This instalment of Tech Explained explores the technology behind 3D printing.
Three-dimensional printing was first invented in the 1980s by engineer and physicist Chuck Hull. He sought to create a way to allow engineers to rapidly create and change prototypes of their designs. Today, 3D printing has exploded from a niche technology to mainstream innovation. The printers come in all sizes – including many designed for use by home hobbyists, and can print in a variety of materials.
Engineers or hobbyists begin by designing the 3D object using specialised software. Once the design is finalised, it is sent for printing. The printer creates the object by building it up from the bottom, layer-by-layer.
There are several different types of printing methods in use. The most common, at least for hobbyists, is filament deposition modelling (FDM). In FDM printing, a solid material, often in the form of thermoplastic pellets, is pushed through a hot nozzle, melts, and is deposited in thin layers to build up the final object. Each time a layer is completed, the nozzle moves up a little bit (or the printer bed moves down) and the next layer is printed on top of it.
In Polyjet printing, tiny droplets of photo-reactive resin are squirted onto the printer bed from several nozzles, in the desired pattern, and then ultraviolet light is shone on the surface to harden it. This process is then repeated hundreds or thousands of times. The big advantage of polyjet printing is that objects can be created in a wide range of colours and patterns. Some polyjet machines can also print with multiple materials simultaneously.
Stereolithography (SLA) and digital laser projection (DLP) printing work in a similar fashion. First, a transparent printer bed is lowered into a pool of liquid resin. Light is then shone up through the bottom of the bed in the desired pattern. As the liquid resin is struck by the light, it solidifies, and forms the first layer of the object. The bed then moves up a few microns and the process is repeated. The only real difference between SLA and DLP is that in SLA a narrow beam traces out the pattern, while in DLP the light is projected onto the resin, creating the entire layer at once.
In selective laser sinstering (SLS), a laser is flashed over a bed of superfine powder in the pattern of the object. When this happens, the powder fuses together to form a layer. More powder is then swept over the top of the layer, and the process repeats. Most SLS printers are very expensive, compared to other 3D printers, but they can produce parts that have almost the same quality as that created by injection molding or other traditional manufacturing processes.
But don’t expect 3D printing to replace mass production anytime soon. Buying a 3D printer is much cheaper than setting up a factory, but the cost to produce each item is much higher. Most 3D printing also cannot match the high-quality finishes of machined goods. Yet, for some uses, 3D printing is already ahead of traditional manufacturing, streamlining a variety of industries such as robotics. At Springwise we have seen 3D printing used for innovations as diverse as creating new bones, popsicles and bridges. In the future, 3D printing may allow people to create almost anything at home, made-to-measure, while saving on shipping, packaging and pollution.
1st August 2018