Esab PCM 875 problem

[therrera]

hello all,

I have an Esab pcm 875 that is having trouble cutting through 1/4" plate. Granted I am using worn elctrodes (but still within spec of 11/16" long) and used but still good tips. I have not used this machine for heavy cutting for many years (maybe 8 years) using it for sheet metal and thin plate. However, now I need to cut 1/4" and up for a project I am doing and find that it is not cutting cleanly through. When I first go her I could rough cut through 3/4" plate and cleanly through 5/8" plate.

I am running 70 psi hooked up to a 50amp plug on a 100 amp circuit. Anyone have any thoughts on this?

Any help is appreciated.

Thanks,

Tony

[farmall]

Ours likes fresh electrodes. If it cuts oddly we replace them although some of them looked decent.

[farmall]

Ours likes fresh electrodes/nozzles.

If it cuts oddly we replace them as a set although some of them looked decent.

[therrera]

Hi Farmall,

with fresh tips and electrodes it cuts like "new" again? You can cut heavy plate with it? I ordered about two dozen sets but they haven't arrived yet.

Thank for the tip, (no pun intended)

Tony

[farmall]

We usually cut 1/2" mild steel. I don't know about any but ESAB brand consumables for those machines, but fresh ones do the trick.

[therrera]

Hello Farmall,

you were right on the money. Once I replaced the tips and electrodes with fresh ones, she cut like new again.

Thanks for the benefit of your experience.

Tony

[Oldiron2]

If the tip hole gets enlarged or wears 'crooked', that obviously affects the heat concentration and the angle and quality of the cut.
The electrodes have a center which I think is tungsten spiked with halfnium, the latter lowering the ionization potential. If the centers on that brand or lot of electrode were shorter, they might be worn out even though the outside is still within the official length. Maybe the specs were just optimistic too.

[therrera]

Hello Oldiron2,

I noticed the center cavity when measuring the acceptable length of the electrodes. What I would do is file the outside down so that it was even with the center and then measured against a full size diagram taped to the lid of replacements that came with the unit when I bought her.

On the tips, I would look through them at a light source to make sure they were round (by eyeball standards) and discarded the ones that had gouged out openings. However despite this care on my part, the torch failed to give a quality cut even though within factory parameters. Fresh ones never failed.

Maybe its like a fresh electrode in stick welding versus a used one. The start of the fresh one is crisp and powerful compared to the used one. I'm sure there's an explanation, but lacking that I just know this is so from experience.

Thanks,

Tony

[ccawgc]

Never file the electrode. You change the dynamics of what is going on in there.
Changing the length of the electrode should make the plasma arc harder to get going.
Electrodes are designed to ware until the halfnium is mostly gone. The halfnium is consumed in the arc and is used to stabilize the arc. It is what makes air plasma possible.
The wares just so deep then gets wider. Soon as the pit starts getting larger the cut starts to suffer. The kerf gets wider, tip wares faster, cut takes longer and doesn't cut as thick.
All plasma torches are designed around good consumables and the correct air flow.
Upset the balance and some thing will not work right.

[therrera]

Hi ccawcg,

I didn't know that. I figured that if the center was wearing down, the outside needed to be evened up with it. Thanks for filling me in. Maybe that's why my cuts were getting bad? I ordered a couple dozen tips and electrodes. She's cutting great again.



Tony