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06 Objects on Demand The Technology behind 3D Printing

Devices that can create real objects from “thin air” may seem like a wishful vision of the future — or an episode of Star Trek — but this type of technology is already here. And while 3D printing can’t actually make objects materialize, the near magic of the process holds nearly endless possibilities, now and for the future.

How does 3D printing work? The answer isn’t straightforward, because there are several different types of 3D printing used to make myriad different objects. Here’s a look at the technologies behind 3D printing, and what’s already being done with these incredible devices.

A brief history of 3D printing

The process of 3D printing is an “additive” technology — a 3D printer creates objects by building up a great number of very thin layers to ultimately produce a whole. The first commercial 3D printer was invented in 1984 by Charles Hull. This early technology, which is still in use today, is based on the technique of stereolithography and uses UV laser beams to harden very thin layers of liquid photopolymer inside a vat. Once the object has been completely created, the excess liquid is drained and the object is cured.

This process, called vat polymerization, was carried over into other types of 3D printing technologies. Another common method is DLP projection, which solidifies object layers by cross-section instead of layers using a projector. A third type of liquid 3D printing, called material jetting or polyjet matrix, prints without a vat using an inkjet-style, multi-nozzle head to emit liquid photopolymer, and the layers are solidified with UV light.

More types of 3D printing

With similar characteristics to material jetting, the material extrusion category of 3D printer uses a computer-controlled print head to deposit semi-liquid material (usually heated thermoplastic), which is then hardened in layers. The most commonly used name for this type of 3D printing is fused deposition modeling (FDM), but there is an exact technology called FDM which is patented and trademarked by the inventor. Other names for material extrusion printing include thermoplastic extrusion, plastic jet printing (PJP), fused filament method (FFM), and fused filament fabrication (FFF).

While most 3D extrusion printers use the same type of material as traditional injection molding, some printers of this type have been designed to print objects using a wide range of materials — from edible printing like cheese and chocolate, to printers that can produce objects in concrete or synthetic stone.

The final broad category of 3D printers uses powdered material, which is selectively stuck together in layers with a type of glue called a binder. There are several different subcategories of 3D printers using powdered build material, including:

  • Binder jetting: Also known as “inkjet powder printing,” this process emits the binder from an inkjet-style print head to adhere successive layers of powder. Gypsum-based composite is the most common powder used, and many of these systems can print with up to five colors at resolutions of up to 600 x 540 dpi.
  • 3D sandcasting: In this process, a binder jetting printer is used to print a mold by spraying binder selectively onto sand. Molten liquid metal is poured into the sandcast, and the sand is simply broken away when the metal cools.
  • Binder jetting metal printing: Similar to the gypsum-based powder process, these 3D printers create objects using metal powder, usually bronze or stainless steel. Each layer is dried with heating lamps, and the printed object is infused with additional powder in a kiln. The resulting object is 99.9 percent pure metal.
  • Selective layer sintering (SLS): Combining layers of powder with laser hardening, this 3D printing technique can create objects from a broad range of powdered materials — including polystyrene, nylon, wax, ceramics, glass, aluminum, titanium, stainless steel, and several alloy metals. When used to produce metal objects, the process is called direct metal laser sintering (DMLS).

Who uses 3D printing?

Currently, 3D printing is most commonly used in commercial applications. There is a broad range of commercial 3D printers available from several different companies, with costs ranging from ten to twenty thousand, to several hundred thousand dollars.

For the most part, commercial 3D printing is used to create prototypes and pre-production molds, but some companies are using these devices to individually create products for sale — a process known as direct digital manufacturing (DDM). Some of the products created with DDM include jewelry, fashion bags, designer sunglasses, furniture, lightning, and custom motorcycles. The dental industry has made highly practical use of 3D printing, with technology capable of producing custom crowns, bridges, and temporary teeth.

For individuals, there are a number of ways to use 3D printing. Online services like iMaterialize, Sculpteo, and Shapeways allow anyone to upload 3D computer models, and the designs are marketed online and printed when customers purchase them. There are also personal 3D printers available at varying levels of complexity, from full DIY kits to build a printer, to plug-and-play models that work with personal computers.

The future is bright with possibilities for 3D printing technology, in both personal and commercial use.