Additive Manufacturing: Direct Metal Laser Sintering

This post was originally created in January 2017.

With all the buzz about Additive Manufacturing, or 3D Printing, in the manufacturing world today, there is a lot of mystery and confusion surrounding the common practices and techniques. So, this week’s blog post will address a common type of 3D printing known as Direct Metal Laser Sintering (DMLS).

What is Direct Metal Laser Sintering?

DMLS is actually part of a broader category, commonly referred to as a Granular Based Technique. All granular-based additive manufacturing techniques start with a bed of a powdered material. A laser beam or bonding agent joins the material in a cross-section of the part. Then the platform beneath the bed of material is lowered, and a fresh layer of material is brushed over the top of the cross section. The process is then repeated until a complete part is produced. The first commercialized technique of this category is known as Selective Laser Sintering.

The Selective Laser Sintering technique was developed in the mid-1980s by Dr. Carl Deckard and Dr. Joseph Beaman and the University of Texas at Austin, under DARPA sponsorship. As a result of this, Deckard and Beaman established the DTM Corporation with the explicit purpose of manufacturing SLS machines.  In 2001, DTM was purchased by its largest competitor, 3D Systems.

DMLS is the same process as SLS, though there is an industry distinction between the two, so it is important to make note of this. DMLS is performed using a single metal, whereas SLS can be performed with a wide variety of materials, including metal mixtures (where metal is mixed with substances like polymers and ceramics).

What Are the Advantages of this Process?

DMLS is quick. It’s one of the fastest rapid prototyping techniques – though, relatively speaking, most techniques are fast. In addition, it can potentially be one of the most accurate rapid prototyping processes, the major limiting factor being the particle size of the powdered material.

Because parts are created on a bed of material, there is no need to use support structures like in other forms of rapid prototyping. This helps to prevent secondary operations and machining.

Another advantage of the material bed is the ability to stack multiple parts into the build envelope. This can greatly increase the throughput of a DMLS machine.

What Are the Disadvantages of this Process?

Of the commercially available rapid prototyping machines, those that use the Direct Metal Laser Sintering technique tend to have the largest price tag. This is usually due to the scale of production these machines are designed for, making them much larger than others.

DMLS can be very messy. The material used is a bed of powdered material and, if not properly contained, will get EVERYWHERE. In addition, breathing in powdered metals can potentially be very hazardous to one’s health. Most machines account for this, but it is certainly something to be cognizant of when manufacturing.

Unlike other manufacturing processes, DMLS limits each part to a single material. This means parts printed on DMLS machines will be limited to those with uniform material properties throughout.

As materials aren’t fully melted in this process, full density parts are not created through this process, so parts will be weaker than those created with traditional manufacturing processes. Full density parts can be created through similar manufacturing processes, such as Selective Laser Melting.

In Conclusion

There are quite a few different ways to 3D print a part, with unique advantages and disadvantages of each process. This post is part of a series, discussing the different techniques. Thanks for reading!

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