Academic journal article Library Technology Reports

Types of Filaments for FDM Printing

Academic journal article Library Technology Reports

Types of Filaments for FDM Printing

Article excerpt

Since FDM printing is the most common type of 3-D printing for libraries to have, this section will do a deep dive on the materials available for libraries to use. The last few years have seen a blossoming of material types available, both in terms of ease of use and of specialty materials that offer unique properties.

The substrate for FDM printers is almost exclusively some form of thermoplastic that is delivered in an extruded wire-like form on a spool and is usually called filament in the generic. The two common diameters for use in FDM printing are 1.75 mm and 3 mm, and a specific diameter is called for by the printhead being used for the printer in question. A printer that uses 1.75 mm diameter filament won't be able to use 3 mm without the hardware being retrofitted for the difference, and a 3 mm printer won't be able to use 1.75 mm filament without at least the software involved being adjusted and perhaps the hardware as well. These restrictions on changing from one size to the other in a given printer are a combination of many possible issues: the path the filament follows through the extruder, the size of the hot-end and its ability to generate heat quickly enough to melt the filament appropriately, and the amount of extrusion programmed into the code that describes a given print. Any or all of these may be a problem if you attempt to move from one filament size to another with your printer.

In general, a library should look at its printers and try to stay within a specific filament size across all of its purchases, thus maximizing the flexibility of its material budget. Early in the 3-D printer movement, 1.75 mm was more popular, but in the current environment, it is a fairly even mix. Both of the 3-D printer companies that I recommend to libraries (LulzBot and Ultimaker, both of which are discussed in chapter 4) use 3 mm filament primarily, so it is a thing to watch for.

As I discuss the different printer types and manufacturers in chapter 4, I'll make a point of talking about what type of filament they are capable of printing because that turns out to be a major limitation for the purchasing decision.

ABS

The original fused deposition printers almost exclusively used ABS (acrylonitrile butadiene styrene) as their substrate for printing. ABS has nearly ideal material properties for rapid prototyping in plastic, as it's a strong, slightly flexible plastic that extrudes cleanly between 220 and 240 degrees C. ABS, the type of plastic used in Lego bricks, is one of the most commonly used industrial and commercial plastics.

ABS requires a heated print bed to ease the thermal shock for FDM printing. Heating the print build plate aids the plastic in both adhering to the plate for stability and in not cooling too quickly, which could lead to thermal deformation, a sort of curling or separation when ABS cools rapidly after being extruded. ABS is sensitive enough in this arena that many people who print ABS learned early that enclosing the printer was a way to increase the stability of prints because it regulated the temperature around the printer. I discovered early in my printing experiments with an early MakerBot printer (Replicator 1) that even a strong breeze blowing in the wrong place (i.e., across the print bed) could wreak havoc with getting a good print out of the printer. Higher-end printers will have an enclosed print area built in, while less expensive ones won't.

One of the advantages of ABS is that it dissolves in acetone. Acetone dissolves ABS completely, but used sparingly it can act as a glue to fuse two ABS printed pieces together permanently. Acetone is also used to make a "glue" to help make the print bed sticky for the initial printed layers. Acetone vapor is heavier than air, and some people have used this property to build acetone vapor baths that act to smooth the edges of layers of an FDM ABS print.

ABS has caught some bad press as the potential effects of off-gassing of the heated plastic and microparticulate effects are studied. …

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