In refolded fold interference patterns, the earlier fold generation (F1) typically develops a non-planar (curved) axial surface due to being subsequently deformed by the later fold generation (F2), while F2's axial surfaces remain relatively planar; hinge line orientations of superposed fold sets can be parallel or non-parallel depending on the interference pattern type (Ramsay's Type 1, 2, or 3).
In this interference structure, both the F1 and F2 hinge lines are parallel (consistent with a coaxial refolding geometry), and the earlier F1 folds have...
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