Welding and Joining

Welding and joining create permanent structural or sealed joints between parts using heat, pressure, or adhesives across metals, plastics, and mixed-material assemblies.

Overview

Welding and joining processes permanently connect two or more parts to carry load, seal fluids or gases, or create integrated assemblies. This category covers fusion welding (MIG/GMAW, TIG/GTAW, Stick/SMAW), resistance welding (spot, projection), high‑energy methods (laser, electron beam, friction), ultrasonic welding for plastics and thin metals, as well as brazing, soldering, and adhesive bonding.

Use welding and joining when you need structural continuity, leak-tight seams, reduced part count, or can’t practically make the part as a single piece. Processes span from manual TIG for precision one‑offs to robotic MIG and resistance welding for high-volume production, plus brazing and adhesives where you must join dissimilar materials or thin, heat‑sensitive sections. Tradeoffs include heat distortion, joint access requirements, inspection complexity, and the need for clear joint design and weld symbols. Critical dimensions usually require post‑weld machining or tight fixturing to hold tolerance. Selecting the right sub‑process depends on material type, section thickness, joint geometry, and production rate.

Common Materials

  • Mild steel
  • Stainless steel 304
  • Aluminum 6061
  • Titanium Grade 5
  • Copper
  • ABS plastic

Tolerances

±0.010"–±0.060" on welded assemblies; tighter features typically machined after joining

Applications

  • Structural frames and weldments
  • Pressure vessels and piping systems
  • Automotive chassis, brackets, and exhausts
  • Bicycle and motorcycle frames
  • Sheet metal enclosures and cabinets
  • Battery packs and electronic housings

When to Choose Welding and Joining

Use welding and joining when you need permanent, load‑bearing or leak‑tight connections and want to reduce part count versus bolted assemblies. These processes fit anything from prototype fixtures to robotic high‑volume weldments, especially where you can accept moderate assembly-level tolerances and plan for post‑weld machining on critical features. They are also key when joining dissimilar or thin materials that can’t be formed as one part.

vs CNC machining

Choose welding and joining when the geometry is easier and cheaper to build from multiple simple pieces than machining from a single block. Welded assemblies often win on cost and material utilization for large structures, long spans, and frames, with only critical interfaces machined after welding.

vs 3D printing

Use welding and joining when part size is large, material is a standard structural alloy, and you care more about cost and throughput than extreme geometric freedom. Welded fabrications are usually more economical for frames, brackets, and heavy structures where AM’s complexity advantage is not required.

vs Casting

Pick welding and joining when you need design flexibility, quick changes, or low-to-medium volumes without paying for tooling. Welded and brazed assemblies let you iterate or customize without new molds, and are better suited to very large parts that would demand massive castings.

vs Mechanical fastening

Choose welding and joining when you want permanent, rigid, or sealed joints and don’t need future disassembly. Welds, brazes, and adhesives remove hardware cost and potential loosening, and are preferred for sealed tanks, frames with tight stiffness requirements, and joints where fastener access is poor.

vs Metal stamping

Use welding and joining when your product consists of multiple stampings or sheet parts that must be assembled into a 3D structure. Spot welding, projection welding, brazing, or adhesive bonding efficiently tie stamped parts together into frames, enclosures, and subassemblies without adding fasteners.

Design Considerations

  • Define joint types and weld symbols clearly (fillet vs groove, intermittent vs continuous) so shops can estimate time and inspection accurately
  • Provide adequate joint access for torches, guns, electrodes, and inspection; avoid deep narrow pockets and hidden seams
  • Dimension from functional datums and identify which faces will be machined after welding to control stack-up and distortion impact
  • Limit extreme thickness transitions and large gaps at joints; design tabs, laps, or backing to control fit-up and reduce filler and rework
  • Call out allowable weld size ranges and distortion/flatness requirements so fixtures and process selection match your real needs
  • Specify materials, coatings, and heat treatments with joining in mind, including weldability, preheat/postheat needs, and adhesive compatibility