3D printing

For methods of applying a 2-D image on a 3-D surface, see Pad printing.

3D printing is a unique form of fabrication that is related to traditional rapid prototyping technology. A three dimensional object is created by layering and connecting successive cross sections of material. 3D printers are generally faster, more affordable and easier to use than other additive fabrication technologies. While prototyping dominates current uses, 3D printers offers tremendous potential for retail consumer uses.

This technology is commonly used in the jewellery, footwear, industrial design, architecture, automotive and medical industries.

Simple Description

Take a 3 dimensional computer drawing, slice it into many very thin layers horizontally, send the layers to a machine that will resemble the following.

A square box with a bottom that can be lowered in sub mm increments, fill the box with powder (usually plaster) drag a roller across the top and make it flat, print an image of a single slice of the object, on the top layer, lwer the bottom of the box, roll another layer of powder on top of this, drag the roller across it and print another image slice, repeat this process until all the layers have been printed, remove excess powder and recover the printed plaster model.

some machines have more than one inkjet printer head, one prints a liquid that sticks the layers together, the other one or more have colour and print the colours of the model around the edges of the profile.

Technologies

Previous means of producing a prototype typically took man-hours, many tools, and skilled labor. For example, after a new street light luminaire was digitally designed, drawings were sent to skilled craftsmen 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. 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 stereo lithography 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 by soaking them in various types of resins including super glue. Artists have been using 3d printers on various ways.</ref>

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.

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.

RepRap open source 3d printer

Main article: RepRap

RepRap is a project released under the GNU General Public License that can 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."

Equipment

3D Printers in action

In the 1990’s the advent of rapid prototyping allows these costs to be reduced so companies can create 3d models fast and effectively. However only in recent years have 3D printers been 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 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.

Advantages of 3D printers

• 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.

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 thermodynamics sets that are cured with different technologies. In the case of lamination systems, thin layers are cut to shape and joined together.

Prototyping technologies and their base materials

1. Selective laser sintering (SLS) - Thermoplastics, metals powders
2. Fused Deposition Modeling (FDM) - Thermoplastics, Eutectic metals
3. Stereolithography (SLA) - Photopolymer
4. Laminated Object Manufacturing - Paper
5. Electron Beam Melting (EBM) - Titanium alloys
6. 3D Printing (3DP) - Various materials

See also

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

References

Bibliography

• Grenda, E. (2006). The Most Important Commercial Rapid Prototyping Technologies at a Glance.
• Wright, Paul K. (2001). 21st Century manufacturing. New Jersey: Prentice-Hall Inc.
• Wohlers, T. (2007). Rapid Prototyping Terms and Descriptions.
• Objet introduces PolyJet Matrix technology (2007). “[2].”

External links

• 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