Sheet Metal Fabrication Process: From Design to Delivery

Sheet metal fabrication transforms flat metal sheets into finished parts through six precise stages. Understanding the workflow helps you communicate requirements clearly and get accurate quotes from manufacturers.

Step 1: Design & DFM Review

Before any metal is cut, your CAD file undergoes a Design for Manufacturability (DFM) review. Our engineers check bend radii, hole-to-edge distances, and material thickness to catch potential issues before production starts. A thorough DFM report saves weeks of back-and-forth and prevents costly mistakes.

Key DFM rules: Minimum bend radius ≥ material thickness. Hole-to-edge distance ≥ 2× material thickness (1.5× minimum). Flange width ≥ 4× material thickness. Distance between holes ≥ 2× material thickness.

Step 2: Blanking (Laser Cutting)

A high-power fiber laser cuts the flat pattern from sheet metal with ±0.1mm precision. For reference, a human hair is ~0.07mm — so we’re cutting to within 1.5 hairs of your target dimension.

Laser cutting handles materials up to 8mm thick (carbon steel), 6mm (stainless), and 4mm (aluminum). For thicker sections or high volumes (>5,000 pcs), stamping provides faster throughput at lower per-part cost — though with higher upfront tooling investment.

Common materials and max laser thickness:

Step 3: Bending (CNC Press Brake)

Flat blanks move to CNC press brakes where they’re formed into 3D shapes. Single bends achieve ±0.1mm tolerance; double bends ±0.2mm. The bend radius must be at least equal to the material thickness to avoid cracking at the bend line.

Pro tip: Specify grain direction on your drawing — bending perpendicular to the grain reduces cracking risk and improves part strength. If your drawing doesn’t specify, we default to perpendicular — but confirming this in your RFQ avoids assumptions.

Bend allowance quick reference (90° bend, 1mm radius): 1mm sheet = 1.57mm allowance. 2mm = 3.14mm. 3mm = 4.71mm. Add this to your flat pattern length.

Step 4: Welding & Assembly

Parts are joined using the appropriate process for the material and application:

• TIG welding — Precision, clean welds ideal for aluminum, stainless steel, and thin materials (0.5-3mm)
• MIG welding — Faster deposition rate for thicker steel sections (2mm+) and longer seams
• Spot welding — Efficient for sheet stack-ups where full-seam welding isn’t required

Complex assemblies use custom jigs and fixtures to ensure consistency across production batches. All welders are certified, and weld quality is verified via visual inspection plus dye penetrant or X-ray testing when specified.

Design tip: If your assembly requires welding, add 0.2-0.5mm clearance at mating surfaces. Tight press-fit tolerances (±0.05mm) are hard to achieve on welded assemblies due to heat distortion.

Step 5: Surface Finishing

The final finish protects the part and determines its appearance. Selection depends on the operating environment:

Step 6: Quality Inspection

Every batch undergoes dimensional inspection using CMM (Coordinate Measuring Machine), digital calipers, height gauges, and surface roughness testers. Critical dimensions are checked against the drawing with full documentation.

Inspection documents available on request:

• First Article Inspection Reports (FAIR) — AS9102 format
• PPAP Level 3 documentation
• Certificate of Compliance (CoC)
• Material certificates (mill test reports)
• Surface finish measurement reports

Why Process Knowledge Matters for Your Quote

When you understand which processes your part requires, your RFQ becomes more precise — and manufacturers can quote more accurately. Compare:

That clarity cuts quote time by 50% and eliminates the “we assumed X, but you wanted Y” surprises. Use the process flow diagram at the top of this page as a checklist for your next RFQ.

Key Takeaways

• DFM review is free leverage: 80% of avoidable cost is locked in at the design stage — bend radii, hole-to-edge distances and tolerance callouts decide price before any metal is cut.
• Laser cutting defines accuracy, bending defines repeatability: the blank is only as good as the flat pattern, and the bend is only as good as the K-factor math behind it.
• Welding is where tolerances stack: fixture design and weld sequencing — not welder skill alone — determine whether an assembly stays within spec.
• Finishing is a functional spec, not cosmetics: call out the finish system (e.g. powder coat type and thickness) on the drawing, not just a color.
• Inspection should produce paper: a supplier who cannot show you a dimensional report for your first article is asking you to take quality on faith.

Every project moves through these six steps whether your supplier talks about them or not. The difference between a smooth order and a delayed one is usually how early the process conversation happens: a drawing that arrives with material grade, thickness, finish system and critical dimensions already specified skips two rounds of clarification emails and goes straight to the laser. If you are still comparing vendors, our companion guide on choosing a sheet metal fabrication supplier in China gives you the exact questions to ask about each of these six steps.