DFM – Design for Manufacturability – is the practice of designing parts with their production method in mind. For OEM buyers sourcing sheet metal and tube parts from China, DFM awareness can reduce unit cost by 15-40% and eliminate the most common causes of order delays.
1. Avoid Unnecessary Tight Tolerances
A hole position tolerance of +/-0.05mm on a bracket that will be bolted to a frame adds significant machining cost compared to +/-0.2mm – yet the assembled function is identical. Before finalizing your drawing, ask: which dimensions are genuinely critical to function? Only those should carry tight tolerances. At Conwhole Hardware, we flag over-specified tolerances in every RFQ as part of our DFM review.
2. Design Bends with Standard Bend Radii
Press brake tooling is available in standard sizes. Designing bends with a radius equal to the material thickness (mild steel) or 1.5-2x thickness (aluminum) ensures standard tooling can be used. Rule of thumb: minimum bend radius = 1x thickness for mild steel, 1.5-2x for stainless, 2-3x for aluminum (grade dependent). Non-standard radii require custom tooling – extra cost and lead time.
3. Respect Minimum Flange Length
A flange too short to grip in the press brake die cannot be formed reliably. Minimum flange length = 4x material thickness. 6x is more comfortable. Very short flanges under 3mm on 1mm material either require special tooling or must be redesigned.
4. Place Holes Away from Bend Lines
Holes punched or laser-cut too close to a bend line will distort during bending. Keep holes at least 1.5x material thickness plus bend radius away from any bend centerline. If your design requires a hole close to a bend, it should be added after bending – which affects production sequence and cost.
5. Specify Surface Finish Early – It Affects Tolerances
Powder coating adds 60-80 micrometers per surface. If a part has a +/-0.1mm tolerance and will be powder coated, the coating may consume half that tolerance. Specify your finish on the drawing, and note whether dimensions are pre-coat or post-coat. For precision fit features, consider anodizing (thinner than powder coat) instead. Send us your drawings for a free DFM review.