Welding and Joining

Welding and joining create permanent or semi-permanent assemblies by fusing, bonding, or brazing parts, balancing strength, distortion control, and inspectability.

Overview

Welding and joining combine two or more components into an assembly using heat, pressure, filler material, or adhesives. Common fusion methods include MIG (GMAW), TIG (GTAW), Stick (SMAW), laser welding, and electron beam welding; solid-state options include friction welding and ultrasonic welding; resistance welding is common for sheet metal; brazing and soldering join with lower heat; adhesive bonding joins dissimilar materials and distributes load.

Choose welding/joining when the part is too large, complex, or cost-sensitive to machine from solid, when you need a sealed or structural assembly, or when modular fabrication improves lead time. Key tradeoffs are heat-affected zone effects, distortion, residual stress, cosmetic variability, and quality control needs (WPS/PQR, welder quals, NDE). Design and fixturing drive repeatability; process selection depends on material, thickness, access, required strength, and production volume.

Common Materials

  • Carbon steel
  • Stainless steel 304
  • Aluminum 6061
  • Titanium Grade 2
  • Copper
  • Inconel 625

Tolerances

±0.010" to ±0.030" (as-welded); ±0.002" to ±0.010" after machining/straightening

Applications

  • Structural frames and weldments
  • Pressure vessel nozzles and shells
  • Sheet metal enclosures and brackets
  • Piping manifolds and tube assemblies
  • Automotive body-in-white spot welds
  • Battery tab and busbar connections

When to Choose Welding and Joining

Choose welding and joining for multi-part assemblies where strength, sealing, or electrical/thermal continuity matters and machining from a single billet would be wasteful. It fits prototypes through production when you can control fit-up and fixturing and accept some post-weld finishing or machining. It’s a strong choice for large structures, sheet metal assemblies, and mixed-material joints that can’t be made as one piece.

vs CNC machining

Choose welding/joining when the part is naturally an assembly (frames, housings, manifolds) and machining from solid would drive high material removal, long cycle times, or size limits. Weldments also let you mix materials or thicknesses to put strength only where needed.

vs Metal injection molding (MIM)

Choose welding/joining when the part is large, thick, or low-to-medium volume and doesn’t justify tooling. Joining also supports design changes and configurable assemblies without retooling.

vs Metal 3D printing (DMLS/SLM)

Choose welding/joining when the geometry doesn’t require internal lattices or enclosed channels and the assembly can be built from standard stock and cut parts. Welding typically wins on cost and lead time for larger parts and higher deposition volumes.

vs Mechanical fastening (bolts/rivets)

Choose welding/joining when you need a sealed joint, higher stiffness, or lower part count without fastener access. It’s also preferred when vibration could loosen fasteners or when assembly envelope is tight.

vs Casting

Choose welding/joining when you need structural features with standard plate/section stock, quick iteration, or localized reinforcement rather than an all-new mold. Welded fabrications are often faster to qualify when design changes are likely.

Design Considerations

  • Call out weld symbol, size, length, and finish requirements; specify code/WPS/NDE only where function demands it
  • Design for consistent fit-up: controlled gaps, tabs/slots, and datum surfaces for fixturing and repeatability
  • Minimize distortion with balanced welds, short stitch patterns, and symmetric joint layouts; leave stock for post-weld machining where needed
  • Provide torch/electrode access and realistic gun angles; avoid deep pockets and tight corners near the joint
  • Specify joint type and edge prep (bevel, land, root opening) to match thickness and required penetration
  • Plan inspection and rework access; avoid burying critical welds where NDE or repair is impractical