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3D Technologies

3D Printers

3D printers might look like something from the future, but they already serve as fundamental tools for many industries. These machines use an additive process to create functional objects from digital files. Their versatile extruders can lay out intricate designs for use in all sorts of situations.

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How Does a 3D Printer Work: The Basics

The printing process can be understood as a few simple steps. It starts with a digital designer. This person creates the blueprint for the project. Once this happens, the 3D printer uses the digital design as a guide. The machine pushes molten plastic through an extruder and layer by layer the object takes shape. When it finishes, the designer can pry the finished prototype from the build plate and clean it up.

How Does a 3D Printer Work: Layers

3D printers rely on computer-aided design (CAD) software to determine the shape and size of a print. Once created, the 3D file goes through a digital slicing process, which cuts the model into printable layers. These printers then use this sliced layer information to determine how much material to extrude and where exactly the material needs to go. They extrude the patterns one layer at a time until the 3D print finishes building.

This additive-build model remains the most common style of 3D printing available, but stereo lithography printers produce similar results. With stereo lithography, the printer controls exposure to a light-sensitive material, solidifying one layer at a time.

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How Does a 3D Printer Work: Print Speed

This building process can take many hours, no matter the style of 3D printer you use. The speed of the printing process depends on the size and complexity of the print. 3D printing software controls the density of the object, and most models use a honeycomb pattern to fill the interior of the print. This process doesn’t require nearly as much filament as full, flat layers and increases the object’s overall print speed.

The density of the interior is not the only factor to consider when creating a 3D file. When you slice a 3D design, you can choose the thickness of the print layers, also referred to as print resolution. Thick layers print faster than thin layers, but they also result in a blockier look for the finished print. Thin layers allow the 3D printer to create much smoother prints, but they can take significantly longer to finish.

What Materials Do 3D Printers Use?

Nowadays, you can purchase plastic filament online. While many consumer 3D printers use some form of plastic, industrial printers can extrude and manipulate many other materials such as wood, nylon, copper and various high-quality plastics. The availability of these alternate materials allows for immense versatility. Some industrial 3D printers even extrude wax, which melts away when cast with metal. Some industrial 3D printers even sinter metal powder into rigid structures.

This wide variety of workable materials ensures that 3D printers work as valuable assets for all sorts of projects. Industries that rely on highly specialized machine parts use them to create replacements and those that rely on working prototypes or short-run products use 3D printers for simple manufacturing.

Now let’s take a look at some of the more popular technologies behind 3D printing:

Fused Deposition Modeling (FDM)/Fused Filament Fabrication (FFF):

Fused Deposition Modeling (FDM) was invented by a man named S. Scott Crump a few years after Chuck Hull initially invented 3D printing. Crump went on to commercialize the technology in 1990 via Stratasys, which actually has a trademark on the term. This is why the same general technology is often referred to as Fused Filament Fabrication (FFF).32

Basically the way in which this technology works is rather simple, and this is the reason why 95% of all desktop 3D printers found within homes and garages today utilize FDM/FFF. A thermoplastic such as PLA or ABS is fed into an extruder and through a hotend. The hotend then melts the plastic, turning it into a gooey liquid. The printer then acquires its instructions from the computer via G-code and deposits the molten plastic layer by layer until an entire object is fabricated. The plastic melts rather rapidly, providing a solid surface for each additional layer’s deposition.

Depending on the maximum temperature of the hotend as well as other variables, numerous other materials besides ABS and PLA may be used, including composites of both materials, nylon, and more.

Stereo lithography (SLA):

As we’ve mentioned above, this was the very first 3D printing technology to be invented in 1986. With 3D Systems holding many of the patents involving this technology, which are in the process of 33expiring over the next few years, there has not been a tremendous amount of competition within the market. This means that the technology has been overpriced and used less often than the FDM/FFF alternative has.

Instead of extruding a material out of a hotend, the SLA process works with a laser or DLP projector combined with a photosensitive resin. Objects are printed in a vat of resin as a laser or other lighting source like a projector slowly cures (hardens) the resin layer-by-layer as the object is formed. Typically SLA machines are able to achieve far better accuracy and less of a layered appearance than FDM/FFF technology can.

Selective Laser Sintering (SLS)/Selective Laser Melting (SLM)/Direct Metal Laser Sintering (DMLS):

All three of these technologies are very similar, yet have marked differences. We’ve found that many individuals use the terms interchangeably when, in fact, there are reasons to use one method over the others. Both Selective Laser Sintering (SLS) and Direct Metal Laser Sintering (DMLS) are in fact the same technology. The 34difference in terminology is based on the materials used. DMLS specifically refers to the layer-by-layer sintering of metal powders using a laser beam, while SLS is simply the same process but with non-metal materials such as plastics, ceramics, glass, etc. Both DMLS and SLS do not fully melt the materials, instead sintering them or fusing them together at the molecular level. When dealing with metals, DMLS is ideal for metal alloys, as the molecules have varying melting points, meaning a full melt can sometimes be difficult to achieve.

On the other hand, when dealing with metals consisting of one material, for instance titanium, Selective Laser Melting (SLM) is the way to go as a laser is able to completely melt the molecules together. All three processes are currently expensive, and out of the budgets of most individuals and even small businesses because of the high powered laser beams that are required. Additionally safety precautions must be taken, meaning additional expenses on the part of the user.

PolyJetting:

A technology invented by the Israeli company Objet, which merged with Stratasys back in 2012, PolyJetting incorporates elements of both inkjet 2D printing and the Stereolithography process. Basically, inkjet nozzles spray a a liquid photosensitive resin onto a build platform in a similar fashion as ink is sprayed onto a piece of paper during a typical 2D printing process. Immediately following the ejection of the material a UV light source is introduced to the material, quickly curing it before the next layer of photosensitive liquid is sprayed on top. The process repeats until an entire object is fabricated. Stratasys currently uses such technologies within their popular Connex family of machines.

Plaster Based 3D Printing (PP)

This is a process requiring the use of two different materials: a powder material (gypsum plaster, starch, etc.) that sits on a print bed, along with a binding ink which is ejected from a nozzle similar35 to that of an inkjet printer onto the bed of powder, hardening it. Once one layer of powder is binded, a rake-like instrument sifts additional powder over that layer and the process continues until an entire object is fabricated. This technology was originally invented at MIT in the early ’90s before being commercialized in 1995 by a company called Z Corporation, which was acquired in 2011 by 3D Systems for $137 million.

Others:

Every week it seems as though new approaches are presented for 3D printing. There are new technologies which have recently been unveiled like that of HP’s Multi Jet Fusion, as well as Carbon3D’s CLIP technology. As we move into the next several years it will be interesting to see which such technologies take hold and which may fall by the wayside.

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