The making of parts and products using a computer-driven, additive process, one layer at a time. 3D printing builds plastic and metal parts directly from CAD drawings that have been cross sectioned into thousands of layers. It provides a faster and less costly alternative to machining (cutting, turning, grinding and drilling solid materials).|
Used for making both prototypes as well as final products, 3D printing evolved from the "rapid prototyping" industry, pioneered by Chuck Hull of 3D Systems in the mid-1980s.
Concept, Prototype and Final Product
Capable of making a part from scratch in just hours, 3D printing is used to create models to determine if a design meets the customer's concept and expectations. It is also used to create prototypes of parts to test their form, fit and function with other parts in an assembly.
Using 3D printing technologies such as laser sintering and electron beam melting, "rapid prototyping" evolved into "rapid manufacturing," in which short runs of actual finished parts are made. Such techniques are also used to create products customized for each person, such as hearing aids, dental crowns and medical implants.
3D printing is also used to make tooling, such as molds and dies, as well as patterns for castings. Either the actual mold or the model to make the mold can be produced more quickly and less costly than with conventional methods.
Additive Fabrication and 3D Printers
Although various techniques are used, all 3D printers use methods of "additive fabrication," methods, building the part one layer at a time, with layers ranging from a millimeter to less than 1/1,000th of an inch. The building material can be a liquid, powder or sheet material that is cured by heat, UV light, a chemical reaction or other method.
The term "3D printing" has evolved to include both rapid prototyping and rapid manufacturing. Initially, 3D printers referred only to the relatively small, inexpensive office-based machines that jet a wax, photopolymer or binder. Increasingly, the term refers to any machine that uses a method of additive fabrication either in the office or shop floor.
There are numerous 3D printing methods, including the cutting of paper, plastic and metal sheets with a laser or knife, and the layers may be glued or fused together. The more common methods use filaments, liquids or powders and are summarized below. See nanofactory and STL.
Known worldwide for his expertise in rapid prototyping and manufacturing, Terry Wohlers writes an industry report describing the applications, players, technologies and past, present and future of 3D printing. For more information, visit www.wohlersassociates.com.
Chuck Hull of 3D Systems, who pioneered rapid prototyping in the mid-1980s, is pictured in front of a stereolithography apparatus (SLA). Prototypes and parts are built from a liquid photopolymer, and each layer is created by a UV laser that cures one cross section at a time. At the end of the job, the whole part is cured once more after excess resin and support structures are removed. (Image courtesy of 3D Systems, Inc., www.3dsystems.com)
Laser sintering machines build prototypes and final parts from powdered plastics and metals that are heated by a laser. At the end of the job, the excess powder is removed and recycled for the next build. This metal part was created in a 3D Systems Sinterstation using the company's LaserForm resin. (Image courtesy of 3D Systems, Inc., www.3dsystems.com)
FDM machines deposit ABS plastic or another type of thermoplastic through a heated nozzle to form the layers. After being extruded, the plastic solidifies. Developed by Scott Crump of Stratasys in the late 1980s, FDM is a popular technology for making prototypes. This shows a close-up of the print head of a Dimension FDM machine from Stratasys (www.dimensionprinting.com).
Using an electron beam that melts metal powder a layer at a time in a vacuum chamber, EBM machines are used to create titanium and cobalt chrome parts. Conventional machining may be required to finish the goods. These engine parts were made with Arcam's CAD to Metal system. (Image courtesy of Arcam AB, www.arcam.com)
The 3D printers from Z Corporation (www.zcorp.com) jet color binders onto powdered, composite materials one layer at a time, enabling the fabrication of fully printed prototypes. All the gears and rods in this demonstration model were created in place as a single unit from bottom to top. At the end of the job, the excess powder was removed between the gears. When any single gear is moved manually, all the others rotate simultaneously.
Similar to inkjet printers, Objet's PolyJet piezoelectric print heads use thousands of nozzles to jet 16 micron layers of photopolymer that are immediately cured by UV light. The model material for the part and the support material that fills the voids come from different nozzles. Because of its 600x600 dpi resolution, PolyJet machines make fast prototypes. (Image courtesy of Objet Geometries Ltd., www.2objet.com)
From CAT scans and MRIs to physical 3D models, surgeons can preview a patient's bones and organs and save hours of time at the operating table. In addition, 3D printers can make generic and custom implants. The model of a human spine (top) was created by Objet's PolyJet technology, while the bottom image shows a finished Stryker knee implant made out of cobalt chrome in a laser sintering machine from Electro Optical Systems (EOS). (Images courtesy of Objet Geometries Ltd. and EOS GmbH.)