What is Metal Additive Manufacturing?

A brief overview from Rennscot MFG - leaders in the industry and specialists in Laser Powder Bed Fusion / Direct Metal Laser Sintering. Metal additive manufacturing is a term that describes the whole metal 3D printing industry. There are a few subcategories of metal additive manufacturing, each based on the way the metal is fused. For the purposes of this article, the three major categories are as follows:  

1) Direct Energy Deposition (DED) 

2) Selective Laser Sintering or Laser Powder Bed Fusion (SLS/LPBF/DMLS) 

3) Binder Jet  

Shown above is a DED printer adding material to a large tube component. This image was sourced from https://all3dp.com/1/directed-energy-deposition-ded-metal-3d-printing-guide/

1) Direct energy deposition functions similarly to MIG welding. A high-energy laser or electron beam melts metal wire, depositing it layer-by-layer to a build plate or existing component. DED’s major advantage is its ability to be added to existing components, but it is not incredibly precise; its finish is fairly rough and always requires machining to clean up the part to its final form. DED is certainly metal additive manufacturing, but it does not fit quite as nicely into the bucket of “metal 3D printing” due to its resemblance to welding.   

Shown above is a build plate full of parts made with selective laser sintering. In this group you can find a racecar exhaust component, an aerospace bracket for NASA, complex geometry to show the machines capabilities, and test bars printed at a variety of angles. On the bottom left of the photo, you can see how smooth LPBF parts are right from the machine. These parts were printed by Rennscot MFG.

2) This process can be identified with a number of acronyms (SLS- selective laser sintering, L-PBF – laser powder bed fusion, DMLS – Direct metal laser sintering). But for the purpose of this article, they all function the same way – they sinter powder into metal with lasers. Very thin layers of metal powder are spread across a build plate and then hit very precisely with high-power lasers. This combines the layer of metal powder to the one below it, very precisely building components as it goes. After thousands of very thin layers (these range from 20 to 120 microns in height), you are left with a fairly clean metal part which can contain geometry impossible to create with other forms of manufacturing.   

Pictured above are some parts printed with binder jet technology. You can see that the surface finish is still a bit hairy. These parts are yet to go through the sintering process and will change dimensionally. Image from source: https://www.3dprintedparts.com/2022/11/30/binder-jetting-the-future-of-production-metal-printing/

3) Binder jet seems similar to (SLS/L-PBF/DMLS) at first, but with one major difference. Binder jet lays metal powder down in very thin layers like (SLS/L-PBF/DMLS), but it uses an adhesive like material to bind the parts together in the powder chamber. Because of this, the parts must be sintered in a high-temperature oven after the printing process to fully fuse the layers together and form a final part. This final sintering process causes the parts to shrink from their printed state. This shrinkage at the end is accounted for by printing the parts “oversized” from the start, but remains the least controlled part of the process.  

Shown above is a selective laser sintering machine in the middle of firing its lasers. To be more particular, these are aerospace parts being printed on an EOS M300-3 at Rennscot MFG.

The selective laser sintering printers (section 2) are generally considered the most precise metal additive manufacturing technology. They offer high-resolution surface finishes and complex geometry with tolerances as fine as .1-.2mm. For this reason, laser sintering is the most ideal process for those working on the world’s most extreme missions, engineering components meant to push the boundaries of what's possible.