An Overview Of The Fused Deposition Modelling Process

Fused Deposition Modelling - 4 November, 2022
An Overview Of The Fused Deposition Modelling Process
Author
Vicki May
Date
4 November 2022
Category
Fused Deposition Modelling
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The most popular 3D printing technology is fused deposition modelling, especially among home users, hobbyists, and small businesses.

It is affordable and relatively fast, and you get high-quality 3D-printed models. But what does fused deposition modelling involve, and how does the manufacturing process work?

The fused deposition modelling 3D printing process involves three main stages. The first is CAD modelling or the design stage. The second is the actual printing part, and the last stage is finishing the model with some refinements. Each step is crucial to make well-printed FDM models.

FDM technology is popular for many reasons, but you may have disappointing results if you don’t understand the process and how it works.

Let’s show you how the FDM process works and how you can get the best results from your fused deposition modelling components.

What Is Fused Deposition Modelling?

Fused deposition modelling, also known as FDM, is a type of additive manufacturing technology. It involves a continuous thread of molten material, typically plastic or composite, in the form of a filament, to be pushed through extruders to build a model one horizontal layer at a time.

FDM is the most widely used type of 3D printing and is particularly popular with home users and small businesses. Many schools teach 3D printing and CAD modelling using FDM printers, and there’s a good chance that you’ve seen FDM printers in action before, even though you might only have known it as generic 3D printing.

It’s also important to note that FDM is not the same as FFF (fused filament fabrication), though they are nearly identical. Proper fused deposition modelling is a patent and trademark that belongs to the corporation Stratasys. FFF is a technology based on FDM but different enough not to infringe on the patent. 

Most third-party FDM printers use FFF, not FDM, but you would be hard-pressed to notice the difference.

The Fused Deposition Modelling Process

Fused deposition modelling consists of a three-step process, and each step has its quirks and tweaks that you must understand and use to your advantage to get the perfect print.

Step 1: CAD Modelling

People often underestimate the importance of CAD (computer-aided design) in the 3D printing process. A poorly designed model won’t print correctly, so starting on the right foot is vital.

CAD modelling is the process of designing the model you want to print. You need to use special software for this. Unfortunately, CAD is not an easy skill to master. Engineers and architects spend years studying the subject and learning how to use CAD software, but that doesn’t mean that you won’t still be able to make a simple design reasonably quickly.

3D printing requires a 3D model rather than a 2D image. You may be able to start your 3D design from a 2D design, but at some point, you will have to bite the bullet and design a 3D model in CAD software.

There are various software programs you can choose from. Perhaps the most popular one is AutoCAD, an ultra-powerful CAD program that architects and engineers use. It is virtually unparalleled in its power, but it has two downsides: it comes with a huge learning curve and is pretty expensive.

Fusion 360 is another option. It is also made by Autodesk, the company that makes AutoCAD, and it has similar capabilities for most basic 3D printing needs. Fusion 360 is much easier to learn than AutoCAD, and there are extensive tutorials on YouTube to help you get started. Private home users can also get Fusion 360 for free.

Another option is Tinkercad. It is also an Autodesk product, so you know it’s pretty powerful, but it is by far the simplest of the three. You can use Tinkercad online for free. It’s a popular platform to teach kids how to do CAD modelling.

There are other options, too. Some are free or open-source, while others are included with other software, like Microsoft’s Paint 3D, which ships free with Windows. Some of these programs aren’t as powerful as others, but you can use almost any program to get started.

But whichever CAD software you use, it’s important to remember to add supports. Depending on what you’re designing, remember that the FDM printing will be building your model from the bottom up. If you design something with a loose-hanging part, like a bridge or the roof of a house, the molten filament will sag since there won’t be a foundation to build that part of the model on.

To solve this issue, design support structures where needed. For example, adding a few temporary pillars under a roof will be helpful. But it would help if you ideally did this during the CAD design process.

Step 2: 3D Printing

The FDM 3D printing process isn’t very hands-on. There are a few preparations that you must make, but once the printing process starts, you can relax and wait for the printer to finish its job. The process involves the following:

Slicing

Once you’re done with your design, the next step is to prepare the model for printing. We call this process “slicing,” You usually do it with special software, like Ultimaker Cura, or software you got with the 3D printer. Whichever software you choose, the slicing process is more or less the same:

  1. Load the model into your slicing software. You should see the model appear within a virtual rendition of your 3D printer.
  2. Tweak your settings. This includes aspects like how fast it should print, which temperature it should use, and how thick or dense the layers of filament should be. Slower prints with thinner layers will take longer, but the print quality will be much higher. The temperature will depend on the type of filament you use.
  3. Click on “Slice.” This will break your model into tiny step-by-step instructions for the FDM printer to follow, which the program will save as a G-code file.

