Manufacturing systems impact sustainable development among others through resource consumption and emissions, but also through working conditions and economic value creation. While planning and designing of production systems traditionally prioritizes economic efficiency, a more holistic approach incorporating environmental and social sustainability is needed. This research develops comprehensive design principles for more sustainable assembly lines based on their potential contribution to key Sustainable Development Goals. Sustainability criteria are systematically transferred into a framework that supports practical implementation in a general planning process. The resulting framework provides specific guidance for both high-level planning and detailed planning phases of assembly systems. The developed principles are a first attempt to enable companies to balance economic requirements with environmental resource conservation and social considerations.