Monday, April 17, 2017

A Three-Dimensional Look at 3D Printing Processes

By Russell Miles


A spaceship model that I created using our Makerbot Replicator FDM printer.


If you've been following the Hack Shack blog for a while, you've probably read a lot about 3D printers. Along with the basics of 3D modeling, we have talked about 3D printed food and 3D printed prosthetics. However, we haven't gone into detail about how our own 3D printer works.

All 3D printers have a few things in common. Nearly all of them use files from Computer Assisted Design (CAD) programs as blueprints to create objects. Most 3D printers build objects piece by piece, either in layers or in small sections. Aside from these few similarities, 3D printers can be vastly different from each other. Let's take a look a few of the most common 3D printing processes and the steps they take to create a finished product.


Fused Deposition Modeling (FDM)

The MakerBot Replicator, which can be seen in the ORHS Hack Shack (image source).
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Fused Deposition Modeling, the most common type of 3D printing, is used in the Hack Shack's MakerBot Replicator. FDM printers use heated plastic to construct objects one layer at a time. An extruder moves horizontally to put the melted plastic in place, and a flat printing bed moves downward as each layer is completed. Picture a tube of frosting moving back and forth, drawing multi-layered designs on a cake. Because these printers build objects vertically, plastic supports are sometimes added to the model. These can be removed after the print.

FDM printers are solid all-around printers because of their fast build times and their ability to print using production-grade plastic. These printers won't break the bank, with some available for a few hundred dollars. Check out this video for a closer look.


Selective Laser Sintering (SLS)

A product of SLS printing before the removal of excess powder (image source).

Unlike FDM printers, Selective Laser Sintering printers don't leave behind support structures or noticeable layer lines. This makes the process ideal for complex parts. A guided laser beam is shot into a bed of powdered material, causing the powder to fuse into a solid object. After one layer of the object is complete, more powder is added to the top. The end products of SLS printing have smooth, uniform surfaces, and can be made of hard nylon, glass, or even metal.

Also unlike FDM printers, SLS printers are very expensive. Most SLS machines cost tens of thousands of dollars, restricting them to industrial use. However, some websites allow you to order SLS-printed parts online. Watch this video explaining the process, or this video in which designers use SLS to print a wearable plastic dress.

Stereolithography (SLA)

Statue produced using stereolithography (image source).

This 3D printing process is the affordable cousin of SLS. While SLS uses powdered material, SLA uses liquid resin that hardens when it comes into contact with a guided laser. Because the resin is not as sturdy as the powder used in SLS, support structures are needed. After the resin is hardened, the supports are removed using a chemical bath. Some SLA materials need to be placed in an ultraviolet oven to harden. This video describes the process more clearly.

One advantage of SLA is the laser's ability to craft finer details than the extruder of an FDM printer can produce. However, while the strong plastic of FDM printers can be used for final products, SLA is typically only used for prototypes or molds. Desktop SLA printers are smaller than most FDM printers, and cost a few thousand dollars.

Other Processes

Product of Laminated Object Manufacturing (image source).

Many printing methods have smaller subcategories. Digital Light Processing (DLP) is similar to stereolithography, but it uses light that is focused using tiny micro-mirrors. Selective Laser Melting (SLM) printers use the SLS process to melt and solidify metal powder, while Electronic Beam Melting (EBM) uses a beam of electrons instead of a laser. Laminated Object Manufacturing (LOM) uses layered plastic sheets to create objects.

Which 3D Printing Process is Right for You?

A 3D bust of Star Wars' Yoda (image source).


If you want to explore 3D modeling as a hobby, you can't go wrong with FDM. The affordability of FDM printers make them ideal for hobbyists, and they can be used to create model figurines or end-use products. You can read our post about painting scale models made with FDM here.

If you want to use 3D printing to create intricate pieces of art, you may want to consider an SLA printer. These are slightly more expensive than FDM printers, but the extra precision may be worth the higher price tag. Keep in mind that SLA-printed objects are not as durable as FDM-printed ones.

If you want to use a 3D printer for manufacturing, SLS is your best bet. These printers can create objects out of multiple materials, and their durability and precision are unmatched. However, for the average person who doesn't need a printer more expensive than their car, it is better to order SLS-printed models online.
Whether you are looking to start 3D printing, or you just want to learn more about this revolutionary technology, I hope this post was helpful. Keep following for more information on 3D modeling and printing technology.


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