm printing system the machine code however does look very similar to any kind any of the other printers with these moving parts where essentially we're just commanding the laser to move to different points and then melt the material in those different sorts of points one thing to know about these printers is that the built object it does have to be removed from this powdered material that it is encased in and oftentimes that powdered material that is not used in the printing process can't simply be reused for another print some of them they have a reuse rate of 30 to 50 percent so you can reuse that material maybe once but oftentimes you can't reuse the material at all so it is advantageous in these sorts of systems to pack the printer with as many parts as you can possibly use because whatever's left over you can't necessarily use in subsequent prints however this method does allow for production ready parts with a lot of interesting materials even different sorts of metals can be used for this um and shatter resistant nylon can be used in sls printers so it is something that's been adopted at the industrial scale a little bit more readily than some of the other 3d printing techniques it is extremely high resolution in many cases leading to almost a monolithic object and also this this lack of a need for printing supports means that there's very little post-processing and compared to some of the other printing methods one thing that i want to mention is an inside here because it is an increasingly common method of 3d printing is binder jetting so this is very similar to sls printing but instead of using a laser to cure the subsequent lines you're actually jetting out a liquid resin that cures the subsequent lines one thing that's really interesting about this method is that you can embed that resin with different colors and like an inkjet printer which means that you can get full color 3d printing and you combine things like sandstone and actually do rock printing with this so these are really interesting systems that are scalable too and i've seen a lot of people working on production ready full color parts as a recap quickly for sls printing and thinking about some of the recent advances too these are high resolution prints printers that allow for production ready parts some of the things that have been coming out recently in this are actually people trying to make desktop sls printers so form labs has something that somewhere between a research level and a hobbyist level that prints centered nylon desktop metal is there's a lot of these companies that have been doing production ready parts out of metal at extremely high resolution so you get actually 3d print a metal part that's ready to go to industry right away and many of the materials that are coming out are increasingly strong and shatter resistant so this is a printing method that has a lot of potential industrial applications there are so many different 3d printing methods that i don't have time to talk about today this year is a polyjet printer from Stratasys that essentially jets out ink much as a paper printer would and then cures that with a laser as it hits the bed that allows for extremely high resolution 3d printing with tons of different materials creating objects like the one that is seen here at the side where you can have these sorts of embedded multi-material prints there are also ways that we can make these functionally graded materials that i mentioned before where you have gradients of stiff and soft this can allow for the creation of artifacts that have all kinds of interesting dynamic behaviors too so these are the sorts of things that i think are going to become increasingly common in the next five to ten years and especially thinking about how we care for these pieces understanding how they were made and what the 3d printer was doing when it was processing that information could allow us to recreate them more faithfully and also think about how they have to be cared for in the future another thing that i think we need to keep an eye on too is thinking about extremely large-scale 3d printing so increasingly people are working on 3d printing concrete to create houses but also very large sculptures so some of these these 3d printed objects while we think of them as is tending to be fairly small desktop pieces they are starting to approach the scale of actual houses too and these sorts of systems are becoming increasingly available there are also printers that can print at the extremely small scale working at below 0.1 millimeter resolution to create these sorts of objects uh there are systems using magnetic fiber alignment in order to rapidly materialize parts so there's all these different interesting emerging technologies out there in the field many of them are variations on the methods that i've talked about today but understanding these fundamentals of what we are actually doing when we are 3d printing an object hopefully allows us to deal with these methods as they emerge there's one thing that i can really emphasize before the end of this is to think about the fact that as we start to have new ways of designing a lot of these technologies are going to be pushed forward even without hardware advancement so we should understand both the limitations on the CAD software and on the different sorts of 3d printing systems out there to really know from start to finish what is the pipeline used to create these objects and what can we expect to see in the next five to ten years thank you all so much for your time i hope that you enjoyed this you can feel free to reach out to me with any other questions that you might have about this and please don't hesitate to ask thank you so much