3-D Printing

 

Nano-3D Printing at it’s finest!

 

3D printing or additive manufacturing  is a process of making three dimensional solid objects from a digital file. 3D printing is achieved using additive processes, where an object is created by laying down successive layers of material. 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. The technology also finds use in the fields of jewelry, footwear, industrial design, architecture, engineering and construction (AEC), automotive, aerospace, dental and medical industries, education, geographic information systems, civil engineering, and many others.

Terminology

Additive manufacturing (AM) also known as 3D printing 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 fabricationadditive processesadditive techniquesadditive layer manufacturinglayer manufacturing and freeform fabrication“.

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.

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.

Technologies

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 are melting or softening material to produce the layers (SLS, FDM) where others are laying liquid materials thermosets that are cured with different technologies. In the case of lamination systems, thin layers are cut to shape and joined together.

As of 2005, conventional additive rapid prototype machines cost around £25,000.

Additive technologies                                             Base materials

Selective laser sintering (SLS)                                     Thermoplastics, metals powders, ceramic powders

Direct metal laser sintering (DMLS)                          Almost any alloy metal

Fused deposition modeling (FDM)                             Thermoplastics, eutectic metals

Stereolithography (SLA)                                                 Photo polymer

Laminated object manufacturing (LOM)                  Paper

Electron beam melting (EBM)                                       Titanium alloys

Powder bed, inkjet head 3d printing,                         Plaster, Colored Plaster
and Plaster-based 3D printing (PP)

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. stereo-lithography (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. Generally, the main considerations are speed, cost of the printed prototype, cost of the 3D printer, choice and cost of materials and colour capabilities.

Molten polymer deposition

Fused deposition modeling (FDM) is a technology developed by Stratasys 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) etc.

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.

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 is the only one that allows for the printing of full colour prototypes. This method also allows overhangs, as well as elastomer parts. 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.

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 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.

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

Resolution

Resolution is given in layer thickness and X-Y resolution in dpi. 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.  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 to give a suitable finish using a traditional subtractive process.

Applications

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

entertainment/retail. 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. Artists have been using 3D printers in various ways. 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 Materialize.

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. 3D printing can produce a personalized 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 where the direct contact of the molding substances could harm the surface of the original object. Even smartphone can be used as 3D scanner: at the 2012 Consumer Electronics Show, Sculpteo unveiled a mobile app that allows people to directly generate 3D file using a smartphone such as the iPhone.

Industrial use

Rapid prototyping

Main article: 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.

Rapid manufacturing

Rapid manufacturing is a new method of manufacturing, with many of its processes still unproven. 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. 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, however, many obstacles still need to be overcome before AM can be considered as a realistic manufacturing choice.

3D printing is now entering the field of rapid manufacturing and it is believed by many experts that this is a “next level” technology. The advantages of 3D printing in rapid manufacturing lie in the relatively inexpensive production of small numbers of parts.

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.

The RepRap is a one of the longest running projects in the Desktop category. The RepRap project aims to produce a 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. 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).

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. Unfortunately 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 fabbster, MakerBot Industries Thing-O-Matic, Ultimaker, Shapercube, Mosaic, Prusa and Huxley 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, which can assist in sustainable development as such technologies are easily and economically made from readily available resources by local communities to meet their needs.

Many of these printers are available in kit form, and some are available as completed products. 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.

3D printing services

Some companies offer an on-line 3D printing service open both to consumers and to industry. 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. Some examples of 3D printing services companies are Shapeways, Kraftwurx, i. materialize and Freedom Of Creation. Thingiverse of MakerBot Industries allows the sharing of 3D printing files and serves as a community resource.

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 todaymentions 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). 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. Parts that formerly were the sole province of subtractive methods can now in some cases be made more profitably via additive ones. However, the real integration of the newer additive technologies into commercial production is essentially a matter of complementing subtractive methods rather than displacing them entirely. 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, 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.


Advertisements
Published on April 27, 2012 at 9:32 am  Leave a Comment  

The URI to TrackBack this entry is: https://socialnomicsingularity.wordpress.com/3-d-printing/trackback/

RSS feed for comments on this post.

Leave a Reply

Please log in using one of these methods to post your comment:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: