3D printing

3D printing is a form of additive manufacturing technology where a three dimensional object is created by successive layers of material^[1]. 3D printers are generally faster, more affordable and easier to use than other additive manufacturing technologies. 3D printers offer product developers the ability to print parts and assemblies made of several materials with different mechanical and physical properties in a single build process. Advanced 3D printing technologies yield models that closely emulate the look, feel and functionality of product prototypes.

In recent years 3D printers have become financially accessible to small- and medium-sized business, thereby taking prototyping out of the heavy industry and into the office environment. It is now also possible to simultaneously deposit different types of materials.

3D printers offer tremendous potential for production applications as well.^[2] The technology also finds use in the jewellery, footwear, industrial design, architecture, engineering and construction (AEC), automotive, aerospace, dental and medical industries.

[edit] Technologies

Previous means of producing a prototype typically took many hours, tools, and skilled labor. For example, after a new street light luminaire was digitally designed, drawings were sent to skilled craftspeople where the design on paper was painstakingly followed and a three-dimensional prototype was produced in wood by utilizing an entire shop full of expensive wood working machinery and tools. This typically was not a speedy process and costs of the skilled labor were not cheap, hence the need to develop a faster and cheaper process to produce prototypes. As an answer to this need, rapid prototyping was born.

One variation of 3D printing consists of an inkjet printing system used by Z Corporation. A 3D CAD file is imported into the software. The software slices the file into thin cross-sectional slices, which are fed into the 3D printer. 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 is the only one that allows for the printing of full colour prototypes. It is also recognized as the fastest method.

Alternately, in DLP, or Digital Light Projection, a 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 is an example of a DLP rapid prototyping system.

Fused deposition modeling (FDM), a technology developed by Stratasys^[3] that is 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. Typically a laser is used to sinter the media and form the solid. Examples of this are SLS (Selective laser sintering) and DMLS (Direct Metal Laser Sintering), using metals.

Finally, ultra-small 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.^[4]

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.^[5] Generally, the main considerations are speed, cost of the printed prototype, cost of the 3D printer, choice of materials, colour capabilities, etc.^[6]

Unlike stereolithography, inkjet 3D printing is optimized for speed, low cost, and ease-of-use, making it suitable for visualizing during the conceptual stages of engineering design through to early-stage functional testing. No toxic chemicals like those used in stereolithography are required, and minimal post printing finish work is needed; one need only to use the printer itself to blow 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.

The democratization of 3D printing is evolving in two streams, firstly with DIY 3D Printers such as MakerBot and RepRap for home 'desktop manufacturing'. The second stream is through online services such as Shapeways that allow users to upload their designs to have them 3D printed in a wide range of materials (currently 20 material options) and shipped worldwide. The creation of tools that enable 3D printing without the direct use of CAD are also currently being implemented.

[edit] Resolution

Resolution is given in layer thickness and X-Y resolution in dpi. Typical layer thickness is around 100 micrometres (0.1 mm), while 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.

[edit] Applications

An example of real object replication by means of 3D scanning and 3D printing: the gargoyle model on the left was digitally acquired by using a 3D scanner and the produced 3D data was processed using MeshLab. The resulting digital 3D model, shown on the laptop's screen, was used by a rapid prototyping machine to create a real resin replica of the original object

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

More recently, the use of 3D printing technology for artistic expression has been suggested.^[7] Artists have been using 3D printers in various ways.^[8]

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.^[9] 3D printing can produce a personalised hip replacement in one pass, with the ball permanently inside the socket, and even at current printing resolutions the unit will not require polishing.

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.

Future applications may allow many of the familiar pieces of furniture in a contemporary home to be replaced by the combination of a 3D printer and a recycling unit. Clothing, crockery, cutlery and books can already all be printed on demand and recycled after use, meaning that wardrobes, washing machines, dishwashers, cupboards and bookshelves may eventually become redundant.

[edit] RepRap

RepRap is a project released under the GNU General Public License which aims to produce an open source self-replicating rapid prototyper; that is, a 3D printer which can print a copy of itself. It can currently only print plastic parts. Research is underway that will let it print circuit boards as well as details in metal. The creator said about the printer that "We want to make sure that everything is open, not just the design and the software you control it with, but the entire tool-chain, from the ground up." ^[10]

[edit] Advantages

• 3D printing improves the iterative design process, enhancing communication and understanding of design intent among all stakeholders
• On-the-fly modeling enables the creation of prototypes that closely emulate the mechanical properties of the target design
• Some technologies allow the combination of black and white rigid materials in order to create a range of grayscales suitable for consumer electronics and other applications
• Save time and cost by removing the need to design, print and ‘glue together’ separate model parts made with different materials in order to create a complete model.
• Online 3D printing services allow for a broad range of materials to be 3D printed and delivered worldwide with no investment cost.

[edit] Equipment

A large number of competing technologies are available in the marketplace. As all are additive technologies, 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 (SLS, FDM) where others lay liquid materials that are cured with different technologies. In the case of lamination systems, thin layers are cut to shape and joined together.

A comparison of two ceramic art objects. The original was created by John Balistreri and then duplicated using a 3D Scanner and printed using 3D Ceramic Rapid Prototyping.

[edit] Prototyping technologies and their base materials

1. Selective laser sintering (SLS): Thermoplastics, metals, sand, glass
2. Fused Deposition Modeling (FDM): Thermoplastics
3. Digital Light Projection (DLP): Photopolymer
4. Stereolithography (SL): Photopolymer
5. Lamination systems: Paper and plastic
6. Electron Beam Melting (EBM): Titanium alloys
7. 3D Printing (3DP): Various materials, including resins
8. 3D Ceramic Printing: Various clay and ceramic materials

In 2006, John Balistreri and others at Bowling Green State University began research into 3D Rapid Prototyping machines, creating printed ceramic art objects. This research has led to the invention of ceramic powders and binder systems that enable clay material to be printed from a computer model and then fired for the first time.

[edit] Comparison of 3D Printers

[edit] See also

Design portal

• Desktop manufacturing
• Digital fabricator
• Direct digital manufacturing
• Instant manufacturing, also known as "direct manufacturing" or "on-demand manufacturing"
• List of emerging technologies
• Rapid manufacturing
• Self-replicating machine
• Solid freeform fabrication

[edit] References

[edit] Further reading

• Easton, Thomas E. (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

Wikimedia Commons has media related to: 3D printing

• Business Week: Printing in 3D Gets Practical
• Something Completely Different - 3D Printing
• Times Online article - Microtrends: 3D Printing
• Technical Articles on 3D printing
• 3D printer reshapes world of copying
• 3D Printing for the Masses
• 'Gadget printer' promises industrial revolution New Scientist
• A Factory on Your Desk