Remote laser welding which has benefits for both productivity and energy saving is receiving increased attention for automotive assembly lines. Introducing this innovative equipment requires a redesign process for assembly elements, for example to substitute resist spot welding with remote laser welding. The mating surfaces related to the welding need to be updated as well, but this is complicated when the shape design includes manufacturing and assembly elements based on current practice which hide the design intent. The challenge is to establish guidelines with the design parameters of automotive door frames and the process parameters of the joining process in order to maintain the design intent. In order to maintain the original design intent of the process planner, the author proposes a propagation model for the production stage which is defined as the interplay between parameters and quantitative comparison. The process parameters of remote laser welding are applied to the flange of the door frame. Also, the shape of each flange is synchronised with the changes according to the result of a quantitative comparison of the productivity and eco-efficiency. A design guideline tool to redesign the flanges was developed inside a commercial CAD system to show the proposed concept. Five flanges of a car door were subjected to redesign for introducing 4-kw remote laser welding with considerations of eco-efficiency, process time and weight change. The tools are shown to illustrate how to maintain design intent in the redesign process, and the concept was realised in a commercial CAD system.