Need help reducing warpage or twist in sheet metal tray induced by heat
Hi everyone. First of all I have to say I am not a mechanical engineer. I am a technician with training in electronics and machining. Since my employer has no mechanical engineers on staff, the job falls on me to do mechanical design to the best of my ability.
My employer makes electronics modules. One system we are working on right now fits in a 20" x 11" x 1/2" aluminum housing. Basically, the housing looks like two interlocking cookie trays. I was asked to design the housing from .025" thick aluminum, and built prototypes from 3003 annealed alloy. (The required bend radii are VERY tight - .005 - .010", and I was uncertain I could do this on my old equipment with a harder alloy.) When I completed the prototypes, they were straight and true, and dimensionally accurate. I wanted to weld the corners of the folded up flanges, but since we don't have any welding equipment, I could not do this.
Our electrical engineer advises me that when he installed our module and other components inside the housing, and ran them up to full power (100 Watts), the assembly twisted and warped. When he removed the heat, the assembly recovered almost fully to it's original shape. I'm not surprised, but I don't know what to do about it. He thinks that making the part out of the same thickness galvanized aluminum might stop the part from twisting. I've ordered material, but I doubt it will be that simple.
I don't know much about metallurgy. Should I be using a different alloy? Would it be helpful if we brought the material up to temperature BEFORE we formed the flanges? Should I try to incorporate some sort of rolled bead into the design to stiffen it? I'm not allowed to change the material thickness.
Thanks for taking the time to read this...