When selecting a material for a 3D printing project you should consider these three major categories; mechanical performance, visual quality, and processing. Even within those three categories, there are many implications to the choices that you make. So much of this will be general information that you can take further as you gain more experience. We are going to talk about a few different common materials today [inaudible] , ABS, PEG, TPU, nylon, and polycarbonate. We will also briefly talk about support materials and composites. Let's start with the most popular material PLA. This material is a low cost commodity polymer. Because of the RepRap project, it became a very commonly used material in printing. So what are some reasons why you would use PLA? To start, it can be printed on any 3D printer. There are no fancy features needed to print this material, it's great low cost filament with a lot of colors in the market. Visually it's glossy and can be painted very easily. One of the trade-offs though. Well, it's fairly strong, has very low toughness, which is why it snaps rather than bends. Also it has very low thermal resistance, so it will tend to slump or warp in hot environments. PLA is well suited for non mechanical applications to do as low toughness and low heat resistance. But it is fantastic for general printing applications or prototyping. ABS has been around 3D printing since the inception of the fused deposition modeling machine by [inaudible].It is still widely used today for its advantages over PLA but has some trade-offs. ABS is not significantly stronger when compared to PLA, however, it is tougher so it will flux more before it fractures and perform better under impact. These traits make ABS an excellent choice for functional prototypes. ABS is a little less glossy than PLA and can also be easily centered and painted. As an added bonus, you can take an acetone vapor bath and completely smooth the print out, making it look more like an injection molded part. With ABS, there are some nice benefits, but to reliably print this material, there are some processing challenges. To start this material tends to warp when it's not evenly heated. So an closed chamber is strongly encouraged. Not all printers can print at this higher temperature as well. So before you use this, make sure that your printer can use ABS material which prints at a higher temperature. PETG is a modified version of the material that's used to make recyclable water bottles. PETG is not nearly used as widely as PLA or ABS but provides some very unique opportunities for 3D printing. It is a tougher material similar to ABS. So it provides some flexible for fracture, It has a higher heat resistance than PLA but not as high as ABS. Visually, it's glossy. There are a wide variety of opaque and transparent PETG filaments which allows for very unique applications to be used within this material. PETG is not that difficult to print with, but it does have some coarse that PLA does not have such as leaving some stringing on the print. But this can be fixed to the properly to improfile. Even though it sounds like ABS and PETG are very similar, there are some significant advantages to PETG. PETG does not warp like ABS does, so it does not need an enclosure to operate. You can print PETG reliably on any printer that has a higher temperature range and a heated bed. TPU and TPE filaments are more commonly known as flexible materials. They are not commonly used, but has significant advantages on the application no one want's them. It has very high impact resistance and will not fracture like most other polymers. These materials are extremely soft. In fact, so soft but they are often categorized by a scale that tells you how soft they are. This scale is called the shore hardness. TPUs are generally harder than TPEs. TPUs tend to be in the 90-95 shore hardness, TPEs go as low as 70, which is similar hardness to neoprene rubber. This material is often thought of as being used in parts that need to be flexible. However, this material is fantastic for absorbing impacts and definitely vibration. One thing to keep in mind when using TPUs and TPEs if you want the part to flux more, use less infill. Painting TPU and TPE is not possible for the vast majority of applications because as it flexes, the paint will crack. Both of these materials require special care when printing. Depending on your machine, your shooting system may not be able to handle a certain materials. For example, machines that use bowden tube is continually handle a shore of hardness of 90 and up. Direct drive machines can handle 80 and up. To use TPU with a shore of hardness of 70, you will often need to modify your direct drive by purchasing a customized print setup for that material. One of my personal favorite materials, nylon, is widely used as an engineering polymer and has a plethora of functional applications. Nylon is significantly stronger than ABS, PETG, and PLA. It's also very tough, has a high impact resistance and has good thermal resistance. As a bonus, it also has a very low coefficient of friction so it can be used or partially to make contact but still move freely. Nylon has many variations and due to recent material developments, there are now many colors to select nylon filament. While painting might not work well for nylon, it can use red dye as a post process to color the part. Well, nylon has a lot of great reasons to use it for mechanical applications. It's challenges come in how you print it. Nylon is very hygroscopic. All polymers absorb moisture, but nylons are one of the worst when it comes to this. Nylon must be kept dry or be dry before printing. To achieve this, many people use a food dehydrator for multiple hours before and during the print. Well, printed adhesion can be difficult also as nylon warps much like ABS. To print nylon, your printer will need to maintain higher print temperatures, have a heated bed, an enclosure, and a filament grind system or drive ox. Polycarbonate is an engineering grade polymer. It is naturally clear but can be made opaque. Polycarbonate is the strongest of the materials that we've discussed today. Not only will it take the most force before it fractures, it is also somewhat ductile and has good impact resistance. Polycarbonate is essentially a much stronger version of ABS. Most often using polycarbonate in your project likely means you don't really need to paint your parts anyways as is most offered for functional applications. Printing polycarbonate is very difficult. It does not want to stick to anything easily and will readily warp. Even with the enclosure or produce still is difficult to overcome. Often, printing on a raft will help this problem. Much like nylon, polycarbonate is extremely hygroscopic and needs to be dried before and during printing to ensure the part comes out correctly. To reliably print polycarbonate, you will need the same equipment as nylon. Let's talk a little bit about some of the more unique materials. There are a lot of new composite materials coming out most recently. You will see some with glass fiber, carbon fiber, and even with wood fiber. These composite materials contain chopped fibroblast, carbon fiber will generally improve the material strength and make it more rigid overall. There's a lot of current research in these areas that show significant improvements of these composite materials. Along with these performance improvements, fiber composite materials warp far less than their counterparts do, which also improves the materials dimensional accuracy. Visually these fiber filled parts of a new texture that hides layer lines. You can see here these two parts, on the right carbon-fiber filled nylon, on the left PLA. Other composite materials like wood and metal films use PLA as a base polymer. They take wood and metal pieces, pulverize them and mix them into the polymer, and then use them as a printing material. These composites are done for visual effect only. They typically will actually hinder the performance of the material. In multi-material systems, you have new options to use differing support materials that are much easier to remove from the printed part. These require specific machines or add on to accomplish this. But they do give you more design and freedom to remove support with. Here are two examples of this, on the left is breakaway supports, on the right soluble. The benefit of using these support materials comes from easier removal as well as better looking parts where the support once was. The 3D printing world is just starting to peek into the vast opportunities in the material world. While many polymer research groups have been working on additive technologies for many years, there's more development now than ever before.
