Additive manufacturing or 3D printing[1] is a process of making three dimensional solid objects from a digital model. 3D printing is achieved using additive processes, where an object is created by laying down successive layers of material.[2] 3D printing is considered distinct from traditional machining techniques (subtractive processes) which mostly rely on the removal of material by drilling, cutting etc.

3D printing is usually performed using a materials printer, and since 2003 there has been large growth in the sales of these machines. Additionally, the cost of 3D printers has gone down.[3] The technology also finds use in the fields of jewellery, footwear, industrial design, architecture, engineering and construction (AEC), automotive, aerospace, dental and medical industries, education, geographic information systems, civil engineering, and many others.

[edit] Terminology

Additive manufacturing (AM) also known as 3D printing[1] is defined by ASTM as the "process of joining materials to make objects from 3D model data, usually layer upon layer, as opposed to subtractive manufacturing methodologies, such as traditional machining. Synonyms include additive fabrication, additive processes, additive techniques, additive layer manufacturing, layer manufacturing, and freeform fabrication".[4]

The term additive manufacturing describes technologies which can be used anywhere throughout the product life cycle from pre-production (i.e. rapid prototyping) to full scale production (also known as rapid manufacturing) and even for tooling applications or post production customisation.

[edit] General principles

The use of additive manufacturing takes virtual designs from computer aided design (CAD) or animation modeling software, transforms them into thin, virtual, horizontal cross-sections and then creates successive layers until the model is complete. It is a WYSIWYG process where the virtual model and the physical model are almost identical.

With additive manufacturing, the machine reads in data from a CAD drawing and lays down successive layers of liquid, powder, or sheet material, and in this way builds up the model from a series of cross sections. These layers, which correspond to the virtual cross section from the CAD model, are joined together or fused automatically to create the final shape. The primary advantage to additive fabrication is its ability to create almost any shape or geometric feature.

The standard data interface between CAD software and the machines is the STL file format. An STL file approximates the shape of a part or assembly using triangular facets. Smaller facets produce a higher quality surface. VRML (or WRL) files are often used as input for 3D printing technologies that are able to print in full color.

Construction of a model with contemporary methods can take from several hours to several days, depending on the method used and the size and complexity of the model. Additive systems can typically produce models in a few hours, although it can vary widely depending on the type of machine being used and the size and number of models being produced simultaneously.

Some additive manufacturing techniques use two materials in the course of constructing parts. The first material is the part material and the second is the support material (to support overhanging features during construction). The support material is later removed by heat or dissolved away with a solvent or water.

Traditional injection molding can be less expensive for manufacturing polymer products in high quantities, but additive fabrication can be faster and less expensive when producing relatively small quantities of parts. 3D printers give designers and concept development teams the ability to produce parts and concept models using a desktop size printer.

[edit] Technologies

There are several technologies. All those available as of 2012[update] were additive, differing mainly in the way layers are built to create parts. Some melt or soften material to produce layers (SLS, FDM), while others lay liquid materials thermosets that are cured with different technologies. Lamination systems cut thin layers to shape and join them together.

As of 2005[update] conventional additive rapid prototype machines cost around £25,000.[6]

[edit] Methods

A number of competing technologies are available to do 3D printing. Their main differences are found in the way layers are built to create parts. Some methods use melting or softening material to produce the layers, e.g. selective laser sintering (SLS) and fused deposition modeling (FDM), while others lay liquid materials that are cured with different technologies, i.e. stereolithography (SLA). In the case of laminated object manufacturing (LOM), thin layers are cut to shape and joined together (i.e. paper, polymer, metal). Each method has its advantages and drawbacks, and consequently some companies offer a choice between powder and polymer as the material from which the object emerges.[7] Generally, the main considerations are speed, cost of the printed prototype, cost of the 3D printer, choice and cost of materials and colour capabilities.[8]

[edit] Molten polymer deposition

Fused deposition modeling (FDM) is a technology developed by Stratasys[9] in the late 1980s and was commercialized in 1990[10] which is used in traditional rapid prototyping,

FDM works using a plastic filament or metal wire which is unwound from a coil and supplies material to an extrusion nozzle which can turn the flow on and off. The nozzle is heated to melt the material and can be moved in both horizontal and vertical directions by a numerically controlled mechanism, directly controlled by a computer-aided manufacturing (CAM) software package. The model or part is produced by extruding small beads of thermoplastic material to form layers as the material hardens immediately after extrusion from the nozzle. Stepper motors or servo motors are typically employed to move the extrusion head.

