Resistance welding variants — identifying projection welding Projection welding is best classified as a __________.

Introduction / Context:
Projection welding is a resistance welding process in which embossed projections or nut bosses concentrate current and force to create multiple nuggets in a single squeeze. It is widely used for attaching fasteners and making crosswire grids.

Given Data / Assumptions:

• Workpieces have pre-formed projections or use engineered nuts/bolts with built-in projections.
• Resistance heating occurs at the projections due to higher current density.
• Multiple nuggets can form in one operation.

Concept / Approach:
Unlike seam welding (wheel electrodes for continuous overlap), projection welding uses flat electrodes and raised projections to localize heat. Multiple projections allow multi-spot welds simultaneously, improving throughput and positional accuracy for fastener attachment.

Step-by-Step Solution:
Identify key feature: localized projections concentrate current.Recognize outcome: multiple nuggets in one press operation.Therefore, classify as a multi-spot resistance welding process.

Verification / Alternative check:
Application notes for nut welding specify projection welding schedules with force and current tailored to collapse the projections uniformly, confirming the multi-spot nature.

Why Other Options Are Wrong:
Continuous spot with wheels is seam welding; manual metal arc is an arc process; butt welding of bars is a different resistance process; laser seam is a fusion process unrelated to projections.

Common Pitfalls:
Inadequate projection height uniformity causing uneven nugget formation; insufficient electrode force leading to expulsion; omitting shunting effects in multi-projection layouts.

Final Answer:
multi-spot resistance welding process using localized projections