We demonstrate a 3D imaging system operating at 235-270 GHz based on a multiple-input multiple-output (MIMO) sparse array with 64 receivers realized in low-cost silicon germanium hetero-bipolar semiconductor technology. The parallel acquisition with a high number of receivers, combined with 12 time-multiplexed high-power transmitters, high-frequency switching and fast data acquisition electronics, enables high image acquisition rates compatible with in-line imaging in an industrial production environment. The system is designed for defect detection in composite thermoplastic parts after their forming process. Such parts are interesting for lightweight automotives given their excellent mechanical properties in combination with a mass manufacturing compatible processing technology. In this contribution we concentrate on the system realization aspects, and present exemplary 3D reconstruction images.