3D Printing Processes – Powder Bed Fusion (Part 5/8)

Selective Laser Sintering is the most commonly used powder bed fusion (PBF) technique. While the other PBF techniques are generally used to create 3D models from thermoplastics, direct metal laser sintering (DMLS) is the PBF technique dedicated and applicable only to creating 3D models from metals and conductive materials.

All PBF techniques are similar in operation except that the method of melting the powder material differs in them. In Selective Laser Sintering, a laser head is used to project a high-power laser beam into the powder material to melt the particles and fuse them. The SLS method can be used to make models of thermoplastics, glass, metal and ceramics. The DMLS technique also uses a high-power laser head, but the feed is always a metal powder or conductive material. The SLM technique is similar to SLS and is used to make 3D structural models for medical and aerospace applications. In the Selective Heat Sintering (SLH) technique, a thermal print head comes into contact with the metal powder to melt it and fuse the metal particles. The electron beam melting (EBM) technique uses an electron beam projector to radiate a high-power electron beam onto metal powder and melt the metal particles for fusion. The EBM technique is generally performed in a vacuum chamber, except in the case where metals and alloys are used to create a working 3D model.

The configuration and mechanism of all PBF techniques are practically the same. In a Powder Bed Fusion machine, there are two chambers where one chamber is filled with powdered building material to feed the other chamber and the second chamber is used to make the 3D model. The 3D model is constructed by melting and fusing particles of powdered construction material using a laser, thermal or electron beam print head. The plastic or metal powder is placed in the storage chamber and fed into the build chamber by rolling a sufficient amount for each layer by a leveling roller or blade. The unrolled powder is filled onto the build platform which has been lowered to a depth equal to the required layer height at the start of the process. The height of the layers is generally kept at or near 0.1 mm. Later, a high-power laser beam or contact thermal print head or high-power electron beam is used to melt and fuse material particles while the head moves along the horizontal plane to create the path for the layer. desired. After laying a single layer, the platform is lowered to a depth equal to the height of the next layer and the powder is rolled out or slid from the storage chamber into the build chamber. Again, the next layer is built by projecting a laser beam or electron beam or contacting a thermal print head along a computer-controlled path. In the same way, all successive layers are constructed. After the final layer is completed, the 3D model is still removed from the remaining powder material. The model is left in the machine for some time to cool down and become completely solidified for a high-quality finish of the 3D model.

PBF techniques are comparatively less expensive and also because it is a powder-based method, it does not require the use of support structures in the manufacture of models or parts. A wide variety of materials, including ceramics, glass, plastics, metals and alloys, can be used to make 3D objects using PBF techniques. However, PBF methods have slow operating speeds and the models created have size limitations. As the process involves melting the construction material, the energy consumption of PBF machines is quite high. The quality of the models created depends largely on the grain size of the powder and not all structural characteristics desired for a functional model can be achieved. This is why the PBF technique is generally limited to prototyping applications.

The construction material used in SHS is generally nylon. SLS, SLM and DMLS techniques are commonly used to make models from steel, stainless steel, aluminum, titanium, cobalt chrome or other metal alloy. The EBM technique is also mainly used for models constructed from aluminum, stainless steel, steel, titanium, cobalt chrome or other metal alloy.

For SHS 3D printing, the Blue Printer is a popular machine. Some examples of SLS 3D printers are ProX SLS 500, sPro 140, sPro 230 and sPro 60 HD offered by 3D Systems. 3D Systems also offers DMLS printers such as ProX DMP 100, ProX DMP 100 Dental, ProX DMP 200, ProX DMP 200 Dental, ProX DMP 300 and ProX DMP 320. Arcam S2, Arcam Q10 and Arcam A2 are popular EBM machines provided by Arcam.

Disclaimer: ProX and Spro are registered trademarks of 3D Systems and EBM is a registered trademark of Arcam. Brand names are used editorially and for the benefit of the brand owner, with no intention of infringing the brand.

In the next article in the series, another Direct Energy Deposition 3D printing process will be discussed.