How 3D printers work

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How 3D printers work
From scale models, to working guns, prosthetic limbs, hearing aids and even an entirely 3D-printed 3D printer, the possibilities for 3D printing look limitless. But how does it work?

3D printing - the process of making three-dimensional solid objects from digital designs - has seen huge growth in the last couple of years, both for individual consumers and small businesses, as well as larger corporations.

From scale models, clothing and manufacturing moulds, to working guns, prosthetic limbs, hearing aids and even an entirely 3D-printed 3D printer, the possibilities for 3D printing look limitless. But how does it work?

3D printing

The concept of 3D printing is by no means new. Chuck Hull invented and patented stereolithography (also known as solid imaging) in the 1986, when he founded 3D Systems, Inc. Since then, advances in technology have made printers smaller and more efficient, but the basic concept remains the same.

Design

Before you can print an object, you need a digital model of that object to work from. An object can be scanned in real life and then imported into the computer, or an entirely new object can be created with the help of CAD (computer-aided design) software.

The digital model effectively serves as a blueprint for the printer, showing the exact size and dimensions of each part of the object. When finished, the design will be converted into an .STL fi le (for "stereolithography" or "Standard Tessellation Language").

Converting the object to .STL will divide it into cross-sectional slices, which are used by the printer to build up the object, layer by layer.

The 3D printing process

3D printing is an additive process, which means that the object is constructed by adding material in layers. This is in contrast to "subtractive" manufacturing, through which an object is constructed by cutting or machining raw material into a desired shape.

Almost all consumer 3D printers use a type of plastic to create objects. The two most popular plastics are Acrylonitrile Butadiene Styrene (ABS), which is also used to make Lego and is chemical-based, and Polylactic Acid (PLA), which is derived from natural sources, such as corn or sugarcane.

PLA tends to be stiffer than ABS. Whichever plastic the 3D printer uses - some can actually use both - the raw material comes in the form of filament, usually 1.75mm or 3mm in width, which is stored on a spool attached to the 3D printer.

When the filament is attached to the printer, it is fed through the print head. The print head contains a heated tube that the fi lament passes through, heating it and liquefying it before it is extruded by the print nozzle.

The liquid plastic is then deposited as ultra-fine lines generally about 100 microns thick, or roughly 0.1mm, which quickly solidifies and fuses to build up layers. Some printers can deposit layers as thin as 16 microns, or 0.016mm.

To make the object 3D, the print head needs to be able to move in multiple dimensions. Many printers use a gantry-type system where the print head is attached to a metal frame, letting it move both horizontally and vertically.

The print bed will then move up and down to add a third dimension. In some printers the print head can move in all three dimensions. Print jobs can take minutes, hours or even days for more complicated objects.

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