[Faris_Mattar]

Hello everyone. I resisted posting the difficulties I faced in my first robotic welding application and tried to learn the hard way. But I reached a point where I couldn't afford more trials to achieve the quality weld I'm looking for. The job is welding a 30 mm thick MS base plate with a 4 mm pole shaft of octagonal cross section. It's a street lighting pole. Previously, I used to weld the sides of the octagon 1 side at a time in a 2F position. The beads would overlap at the corners as shown. I know these are considered stress points. I wanted to improve the welding by making the robot follow the path marked in red, where I would have much better(and less) tie-ins on a flat surface instead of the corners. The new method created new difficulties for me. I have to weld in what could be called 3F(45-degree inclined uphill), 2F, and another 3F(45 inclined downhill). I managed to get decent fillet beads in 2F and 3F downhill, but I'm struggling with uphill. The video shows a root pass.
I'm sorry if my post is very long. I need to provide as much information as possible, hoping I could get some help here.

After setting and tuning. I managed to get a good root pass bead in uphill 3F, which was the closest to 2F and downhill 3F (fillet size, fusion at the toes, and not convex. But when I attempt a fill pass(to get a larger throat/leg length with the same fusion at the toes), the results are miserable.

The weld bead in this position shrinks in the middle like crazy!!!

Actual weld parameters with every position for the root pass which is worked well for the job.
Welding process: Dual Shielded Flux Cored Welding with 100% CO2

2F
<arc voltage =29V>
<welding current=220 A> (The robot I'm using allows me to set welding current not WFS).
<travel speed=10mm/sec>
<CTWD=30 mm>
<work angle is around 60 degrees>
<5 degrees pull angle>
<no weaving>

3F Inclined downhill
<arc voltage =28V>
<welding current=230A>
<travel speed=9mm/sec>
<CTWD=30 mm>
<work angle is around 60 degrees>
<15 degrees pull angle>
<no weaving>

3F Inclined uphill
<arc voltage =26V>
<welding current=170 A>
<travel speed=11mm/sec>
<CTWD=25 mm>
<work angle is around 60 degrees>
<15 degrees push angle>
<+/- 1.5 mm weaving with a 0.1 sec pause on toes.

While welding in 3 positions with a single arc, the bead behaved as follows:

In inclined uphill the bead is convex with bad fusion at the toes.
In Flat position the bead is flat with better fusion at the toes.
In Inclined downhill the bead is concave with over fusion at the toes.

After tuning the parameters above, I managed to achieve a fast root pass weld bead that showed the best consistency in the bead profile between the 3 positions. In other words, I managed to get all fillet beads as flat as possible. Although the tie-ins are yet to be done right, grinding was required at the tie-ins.

I'm not able to do the same for the fill pass, which had a bad result (shown in photo).

Inclined Uphill fillet bead is shrinking no matter what I did.
Flat position fillet bead was maintained flat with very good fusion at the toes.
Declined downhill fillet showed decent improvement and was flatter rather than concave and was close to the flat position bead.

Below are the changes applied to the second pass:

I reduced the travel speed slightly.
I tried to keep CTWD as they were in the root pass because I didn't want to impact the effective electrical resistance and get increased current.

The result with 2F and downhill 3F were very good and met the required quality. But the result with 3F uphill is very bad. Bead shrinkage is much more dominant in this pass. I increased weaving to +/- 2 mm. Arc voltage is not going up(26V) even though I set it above 30V. I set the current at 185 A. The actual current would be around 170A.

The resulting fillet bead is too convex, very bad fusion at toes, leg length is bad as well.