3D printing

Three-dimensional printing is a method of converting a virtual 3D model into a physical object. 3D printing is a category of rapid prototyping technology. 3D printers typically work by 'printing' successive layers on top of the previous to build up a three dimensional object. 3D printers are generally faster, more affordable and easier to use than other additive fabrication technologies.

Technologies

One variation of 3D printing consists of an inkjet printing system. Layers of a fine powder (plaster, corn starch, or resins) are selectively bonded by "printing" an adhesive from the inkjet printhead in the shape of each cross-section as determined by a CAD file. This technology is the only one that allows for the printing of full color prototypes. It is also recognized as the fastest method.

Alternately, these machines feed liquids, such as photopolymer, through an inkjet-type printhead to form each layer of the model. These Photopolymer Phase machines use an ultraviolet (UV) flood lamp mounted in the print head to cure each layer as it is deposited.

Fused deposition modeling (FDM), a technology also used in traditional rapid prototyping, uses a nozzle to deposit molten polymer onto a support structure, layer by layer.

Another approach is selective fusing of print media in a granular bed. In this variation, the unfused media serves to support overhangs and thin walls in the part being produced, reducing the need for auxiliary temporary supports for the workpiece.

Finally, ultrasmall features may be made by the 3D microfabrication technique of 2-photon photopolymerization. In this approach, the desired 3D object is traced out in a block of gel by a focused laser. The gel is cured to a solid only in the places where the laser was focused, due to the nonlinear nature of photoexcitation, and then the remaining gel is washed away. Feature sizes of under 100 nm are easily produced, as well as complex structures such as moving and interlocked parts.

Each technology has its advantages and drawbacks, and consequently some companies offer a choice between powder and polymer as the material from which the object emerges. . Generally, the main considerations are speed, cost of the printed prototype, cost of the 3D printer, choice of materials, color capabilities, etc.

Unlike "traditional" additive systems such as stereolithography, 3D printing is optimized for speed, low cost, and ease-of-use, making it suitable for visualizing during the conceptual stages of engineering design when dimensional accuracy and mechanical strength of prototypes are less important. No toxic chemicals like those used in stereolithography are required, and minimal post printing finish work is needed. One need only brush off surrounding powder after the printing process. Bonded powder prints can be further strengthened by wax or thermoset polymer impregnation. FDM parts can be strengthened by wicking another metal into the part.

Resolution

Resolution is given in layer thickness and X-Y resolution in dpi. Typical layer thickness is around 100 microns (0.1 mm), while X-Y resolution is comparable to that of laser printers. The particles (3D dots) are around 50 to 100 microns (0.05-0.1 mm) in diameter.

Applications

Standard applications include design visualization, prototyping/CAD, metal casting, architecture, education, geospatial, healthcare, entertainment/retail, etc.

More recently, the use of 3D printing technology for artistic expression has been suggested.

3D printing technology is currently being studied by biotechnology firms and academia for possible use in tissue engineering applications where organs and body parts are built using inkjet techniques. Layers of living cells are deposited onto a gel medium and slowly built up to form three dimensional structures. Several terms have been used to refer to this field of research: Organ printing, bio-printing, and computer-aided tissue engineering among others.

See also

• Direct Digital Manufacturing
• List of emerging technologies
• Rapid prototyping
• Stereolithography
• Solid freeform fabrication
• Self-replicating machine
• 3D microfabrication
• Digital fabricator
• Desktop manufacturing

External links

• Times Online article - Microtrends: 3D Printing
• The Rapid Prototyping Home Page
• Castle Island's Worldwide Guide to Rapid Prototyping Overview of 3D Printing
• The Clanking Replicator Project: Bootstrap your own self-replicating, rapid prototyping machine
• Technical Articles on 3D printing from consultancy firm Wohlers Associates
• 3D printer reshapes world of copying on Post-Gazette.com
• Manufacturing Engineering Centre (MEC), Cardiff University, UK. Fused Deposition Modelling (FDM)
• Manufacturers and Developers of Additive Systems
• Fab@Home - A relatively inexpensive 3D printer for home experimentation
• Custom Fit European RM Project