How 3D Printers Work?

Layer by layer, 3D printers build objects out of gooey plastic. Here’s how the process works, plus a few professional technologies that could soon be available to the average maker.

There is a lot of excitement building around what 3D printers can and might do. But how does a 3D printer work? It’s actually not very complicated. 

Here are the mechanics behind the most common consumer-level printers that extrude plastic.
In goes filament, out comes gooey plastic.

3D printer owners choose between two types of plastic: 

Acrylonitrile Butadiene Styrene (ABS) 

Polylactic Acid (PLA). 

Some printers work with just one, other printers work with both. The plastic comes as strands of filament that are usually a standard 1.75 millimeters or 3 millimeters in width.

ABS, which is used to make Lego, is chemical-based and works at slightly higher temperatures. 

PLA is derived from natural sources, such as corn or sugarcane. It’s more rigid and glossy than ABS. Outside of 3D printing, it can be used to make biodegradable packaging.

Filament, which is usually stored on a spool attached to a 3D printer, can be expensive. 

MakerBot charges £40 for 2.2 pounds of PLA, though PLA or ABS can be had for half the price on eBay. The company estimates one 2.2 pound spool of filament is enough to print 392 chess pieces.

The price is likely to drop as 3D printers become more common and filament is manufactured on a larger scale. One current way to drop the cost is to use a filament extruder.This is when you feed in cheaper plastic beads or recycled plastic and out comes strings of filament.

Once you’ve obtained the filament, it is fed into the 3D printer’s print head. Generally, this is a boxy shape with a nozzle sticking out of it.

A gear pulls the piece of filament through the print head. Just before it is extruded by the pointed nozzle, the filament passes through a heated tube and liquifies. The nozzle deposits it in ultra-fine lines generally about 0.1 millimeters across. The plastic solidifies quickly, sealing together layers.
ABS generally needs to be printed on a heated surface, otherwise the bottom layer of plastic curls up.

PLA can be printed on a non-heated surface.

Most printers have one print head, which means objects are printed in one color, or the filament has to be switched out during the print job. Some printers have two or three print heads. This allows objects to be printed in two or three different colors.
Back and forth, layer by layer. Just watching the magic happen. The magic of turning your incredible idea from your thoughts to a 3D reality.
3D printing is additive manufacturing. That means the plastic is built up one layer at a time.

The print surface — which is called the print bed — and print head work together to print in three dimensions. On a MakerBot Replicator 2, the print head is suspended on a gantry system. Two metal bars that run across the top of the Replicator support the print head. The print head can move back and forth along them. At the edge of the printer, the two metal bars connect to another two bars. This allows them to move forward and backward, and the print head to move in four directions altogether. The print bed moves up and down to add a third dimension. 

Other 3D printers like RepRaps, the open source DIY printers that started the consumer 3D printing trend, sometimes work slightly differently. The print bed may move up, down, forward and backward while the print head only moves side to side. Or there are more unusual systems, such as the DeltaMaker, where the print head moves in three dimensions.

Print jobs can take minutes, hours or days, depending on the size and density of an object.