Electron Beam Metal 3D Printer (Additive Manufacturing Machine)

Classification of metal 3D printers

Metal 3D printers are classified as follows, according to the type of material, heat source, and build method. The method of JAM-5200EBM manufactured by JEOL is classified as the electron beam powder bed method (EBM or EB-PBF).

Please check the following column for the features of each type of metal 3D printer and the additive manufacturing (AM).

What is an electron beam metal 3D printer?

An electron beam metal 3D printer is an additive manufacturing machine that builds 3D parts from metal powder, typically using the powder bed method. In a vacuum chamber, a layer of metal powder raw material is spread. Then areas to be built are selectively melted using a heat source, such as an electron beam. After that, another layer of metal powder is spread and melted, thus layers are continually added (additive manufacturing). The part is extracted by removing the extra powder surrounding the part.

Structure of electron beam metal 3D printers

The electron beam source of the electron beam metal 3D printer consists mainly of an electron source, magnetic field lens, and deflection coil. Electrons emitted from the cathode (electron source) are accelerated with a high voltage and condensed into a beam by the magnetic field lens. In addition, the deflection coil is used to move the electron beam focused into a spot to an arbitrary position and perform scanning.
Inside the vacuum chamber, there is a powder hopper which stores metal powder and discharges it below, a recoater which pushes the discharged metal powder onto the build table and smooths it, and heat shields which maintain the temperature of the build surface and prevent metal deposition on the surroundings. There is also a Z-axis drive which can move the build surface (base plate) up or down, and a build tank which can store the part melted and sintered on the base plate and the surrounding metal powder by lowering the Z-axis drive.

Build process in the electron beam powder bed method

The following 4 steps make up the major process of the electron beam powder bed method.

3D digital design data is loaded into the dedicated software. The support material is set, and 2D slice data for each layer and irradiation condition of the electron beam are prepared.

The prepared data are loaded into the 3D printer and the 3D printer is evacuated.

Electron beam scanning preheats the entire base plate.

Step 1: Lowering the Z-axis stage

The base plate (Z-axis stage) in the build tank lowers by one layer.

Step 2: Spreading powder

The recoater moves right and left to evenly spread the metal powder to form a powder bed.

Step 3: Preheating (entire powder bed surface)

The electron beam is irradiated over the entire powder bed surface of the build area at high speed to preheat the metal powder. This preheating lightly bonds the metal powder together and prevents the powder from scattering during the build.

Step 4: Melting (build area)

The area to be built is selectively irradiated with an electron beam to heat it, melting and solidifying the metal powder.

This process is repeated to form the 3D structure based on the 3D data, layer by layer.

After the final layer is built, the entire build volume inside the build tank is cooled and the metal 3D printer is vented. The part is taken out as a mass surrounded by temporarily sintered powder (powder cake). The part inside is extracted by blasting away the temporarily sintered powder with the powder recovery system (PRS).

Advantages in using an electron beam as a heat source

• High power

  A high-power electron beam source of 4.5 kW to 6 kW is installed as an electron source in general to enable fast-speed builds and refractory metal builds.

• High transmission efficiency

  An electron beam enables highly efficient energy transmission because there are no optical components that introduce energy loss between the cathode (electron source) and irradiation target.

• High energy conversion rate

  An electron beam is a high-speed stream of electrons, and their kinetic energy is converted into thermal energy when irradiated onto the target. While the absorption rate of a laser (a form of light) differs depending on the reflectance of different materials, the heat conversion efficiency of an electron beam is as high as 80% or more regardless of the material.

• High-speed scanning

  As the irradiation position of an electron beam is electrically controlled by using an electromagnetic coil, extremely high-speed scanning is possible. With the electron beam source used in metal additive manufacturing, it is possible to move an electron beam at speeds exceeding 1,000 m/s.

• Preheating

  As an electron beam enables high-power and high-speed scanning, the powder bed surface on the base plate can be preheated from a few hundred ℃ to over 1000 ℃ in a short time. This preheating step can reduce the residual stress in the built part to help improve the mechanical properties and suppress the deformation or cracking of the built part.

• Processing in a vacuum

  Electron beam irradiation is performed in a vacuum. This vacuum processing step can reduce the inclusion of impurities in the metal melting process, resulting in high-quality builds. However, some electron beam metal 3D printers require the introduction of an inert gas during a build.

Build materials for electron beam metal 3D printers

As the electron beam method is suitable for builds using various metals, materials are used according to the industrial field.

• Titanium alloys: Aviation and Aerospace/Biomedicine
• Nickel-based alloys: Aviation and Aerospace/Power Generation
• Pure copper: Coils/Conductive Parts/Heat Exchangers

Conclusion

Electron Beam Metal 3D printers utilize a vacuum environment and a high-energy-density electron beam to achieve high-density builds using active and refractory metals. The hot process with preheating can minimize distortion of parts. Electron beam metal 3D printers have built a strong track record particularly in builds using hard-to-machine materials such as titanium alloys, nickel-based alloys, and tungsten that are required in aerospace, medical, and energy industries.

In the future, build precision and monitoring functions are expected to improve, leading to increased implementation at production sites. At production sites that prioritize the reliability and production efficiency of complex and high value-added components, electron beam metal 3D printers are expected to increasingly strengthen their presence as a strategic technology. JEOL will continue to support the development of technologies by integrating additive manufacturing technology that has the potential to drive innovation with measurement and analysis technologies to ensure consistent quality.