We built the frame using 1" aluminum square tubing, which seemed to offer the best balance between weight and strength. The individual pieces were cut to length on a milling machine and the edges that were going to be butt or T-joint welded were chamfered to reduce the amount of weld bead that would need to be ground down afterwards. Jerad TIG welded the frame together using his new beefy Bessey corner clamps, it only took him a couple of hours.
The enclosure itself was made of 16 gauge 304 stainless steel. 12 and 14 gauge were considered at first because less structural members would be needed, but the cost of thick stainless was prohibitive. The 32" overall length emerged from the hassles of transporting the original Bartendro. Two people were required to move the machine, and it could only fit into a sedan that had its passenger seat removed, and still it would gouge chunks out of the interior in the process. The design criteria were simple: fit through a door frame, fit in the trunk of my Honda Accord, and be able to be carried by one person. Getting the sheet metal sheared and bent took about a week to get from the metal workers. Then the stainless steel tee fittings were post-machined and welded to the enclosure. Their precise outer diameters helped maintain a consistent and repeatable weld joint.
The PVC coating on the sheet metal was really important in ensuring the finished product looked good and wasn't scratched up from the cutting and bending processes. I learned that it is really important to make holes in the stainless steel sheet first before making holes in the aluminum. Aluminum is really soft relatively, and is very easy and forgiving to make holes in later compared to stainless steel. Stainless work hardens quickly, meaning one cannot be timid when making a hole or cutting because it only makes matters worse.
Unfortunately, when the tee fittings were welded in place, the sheet metal warped a little on the narrow stretches, alternating between concave and convex. The additional members that were welded across helped to keep things uniform, but it was the use of panel clamps that made keeping things straight possible. They are quite useful tools, used frequently on auto body work, they allow sheet metal to be held in place yet still allow for minor shifts to help in the alignment process. Once the main panel was lined up, it was secured with an abundance of clamps. Holes were drilled and tapped into the frame and the panel fastened with shiny button head screws.