What’s meant when someone mentions “3D printing”? The media, especially mainstream marketing, portrays 3D printing as a magical technology of the future that’s capable of replicating complex objects. But that makes it hard to put a finger on what exactly 3D printing is, technically speaking. In reality, there are many different 3D printing technologies, but fused deposition modeling (FDM), which this article focuses on, is the most common.
FDM works by using thermoplastic filament, which is basically a cord of plastic that can be melted, selectively deposited, and cooled. This is repeated, layer by layer, until an entire model is formed.
This technology was created by people who wanted to rapidly prototype parts. Even today, rapid prototype production is one of the biggest benefits of FDM and 3D printing in general. Not surprisingly, 3D printing has also become a potent manufacturing solution.
Before we proceed with the details of how FDM works, there’s one more thing worth mentioning. In case you’ve already done some research on 3D printing, you may have noticed that some sources use the term “FFF”, which stands for “fused filament fabrication”, instead of “FDM”. That’s because the term FDM was originally trademarked by Stratasys, and the other abbreviation is a more general term. Remember, it’s the same technology, only the names are different. Today, most people (including us!) use “FDM”.
Now, let’s really get started!
The easiest way to understand how FDM works is to first learn the parts of an FDM 3D printer. Before we talk about specific parts, though, it’s worth mentioning that most 3D printers use three axes: X, Y, and Z. The X- and Y-axes are responsible for left, right, forward, and backward movements, while the Z-axis handles vertical movement.
Now, let’s look at the main components of a 3D printer.
The build platform (also called a print bed) is essentially the surface on which the parts are made. Build platforms usually include heated beds to make it easier for parts to stick to them, but more on that later.
The extruder is the component responsible for pulling and pushing the filament through the printhead. Depending on the extruder (direct or Bowden), the extruder and the printhead are sometimes considered to be the same thing (i.e. the block that moves along the gantry or gantries). This is often the case when considering or discussing entire extruder and hot end assemblies. From this perspective, the extruder consists of two sub-components: the cold end and the hot end.
The cold end is the mechanical portion that consists of a motor, drive gears, and other small components that push and pull the filament. Regardless of naming conventions, the extruder always consists of at least the cold end.
The hot end contains a heater and a nozzle. The former heats up the filament so that it can be extruded out of the latter. In the case of a Bowden extruder, the hot end is never considered to be part of the extruder.
There can be one or more printheads on a printer, though most printers only have one. On the printhead, between the cold and hot ends, are a heatsink and fan, which help to prevent heat creep.
In addition to the heatsink fan, there’s usually at least one other fan for cooling the molten filament after it exits the hot end. This is usually called the part cooling fan.
Some modern 3D printers have a touchscreen that’s used for controlling the 3D printer. On older printers, a simple LCD display with a physical scroll and click wheel may be present instead of a touch interface. Depending on the model, an SD card slot and a USB port might also be present.
The process starts when you send a 3D model file to the printer. The file contains a set of instructions for everything, including temperatures for the nozzle and build platform as well as printhead movement and the amount of filament to extrude.
When the print job starts, the nozzle heats up. When the nozzle reaches the required temperature to melt the filament, the extruder pushes the filament into the hot end. At this point, the printer is ready to start 3D printing the part. The printhead lowers and starts depositing molten filament, squeezing out the first layer between the nozzle and the build surface. The material cools and begins to harden shortly after exiting the nozzle, thanks to the part cooling fan (or fans). After the layer is complete, the printhead moves up along the Z-axis by a tiny amount, and the process repeats until the part is complete.
Naturally, if you want to 3D print a part, you need a 3D model of that part. 3D models are created using 3D modeling software, such as CAD (computer-aided design) software. Here are some examples of popular 3D modeling programs:
However, most 3D printing beginners don’t have the skills required to use such software. If that’s the case, don’t worry, because there are other solutions.
