Hobart 40i inconsistent/consumables cutting 3/16"

Cutting 3/16" plate (architectural plates), some of them are a continuous cut of say 8’ and sporadically, toward the latter 1/3 of the cut, the arc will behave erratically. It will suddenly not fully pierce, show top dross and sometimes suddenly cut as intended at intervals before completing the cut.

I’m cutting the 3/16" at 40a and 75ipm using the thicker tip to material gap that came with the table. I’m running 80psi air with an inline moisture filter.

It’s only happening on the lengthy nonstop cuts. The smaller plates cut without issue.

Are you maintaining the CFM & PSI on the air for the duration? I don’t know if the Hobart shows you any indication but the Hypertherm has a set of lights where it shows the quality of the air supply - over or underpressure for the operation and on long cuts I have seen it flicker on the too-low side.

Also, there’s a duty cycle for the power supply on the torch - make sure you’re not exceeding that (your manual should tell you what it is - like 10 minutes at 40A, 15 minutes at 35A, etc. where it needs to stop and cool before proceeding).

Hey James,
I don’t believe I’m having a CFM/PSI issue. The Hobart does have indicator lights but I didn’t notice any on when it began behaving erratically. I’m wondering if this issue is related to a previously “moisture affected” electrode. I switched my air supply after realizing moisture was causing a bunch of misfires and at that time I also replaced the tip but didn’t have a fresh electrode. It didn’t look especially bad but when this erratic cutting occurred, it was clear the fresh tip was wearing far quicker than should be.

The duty cycle is 50% and this plate was less than 4 minutes so I don’t think that was the issue.

I have new electrodes and tips arriving tomorrow so I’ll be able to do another test and I’ll be sure to pay attention to the indicator lights as well.

Ok so here’s what I found tonight when my new consumables arrived.

I did lower the fluid level in the water table a bit because I know a few of my misfires have been due to splashback in the torch.

I also bought longer torch head securing screws so I could drop the insulated cup into the holder instead of just the threaded on retainer which was getting mis-shapen by the tightening of the torch holder around it.

With the new consumables and the lowered fluid level I finally produced consistent perfect cuts on this 3/16 plate.

Is there a formula for how many tips will need replacing in comparison to electrodes? In my experience it’s about 4 to 1…?