Remember the scene in the film The Mummy when the mummy's head rises out of the desert sand? You see the features of his face, and his mouth opens with a frightening roar? That's sort of what it looks like when you use the form of 3D printing known as Selective Laser Sintering, or SLS.
Okay, maybe that's a stretch. But not by much.
Unlike other 3D printing technologies which use heated, extruded materials (FDM) or liquid polymers (SLA), SLS uses the intense heat of a laser to join and harden fine, powered material, such as plastic, glass or metal. The laser traces the pattern of the part into a bed of powder, over and over again. As with SLA, the material bed lowers as each layer is created.
Here's a video, along with narration of the SLS technique, for an even clearer picture:
As the professor in the video states, the main advantage of using SLS is that the geometric complexity of the parts are only limited by the imagination of the user. I take that to mean, (almost) anything goes!
There are pros and cons, of course:
- Smooth finish.
- Highly durable.
- Excess material is recyclable.
- Don't have to print support material. The powder acts as its own support structure. This saves cleaning time after the part is formed as it's relatively easy to brush away the powder.
- More expensive. The machinery and the material are more expensive than FDM.
- Less accessible. Because of the investment, individuals or smaller companies are unlikely to purchase SLA printers for themselves.
Here's a good side-by-side comparison from the Sculpteo website demonstrating what a simple object printed using SLS looks like compared to FDM:
Photo courtesy of sculpteo
You can see the FDM top was printed in two halves then glued together. The imperfections in the surface are clearly visible. On the other hand, the SLS top looks smooth and finished, and was printed in one piece. The Sculpteo website does a great job of describing the differences in these two forms of 3D printing, using visuals. It's worth a look.
SLS is great for creating parts for making molds and testing, prototyping and even low volume production runs. Because the parts are so lightweight, it's ideal for automotive and aerospace parts, or other tools and fixtures.
Additive manufacturing is an industry that is rapidly evolving. In fact, here's a recent story about the how the combination of 3D printing, CAD software and virtual reality are already affecting the manufacturing industry. As materials and techniques become more refined there's little doubt we'll see 3D printing take an even bigger role in the manufacturing process.