For starters, there are simpler CAD software options, such as Tinkercad, a program that almost anyone can use without any prior experience. It’s an online app acquired in 2013 and since further developed by Autodesk, one of the industry’s leading CAD software creators.
With so many people gaining access to 3D printers in recent years, numerous sites have emerged as repositories for 3D models. Here are some of the most popular ones:
This way, anyone can get their hands on a model – no modeling skills required!
Once a model is finished in 3D design software, it still needs to be prepared using a special kind of software that translates the model into the script of machine instructions we mentioned earlier. This is done using slicing software, also referred to as a slicer. After importing your 3D model to the slicer, you can adjust the settings to meet your requirements. You can use the slicer to set many important parameters, such as printing speed, temperature, wall thickness, infill percentage, layer height, and many others.
The resulting file consists of G-code, the “language” of 3D printers and CNC machines. G-code is essentially a long list of instructions that the 3D printer will follow to build your model. In other words, 3D printing is impossible without G-code files!
One of the main functions of a slicer is to analyze your model and determine whether or not to generate support material. Specifically, supports are needed for parts with severe overhangs. The slicer lets you choose where to put supports and how dense you want them to be. Some slicers even offer users the ability to choose different types of support structures, which might be easier to remove or more stable.
When it comes to slicing software, there are a variety of options to choose from. Check out our slicing software guide to help you choose!
Infill is another setting that has a big impact on your 3D prints. Infill refers to the internal filling inside a part, and it plays a significant role in a part’s strength, weight, and print time. You can adjust your infill with two settings in your slicer, namely infill pattern and density.
Infill density refers to how full the print’s interior is, and it’s defined as a percentage. A print with 0% infill is hollow, while 100% infill means it’s completely solid. For most standard prints, an infill density of 15-50% is recommended. If you need to make your part stronger, try increasing the infill. Keep in mind that higher infill densities require more filament and longer print times.
You can also select an infill pattern for your print. For models and figurines, lightning, line, and zig-zag patterns in Cura are best, since they lead to quicker print times. Standard prints like pots and containers will work best with grid and triangle. And if you’re printing something that requires strength like a shelf bracket, cubic, gyroid, and octet patterns are the way to go.
After slicing a model, a couple of steps need to be taken before a 3D printer is ready to print:
Take a look at our bed leveling tutorial for more information on this important step!
As we’ve already mentioned, FDM 3D printers use spools of filament as the material for creating parts. These filaments are basically specially-engineered thermoplastics that are capable of being melted and cooled without losing their structural integrity.
Fortunately, filaments for FDM – especially the common materials – are among the cheapest materials used in the 3D printing world. They usually come in two different diameters: 1.75 mm and 3 mm (or 2.85 mm). Apart from the diameter, filaments also come in different spool sizes. A quick glance at the market reveals that the most common sizes are 500 g, 750 g, 1 kg, 2 kg, and 3 kg.
One of the best features of FDM 3D printers is that they can work with a variety of filament types. Here are just some of the different types of filament that are used in FDM 3D printing:
Check out our filament guide to learn about the most popular 3D printing filament types. In it, we go over their uses, properties, and where you can buy them.
Post-processing is the final step of the 3D printing process (although, we advocate recycling). Depending on your requirements, you may need to perform some of the following common post-processing steps for an FDM 3D printed part:
Want to learn more about post-processing? Check out our post-processing guide that’s suitable for beginners!
The following are some of the most common issues beginners might run into when beginning to 3D print.
3D printers, like any tool, require regular maintenance to continue functioning.
Filament storage is an important aspect of 3D printing, especially if you have several spools lying around. It’s important because if the spools are left, say, on a desk for a while, dust and moisture settle in and could potentially ruin the filament’s properties.
There are plenty of filament containers on the market, as well as vacuum bags. These prevent the filaments from getting dusty and acquiring moisture.
Filament dryers are also sometimes used. These devices keep your filaments healthy or make them healthier by drawing out any absorbed moisture. Check out our article featuring ways to safely store filament for more information.