Electron Beam Melting is one of the main metal 3D printer technologies, having been commercialized by Arcam in recent years. It’s similar to Direct Metal Laser Sintering, though with one key difference we’ll explain below.
EBM falls under the Powder Bed Fusion umbrella along with DMLS and SLM, as does Selective Laser Sintering if you include plastics. It is a purely metal printing technology; you cannot print plastic polymers with EBM.
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Electron Beam Melting: Introduction
Although not as well-known as stereolithography or fused deposition modeling, EBM is used fairly regularly in industrial metal 3D printing. Electron Beam Melting is similar to SLS in that both 3D print from a powder bed through powder bed fusion. Since its invention, the technique has thus far only been used by Arcam in the four current EBM 3D printers.
Electron Beam Melting 3D Printing
In EBM, fully dense metal components are created from a powder bed of metal powder and melted by a powerful electron beam. Each layer is melted according the the 3D printer model sent to the 3D printer.
Electron Beam Melting uses a high-power electron beam to melt the metal powder. This electron beam is managed through electromagnetic coils which allow for extremely fast and accurate beam control. In addition, this allows several different ‘melt pools’ (different objects within the same build at the same time) to be maintained simultaneously.
This slide below outlines the core elements of Electron Beam Melting:
The Electron Beam Melting process takes place in a vacuum and at high temperatures. This results in metal parts produced with better material properties than through casting. Maintaining a clean and controlled build environment is a key factor in maintaining the chemical specifications of the 3D printed part. For this reason, EBM printers typically require trained operators to monitor printing.
The electron beam heats the entire powder bed to an optimum melting temperature when printing each layer. This temperature depends on the metal powder used — some have far higher melting points. This heating of the powder bed means that parts printed using Electron Beam Melting are free from residual stresses and have better mechanical properties.
In EBM, the build envelope can be filled by multiple objects built at the same time as long as they are all attached to the build platform.
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Electron Beam Melting Post-Processing
After printing, any unsolidified powder can be retrieved and reused in a future print. This saves money and is far more efficient than other 3D printing methods where as little as 20% of the total powder used is actually sintered.
EBM, like FDM and SLA, requires the use of supports when 3D printing. This is to anchor parts to the build platform and prevent overhanging pieces from becoming unstable. In addition, these supports transfer heat away from where the powder is being melted, reducing thermal stress on the part. This helps to prevent warping and general deformation that can occur with high temperatures.
Laser vs Electron Beam: DMLS vs EBM
Electron Beam Melting uses, as the name suggests, an electron beam. This differs from Direct Metal Laser Sintering as a laser (with photons) is used instead.
A tungsten filament is heated in a vacuum to produce these electrons. They are projected at high speeds towards the metal powder on the powder bed in order to heat it. A vacuum is used because this stops the metal powder from oxidizing when it is heated.
Electron Beam Melting Materials
Electron Beam Melting relies on electrical charges to 3D print, and therefore materials must be conductive to be used. This means that polymers and ceramics cannot be used with electron beam melting.
Commonly used metal powders include titanium and chromium-cobalt alloys. These materials are expensive however, costing between $350-450 per kg.
Advantages and Disadvantages of Electron Beam Melting
Electron Beam Melting Advantages
- Strong metal parts: Parts 3D printed with EBM have very high density (over 99%).
- Scalable: Multiple parts can be produced simultaneously as the beam can separate powder in several places at once.
- Prints faster and with less supports than DMLS: Requires less supports due to there being less thermal stress on parts, with the electron beam’s ability to scan the whole layer at once making it faster, too.
- Reusable powder: Unused powder can be recovered and reused, saving money and the environment.
Electron Beam Melting Disadvantages / Limitations
- Not versatile: Limited availability of materials for use in EBM.
- Expensive: Requires an industrial level 3D printer and expensive materials. Printers can cost upwards of $250,000, with materials costing over $300 per kg.
- Parts usually require a lot of post-processing.
- Surface finish: Parts have a less smooth surface finish than DMLS.
- Limited build size: the largest EBM 3D printer has a build volume of around 350 x 350 x 380 mm. Some DMLS 3D printers such as Concept Laser’s X Line 2000R have a print volume of 800 x 400 x 500 mm.
Applications of Electron Beam Melting
Electron Beam Melting has applications in industries such as in the aeronautics and Motorsports industries due to the strong, high-density parts it can produce. Electron Beam Melting is also used in the biomedical industry to manufacture prostheses. Mostly however, EBM is used for small series parts and prototypes to check the structure of parts.
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