Additive Manufacturing: What is Fused Deposition Modeling?

This post was originally created on December 8, 2016.

With all the buzz about Additive Manufacturing, or 3D Printing, in the manufacturing world today, there is a lot of mystery and confusion surrounding common practices and techniques. This week’s blog post will address a common type of 3D printing known as Fused Deposition Modeling (FDM).

But first, What is Additive Manufacturing?

Additive manufacturing is the process of creating a part by laying down a series of successive cross-sections (a 2D “sliced” section of a part). It came into the manufacturing world about 35 years ago in the early 1980s, and was adapted more widely later in the decade. Another common term used to describe additive manufacturing is 3D Printing – a term which originally referred to a specific process, but is now used to describe all similar technologies.

Now that we’ve covered the basics of 3D Printing, What is Fused Deposition Modeling?

It is actually part of a broader category, commonly referred to as a Filament Extrusion Techniques.  Filament extrusion techniques all utilize a thin filament or wire of material. The material, typically a thermoplastic polymer, is forced through a heating element, and is extruded out in 2D cross section on a platform. The platform is lowered and the process is repeated until a part is completed. In most commercial machines, and higher-end consumer grade machines, the build area is typically kept at an elevated temperature to prevent part defects (more on this later). The most common form, and the first technology of this type to be developed, is FDM.

The Fused Deposition Modeling Technique was developed by S. Scott Crump, co-founder of Stratasys, Ltd. in the late 1980s. The technology was then patented in 1989. The patent for FDM expired in the early 2000s. This helped to give rise to the Maker movement, by allowing other companies to commercialize the technology.

It should also be noted that Fused Deposition Modeling is also known as Fused Filament Fabrication, or FFF. This term was coined by the Reprap community, because Stratasys has a trademark on Fused Deposition Modeling.

What Are the Advantages of this Process?

  • Fused Deposition Modeling machines are by far among the most affordable of rapid prototyping devices. They constitute the vast majority of commercially available small-scale machines. This is, again, partly due to the expiration of the patent on this technology, allowing many new entrepreneurs to enter the field.
  • This technology is also widely used. It is very common in many different industries, and is the one most often used in small to medium scale businesses and among home inventors.
  • There are many different types of materials that can be used with FDM technology, allowing for a wide range of available part properties.
  • A unique advantage of FDM is the ability to reduce part weight by creating partially hollow parts. Instead of printing a solid core, a cross-hatched pattern can be used instead. This allows for weight reduction and decreased print time without drastically compromising structural integrity. However, whether or not it can be applied on a given project is largely dependent on the user’s defined specifications.
  • With the use of multiple extrusion heads, multiple materials can be applied to a single part. Though this is primarily used to build supports, it can also be used to give a part different structural characteristics.

What Are the Disadvantages of this Process?

One of the major limiting factors of parts produced using an FDM technique is the orthotropic part properties – that is to say, the part will have different structural properties in different directions. For example, the material will be much weaker in the Z direction as opposed to the X and Y directions, the Z high being the direction of the layers. This can be an issue if your prototypes need to be used in any kind of testing.

Dimensional accuracy with this process, while it can be very accurate, is limited by the thickness of the filament. Thus, the FDM process can be less accurate compared to other prototyping techniques.

Any type of filament extrusion will also require the use of supports. This can either be a separate material (printed with a second extrusion head) or a lattice structure using one material. This adds a mandatory secondary removal process and waste whenever a part is produced.

Another possible issue with FDM is the curling of material. This is when the part begins to warp and bow towards the top of the machine. This can completely ruin a part, depending on the severity. This phenomenon can be attributed to the shrinkage of the material during the cooling process – more specifically, uneven shrinkage. The effects of curling can be lessened by encasing the print area and elevating the temperature to ensure that the part cools at an even rate.

In Conclusion

There are quite a few different ways to 3D print a part, with unique advantages and disadvantages to each method. This post is part of a series discussing the different techniques; check out part 1 here if you haven’t already. Thanks for reading!

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