Resistance Welding

Resistance welding joins overlapping metal parts by clamping them between electrodes and fusing with localized heat from electrical current, ideal for fast, repeatable spot or seam welds.

Overview

Resistance welding (RSW) joins metal parts by clamping them between copper electrodes and passing high current through the joint. The electrical resistance at the interface generates heat, forming a weld nugget without filler metal or open arc. Common sub-processes are spot welding for discrete welds and seam welding for continuous, leak-tight joints.

Use resistance welding for conductive metals in overlapping (lap) joints, especially thin sheet and strip. It shines in medium to very high volumes where cycle time, automation, and consistency matter more than cosmetic perfection. Typical applications include automotive body panels, battery tabs, and appliance housings. Tradeoffs: you need good access for electrodes, consistent material stack-up, and controlled surface condition; thick sections, poor conductivity control, or heavy coatings can cause quality problems. Expect strong, repeatable welds, but visible electrode marks and limited reach into deep or complex geometries.

Common Materials

  • Low carbon steel
  • Stainless steel 304
  • Galvanized steel
  • Aluminum 5052
  • Copper alloys
  • Nickel alloys

Tolerances

±0.010" to ±0.030" on weld location and part fit-up

Applications

  • Automotive body panels and reinforcements
  • Battery tabs and bus bars
  • Appliance enclosures and brackets
  • HVAC ducting and sheet metal housings
  • Wire and terminal welds
  • Fuel tanks and leak-tight seams

When to Choose Resistance Welding

Choose resistance welding for overlapping metal joints in thin to medium-gauge materials where you need very short cycle times and easy automation. It fits best for repeatable, fixture-friendly parts at medium to high production volumes, with good access for clamp-style electrodes and controlled material thickness and coatings.

vs MIG (GMAW)

Pick resistance welding when you need very fast, automated joining of thin sheet with minimal filler and low heat input to the surrounding area. Compared to MIG, RSW suits lap joints, high-volume fixtured production, and situations where you want to avoid spatter and large weld beads on visible surfaces.

vs TIG (GTAW)

Choose resistance welding over TIG when speed and repeatability matter more than cosmetic bead appearance or access flexibility. RSW offers much shorter cycle times, easy automation, and no filler wire handling, making it better for production spot joints in stampings and assemblies rather than precision hand-welded seams.

vs Stick (SMAW)

Use resistance welding instead of Stick for thin sheet, production environments, and situations where you can fixture and clamp parts. Stick suits field work and thick, structural sections; RSW excels in factory settings with repetitive joints, cleaner environments, and the need for consistent nugget size and location.

vs Laser Welding

Select resistance welding when parts allow electrode access and you want lower capital cost and simpler process control than laser systems. RSW is robust for overlapping joints in coated steels and doesn’t require precise beam alignment or advanced optics, at the cost of larger heat-affected zones and visible electrode marks.

vs Brazing & Soldering

Prefer resistance welding when you need a fusion joint with higher strength and better structural performance in lap joints. RSW avoids filler alloys and flux, shortens cycle time, and integrates well with automated lines, as long as your materials are suitably conductive and stack-up thicknesses stay within process limits.

Design Considerations

  • Keep total stack-up thickness within a narrow range and specify it clearly so the shop can select appropriate electrode size and current
  • Provide flat, clean electrode contact areas with enough clearance around the weld spot for standard electrode caps
  • Control coatings and surface condition; highlight any galvanized, painted, or plated areas and where coatings will be removed before welding
  • Dimension weld locations from robust datums and avoid placing welds too close to edges, bends, or holes to prevent burn-through and distortion
  • Specify required weld nugget diameter, number of welds, and spacing rather than vague “weld as needed” notes
  • Add locating features or tabs to aid fixturing and repeatable clamping, especially for multi-spot patterns or seam welds