Assembly system design and development is still characterized by uncertainty resulting in increased lead-times in the design and development process and ineffective assembly system solutions. One important reason for this situation is that companies do not use methods for assembly system design and development in the extent needed, simply because there are no methods applicable. Methods developed by academia are still too complicated and not distinct enough, in quantifiable means, concerning the link to assembly system design. In this research four case studies in four different companies have been executed with the objective to find out more about how industry handles assembly system design and if there are possibilities for improvement. The findings in the case studies unambiguously point out that there is a need for a guideline supporting the assembly system design, development and re-design phases. The case studies do also indicate that the information from DFA/DFA2 analysis, valuable for the assembly system design process, is not used within the subsequent assembly system design phase. An assembly system design guideline that uses information and results from the DFA work, together with internal and external demands, would facilitate the assembly system design and development process. This paper will introduce a framework for such a method.