Sheet Metal Design Basics in Fusion 360 A beginner's guide to bends, flanges, and flat patterns If you've ever tried to design an enclosure, bracket, or panel and wondered why your regular solid modeling tools feel clunky for the job, you've run into the exact problem sheet metal design solves. Fusion 360's Sheet Metal workspace is purpose-built for parts that start life as a flat piece of metal and get bent into shape — think electronics enclosures, brackets, chassis panels, and HVAC ductwork. This guide walks you through the core concepts so you can go from a blank sketch to a manufacturable flat pattern with confidence. Why Sheet Metal Is a Different Workspace In standard solid modeling, you extrude, fillet, and shell your way to a shape. Sheet metal parts behave differently in the real world — they're formed from a single flat sheet using a brake press, so every bend has to "unfold" back to a flat state without distortion. Fusion 360 handles this by using rules rather than raw geometry. Once you set your sheet metal thickness, bend radius, and relief style, every feature you add — flanges, bends, corners — respects those rules automatically. This is what makes it possible to hit Unfold or Flat Pattern at any point and see exactly what the manufacturer needs to cut. Step 1: Set Up Sheet Metal Rules Before creating any geometry, open the Sheet Metal Rules dialog and define: - Thickness — the actual gauge of material you're using (e.g., 1.5mm steel, 2mm aluminum) - K-Factor or Bend Table — determines how the material stretches at the bend, which affects your flat pattern's accuracy - Bend Radius — typically matches your press brake tooling - Relief Shape and Size — the notches cut at bend intersections to prevent tearing Getting these values close to your actual manufacturing process up front saves you from flat patterns that don't match reality later. Step 2: Create the Base Flange Every sheet metal part starts with a Base Flange — essentially an extrude, but constrained to your sheet thickness. Sketch a profile on any plane, switch to the Sheet Metal workspace, and select Flange > Base Flange. Fusion automatically applies your rule set thickness instead of letting you type an arbitrary value. This is the flat "seed" your entire part grows from. Step 3: Add Flanges and Bends From here, you build outward using two main tools: - Flange — extends a new wall from an existing edge, with a bend automatically inserted at the transition. You control the flange length, bend angle, and whether the bend goes up or down. - Bend — adds a bend line across an existing flat face without adding new material, useful for splitting one panel into two angled sections. A common beginner mistake is chaining flanges without checking how corners will resolve. Fusion offers several corner types (butt, overlap, rip) — picking the wrong one can either leave a manufacturing gap or create material that physically can't exist when the sheet folds. Step 4: Handle Corners and Reliefs When two bends meet at a corner, material has to go somewhere. Fusion's Corner tools let you round, chamfer, or trim these intersections cleanly. If you skip this step, your flat pattern may show overlapping or torn geometry — a red flag that a real manufacturer would reject the file. Relief cuts (already defined in your rules) get applied automatically here too, so bends near corners don't crack the material during forming. Step 5: Unfold and Generate the Flat Pattern This is where sheet metal design proves its value. Once your 3D bent model is complete, switch to the Flat Pattern environment and select Create Flat Pattern. Fusion calculates exactly how the part unrolls, accounting for your K-factor, and gives you a 2D layout ready for laser cutting, punching, or export as a DXF. Before sending this to a manufacturer, check for: - Overlapping geometry after unfolding - Bend lines that land on holes or slots (these should usually be offset) - Consistent grain direction if your material is directional Common Mistakes to Avoid - Ignoring K-factor — using the default value instead of your actual material's stretch behavior will throw off your flat pattern dimensions, sometimes by several millimeters on larger parts. - Adding holes before bends — features placed too close to a bend line will distort. Add mounting holes after the geometry is finalized, and keep them a safe distance from bend zones (a good rule of thumb is at least 2–3x material thickness). - Mixing solid and sheet metal workflows — converting a solid body to sheet metal after the fact often produces broken flat patterns. Start in the Sheet Metal workspace from the beginning whenever possible. Putting It Into Practice The best way to internalize these concepts is to design something simple first — a basic L-bracket or a small electronics enclosure with two or three bends. Once flat pattern generation feels predictable, you can move on to more complex parts with multiple flanges, cutouts, a