Printing

Now you’re ready to start printing. You can often print directly to your FDM machine through a USB cable, or you may have to save the G-code file to an SD Card and insert it into the printer to start the process.

The printer will begin by warming up the bed and the nozzle. The temperatures will depend on the settings you choose, based on the type of filament you use. PLA, one of the most common filaments, requires a nozzle temperature of approximately 160°C to 180°C (±350°F). Unlike the nozzle, the bed will be much cooler and safe to touch.

The printer will start to move as soon as the bed and the nozzle have reached their temperatures. The first movement is the nozzle depositing a thin layer of molten filament in a straight line near the edge of the bed. The printer does this to clean the nozzle and ensure a consistent stream of filament.

The second movement will be an outline of the shape you want to print, mainly to ensure that there are no obstructions in the way of the nozzle.

After this, the actual printing will begin. If your printer has a bed that moves along the Z-axis (most common with FDM printers), the bed will be at the top, directly below the nozzle. If it doesn’t have a moving bed, but rather the nozzle moves up and down the Z-axis (most common with FFF printers), the nozzle will be at its lowest point.

Now the FDM machine will start pushing the filament from the reel through a thin pipe and into the nozzle. The filament will melt and extrude through the nozzle in thin lines. These lines will form layers on the printing bed, where a fan (usually built into the nozzle) cools it down so the filament can harden almost instantly.

The G-code file you created contains instructions about the positioning of the nozzle in each step. The nozzle will move around the X- and Y-axes with the help of stepper motors to get the position perfectly right. All this time, the filament will keep on extruding and forming a layer on the bed.

Once the printer has finished forming the bottom layer, the bed will lower slightly (or the nozzle will rise slightly) to form the next layer on top of the first layer. This process continues until the entire model is complete. Note that it could take hours to finish depending on its size, amount of detail, and the settings you applied during slicing.

Step 3: Finishing

When the printer finishes, the nozzle and bed will retract to the “home” position, giving you free access to remove the model. Removing the model from the bed could be slightly tricky if you don’t do so immediately, but heating the bed will solve this problem. 

Very few 3D prints come out of the FDM printer looking perfect, and there are usually a few things you must do to finish it.

Remove The Supports

If you added any support structures during the CAD modelling or preparing process, now is the time to remove them. Some FDM printers can add supports using materials that you can dissolve away, which is an ideal way to do so, but this requires a printer with two nozzles, one for the actual filament and another to build the supports.

More often than not, though, you will have to remove the support structures yourself. This could leave a mark on the model, so it’s essential to plan for that during the CAD modelling process. You can use some pliers to remove the supports manually. If there are some marks, a fine file can often remove them, and you can fill any gaps with a bit of autobody filler.

Make The Surface Smooth

One common downside of FDM printing is that it could lead to a rough surface created by the layers of filament. Some settings will lead to a smoother surface (like slower printing speeds and thinner filament lines). However, if you find the surface too rough, you can do a few things to smoothen it:

  1. You can sand the surface. If it’s very rough, you should start with a coarser sandpaper and gradually move to a finer one, but keep in mind that the sandpaper shouldn’t be too coarse to begin with. Test the sandpaper on a sample print or a small area first to ensure you’re using the right one.
  2. Bead blasting may be a good option if you can. It is a faster and more effective way to smoothen the surface than sanding, and it will be easier to reach fine details and small surfaces.
  3. Tumbling may also work if you print using sturdier materials and if you designed the model with thicker outside walls. This also allows you to smoothen more than one model simultaneously.

At Prototal UK, our vapour smoothing can achieve surface finishes similar to those achieved in injection moulded components.

Paint Your Model

After achieving the desired smoothness level, you may want to paint your model. You should first ensure that the surface is clean, dry, and dust-free and that you have cleared away all the blemishes. 

You should ideally use an airbrush to paint the model since it will help you to distribute the paint evenly over the surface. Apply only a thin layer, then let it dry for about 30 minutes before applying the next.

Conclusion

Fused deposition modelling is a great and affordable way to make 3D-printed models from the comfort of your home. We don’t often think about what a marvel that technology is. As great as it is, plenty of things could go wrong with your print. Knowing how the fused deposition modelling process works will help you to avoid those problems and achieve perfect prints.

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