I worked at a job where they were anal about reducing welding to avoid distortion and save time.

A few suggestions to others from what I learned too many years ago.

1) On the end caps. Crop the corners of the end caps. On a 100x100 square you can crop 20mm off each end of each corner. Welding in the corner is harder and provides almost no additional stiffness. Now you have welded 240mm of weld versus 400mm. [(100-(2x20)) x 4] That is a 40% saving, with no reduction in strength or stiffness. If you are buying the wire /electrode and the shielding gas that is a big saving in money.

2) On the end caps. Fit them just inside the ends about 8 mm. A fillet weld is about 1/3 to 1/4 the weld volume of an outside corner weld and requires no grinding. It then saves time and grinding wheels as well. Combine this with Item 1 and you will save almost 60% of the welding.

3) On continuous welds. Stitching is good, but with 3mm material, the stitches should be about 30mm max, probably less.

4) On continuous welds, backstep. So a 30mm or shorter weld is made. You move somewhere else and make another 30mm weld. Continue all over the assembly. Now come back to the first and move 30mm away from the previous weld. Then weld back to the previous weld. The previous weld has locked the joint. When you start the back step weld, the parent metal is cold. When you reach the previous weld, the parent metal is getting hot. It cannot distort because it is locked by the previous, now cold, weld.

5) Use chalk and label the weld sequence in advance. So 1, 2, 3, etc. Go diagonally in a symmetrical pattern. Think of the sequence used in torquing down a 6 cylinder engine head.

6) Weld fillet size appears a bit oversize all over. The basic rule of thumb is the fillet size is 1.5mm smaller than the thinner of the 2 materials. Here we have 3mm to 3mm and other sizes to 3mm. So the full strength fillet weld is about 1.5 to 2mm

7) When making any brackets to fit between 2 adjacent pieces, such as 90 degree corner brace, crop the corner at least 20 percent back. You can't weld in there, you don't need to grind off the existing weld, and you save time and reduce the weight of the structure. Strength and stiffness do not change. Time and materials change.

How to determine the approximate backstep length is to observe the back of the material while it is being welded. When it starts to glow red on the back size and clearly show the weld heat, stop. It is when the base material gets red hot that distortion is introduced.

When welding heavy section or thicknesses, like 8 or 10mm stock to 3mm stock, the limiting strength factor is the 3mm material. So the fillet size is determined by that thinner material. It seems counter intuitive to use a 2mm weld when fastening an 8mm plate to the 3mm thick thin material, but it is correct.

Just my thoughts on how to build faster, easier, and cheaper.

What you have done will work very well. It is just that I am lazy and usually pressed for time, so I want all the work savings I can find. Many others are in the same mindset.

Regards