What is Selective Laser Melting (SLM)?

What is Selective Laser Melting (SLM)?

Feb 1st 2024

Since it was first developed in 1995 at the Fraunhofer Institute ILT in Germany, Selective Laser Melting (SLM) has become one of the most powerful additive manufacturing techniques for producing 3D metal parts. It’s a widely used process surpassing traditional manufacturing techniques which rely on subtracting material. 

In this blog, we’re exploring the SLM 3D printing process in detail, the advantages and disadvantages it offers, its industrial applications, and whether it can be a useful technique to catapult your manufacturing business to the next level.

What is Selective Laser Melting (SLM)?

SLM is a Powder Bed Fusion (PBF) 3D printing technique that relies on layer-by-layer fusion to create parts similar to Selective Laser Sintering (SLS) and Direct Metal Laser Sintering (DMLS). But unlike SLS, SLM and DMLS fully melt the material into a liquid state before fusing it. 

SLM and DMLS are sometimes used interchangeably since they share the same underlying process but the difference lies in that while DMLS primarily uses metal alloy powders, SLM uses single metal powders. SLS on the other hand uses polymer powder. It’s important to understand the distinction between the three to avoid confusion.

How Does SLM 3D Printing Work?

The Selective Laser Melting process begins with the creation of a 3D CAD model of the part, which is then sliced into layers using 3D printing software to instruct the printer on how to and in what thickness to print the layers. The printer is filled with an appropriate metal powder such as stainless steel or titanium, and an inert gas like argon which prevents the metal from oxidizing due to the hot laser. The build platform is also pre-heated to reduce the temperature difference between the laser and metal as it can cause deformations.

When the temperature is right, the Selective Laser Melting printer kicks into action and a thin, uniform layer of powder is deposited on the build platform, then melted and fused before moving on to the next layer. The build platform moves down for each layer and the process is repeated until the product is finished. The final part is removed from the build platform after everything has cooled down.

Selective Laser Melting Post-Processing

Creating parts using SLM requires the use of support structures that act as heat sinks to prevent the part from developing defects due to excessive heat, and protect it from warping during cooling. The finished parts produced using SLM are also encased in the unused powder. 

Both the support structures and the unused powder have to be removed during post-processing using metal cutters and brushes or compressed air respectively, after which the part is ready for further post-processing such as heat treatment, stress-relieving, smoothing/polishing, etc to improve its mechanical properties. The unused powder can also be recycled for future Selective Laser Melting processes.

Advantages of SLM

SLM 3D printing is a popular additive manufacturing technique because it offers various advantages over other 3D printing methods. Here are some of the advantages of SLM:

  • Produces precise and intricate metal parts possessing high strength and durability.
  • Can work with a diverse selection of materials, including alloys, to fit customized design needs.
  • Capable of producing complex parts and whole assemblies, eliminating the need for creating multiple parts.
  • Produces parts with exceptional speed, significantly reducing production times for large-scale manufacturing.
  • Minimizes material waste as compared to traditional methods. Leftover powder can be recycled and reused for reduced manufacturing costs.

Disadvantages of SLM

As with every other additive manufacturing process, Selective Laser Melting comes with its share of challenges that may make it less desirable than other methods for many manufacturers. Here are the disadvantages of SLM:

  • Parts require extensive post-processing to reduce residual stress and improve surface finish, density, durability, and other mechanical properties.
  • The use of support structures causes wastage as they have to be removed and cannot be reused, raising production costs.
  • The build size of the final part is restricted, making it unsuitable for printing larger objects.

Applications of SLM 3D Printing

Despite its shortcomings, Selective Laser Melting is a fantastic 3D printing method with impressive versatility. It’s already being used in numerous high-end applications across industries. 

  • The design flexibility and light weight of the final part are especially advantageous in aerospace and automotive for creating structural components that are strong, reliable, and reduce fuel usage. 
  • SLM is popular in the healthcare industry for the production of custom implants and prosthetics that deliver a better fit and performance. 
  • Mechanical and chemical industries require parts that can withstand extreme pressure, making SLM an excellent choice for this purpose as well.

Does Your Business Need SLM?

Selective Laser Melting can present certain challenges, but its design efficiency and the reliability of the parts produced make it a popular choice among manufacturers for small-scale production and rapid prototyping. If this describes the needs of your business, don’t hesitate to invest in quality SLM printers. If you’re looking for large-scale production, then you’ll want to consider Binder Jetting instead.

No matter which additive manufacturing method you choose to meet your production needs and propel your business to new heights, KBM Advanced Materials is here as the inventory bridge for all your raw material needs. If you have any questions about SLM 3D printing or need information on ordering metal powders for SLM online, contact us today!