Direct answer
A weld-cost model converts the specified joint volume into deposited mass, adjusts consumable input for process deposition efficiency, estimates arc time from deposition rate, and then adds fit-up, handling, interpass work, inspection, rework risk, equipment, energy, gas, and overhead.
What this calculation tells you
A bottom-up estimate explains why the same weld length can have very different cost by joint, position, access, process, quality level, and batch size. It also provides production assumptions that can be compared with completed work.
It cannot select a weld design, qualified procedure, inspection plan, staffing level, or safe production method.
Where it is used
Fabrication estimating
Price defined welds by joint, position, process, length, and production conditions.
Production planning
Forecast arc hours, labor, consumables, gas, equipment, and station capacity.
Process improvement
Compare estimated and recorded deposition, operating factor, and rework by weld family.
Make-or-buy analysis
Compare documented in-house scope with supplier quotations and exclusions.
Common situations
- A small intermittent weld has high positioning and stop-start time.
- Out-of-position work lowers deposition and operating factor.
- Fit-up gaps increase weld metal beyond the drawing model.
- Inspection and traceability requirements add non-arc labor.
Start with the specified joint
Calculate or schedule the deposited section from the approved groove or fillet geometry, root conditions, reinforcement convention, and weld length. Separate weld types instead of averaging unlike joints.
Add only justified allowances for fit-up and process, because systematic oversizing should not become the estimating norm.
Translate deposit into consumables and time
Use filler density, deposition efficiency, and deposition rate appropriate to the process, wire or electrode, current range, position, and transfer mode. Distinguish deposited metal from purchased filler.
Arc time is deposited mass divided by achieved deposition rate; total labor then reflects a measured or justified operating factor.
Include the whole production route
Preparation, fit-up, tacking, positioning, preheat, interpass cleaning, consumable changes, movement, inspection, repair, documentation, and post-weld work may dominate short or complex welds.
Gas, power, equipment, extraction, handling, supervision, and facility overhead need consistent allocation.
Close estimates against job records
Compare actual labor, filler, gas, arc time, inspection, and rework with the original assumptions by joint family. Update evidence without hiding one-off disruption inside every future rate.
- Keep safety controls in the method and cost.
- State exclusions clearly.
- Never optimize cost by departing from the approved procedure.
Practical questions
Frequently asked questions
Why is labor much longer than arc time?
Fit-up, positioning, handling, cleaning, waiting, inspection, documentation, and other necessary activities reduce the arc-on operating factor.
What is deposition efficiency?
It is the share of consumed filler that becomes deposited weld metal under the stated process; stubs, spatter, and other losses reduce it.
Can cost per metre be reused for every weld?
Only for genuinely comparable joint, size, position, access, quality, process, batch, and production conditions.
Further reading
Authoritative sources
Use these primary and professional resources to check definitions, conventions, or requirements that may extend beyond this guide.