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Production Methods: What's the Difference Between Selective Laser Sintering, Direct Metal Laser Sintering, Laser Melting and LaserCusing?

By Rain Noe - February 18, 2014

in Materials | Digital Fabrication

As an industrial designer, if you confuse extruding with embossing during a job interview or at an engineering meeting, you'll get some funny looks. But if you screw up the difference between laser sintering and laser melting, you're likely to be given a bit more slack. That's because there's a lot of confusion about the difference between Selective Laser Sintering (SLS), Direct Metal Laser Sintering (DMLS), Selective Laser Melting (SLM) and LaserCusing (no sexy acronym), and in fact, some vendors of these technologies themselves do not always draw clear distinctions between their capabilities. As conflicting information is being circulated, here we will attempt to explain the difference between the terms. (And hopefully those of you in our readership directly experienced with these technologies will sound off in the comments.)

First off, all four procedures follow the same basics:

1. A designer/engineer designs a part 2. Software cuts that part up into virtual slices on the horizontal plane 3. A chamber in the production machine is filled with powder 4. A laser runs over the powder, solidifying it and building up a thin layer of material 5. Layer after layer is built up from bottom to top, until the part is finished 6. The leftover powder is re-usable, leaving no wasteSelective Laser Sintering and Direct Metal Laser Sintering are essentially the same thing, with SLS used to refer to the process as applied to a variety of materials—plastics, glass, ceramics—whereas DMLS refers to the process as applied to metal alloys. But what sets sintering apart from melting or "Cusing" is that the sintering processes do not fully melt the powder, but heat it to the point that the powder can fuse together on a molecular level. And with sintering, the porosity of the material can be controlled.

Selective Laser Melting, on the other hand, can do the same as sintering--and go one further, by using the laser to achieve a full melt. Meaning the powder is not merely fused together, but is actually melted into a homogenous part. That makes melting the way to go for a monomaterial, as there's just one melting point, not the variety you'd find in an alloy. To nutshell it, if you're working with an alloy of some sort, you'll go SLS or DMLS; if you're working with say, pure titanium, you'll go with SLM.

As for Laser Cusing? Though there are some technical distinctions, it's essentially a trade name for SLM, something like Xeroxing is to photocopying. Further adding to the confusion is that DMLS might stand for Direct Metal Laser Sintering—yet "DMLS" is also a trade name for Selective Laser Melting. 3D printing consultant Joris Peels, who previously worked for both Shapeways and i.materialise, describes the distinctions between these technologies thusly:

Some people use the terms interchageably, others maintain that there are sharp differences between them and others think that it is just a bunch of Germans who used to all be friends playing word games in English.

...Essentially there were several companies and institutes developing these technologies and they had a falling out and now due to marketing and patent issues they all refer to the same technology by different names.

The one laser technology whose nomenclature all manufacturers can agree on is also the newest: DMSL, or Direct Mogul Skier Lasering, which recently made its debut at Sochi.

Yeah, I know, getting a lot of mileage out of that clip. Sue me.

Previously: There's More Than One Way to Additively Manufacture a Metal

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Filemon Schoffer

8 years ago

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I know this is a somewhat older post but I actually used this a lot to help explain the differences to people. So, thanks!

To help add some clarity to it all we just released an overview of all 3D printing technologies here: 3dhu.bs/AMTech (sorry for the plug, but I truly believe it's a useful reference so figured I'd share).

Although you're correct in your article about the difference between DMLS and SLM, I decided to merge them nonetheless as the differences are patent and trademark related and don't reflect in applications that much. Thus, all the same for the user.

Curious about your thoughts on the decision.
Cheers!
Filemon

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Omer Kucukyildiz

9 years ago

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"To nutshell it, if you're working with an alloy of some sort, you'll go SLS or DMLS; if you're working with say, pure titanium, you'll go with SLM."

I do not fully agree with this, but I think I understand your point.

In many papers on SLM, metals such as Ti6Al4V Titanium alloy or 316L stainless steel are used and both of them are in fact alloys in their powder form, eg. they are either soluble, form an intermetallic phase etc. Even when selective laser melting aluminum, it is often alloyed with silicium in order to improve its flowability and mechanical properties. However, for SLS or DMLS, it is possible to diffuse two different materials which are initially not alloyed, but mixed in a heterogeneous form. So I do not think you can make such a distinction between the two manufacturing methods.
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ScienceWorks

10 years ago

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You've missed an important point: SLS is not actually sintering. You'll have to ask Carl Deckard why he named a melting process sintering, but there is no question that the powder is completely melted in SLS.
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- Jouko Lehtomäki
  
  8 years ago
  
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  Are you sure about Carl Deckard's invention (SLS)? If you look at his patent claims (https://www.google.com/patents/US5155324), you don't find "melting" or "melt" anywhere but it's "sintering" all the time.
  
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