The molten polymer used is often Acrylonitrile butadiene styrene (ABS), Polycarbonate (PC), Polylactic acid (PLA), PC/ABS, Polyphenylsulfone (PPSU), Ultem 9085 etc.

[edit] Granular materials binding

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. Typically a laser is used to sinter the media and form the solid. Examples of this are selective laser sintering (SLS), using metals as well as polymers (i.e. PA, PA-GF, Rigid GF, PEEK, PS, Alumide, Carbonmide, elastomers), and direct metal laser sintering (DMLS).

Electron beam melting (EBM) is a similar type of additive manufacturing technology for metal parts (i.e. titanium alloys). EBM manufactures parts by melting metal powder layer by layer with an electron beam in a high vacuum. Unlike metal sintering techniques that operate below melting point, the parts are fully dense, void-free, and very strong.[11][12]

The CandyFab printing system uses heated air and granulated sugar. It can be used to produce food-grade art objects.

Another method consists of an inkjet 3D printing system. The printer creates the model one layer at a time by spreading a layer of powder (plaster, or resins) and inkjet printing a binder in the cross-section of the part. The process is repeated until every layer is printed. This technology allows for the printing of full colour prototypes and allows overhangs, as well as elastomer parts. Bonded powder prints can be further strengthened by wax or thermoset polymer impregnation.

[edit] Photopolymerization

The main technology in which photopolymerization is used to produce a solid part from a liquid is stereolithography (SLA).

In digital light processing (DLP), a vat of liquid polymer is exposed to light from a DLP projector under safelight conditions. The exposed liquid polymer hardens. The build plate then moves down in small increments and the liquid polymer is again exposed to light. The process repeats until the model is built. The liquid polymer is then drained from the vat, leaving the solid model. The ZBuilder Ultra[13] is an example of a DLP rapid prototyping system.

The Objet PolyJet system uses an inkjet printer to spray photopolymer materials in ultra-thin layers (16 micron) layer by layer onto a build tray until the part is completed. Each photopolymer layer is cured by UV light immediately after it is jetted, producing fully cured models that can be handled and used immediately, without post-curing. The gel-like support material, which is designed to support complicated geometries, is removed by hand and water jetting. Also suitable for elastomers.

Ultra-small features may be made by the 3D microfabrication technique of multiphoton 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, because of 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.[14]

Yet another approach uses a synthetic resin that is solidified using LEDs.[15]

[edit] Resolution

Resolution is given in layer thickness and X-Y resolution in dpi.[citation needed] Typical layer thickness is around 100 micrometres (0.1 mm), although some machines such as the Objet Connex series can print layers as thin as 16 micrometres.[16] X-Y resolution is comparable to that of laser printers. The particles (3D dots) are around 50 to 100 micrometres (0.05-0.1 mm) in diameter.

In some cases the printing method is able to deliver sufficient resolution for the application, but in many cases some extra work is required to shape the surface accurately or give a suitable finish by removing excess material (subtractive process).

[edit] Applications

“	Three-dimensional printing makes it as cheap to create single items as it is to produce thousands and thus undermines economies of scale. It may have as profound an impact on the world as the coming of the factory did....Just as nobody could have predicted the impact of the steam engine in 1750—or the printing press in 1450, or the transistor in 1950—it is impossible to foresee the long-term impact of 3D printing. But the technology is coming, and it is likely to disrupt every field it touches.	”
—The Economist, in a February 10, 2011 leader[17]

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

[edit] Research into new applications

Other applications would include reconstructing fossils in paleontology, replicating ancient and priceless artifacts in archaeology, reconstructing bones and body parts in forensic pathology and reconstructing heavily damaged evidence acquired from crime scene investigations.

