What is 3D Printing? An Overview.

September 15, 2012

There are a variety of very different types of 3D printing technologies, but they all share one core thing in common: they create a three dimensional object creating it layer by successive layer, until the entire object is complete.

Each of these layers is a thinly sliced, horizontal cross-section of the eventual object. Imagine a multi-layer cake, with the baker laying down each layer one at a time until the entire cake is formed. 3D printing is similar, but just a bit more precise than 3D baking.

It Begins with a Digital File

Each 3D-printed object begins with a digital Computer Aided Design (CAD) file, created with a 3D modeling program, or which was scanned into a 3D modeling program with a 3D scanner. To get from this digital file into instructions that the 3D printer understands, software then slices the design into hundred or thousands of horizontal layers.

The 3D printer reads this file, and proceeds to create each layer exactly to specification. As the layers are created, they blend together with no hint of the layering visible, resulting in one three dimensional object.

Off to the 3D Printer

An Objet 3D Printer and its workflow

The 3D printer could be a Fused Deposition Modeling (FDM) printer, somewhat similar to current 2D inkjet printers but with an additional axis, which deposits droplets of melted material through a nozzle to form each layer. It could be a selective laser sintering (SLS) printer, where the object is built up in a bed of powdered material by a scanning laser beam that fuses bits of the powder together, again, one layer at a time. Or it could be one of several other technologies.

3D printing is also called “additive manufacturing,” using an “additive process.” This is as opposed to what is called a “subtractive process.” To explain the difference, imagine a sculptor chiseling a block of stone — he chips away until he has the sculpture just as he wants it, and then throws out what’s been whittled away. He began with block of material and then subtracted from it. This is a subtractive process. In the manufacturing world, this is analogous to material being cut, drilled, milled or machined off. But in additive manufacturing, the 3D printer doesn’t take anything away — it simply creates each bit of the object where it needs it, layer by layer, successively, in an additive process.

Commercial 3D printers

While most people have yet to even hear the term 3D printing, the process has been in use for decades. Manufacturers have long used the printers in the design process, to create prototypes for traditional manufacturing. But until the last few years, the equipment has been expensive and slow.

Now, fast 3D printers can be had for tens of thousands of dollars, and end up saving the companies many times that amount in the prototyping process. For example, Nike uses 3D printers to create multi-colored prototypes of shoes. They used to spend thousands of dollars on a prototype and wait weeks for it. Now, the cost is only in the hundreds of dollars, and changes can be made instantly on the computer and the prototype reprinted on the same day.

Some companies are using 3D printers for short run or custom manufacturing, where the printed objects are not prototypes, but the actual end user product. As the speeds of 3D printing go up and their price comes down, look for more and more of this. And expect more availability of personally customized products.

Personal 3D Printers

A Huxley RepRap 3D printer that has printed out its own parts.

So far we’ve only talked about commercial 3D printers. There is a whole other world of 3D printers: personal and DIY hobbyist models. And they are getting cheap, with prices typically in the range of $300 – $2,000.

The RepRap open source project really ignited this hobbyist market in the same way the Apple I microcomputer ignited the hobbyist desktop computer market in the late 1970s. For about a thousand dollars, people have been able to buy the RepRap kit and put together their own personal 3D printer, complete with any customizations they were capable of making. And what’s more, these printers print most of the parts for more printers. Complete self-replication, including electronic circuit boards, is the goal.

The interest in RepRap spawned scores of other low-cost 3D printers, both DIY and fully-assembled, and as the prices keep coming down, it puts 3D printers into more and more and more hands.

But do you have to be an engineer or a 3D modeling expert to create 3D models on your own 3D printer? No, not at all. While complex and expensive CAD software like AutoCAD and Solidworks have a steep learning curve, there are a number of other programs, many free, that are very easy to learn. The free version of Google SketchUp, for example, is very popular for its ease of use; and the free Blender program is popular for its advanced features.

If you don’t have your very own 3D printer, not to worry, there are 3D printing service bureaus like Shapeways and Ponoko that can very inexpensively print and deliver an object from a digital file that you simply upload to their user-friendly website. It’s almost as easy as ordering a custom t-shirt from Cafepress or Zazzle.

Even if you don’t design your own 3D model, you can still print some very cool pieces. There are model repositories such as Thingiverse, 3D Parts Database and 3D Warehouse that have model files you can download for free.

