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Additive manufacturing (AM) is a rapidly developing field which potentially decreases the manufacturing costs and enables increasingly complex antenna shapes. Metal-based AM might be particularly useful to manufacture antennas at mmwave range, because there antennas are physically small enough making additive manufacturing cost efficient, and manufacturing accuracy could still suffice for good electrical performance. In this paper, two additively manufactured and an identical machined fully metallic Ka-band Vivaldi antenna arrays are compared. The manufactured antenna arrays are compared using RFmeasurements to conclude the feasibility of AM for manufacturing antenna arrays at mm-wave frequencies. Comparison of the measured radiation patterns and realized gains of each of the antenna arrays between 26 and 40 GHz shows close to identical radiation patterns for all the arrays. A loss in realized gain of 0.5-1.5 dB is observed in the AM arrays when compared to the machined array due to the used materials and the surface roughness.

With the improvement in technology, additive manufacturing using metal powder has been a go-to method to produce complex-shaped components. With complex shapes being printed, the residual stresses (RS) developed during the printing process are much more difficult to control and manage, which is one of the issues seen in the field of AM. A simplified finite element-based, layer-by-layer activation approach for the prediction of residual stress is presented and applied to L-shaped samples built in two different orientations. The model was validated with residual stress distributions measured using neutron diffraction. It has been demonstrated that this simplified model can predict the trend of the residual stress distribution well inside the parts and give insight into residual stress evolution during printing with time for any area of interest. Although the stress levels predicted are higher than the measured ones, the impact of build direction on the development of RS during the building process and the final RS distributions after removing the base plate could be exploited using the model. This is important for finalizing the print orientation for a complex geometry, as the stress distribution will be different for different print orientations. This simplified tool which does not need high computational power and time can also be useful in component design to reduce the residual stresses.

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