By 2005, academic journals had begun reporting on the possible artistic applications of 3D printing technology.[18] By 2007 the mass media had followed, with an article in the Wall Street Journal[19] and Time Magazine listing a 3D printed design among their 100 most influential designs of the year.[20] During the 2011 London Design Festival, an installation, curated by Murray Moss and focused on 3D Printing, took place in the Victoria and Albert Museum (the V&A). The installation was called Industrial Revolution 2.0: How the Material World will Newly Materialise..[21]

As of 2012[update] 3D printing technology was 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 or sugar matrix and slowly built up to form three dimensional structures including vascular systems.[22] Several terms have been used to refer to this field of research: organ printing, bio-printing, and computer-aided tissue engineering, among others.[23] 3D printing can produce a personalized hip replacement in one pass, with the ball permanently inside the socket; at available printing resolutions the unit does not require polishing.

A proof-of-principle project at the University of Glasgow, UK, in 2012 has shown that it is possible to use 3D printing techniques to create chemical compounds, including new ones. They first print bespoke chemical reaction vessels, then use the printer to squirt reactants into them as "chemical inks" which then react.[24] They have produced new compounds to verify the validity of the process, although not seeking anything with a particular application.[24] They used the Fab@Home open source printer, at a stated cost of US$2,000.

The use of 3D scanning technologies allow the replication of real objects without the use of molding techniques, that in many cases can be more expensive, more difficult, or too invasive to be performed; particularly with precious or delicate cultural heritage artifacts[25] where the direct contact of the molding substances could harm the surface of the original object. Even a smartphone can be used as 3D scanner: at the 2012 Consumer Electronics Show, Sculpteo unveiled a mobile app that allows a 3D file to be generated directly with a smartphone.[26]

[edit] Industrial uses

[edit] Rapid prototyping

Industrial 3D printers have existed since the early 1980s, and have been used extensively for rapid prototyping and research purposes. These are generally larger machines that use proprietary powdered metals, casting media (i.e., sand), plastics or cartridges, and are used for many rapid prototyping uses by universities and commercial companies. Industrial 3D printers are made by companies such as ExOne, Objet Geometries, Stratasys, 3D Systems, EOS GmbH, and Z Corporation.

[edit] Rapid manufacturing

Advances in RP technology have brought about the ability to use materials that are appropriate for final manufacture. These advances in material use have brought about the prospects of directly manufacturing finished components. The advantages of 3D printing in rapid manufacturing lie in the relatively inexpensive production of small numbers of parts.

Rapid manufacturing is a new method of manufacturing, with many of its processes still unproven. 3D printing is now entering the field of rapid manufacturing and it is believed by many experts that this is a "next level" technology.[27] Some of the most promising processes are adaptations of well established rapid prototyping methods such as laser sintering (LS). However, due to the immaturity of 3D printing, these techniques are still very much in their infancy, and many obstacles still need to be overcome before RM can be considered as a realistic manufacturing choice.[28]

[edit] Domestic and hobbyist uses

Domestic 3D printing is mainly for hobbyists and enthusiasts as of 2012[update], rather than practical household applications. Designs such as a working clock have been made, not as a practical, or particularly accurate timepiece, but as an interesting project.[29]Gears have been printed for home woodworking machines[30] and other purposes.[31] 3D printing is also used for ornamental objects. One printer (the Fab@Home) makes a point of including chocolate amongst the materials that can be printed. Web sites associated with 3D printing tend to include backscratchers, coathooks, and so on. The RepRap Web site includes such examples. The Fab@Home gallery had many objects without practical application, but included examples of what is possible such as a flashlight/torch using conductive ink for the electrical circuit, a battery-powered motor, a case for an iPod, a silicone watch band, and a translucent cylinder completely enclosing a brown box, something difficult to fabricate any other way.[32]

