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DMLS 3D printed automotive component

What is DMLS 3D Printing?

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When you think of materials for 3D printing functional prototypes and end-use parts, we’re betting that plastic comes immediately to your mind. But did you know that it is also possible to 3D print objects using metal?

Get to know the basics of direct metal laser sintering, also known as DMLS 3D printing. Find out why the process is worth considering for your next project, learn about how DMLS works, discover the materials and finishing options available, and the advantages and disadvantages of the process to bear in mind.

What is DMLS 3D printing?

Direct metal laser sintering (DMLS) is a metal additive manufacturing (metal AM) technique that belongs to the Powder Bed Fusion family and is often referred to as the metal counterpart of selective laser sintering (SLS). It works by heating up powdered metal, layer by layer, at select points so that the layer fuse into a single unit.

DMLS opens up a whole new world of creative possibilities in applications in multiple industries. It allows us to build a single metal object and incorporate complex shapes into it that are nearly, if not completely impossible to make through traditional manufacturing methods. And as DMLS technologies advance, the number of possibilities will only increase.

How does DMLS 3D printing work?

The DMLS 3D printing process begins with a CAD model that needs to exported into a 3D printable file format  (an STL format). Using your model, the DMLS process uses a high-power laser beam to selectively fuse a layer of metallic powder together. The process repeats layer-by-layer until the final object is formed.

 

CNC machining after DMLS

Once a part is printed, it’s not uncommon to turn to additional machining options.

  • Removing Support Structures: Unlike its plastic counterpart SLS, DMLS requires support structures to prevent specific features from sinking through the powder. These supports are often made using the same metal as the build and will need extensive post-processing (often via machining or wire cutting) to be removed, which can be time-consuming and costly.
  • Tighter Tolerances: DMLS can produce accurate parts, with tolerances to 0.1mm. When critical features require tighter tolerances, parts can be machined.

Designing parts for DMLS

Certain features, such as wall thickness, in DMLS designs can be tricky and differ depending on material selection, orientation, and resolution. Staying within a set of geometric recommendations can help ensure better part quality and a successful print.

Find out how to design mating parts, pins, overhangs and more, in our DMLS 3D Printing Design Guide.

DMLS vs SLM

DMLS is often interchanged with selective laser melting (SLM). The main difference between them is that the laser in SLM heats up the powdered metals until they melt into liquids and join together. In the DMLS process, the laser only heats the materials up just enough to allow the surfaces to meld into one another.

Direct metal laser sintering allows us to combine different types of metal powders, or even incorporate plastic materials, because we don’t have to wait for each individual component to reach its melting point.

The DMLS process produces a porous metal part, while SLM printers yield a much more uniform build. As we mentioned in the previous section, porous metals are great for manufacturing prosthetics. But there is a slight disadvantage, as well, which we’ll discuss later in the article.

Metal 3D printing material options

A key strength of metal AM is the ability to process high-strength metals, such as Inconel and Cobalt Chrome, that are otherwise difficult to machine. Between DMLS and SLM, manufacturers have a wide selection of metal and metal alloy powder materials to choose from. Below is a list of materials commonly used in metal 3D printing.

 

Materials Characteristics
Aluminium Alloy
  • Good mechanical and thermal properties
  • Good electrical conductivity
  • High strength to weight ratio
  • Low density
Titanium Alloy
  • Good mechanical and thermal properties
  • Excellent corrosion resistance
  • High strength to weight ratio
  • Outstanding biocompatibility
Stainless Steel
  • Good ductility and weldability
  • Excellent corrosion resistance
  • High durability
  • Highly aesthetic
Nickel Superalloys (Inconel)
  • Excellent mechanical properties
  • Excellent corrosion and oxidation resistance
  • High temperature resistance
  • Used in extreme environments
Cobalt-Chrome Superalloys
  • Excellent mechanical properties
  • Excellent corrosion resistance
  • Great properties at elevated temperatures
  • Biocompatible

DMLS post-processing options

Finished DMLS parts have a grainy structure that often requires extensive post-processing to achieve a smooth, aesthetic finish. The surface quality can be improved through various surface finishing techniques, such as media blasting, sanding and spray painting. Surface finishing options, such as electroplating and polishing, can also be applied to DMLS components to enhance functionality.

Applications of DMLS

Several different industries use DMLS to produce high performance functional end-use parts.

The medical and dental industries, for example, use DMLS 3D printing to build custom prosthetics that support existing bones or replace bones that are lost using biocompatible metals. In this application, the porous nature of DMLS parts is perfect because it allows the bone to grow into it, thus strengthening the entire structure.

DMLS works with lightweight metals like titanium and aluminium. It also allows for greater design freedom, which provides automotive and aerospace sectors the opportunity to produce lightweight complex parts while maintaining the same structural strength.

Advantages of DMLS

  • Wide Range of Material Selection: Between DMLS and SLM, manufacturers have a wide range of metal and metal alloy powder materials to choose from.
  • Strong Functional Parts: The powdered metals we use for the DMLS 3D printing at HLH Rapid come with strong mechanical and dynamic properties. This makes them the perfect materials to utilize for functional end-use parts.
  • Complex Designs: Since DMLS builds metal parts and prototypes layer by layer, it can produce complex geometries in a single product – something that just isn’t possible to achieve in traditional manufacturing.
  • Recyclable Material: The leftover metal and metal alloy powders from a DMLS print can be reused and recycled into another project.

Disadvantages of DMLS

  • Relatively Smaller Builds: Direct metal laser sintering is limited to producing relatively small build volumes (280 x 280 x 280 mm) compared with other manufacturing technologies.
  • More Expensive Than Plastic 3D Printing: Between the cost of the special machines and the materials, DMLS is typically more expensive than plastic 3D printing methods.
  • Porous Parts: DMLS parts are more porous than the prints from other metal 3D printing technologies, which could compromise their overall appearance and integrity depending on the desired application.
  • Requires Extensive Post Processing: DMLS parts usually require extensive post-processing – to remove metal support structures, machine tighter tolerances, add protective coatings or improve aesthetics – which significantly adds to the cost.

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