What are key DFM guidelines for sheet metal design?

Key sheet metal DFM guidelines include: maintaining minimum bend radius equal to material thickness to prevent cracking, keeping minimum flange length at 4x material thickness, ensuring adequate hole-to-edge and hole-to-bend distances (typically 2-3x thickness), using standard tooling sizes for punched features, designing for grain direction in bends, avoiding narrow cuts that cause die wear, and specifying bend relief to prevent tearing. Consider flat pattern developability early in design.