The open source Fab@Home project[33] has developed printers for general use. They have been used in a research environment to produce chemical compounds with 3D printing technology, including new ones, initially without immediate application as proof of principle.[24] The printer can print with anything that can be dispensed from a syringe as liquid or paste. The developers of the chemical application envisage that this technology could be used both in industry and for domestic use, so that "people in far-flung regions could make their own headache pills or detergent. The technique might also allow people to print and share recipes for niche substances that chemical or pharmaceutical companies don't make – because there aren't enough customers, or they simply haven't dreamed up those ideas."[34]

[edit] Printers for domestic use

There are several projects and companies making efforts to develop 3D printers suitable for desktop use at a price many households can afford, many of which are related. Much of this work was driven by and targeted to DIY/enthusiast/early adopter communities, with links to both the academic and hacker communities.[35]

The RepRap is a one of the longest running projects in the Desktop category. The RepRap project aims to produce a free and open source software (FOSS) 3D printer, whose full specifications are released under the GNU General Public License, and which can print many of its own parts (the printed parts) to create more machines. As of November 2010, the RepRap can print plastic parts, and requires motors, electronics, and some metal support rods to be completed.[citation needed] Research is under way to enable the device to print circuit boards, as well as metal parts. Several companies and individuals sell parts to build various RepRap designs, the average price of a RepRap printer kit being €400 (US$537).[citation needed]

Because of the FOSS aims of RepRap, many related projects have used their design for inspiration, creating an ecosystem of many related or derivative 3D printers, most of which are also Open Source designs. The availability of these open source designs means that variants of 3D printers are easy to invent; however, the quality and complexity of various printer designs, as well as the quality of kit or finished products, varies greatly from project to project. These printers include the Airwolf 3D, fabbster, MakerBot Industries Thing-O-Matic, Ultimaker, Solidoodle 2, Shapercube, Mosaic, Prusa, Huxley, and Afinia 3D printers. This rapid development of open source 3D printers is gaining interest in both the developed as well as the developing world as it enables both hyper-customization and the use of designs in the public domain to fabricate open source appropriate technology through conduits such as Thingiverse. This technology can also assist in sustainable development as such technologies are easily and economically made from readily available resources by local communities to meet their needs.[36]

The open source Fab@Home project[33] has developed printers for general use which can use anything squirtable through a nozzle, from chocolate to silicon sealant and chemical reactants. Printers to the project's designs were available from suppliers in kit or assembled form at prices in the region of US$2000 as of 2012[update].

Many of these printers are available in kit form, and some are available fully assembled. The Solidoodle 2, a 6x6x6 inch printer is available fully assembled for US$499. Prices of printer kits vary from US$350 for the open source SeeMeCNC H-1, US$500 for the Printrbot, both derived from previous RepRap models, to US$2000 for the Makerbot Replicator (dual-extruder edition) which prints either two colors or abs/pla and a water-soluble support material.[citation needed]

[edit] Printers for commercial and domestic use

The development and hyper-customization of the RepRap-based 3D printers has produced a new category of printers suitable for both domestic and commercial use. The cheapest available machine in the assembled form is the Solidoodle 2 while the RepRapPro's offering of Huxley kit priced at around US$680 is one of the cheapest and reliable DIY kit. There are other high-end kits and fully assembled machines available like Ultimaker, Airwolf 3D AW3D v.4 and others which are RepRap-based machines enhanced to print at high speed and high definition. Depending on application, the degree of printing resolution and speed of manufacturing lies between a personal printer and an industrial printer. More information on a price comparison can be found here.

[edit] 3D printing services

Some companies offer an on-line 3D printing service open both to consumers and to industry.[37][38] People upload their own 3D designs to a 3D printing service company website, designs are printed via industrial 3D printers and then shipped to the customer.[39] Some examples of 3D printing services companies are Shapeways,[40] Kraftwurx,[41] i.materialise[42] and Freedom Of Creation.[43]Thingiverse of MakerBot Industries allows the sharing of 3D printing files and serves as a community resource.

