Arcam’s Electron Beam Melting (EBM)
Arcam supplies equipment for the manufacture of fully dense metal parts by electron beam melting (EBM). EBM technology uses a strong electron beam (4 kW power)
FIGURE 5.4 LENS MR-7 system.
to create part layer by layer of melting metal powder. The EBM process is conducted in a vacuum at an elevated temperature of 1000°C, resulting in stress-relaxed parts that have stronger material, mechanical, and chemical properties than cast and forged. The process is based on high-level energy utilization that delivers high melting capacity and high productivity.
The EBM process is planned primarily for the manufacture of refractory and resistant materials (tantalum, niobium, molybdenum, tungsten, vanadium, hafnium, zirconium, titanium) and their alloys. The EBM process is characterized primarily by high-speed production, rapid tooling, and complex geometry components with similar mechanical features to heat-treated materials. The Italian company Bticino has used EBM technology to produce light switch injection molding equipment in ABS plastic with a production volume of 1 million parts per year, with cobalt chromium alloy conformal cooling channels with high abrasion resistance and chemical corrosion. They were able to improve productivity, reduce cycle time, and lower the cost of production. Additionally, the efficiency of the manufactured parts has also been enhanced by improving the cooling system. The EBM tools in CoCr, a material with excellent wear and corrosion resistance properties, enabled BTicino to manufacture tools with extended geometrical freedom and longevity. Electron beam melting (EBM) is a new alternative for rapid manufacturing and prototyping of metal components. This technique is quickly gaining interest because of its ability to produce completely dense components, with properties comparable to those of wrought materials, at a cost and speed substantially lower than those of metal-based additive manufacturing methods.
EBM not only produces unparalleled strength-to-weight ratios, decreases the cost of raw materials, and decreases the weight of the parts, but also opens the door to new design configurations. EBM technology stands out for its ability to produce parts of titanium in hours versus days. For industries such as aerospace, this technology creates new opportunities for prototyping and low-volume component production. Time, costs, and challenges of machining or investment casting are eliminated, making titanium parts readily available for functional testing or installation on mechanical systems. EBM is patented by Arcam and distributed by Stratasys in the United States.
As the name suggests, EBM uses an electron beam to melt titanium powder. Additive manufacturing processes build parts on a layer-by-layer basis. After one layer of titanium powder is melted and solidified, the process is repeated for subsequent layers. Within the electron beam gun, the incandescent filament of tungsten and the electron cloud boil (Figure 5.5a). These electrons flow through the gun at about half the speed of light. Two magnetic fields are organizing and directing fast-moving electrons. The first act as a magnetic lens which focuses the beam on the desired diameter and the second magnetic field deflects the beam to the target point of the powder bed. When high-speed electrons strike metal powder, the kinetic energy is instantly transformed into thermal energy. Raising the temperature above the melting point, the electron beam quickly liquefies the titanium powder. Arcam A2 (Figure 5.5b) developed by Arcam is capable of manufacturing parts up to 7.87 in. x 7.87 a.m. x 13.0 a.m. (200 mm x 200 mm x 330 mm in length). Parts produced with EBM are near-net shape like those made with metal-casting processes. As the electron beam completely melts the titanium, the liquefied metal conforms to the surrounding metal powder, which creates a surface finish similar to a precision sand casting; as a result, some light secondary grinding or grinding may be needed.