A fabrication shop in Tennessee used IronKit to compare 0.035" vs. 0.045" ER70S-6 wire for their structural GMAW work. At $0.65/lb wire cost and 95% deposition efficiency, the per-pound deposited cost is just $0.68/lb — far lower than SMAW. The 0.045" wire proved more economical on material above 3/16" despite costing the same per pound, because the higher current capacity (240–300 A) increased the deposition rate by 40%, reducing labor cost per pound deposited. The shop switched their primary process from 0.035" to 0.045" on anything above 3/16" and cut their welding labor cost by 22% on structural packages.
Frequently Asked Questions
When should I use 0.035" vs. 0.045" ER70S-6?
0.035" is best for thin material (under 3/16"), light gauge, short circuit transfer for vertical/overhead, and root passes. 0.045" is better for structural plate 3/16" and above — higher deposition rate in spray or pulsed transfer reduces labor cost per pound by ~50% versus 0.035".
What is deposition efficiency and why does it matter?
Deposition efficiency is the percentage of wire purchased that ends up as weld metal. ER70S-6 runs 93–95% in spray transfer — most of the wire becomes weld metal with minimal spatter. Low efficiency means you're buying wire that becomes spatter on the fixture, not weld. Compare to SMAW at 62% — GMAW wins on material utilization.
Why does the wire cost the same per pound but 0.045" is cheaper per inch of weld?
Because a 5/16" fillet weld requires a fixed volume of metal per inch. A larger wire at higher current deposits that volume faster. The material cost per inch is similar (same weld volume), but the labor cost is dramatically lower for 0.045" because it takes less time. The per-pound wire cost is a red herring — look at per-inch weld cost.
Does spool size affect effective wire cost?
Yes, but the impact is small. 25-lb spools are standard structural shop pricing ($0.63–$0.67/lb). 33-lb Acutrode-style bulk spools save $0.03–$0.05/lb and reduce changeover time. For a shop running 500+ lb/month of wire, the bulk spool savings are meaningful — about $15–$25/week.