STEMscopes Asks: How does 3D Printing Work?

Posted by Marissa Alonzo on June 30, 2015
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3D printing has been in the news and on people’s minds a lot lately in light of rapid advances in the technology, its accessibility to individual households, and exciting research into potential applications. As new as this technology seems, though, the first 3D printing method, called stereo lithography, was actually invented in the mid-1980s by Chuck Hull.

There are many types of 3D printers and variations on the process, but at the core, 3D printing involves turning a digital “blueprint” into a three-dimensional solid object through an additive or subtractive manufacturing process. An additive process adds layer upon layer of material until the object is created, which has the potential to waste far less raw material. The traditional subtractive manufacturing processes are used to cut the raw material into the final object’s shape.

3D printing can be used to make an entirely new object or to replicate an existing object. To produce a new object, a 3D modeling program is used and then saved as a computer-aided design (CAD) file.  If a replicated object is desired, a 3D scanner is used to create a digital blueprint for the printer.


Once the computerized design is created, the software is used to prepare the file for printing by translating instructions for hundreds or thousands of horizontal layers, each a cross-section of the overall design. 3D printers build objects one layer at a time. This creates sliced versions of the file (a .STL file, for “stereo lithography” or “Standard Tessellation Language”) that tells the printer how to make each layer.

The last step of the process is the printing. The 3D printer reads the file and follows each instruction to make each layer in turn. During the creation, the layers are blended or fused to each other so that the end product is a single object. Each layer is usually about 100 microns (0.1 millimeters) thick, and some printers are capable of printing layers as thin as 16 microns.

The most common type of 3D printing process is material extrusion, in which the material, usually a plastic filament or metal wire, is heated into a liquid form, then extruded through the print nozzle and deposited in layers. As each layer is deposited, the material solidifies and bonds to the layer below.

The stereo lithography method, another 3D printing process, uses liquid resin that is solidified using UV lights, an accurate but expensive process. Material jetting, is a process that uses a printer head similar to that found on an inkjet printer. It is used to deposit material in layers, allowing for multiple materials to be used by adding extra nozzles. Lastly, powder bed fusion is a process in which layers of powder are deposited and heated with a laser or electron beam, fusing them together. The many methods available differ in the types of materials they can print, their cost, their level of accuracy, their speed, and the extent of post-processing (e.g., removing support structures) required.

The possible applications of 3D printing are rapidly expanding. 3D printing started out largely as a fast way of making prototypes. Other current applications include reconstructing fossils, reconstructing damaged crime-scene evidence, and creating architectural models. Many biomedical applications are emerging, such as prosthetic limbs, hearing aids, and tissue engineering. Researchers are even exploring how to 3D-print meat, which may offer a way of producing food with less environmental impact compared to raising animals. Large-scale 3D printers may eventually be capable of printing homes. On the whole, 3D printing offers considerable potential in terms of both the variety of uses and its ability to produce useful objects with dramatically less waste and energy than traditional manufacturing processes.