We don't take shortcuts. Fireboxes and supportive lips are formed to ensure utmost stability and longevity.
Forming is a process involving taking a single flat plate of steel or stainless and inserting it into a machine called a hydraulic press brake. The press lowers an upper die which creases/folds the plate material. We put the first creases on two of the edges to form lips. Then flip the plate over and reinsert more of it into the brake to put two creases in the center. The result is a "taco" shape tub with lips. That's one single piece of plate forming the back, front, bottom of the firebox and lips. Then we fold the end caps with lips. They are fully welded onto the "taco" bucket form to create a full box.
Flat metal plate is pretty easy to bow under heat. When you add a creases down the length of the plate it becomes much more rigid and structurally sound.
Many competitors offer fireboxes without four lips. Those boxes are much more susceptible to "warping" or changing shape under heat.
Sep 17th 2018