Prior Situation

A Fredrick, CO fabricator of vehicle hydronic heating systems welded their heat exchangers using semi-automatic 035 solid MIG wire in the short circuit transfer. With 40’ of weld in every exchanger, it was clear welding costs represented a huge labor cost reduction opportunity. Our suggestion was converting to hard automation / pulsed MIG.

To keep things simple, we focused on two areas only: 1) Increasing deposition rate (without over-welding) on the slot welds that secure internal heat dissipating fins to the cylinder, and 2) increasing travel speed on the circumferential cylinder cap lap weld. Also, because the welds were on 12g parts, we could entertain a hotter, more fluid and faster mode of weld transfer.

PE Solution

First, we changed mode of transfer from slow short circuit to high speed pulsed MIG. Second, we changed from solid MIG wire to high deposition metal-cored MIG wire. Last, we incorporated a hard automation turntable to hold the 12” dia cylinder. Through trial and error, we increased deposition rate on the fin slot welds from 9.1 to 13.6 lbs/hr, a 49% increase, without over-welding. The turntable would index to the next tacked fin with a foot pedal.

Then, with a fixed torch at 11 o’clock, we deposited a perfect cap lap weld in just under 17 seconds, a 465% increase. Previously, it took 96 seconds to deposit the same weld. Both welds had substantially reduced spatter.

Success Highlights: $46,200 in annual savings

• 96% reduction in cost per ft. of weld (slot welds)
• 454% increase in surface travel speed (circuit welds)
• 50% slot weld spatter reduction
• Improved circuit weld quality, leak reduction
• Investment of $14k for turntable and pulsing power source

Author: Bob Page