Electromagnetic performance of Ti6Al4V and AlSi7Mg0.6 waveguides with laser beam melting (LBM) produced and abrasive flow machining (AFM) finished internal surfaces

Metal additive manufacturing processes, such as laser beam melting (LBM), can play a key role in developing antenna-feed chains because monolithic and multifunctional parts can be manufactured with high geometric freedom in the design phase. Using LBM technology, lighter and more compact antennas can be produced and manufacturing costs can be reduced. However, the surface roughness of internal surfaces in waveguides produced by LBM is much higher (about 10 μm Ra) than that produced by conventional manufacturing technologies. Consequently, such high surface roughness of the internal surface can affect electrical current propagation through the waveguide and corresponding transmitted power. In this paper, abrasive flow machining (AFM) was used to reduce the surface roughness of the internal surfaces of four different waveguides used at both K and Q bands. A significant reduction in the transmission loss at both K and Q bands was observed as their internal surface roughness decreased from about 10 μm to 1 μm Ra. This was assumed to be due to an increase of the internal surface electrical conductivity with the decrease of roughness in waveguides channels.