[edit] History

In the history of manufacturing, and most especially of machining, subtractive methods have often come first. In fact, the term "subtractive manufacturing" is a retronym developed in recent years to distinguish traditional methods from the newer additive manufacturing techniques. Although fabrication has included methods that are essentially "additive" for centuries (such as joining plates, sheets, forgings, and rolled work via riveting, screwing, forge welding, or newer kinds of welding), it did not include the information technology component of model-based definition; and the province of machining (generating exact shapes with high precision) was generally a subtractive affair, from filing and turning through milling and grinding. For example, an encyclopedia article on threading today mentions both additive and subtractive methods as well as various integrations of the two, whereas an article on the same topic 20 years ago would not have contained the words "additive" and "subtractive" and would probably not have mentioned any additive techniques at all (let alone naming and differentiating them via use of those labels).

Additive manufacturing's earliest applications have been on the toolroom end of the manufacturing spectrum. For example, rapid prototyping was one of the earliest additive variants, and its mission was to reduce the lead time and cost of developing prototypes of new parts and devices, which was earlier only done with subtractive toolroom methods (typically slowly and expensively).[44] However, as the years go by and technology continually advances and disseminates into the business world, additive methods are moving ever further into the production end of manufacturing—sometimes even in ways that the pioneers of the techniques didn't foresee.[44] Parts that formerly were the sole province of subtractive methods can now in some cases be made more profitably via additive ones. Early examples of 3D printing occured in the 1980s, though the printers then were large, expensive and highly limited in what they could produce. [45]

Predictions for the future of commercial manufacturing, starting from today's already-begun infancy period, are that manufacturing firms will need to be flexible, ever-improving users of all available technologies in order to remain competitive. It is also predicted by some additive manufacturing advocates that this technological development arc will change the nature of commerce and globalisation, because end users will be able to do much of their own manufacturing rather than engaging in trade to buy products from other people and corporations. [45] However, the real integration of the newer additive technologies into commercial production is essentially a matter of complementing traditional subtractive methods rather than displacing them entirely.[46] As an example of a possible future application, an open source group emerged in the United States in 2012 that is attempting to design a firearm that may be downloaded from the internet and "printed" on a 3-D Printer.[47] The weapon would however still need bullets fabricated by traditional methods. Calling itself Defense Distributed, the group wants to facilitate "a working plastic gun that could be downloaded and reproduced by anybody with a 3D printer."[48]

[edit] Exhibits

Between 2011 and 2012 a 3D printing focused exhibit was held at Disseny Hub Barcelona. It was called Full Print3d. Printing Objects.The permanent exhibition, Full Print3d. Printing objects provided an introduction to digital fabrication through a series of projects that illustrate the conceptual implications of this type of production for design.[49]

