Welding (Sheet Metal)

Sheet metal welding permanently joins metal panels and brackets with localized heat, enabling strong, sealed, structural assemblies from multiple cut and formed pieces.

Overview

Welding for sheet metal joins two or more metal pieces using localized heat to create a permanent metallurgical bond. In fabrication shops this typically means MIG, TIG, spot welding, or seam welding on laser-cut and formed parts. It’s used to build brackets, frames, enclosures, and structures from thinner gauge stock.

Choose sheet metal welding when you need high joint strength, good stiffness, or sealed seams, and the assembly doesn’t need to be disassembled later. It works well for low to high volumes if the design is weld-friendly and fixturing is straightforward. The main tradeoffs are heat distortion, added labor cost, and the need for access to both sides for some welds. Welds may also require post-processing such as grinding, leak testing, or cosmetic finishing to meet appearance or sealing requirements.

Common Materials

  • Mild steel
  • Galvanized steel
  • Stainless steel 304
  • Stainless steel 316
  • Aluminum 5052
  • Aluminum 6061

Tolerances

±0.020"–±0.060" on overall welded assemblies; tighter features typically require post-weld machining or secondary operations

Applications

  • Equipment frames and bases
  • Sheet metal enclosures and cabinets
  • HVAC ducts and welded seams
  • Automotive and machinery brackets
  • Battery and electronics housings
  • Welded tanks and reservoirs

When to Choose Welding (Sheet Metal)

Use sheet metal welding when you need permanent, high-strength joints between thin metal parts, especially where fasteners would loosen, leak, or take too much space. It suits structural frames, sealed seams, and cosmetic assemblies at low to high volumes when you can tolerate some heat-affected zones and design for good weld access.

vs Cutting

Choose welding over cutting when your goal is to join multiple sheet metal parts into a single structure rather than separate them from stock. Cutting defines part geometry; welding turns those discrete cut pieces into a rigid, functional assembly with load-bearing joints and sealed interfaces.

vs Forming

Choose welding over forming when the geometry or strength you need cannot be achieved by bending a single blank, such as closed frames, complex 3D structures, or reinforced corners. Forming is great for single-piece shells; welding adds ribs, brackets, and multi-part structures that would be impossible or too costly to form alone.

vs Punching

Choose welding over punching when you need to assemble multiple punched or laser-cut pieces into a rigid or sealed assembly. Punching creates holes and features in flat stock; welding is then used to connect those components into frames, boxes, and welded subassemblies that carry load or require continuous joints.

vs Fastening

Choose welding over fastening when you need permanent joints, better stiffness, or leak-tight seams, and service disassembly is not required. Welding removes hardware cost and potential loosening, at the expense of higher heat input, more fixture control, and more challenging rework.

vs Hydroforming

Choose welding over hydroforming when volumes are low to medium, tooling budgets are limited, or the shape can be built from standard cut and bent parts. Hydroforming shines for complex, high-volume single-piece shells; welding lets you combine simpler sheet metal parts into similar geometries without expensive forming dies.

Design Considerations

  • Specify weld types, sizes, and critical seams clearly on the print; avoid leaving weld requirements ambiguous for the shop
  • Design joints with natural fit-up: use tabs, slots, and locating features so parts self-fixture and reduce welding time and distortion
  • Provide adequate weld access for torch or gun angles, including clearance around flanges, corners, and inside boxes
  • Avoid over-welding; call out minimum effective fillet sizes and intermittent welds where structurally acceptable to reduce cost and distortion
  • Place tight tolerances away from weld seams and plan to hold them with formed or machined datums rather than relying on weld accuracy
  • Consider post-weld processes—grinding, leak testing, coating—and design joints and access so these can be done quickly and consistently