ASELSAN A.S., Ankara, Turkey
Electron beam melting has been used recently in additive manufacturing by various researchers. In those electron beam melting applications, the electron energy can be 60 to 100 keV, the beam current can be around 10 mA to 100 mA, and the beam spot size can be as small as 200 µm according to electron energy and beam current. Those parameters can result in very high beam power densities. The diagnostics of this powerful beam can be quite a problematic issue. As the electron beam current required for the application is quite similar to DC current, fast undestructive current measurement techniques for current beam profile and beam position are very limited in performance. Therefore, some destructive techniques to measure current and other beam properties are essential. As part of the beam diagnostics for electron beam melting application for additive manufacturing, the authors proposed a complete beam diagnostics system to measure the electron gun’s capabilities and associate electromagnetic lens systems. The following properties have been diagnosed as part of this research work: i) Beam Current, ii) Beam Spot size for enlarged and focused beams, iii) Scanning velocity of the deflected beam, iv) Profile of the beam. The authors proposed methods to measure focused beam spot size and deflected beam scanning velocity using Secondary Emission Grid Sensors. Moreover, the authors proposed a new technique to measure beam profile using consecutively placed several copper plates with beam guiding holes of various diameters. The proposed beam profile measurement method effectively determines the useful beam radius for metal powder melting properties specifically to additive manufacturing applications.
