Welding outside THE BOX
Dalton Roofing Service was hired to put the finishing touches on the center. The Lansing, Mich.-based roofing firm was faced with a number of challenges. First, university officials said the building's facade had to match an existing older building. In addition, the box-like decorations that adorned the facade could not be made of wood, as was the case with the previous structure.
"The building had to be 100% fire proof, and Michigan State was looking for a material for these particular decorations that would be more durable than wood," said Ron Turkus, Dalton Roofing sales manager. "We had to make adjustments to our process. Steel would have been too heavy so we decided to use aluminum as a wood substitute to create the boxes for the facade."
Ten-foot sheets of .040 in. aluminum were used to make the more than 430 decorations required. The metal was to be manually cut using a Tennsmith saw and sheared to the appropriate size, then bent three times using a Tennsmith brake to form each box. Next, two shorter (1.5. X 6 X 21) boxes would be welded to one longer (2 X 13.5 X 21) rectangular box. One finished ornament would require 30 welds totaling 220 in.
TIG would not cut itWhen they began, Dalton selected a TIG unit to handle the welding. However, it quickly became apparent that the TIG machine wasn't the right match for this particular job.
"The TIG unit was giving off high frequency interference, causing our computer to fault," said Dennis Wilcox, Dalton project manager. "Grounding the TIG unit to the specifications recommended in the manufacturer's handbook would have taken too much time and effort for a process that was too slow from the start."
Pulsed MIG welding provided the solution. Dalton chose the Millermatic¿ all-in-one pulsed MIG welding system. It allows operators to pulse weld on aluminum as thin as 19 gauge (.39 in.) or as thick as 3/8 in. with the Miller's Spoolmate¿ 185 spool gun. Dalton officials said this capability, along with a 35 to 210 amp output (160 amps at 60 percent duty cycle) made it perfect to complete the project. Because the welding current pulses between a high peak current and a low background current, the pulsing process lowers the average heat input. This prevents burn through, while pulse of peak amperage still provides good bead wet-out, creating smooth welds.
The scraps from the initial shearing of aluminum were used to form the box's end caps. The caps were bent and notched so they slid into the end of each box. Next, the cap was held in place with clamps and rubber stoppers (to not scratch the aluminum), then welded.
Dalton used a little creativity to ensure there wasn't any warping or burn-through while welding the aluminum. Wilcox said a steel bar was placed through the box opening from end-to-end. As it was welded, the steel dissipates the heat, enabling them to weld without burn-through.
"Finally, an aluminum mounting bracket is welded to the backside," said Wilcox. "There are no screws in the aluminum brackets whatsoever. There's nothing to corrode and no way water will find it's way in. The boxes are 100% watertight when we're finished."