Copper welding

Copper conducts heat away from the weld pool, so preheat is often needed on thicker sections. ETP copper containing oxygen can become porous when welded in a reducing atmosphere; oxygen-free copper avoids that. Brazing with silver filler is the practical route for busbar joints and keeps the heat-affected zone small.

The commercial consequence is that copper is priced on its own material line, not blended into a steel rate. Material grade, thickness, tolerance and finish are quoted separately from conversion, so a change of specification is visible in the price.

Ganesh quotes to the drawing first and to ISO 2768 general tolerances where the drawing is silent. For copper welding, the practical starting points are in the table below. They are starting points, not a guarantee: the part geometry, thickness and fixturing decide what can actually be held, and the quotation states the tolerance offered.

Welding fixtures are designed and built in the Ganesh tool room, which is why assembly geometry is controlled by steel, not by a welder's eye. Busbars and current-carrying parts are specified by conductivity, not just by grade name; ETP C11000 is the common baseline and oxygen-free copper is reserved for vacuum or brazing duty. The route is quoted as one sequence so the customer does not have to coordinate a cutter, a former, a welder and a coater.

Welding is the wrong joining method for a busbar that must maintain conductivity across the joint; a bolted or brazed joint is electrically better and easier to inspect.

A manufacturability review before quotation is the cheapest place to find this out. Send the drawing, material, finish and annual quantity and the review comes back in writing.

• Busbar joints
• Earthing assemblies
• Heat exchangers
• Terminal lugs

Weld when the assembly cannot be formed as one part or must be shipped knocked down. Robotic MIG pays back on repeat assemblies where the fixture holds the joint in the same place every cycle; below a few hundred identical assemblies a year, a fixture and manual MIG are usually more economic. Do not weld where the customer needs a flat, unmarked panel or where the assembly must be disassembled for service. For copper the practical constraint is conductivity and heat: cutting parameters, bend radius and joint method are all set by the temper and the electrical requirement, not by the shape alone. Copper parts are often single-source by specification rather than by process, so the decision that matters is the temper and the edge condition, both of which should be on the drawing before a supplier is chosen.

State the weld symbol or size, whether welds are structural or sealing, the finish requirement on the weld (dressed or as-welded), and the dimensional tolerance on the assembled frame rather than on the individual parts. Say whether the assembly is coated after welding, because that changes the access and the masking plan.

Inspection covers weld size and length, visual defects, distortion against the assembly drawing and, where specified, penetration or leak testing. Fixtures are maintained in the tool room. Weld and dimensional records are kept with the batch, and material is traceable to mill certificates.

Cost splits into fixture amortisation, fit-up, weld time, cleaning and inspection. Fit-up is usually the largest labour element: a part that locates itself in the fixture takes a fraction of the time of one that has to be measured and clamped. Distortion correction, if it is needed, is pure rework cost. On copper, material is quoted as its own line at the prevailing rate for the grade and thickness, so a change of specification is visible rather than hidden in a blended rate.