[edit] References

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2. ^ "3D Printer Technology - Animation of layering". Create It Real. http://www.createitreal.com/index.php/en/3d-printer/48. Retrieved 2012-01-31. 
3. ^ Sherman, Lilli Manolis. "3D Printers Lead Growth of Rapid Prototyping (Plastics Technology, August 2004)". http://www.ptonline.com/articles/200408cu3.html. Retrieved 2012-01-31. 
4. ^ Reprinted, with permission, from ASTM F2792-10 Standard Terminology for Additive Manufacturing Technologies, copyright ASTM International, 100 Barr Harbor Drive, West Conshohocken, PA 19428. A copy of the complete standard can be obtained from ASTM International.
5. ^ D. T. Pham, S. S. Dimov, Rapid manufacturing, Springer-Verlag, 2001, ISBN 1-85233-360-X, page 6
6. ^ http://www.bath.ac.uk/pr/releases/replicating-machines.htm
7. ^ Sherman, Lilli Manolis (2007-11-15). "A whole new dimension - Rich homes can afford 3D printers (The Economist, November 15, 2007)". http://www.economist.com/theworldin/displaystory.cfm?story_id=10105016. Retrieved 2012-01-31. 
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10. ^ Fdm (Fused Deposition Modeling)
11. ^ Hiemenz, Joe. "Rapid prototypes move to metal components (EE Times, 3/9/2007)". http://www.eetimes.com/design/industrial-control/4013703/Rapid-prototypes-move-to-metal-components. Retrieved 2012-01-31. 
12. ^ "Rapid Manufacturing by Electron Beam Melting". SMU.edu. http://www.smu.edu/Lyle/Departments/ME/Research/CLAM/Research/Rapid_Manufacturing. Retrieved 2012-01-31. 
13. ^ "Zbuilder Ultra". 3D Systems. http://www.zcorp.com/en/Products/Rapid-Prototyping-Machines/ZBuilder--andtrade--Ultra/spage.aspx. Retrieved 2012-01-31. 
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15. ^ "The World’s Smallest 3D Printer". TU Wien. 12 September 2011). http://amt.tuwien.ac.at/projekte/micro_printer. Retrieved 2012-01-31. 
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18. ^ Séquin, Carlo H.. "Rapid prototyping: a 3d visualization tool takes on sculpture and mathematical forms (Communications of the ACM - 3d hard copy, Volume 48 Issue 6, June 2005, pp. 66-73)". http://dl.acm.org/citation.cfm?doid=1064830.1064860. Retrieved 2012-01-31. 
19. ^ Guth, Robert A.. "How 3-D Printing Figures To Turn Web Worlds Real (The Wall Street Journal, December 12, 2007)". http://www.zcorp.com/documents/194_2007-1212-Wall%20Street%20Journal-3DP%20Turns%20Web%20World%20Real.pdf. Retrieved 2012-01-31. 
20. ^ Bathsheba Grossman's Quin.MGX for Materialise listed in Time Magazine's Design 100
21. ^ Williams, Holly (2011-08-28). "Object lesson: How the world of decorative art is being revolutionised by 3D printing (The Independent, 28 August 2011)". London. http://www.independent.co.uk/arts-entertainment/art/features/object-lesson-how-the-world-of-decorative-art-is-being-revolutionised-by-3d-printing-2342500.html. Retrieved 2012-01-31. 
22. ^ "3D-printed sugar network to help grow artificial liver", BBC, 2 July 2012.
23. ^ Silverstein, Jonathan. "’Organ Printing’ Could Drastically Change Medicine (ABC News, 2006)". http://abcnews.go.com/Technology/story?id=1603783&page=1. Retrieved 2012-01-31. 
24. ^ a b c MD Symes et al., Integrated 3D-printed reactionware for chemical synthesis and analysis, Nature Chemistry 4,349–354 (2012), doi:10.1038/nchem.1313
25. ^ Cignoni, Paolo; Scopigno, Roberto (June 2008). "Sampled 3D models for CH applications: A viable and enabling new medium or just a technological exercise?" (PDF). Association for Computing Machinery (ACM) Journal on Computing and Cultural Heritage 1 (1): 1. doi:10.1145/1367080.1367082. http://vcg.isti.cnr.it/Publications/2008/CS08/. 
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27. ^ Wohlers Report 2009, State of the Industry Annual Worldwide Progress Report on Additive Manufacturing, [create ihttp://www.wohlersassociates.com/ Wohlers Associates], ISBN 0-9754429-5-3
28. ^ Hopkinson, N & Dickens, P 2006, 'Emerging Rapid Manufacturing Processes', in Rapid Manufacturing; An industrial revolution for the digital age, Wiley & Sons Ltd, Chichester, W. Sussex
29. ^ 3D printed clock and gears
30. ^ 3D printed planetary gears
31. ^ Successful Sumpod 3D printing of a herringbone gear
32. ^ Fab@Home gallery of objects made
33. ^ a b New Scientist magazine: Desktop fabricator may kick-start home revolution, 9 January 2007. Online edition available to subscribers
34. ^ New Scientist magazine: Make your own drugs with a 3D printer, 17 April 2012. Online edition available to subscribers
35. ^ Kalish, Jon. "A Space For DIY People To Do Their Business (NPR.org, November 28, 2010)". http://www.npr.org/templates/story/story.php?storyId=131644649. Retrieved 2012-01-31. 
36. ^ Pearce, Joshua M.; et al.. "3-D Printing of Open Source Appropriate Technologies for Self-Directed Sustainable Development (Journal of Sustainable Development, Vol.3, No. 4, 2010, pp. 17-29)". http://www.ccsenet.org/journal/index.php/jsd/article/view/6984. Retrieved 2012-01-31. 
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40. ^ Drell, Lauren. "Everything you wanted to know about 3D printing but were too afraid to ask (mashable.com, February 28, 2012)". http://mashable.com/2012/02/28/3d-printing-shapeways/. 
41. ^ "Kraftwurx, more than just a 3D printing service". 3Ders. November 25, 2011. http://www.3ders.org/articles/20111125-kraftwurx-more-than-just-a-3d-printing-service.html. Retrieved 2012-01-29. 
42. ^ Evans, John. "3D Printing - i.Materialise service offers Titanium (Design & Motion, January 19, 2011)". http://designandmotion.net/rapid-prototyping/3d-printing-i-materialise-offers-titanium/. Retrieved 2012-01-29. 
43. ^ Terdiman, Daniel. "3D printing creating 'a whole new world' (CNET News, June 20, 2011)". http://news.cnet.com/8301-13772_3-20072236-52/3d-printing-creating-a-whole-new-world/. Retrieved 2012-01-29. 
44. ^ a b Vincent & Earls 2011.
45. ^ a b Jane Bird (2012-08-08). "Exploring the 3D printing opportunity". The Financial Times. http://www.ft.com/cms/s/0/6dc11070-d763-11e1-a378-00144feabdc0.html#axzz24gFn5Cal. Retrieved 2012-08-30 (registration required). 
46. ^ Albert 2011.
47. ^ Greenberg, Andy (2012-08-23). "'Wiki Weapon Project' Aims To Create A Gun Anyone Can 3D-Print At Home". Forbes. http://www.forbes.com/sites/andygreenberg/2012/08/23/wiki-weapon-project-aims-to-create-a-gun-anyone-can-3d-print-at-home/. Retrieved 2012-08-27. 
48. ^ Poeter, Damon (2012-08-24). "Could a 'Printable Gun' Change the World?". PC Magazine. http://www.pcmag.com/article2/0,2817,2408899,00.asp. Retrieved 2012-08-27. 
49. ^ Full Print3d. Printing Objects

