Welding (Sheet Metal)

Sheet metal welding joins cut and formed panels into rigid assemblies using localized heat or resistance, balancing strength, distortion control, and access for tooling.

Overview

Sheet metal welding permanently joins sheet components into a single assembly using heat input (fusion) or electrical resistance (spot/seam). It’s commonly used after cutting and forming to build frames, enclosures, brackets, and tanks where fasteners would add cost, leak paths, or loosen over time. Spot welding and seam welding are typical for lap joints in thin-gauge steel and stainless.

Choose welding when you need high joint strength, good stiffness-to-weight, or sealed seams, and you can control heat distortion with fixturing and weld sequencing. Key tradeoffs: weld shrinkage can move features, surface finish around welds often needs cleanup, and corrosion resistance may require post-weld finishing (passivation, coating). Quoting depends heavily on joint access, weld length/count, fit-up gaps, and inspection requirements.

Common Materials

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

Tolerances

±0.030" to ±0.060" (as-welded assembly; tighter with fixturing and post-weld machining)

Applications

  • Sheet metal enclosures and cabinets
  • Welded machine frames and bases
  • Stainless food-service carts and guards
  • HVAC plenums and duct transitions
  • Welded tanks and drip trays
  • Battery trays and mounting brackets

When to Choose Welding (Sheet Metal)

Choose sheet metal welding for multi-piece assemblies that must be rigid, durable, or sealed, especially at low to medium production volumes. It fits parts with accessible joints and where minor post-weld finishing or straightening is acceptable. It’s a strong option when you want permanent joints without added hardware.

vs Cutting

Choose sheet metal welding when the part can’t be made as a single flat pattern and needs multiple pieces joined into a 3D assembly. Welding adds structural continuity and can create sealed seams that cutting alone can’t provide.

vs Forming

Choose sheet metal welding when bend limitations, tool clearance, or part size prevent forming the geometry from one blank. Welding lets you build complex box structures or attach stiffeners without forcing extreme bends or large dedicated tooling.

vs Punching

Choose sheet metal welding when you need structural joining rather than holes, louvers, or features made in a flat sheet. Punching can prepare tabs/slots and access holes, but welding is what turns those prepared pieces into a rigid assembly.

vs Fastening

Choose sheet metal welding when you need a permanent joint, higher stiffness, or a sealed/leak-tight seam without gaskets. Welding also removes BOM cost and assembly time tied to inserts, rivets, and torque/retention risks.

vs Hydroforming

Choose sheet metal welding when the geometry is best built from multiple simple pieces and volumes don’t justify specialized forming setups. Welding supports mixed materials and local reinforcements that are difficult to integrate into a single hydroformed shell.

Design Considerations

  • Specify joint type and weld size/length (and whether continuous or stitch) on the drawing; avoid leaving welds to shop discretion
  • Design for access: maintain torch/electrode clearance and avoid closed corners that trap tools or force awkward weld positions
  • Control distortion by using symmetric welds where possible and call out critical datums/features to be held after welding
  • Use tabs/slots, locating features, or formed flanges to self-fixture parts and reduce fit-up time and gap variability
  • Avoid tight post-weld tolerances on thin sheet; if needed, plan post-weld machining, reaming, or straightening operations
  • Define cosmetic requirements (grind flush vs as-welded) and corrosion protection (passivation, plating, powder coat) to prevent surprises in cost and appearance