How 3D Printing Works
January 8, 2014,
3D printing is also called additive manufacturing - and this is a helpful visual definition, because it means just that: making something by adding layer by layer.
But how does the printer know exactly where to put those layers? It needs instructions, so a virtual model of the object to be printed is created with a CAD (computer aided design) program. The result is an .STL file, the standard files used in the 3D printing industry. There are many CAD programs out there to choose from, including free programs like Tinkercad.
There are other methods to create a virtual model, such as making a scan of a real object or using a pre-made file shared by someone else on communal sites such as MakerBot's site Thingiverse, where MakerBot owners can access a "universe of things." Over 28,000 files for objects can be downloaded and printed.
Slicing into layers
In order for the file to be printed, a print program "slices" the virtual model into hundreds or thousands of horizontal layers. The printer reads the slices, which are 2D views of the model, and creates the object by depositing one thin layer of material at a time and building up the layers incrementally.
There are different 3D printing technologies on the market. MakerBots feature a technology that uses a filament to feed an extruder, where it is heated and then used to draw an image over and over. The material cools quickly.
The most common 3D printing material used, according to 3D Hubs, which tracks 3D printing trends, is ABS plastic. However, corn-based PLA, which is compostable in a professional composting facility, is a close second and gaining ground, according to the folks at MakerBot. The Maker-Bot Replicator 2 Desktop 3D Printer, the company's fourth-generation machine, prints PLA. Other materials that can be extruded include wood pulp, metal and ceramic.
|MakerBots use PLA fi lament, a corn-based material.
It gets fed through an extruder, which heats up the
material then uses it to draw an image over and over.
The PLA cools quickly as it is printed.|
Erin Arden, training manager at MakerBot, described the extruder system as being "like a glue gun." She said the extruder draws out the pattern, moving along an x and y axis. The pattern is built up on a flat surface, called a build plate. The build plate moves on the z axis - that's the third dimension - get it? The build plate drops down for every layer.
Layers can achieve the thinness of paper - 100 microns. But printing at 100 microns will take a long time. 200 microns is standard while 300 microns would be low quality, but a very fast print job.
Support from inside
Cubic build volume is currently 11" by 6" by 6". In order to build larger objects, users build the components and assemble the pieces. This was the case with Verlan dress designed by Frances Bitonti and printed on two MakerBots Replicators. It took two weeks to produce the dress's 59 parts, which were then assembled.
As the object is being printed, if necessary, a honeycomb structure can be built simultaneously on the inside for support - this is called infill. And the density can be adjusted, creating lighter or heavier objects. One can also print a project with external supports that can be removed when the task is complete.
If a project calls from multiple colors - these can be done as separate pieces and assembled or the print job can be paused and the filament changed.
If this all sounds extremely futuristic, it is and it isn't. Manufacturers are already using CAD files, of course, to create their designs. And the communal nature of 3D design means late adopters can avoid a lot of trial and error by learning from others, eager to share their experience. Classes are available; MakerBot, for example, offers three-hour sessions designed to get new users out of the box and up to speed.