[edit] See also

[edit] Bibliography

• Vincent; Earls, Alan R. (February 2011). "Origins: A 3D Vision Spawns Stratasys, Inc. Today's Machining World's new feature "Origins" tells us the stories of how successful technologies, companies and people got their start. This month we interview a pioneer of rapid prototyping technology, Scott Crump, the founder and CEO of Stratasys Inc". Today's Machining World (Oak Forest, Illinois, USA: Screw Machine World Inc) 7 (1): 24–25. http://www.todaysmachiningworld.com/origins-a-3d-vision-spawns-stratasys-inc/. 
• Albert, Mark [Editor in Chief] (2011-01-17). "Subtractive plus additive equals more than ( − + + = > ): subtractive and additive processes can be combined to develop innovative manufacturing methods that are superior to conventional methods ['Mark: My Word' column—Editor's Commentary"]. Modern Machine Shop (Cincinnati, Ohio, USA: Gardner Publications Inc) 83 (9): 14. http://www.mmsonline.com/columns/subtractive-plus-additive-equals-more-than. 

[edit] Further reading

• Easton, Thomas A. (November 2008). "The 3D Trainwreck: How 3D Printing Will Shake Up Manufacturing". Analog 128 (11): 50–63. 
• Wright, Paul K. (2001). 21st Century Manufacturing. New Jersey: Prentice-Hall Inc.

[edit] External links