What do all these people print? It’s limitless. Some print things like jewelry, some print replacement parts for appliances such as their dishwasher, some invent all sorts of original things, some create art, and some make toys for their kids. With the many types of metal, plastic, glass and other materials available (even gold and silver), just about anything can be printed.

3D Printing Methods

Stereolithography (SLA)

3D Systems explains the process of Stereolithography

The first commercially available 3D printer (not called a 3D printer back then) used the stereolithography (SLA) method. This was invented in 1986 by Charles Hull, who also at the time founded the company, 3D Systems. A SLA 3D printer works by concentrating a beam of ultraviolet light focused onto the surface of a vat filled with liquid photocurable photopolymer (resin). The UV laser beam draws out the 3D model one thin layer at a time, hardening that “slice” of the eventual 3D model as the light hits the resin. Slice after slice is created, with each one bonded to the other, and next thing you know you have a full, extremely high-resolution three dimensional model lifted out of the vat. Unused resin is reusable for the next job.

Fused Deposition Modeling (FDM)

Stratasys explains Fused Deposition Modeling at a trade show

Also invented in the late 1980′s, by Scott Crump, was Fused Deposition Modeling (FDM) technology. With patent in hand, he and his wife founded Stratasys in 1988. With FDM, the object is produced by extruding small beads of melted thermoplastic material to form layers as the material hardens immediately after it leaves the extrusion nozzle. It is one of the lesser expensive 3D printing methods. Most FDM printers print with ABS plastic (think Lego), as well as PLA (Polylactic acid), a biodegradable polymer, which is produced from organic material.

The actual term “Fused Deposition Modeling” and its abbreviation “FDM” are trademarked by Stratasys. RepRap uses a similar process, but has called it “Fused Filament Fabrication” (FFF), so as to not step on the trademark. With FFF, the material is fed via filament from a spool of the material.

Selective Laser Sintering (SLS)

3D Systems demonstrates the SinterStation Pro SLS 3D printer

The 1980′s were big for inventing 3D printing technologies. Not only were SLA and FDM invented and patented then, but so was Selective Laser Sintering (SLS), by Carl Deckard and colleagues at the University of Texas in Austin. SLS works similarly to SLA, but instead of liquid photopolymer in a vat, you’ll find powered materials, such as polystyrene, ceramics, glass, nylon, and metals including steel, titanium, aluminum and silver. When the laser hits on the powder, it is fused at that point (sintered). All unsintered powder remains as is, and becomes a support structure for the object. The lack of necessity for any support structure with SLS is an advantage over SLS over SLA — none to remove after the model is complete, and no extra waste was created. All unused powder can be used for the next printing.

Other Methods

There are other variants of these technologies. For example there is Selective Laser Melting (SLM), which is like SLS but fully melts the power rather than just fusing the powder granules under lower temperature. This is similar to Electron Beam Melting (EBM) which is uses an electron beam instead of a UV laser. And then there is a completely different technology called Laminated Object Manufacturing (LOM), where layers of adhesive-coated paper, plastic, or metal laminates are successively glued together and cut to shape with a knife or laser cutter.

3D Printing is a Game Changer

Instantly printing parts and entire products, anywhere in the world, is a game changer. But it doesn’t stop there. 3D printing will affect almost every aspect of industry and our personal lives.

Medicine will forever be changed as new bioprinters actually print human tissue for both pharmaceutical testing and eventually entire organs and bones.

Architecture and construction are changing as well. Now, 3D-printed models of complex architectural drawings are created quickly and inexpensively, rather than the expensive and time-consuming process of handcrafting models out of cardboard. And experimental, massive 3D printers are printing concrete structures, with the goal of someday building entire buildings with a 3D printer.

Art is already forever changed. Digital artists are creating magnificent pieces that seem almost impossible to have been made by traditional methods. From sculptures to light fixtures, beautiful objects no longer need to be handcrafted, just designed on a computer.

And there are developments where you least expect them: for example, archeologists can 3D scan priceless and delicate artifacts, and then print copies of them so they can handle them without fear of breakage. Replicas can be easily made and distributed to other research facilities or museums. It has been used to create a full-size reproduction of King Tutankhamun’s mummy and to repair Rodin’s sculpture, The Thinker.

The Future of 3D Printing

This is a disruptive technology of mammoth proportions, with effects on energy use, waste, customization, product availability, art, medicine, construction, the sciences and of course manufacturing. It will change the world as we know it. Before you know it.

Source: 3dprinter.net

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