3D printing hands on: Swappable extruders on the Ultimaker 3 provide material flexibility

The Ultimaker 3 is one of the first consumer-friendly, professional-level dual extruder 3D printers on the market. We set up the machine and learn about the different extruders it uses.
Written by David Gewirtz, Senior Contributing Editor

Last week, we took a first look at the dual-filament Ultimaker 3 printer. This week, we dive into one of the key features that provides the printer with its power and flexibility: its extruders.

Before we go on, let's talk about the purpose of an extruder. An FDM (fused deposition modeling) printer takes in plastic filament, heats it up, and deposits it in very thin layers, layer after layer. The purpose of an extruder is to heat up the filament to a very precise temperature, and squish the molten plastic out, building up the object being printed.

Extruders work with two other key 3D printing components: the drive motor and the positioning system. Some extruders include the ability to pull the plastic from a roll, but other extruders simply heat the plastic at the point of contact. For those that simply do the heating, there's a motorized feeding mechanism somewhere else in the printer that actually pushes the filament into the extruder. On the Ultimaker 3, there are two of these feed motors, both located on the back of the machine.

The other component that works with the extruder is the positioning mechanism. Most 3D printers use Cartesian positioning, moving a positioning gantry and the build plate along the X, Y, and Z axes so the extruder can place the filament at the exact right location during printing. Another type of positioning mechanism is used in delta printers, which use three hanging arms that move together. I have a Dreammaker Overlord delta printer in the lab, and I'll be showing that to you in coming weeks.

Most printers come with a single extruder that's built right into the machine. The MakerBot and Ultimaker machines, however, come with removable, replaceable extruders. This allows for different filament types to be used on a printer, while tuning the extruder appropriately for specialty plastics.

In the case of the MakerBot, their Smart Extruder+ is the mainstay of their printing. But they've recently come out with a Tough PLA filament, which comes with a version of the Smart Extruder+ specifically designed for that filament. I have one of those in the lab, too. As soon as I figure out how to emulate a MythBusters episode without the training, skill, gear, or wisdom of experience of an Adam Savage or Jamie Hyneman, I'll run some tests for you on the Tough PLA.

The Ultimaker 3 comes with three extruders, two that are identified as AA extruders and one that's identified as a BB extruder. AA extruders are used for traditional filament, while the BB extruder is used for PVA (polyvinyl acetate), the plastic used for dissolvable filament.

On the Ultimaker 3, you can use one AA extruder for regular filament with one BB for dissolvable filament, or you can use two AA extruders and print in multiple colors.

There's one other big advantage to the removable extruders used by MakerBot and Ultimaker. If your extruder breaks (or you break it), you can replace it without having to perform major surgery on your printer. MakerBot's replacement extruders are $250 and include the filament drive mechanism. Because the drive mechanism is external to Ultimaker's print cores (what they call their extruders), replacements are only $99 each.

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