A flat wideband lens antenna operating in the Ka band is presented. The design corresponds to the transformation of a hyperbolic lens via quasi-optic transformation into a flat lens. The implementation of the lens is made using 3D printing technology as it allows cheap and precise manufacturing of the complicated shapes obtained with the transformation. The required refractive indices are calculated and implemented with varying infill percentages of the used filaments in each transformed layer. The experimental results show excellent agreement with the simulations, including low losses. The presented design is a low-cost antenna with the measured gain above 23 dBi in the whole Ka band (26.5-40 GHz).