What is Electron Beam Melting? How it works?
Electron Beam Melting, or EBM, is a metal additive manufacturing method. It is one of the main methods used for printing 3D part although SLM/DMLS are more popular. EBM comes under the umbrella of Power Bed Fusion in which powder material are fused together using concentrated energy beams. This method is mainly used by Arcam in their 3D printers. Arcam was bought by General Electric (GE) so these 3D printers now come under their umbrella.
As the name suggests, EBM uses high energy electron beams to melt the powder material. These electron beams are controlled by electromagnetic coils which makes it fast and highly accurate as there are no moving part involved. Electron Beam Melting takes place in a vacuum chamber at high temperatures, which has its own advantages which we will discuss down below.
Electron Beam Melting shares some similarities with SLM/DMLS 3D printing methods as all these methods come under Power Bed Fusion. EBM printers have four main components: Electron gun, build platform, powder material, re-coater.
The printing process starts by creating a vacuum in the build chamber. This prevents oxidation or unwanted reaction between the molten powder and air molecules. In SLM/DMLS 3D printing method, unwanted reactions are also prevented filling the build chamber with inert gases. This also reduces contamination of molten powder.
As a vacuum is created inside the build chamber, the re-coater spreads a thin layer of powder on the build platform. The height of this layer determines the vertical resolution of printed parts. Electron beams then heat up the build platform to optimal temperature and proceeds to melt the powder. This is done in two steps: first contour melting is done in which an outline or contour is mapped by melting the powder accordingly. In second step, hatch melting is done in which powder inside the contour created is melted.
As each layer is completed, the build platform is lowered by exactly one-layer thickness and a fresh layer of powder is spread by re-coater across the build platform. This process is repeated until the entire part is printed.
In electron beam melting method, some post processing is required before the part can be put to use. Removing unfused powder is compulsory after every print because the part is encapsulated in unfused powder. This can be done by using compressed air. Only around 20% of powder is melted in the entire printing process and the unfused powder can be reused in the next print thus saving money and increasing efficiency.
EBM printed parts can require some support structures, depending on the design of the part to be printed. This further increase post processing as removing metallic support structure takes some time.
Although electron beam melting shares some similarities with other metal printing method, its characteristics vary significantly from them. Creating a vacuum inside the build chamber not only prevents unwanted reactions between molten powder and air molecules, it also provides a clean and controllable environment which further reduces any contamination.
Use of electron beams also increases the print speed as it lacks any moving parts thus providing a fast and highly accurate melting process. While contour printing and hatch printing is done temperature may go up to 1000 degree C or higher, this helps in releasing any residual stress which eliminates the need for further heating while post processing it. Some of the metal powders used in EBM printers are Cobalt-Chrome alloy, Titanium alloys and Inconel 718.
Electron Beam Melting is a fast and highly accurate additive manufacturing process. It is faster than the other metal 3D printing methods due to the use of high-power electron beams to melt the powder. Arcam EBM printers are used extensively for aerospace and orthopaedics applications. However, its cost of printing makes it suitable only for industrial applications, which is the case with most of the metal 3D printing methods.