We have presented an open-source second-generation Maskless Array Synthesizer (MAS 2.0) suitable for routine ultra-large-scale synthesis of nucleic acids. The device is engineered to be highly robust and reliable such that it can be used routinely and with minimal maintenance in common laboratory environments. We provide detailed information on its use in the context of nucleic acid synthesis, but its applicability can be extended to other sequence-defined linear polymers such as peptides. Detailed mechanical drawings, CAD files, software source code, and extensive operating instructions and protocols are provided in the supplementary materials that allow the construction and operation of the MAS 2.0.