{"id":164162,"date":"2021-12-08T11:10:59","date_gmt":"2021-12-08T03:10:59","guid":{"rendered":"https:\/\/facfox.com\/docs\/?post_type=kb&p=164162"},"modified":"2022-08-12T17:29:37","modified_gmt":"2022-08-12T09:29:37","slug":"direct-metal-laser-sintering-dmls-simply-explained","status":"publish","type":"kb","link":"https:\/\/facfox.com\/docs\/kb\/direct-metal-laser-sintering-dmls-simply-explained","title":{"rendered":"Direct Metal Laser Sintering (DMLS) \u2013 Simply Explained"},"content":{"rendered":"

3D printing isn’t just confined to plastic. Learn all about direct metal laser sintering, one of few 3D printing technologies capable of making parts directly from metal.<\/p>\n

What Is DMLS?<\/h3>\n
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Removing a DMLS print from the powder. Source: Protolabs<\/figcaption><\/figure>\n

Direct metal laser sintering (DMLS), also called selective laser sintering (SLS), is a type of metal additive manufacturing or 3D printing. It\u2019s used for both for rapid prototyping and mass production of metal parts.<\/p>\n

The method is very similar to selective laser melting (SLM), also called direct metal laser melting (DMLM), but on a molecular level, the powder is only sintered (not melted) together. This results in parts that are more less porous than the melting method. The advantage to this is that you can easily print from alloys containing materials with different melting points. You can even combine metal and plastic materials. A good example is Alumide, which is a mixture of nylon powder + aluminum powder.<\/p>\n

Another difference between sintering and melting in these two processes is the temperature used to fuse the metal powder. SLM heats the metal powder until it fully melts into a liquid. DMLS does not melt the metal powder, so less energy is needed. Sintering heats particles enough so that their surfaces weld together.<\/p>\n

The working material for this 3D printing process is finely powdered metal. Typically the manufactured size of the metal particles is 20 \u2013 40 micrometers. The particle size and shape limit the detail resolution of the final part. Smaller metal particle size and less variation allow better resolution.<\/p>\n

Other resolution limits in this technology are the layer height and the size of the laser spot. Like other 3D printing processes, the model is divided into many fine layers, which are then printed one-by-one to build the final part.\u00a0Printable layer heights are approximately the maximum size of the metal powder used.<\/p>\n

Legal History<\/h3>\n
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Powdered metal bed printing multiple parts. Source: eos.info<\/figcaption><\/figure>\n

The DMLS story begins in the 90s with the invention of\u00a0selective laser sintering (SLS)<\/a>,\u00a0as described by\u00a0Carl Deckard<\/a>\u2018s now expired patent. In parallel, EOS, a company in Munich, Germany, was also developing additive manufacturing technologies, including laser sintering for plastics and metals.<\/p>\n

Advances of the technology continued with associated licensing agreements (and legal battles) until EOS ultimately\u00a0gained the worldwide rights for SLS.\u00a0The company then proceeded to champion DMLS (nee SLS) technology, producing the first commercial DMLS printers in 1995. EOS continues to be the leader in DMLS technology today.<\/p>\n

SLM technology was developed in the same timeline as DMLS at the\u00a0Fraunhofer Institute for Laser Technology in Aachen, Germany. This technology advanced over the\u00a0following years,\u00a0albeit with multiple licensing issues and court cases. These issues were not related to the technology itself but to the breaking of licensing agreements. While EOS emphasizes DMLS, they also hold an interest in the SLM technology through their licensing arrangements with Trumph GmbH.<\/p>\n

How DMLS Works<\/h3>\n
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A diagram showing the DMLS process. Source: eos.info<\/figcaption><\/figure>\n

DMLS follows the basic process sequence for most 3D printing technologies: model, slice, and print layer-by-layer. Once a 3D model is created and sliced with the\u00a0appropriate software, the\u00a0code needed for the printer to make the part is supplied to the printer, and the\u00a0physical process can begin.<\/p>\n

To start, the DMLS printer hopper is filled with the\u00a0desired metal powder. Printer heaters bring the powder to a temperature near the sintering range of the alloy. The printer uses an inert gas, which protects the heated powder and part as it is built.<\/p>\n

The build begins with dispensing a thin layer of metal powder onto the build platform. The laser then begins its path for this layer, selectively sintering the powder into a solid. The sequence of dispensing a layer and sintering continues\u00a0until part completion.<\/p>\n

After the part is left to cool, the surrounding loose metal powder is removed from the printer. The last steps include support removal as well as any post-processing needed.<\/p>\n

DMLS parts can be treated like metal parts produced by conventional metal working for further processing. This may include machining, heat treatment, or surface finishing.<\/p>\n

These process steps are shared with SLM, just with the laser\u2019s power turned up to \u201cmelt\u201d.<\/p>\n

Advantages and Limitations<\/h3>\n
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The equipment needed to perform DMLS doesn’t come cheap. Source: multistation.com<\/figcaption><\/figure>\n

As DMLS and SLM are functionally the same, they share many advantages and limitations, with a few exceptions. Naturally,\u00a0both share many advantages with\u00a0other 3D printing technologies. In particular, building an object layer-by-layer allows for the efficient and affordable production of complex internal and external geometries. This is simply not possible with subtractive (machining) or formative (molding) processes.<\/p>\n

That said, let\u2019s take a look at some of the things that stand out for DMLS (and SLM).<\/p>\n

Advantages<\/strong><\/p>\n