Brand New to Plasma Cutting and have questions

[norcalvp]

I recently made the jump and purchased a longevity Weldall 160PI for home use, and have a bunch of questions being that I have never used a plasma cutter before. So far I've been trying to figure it out on my own, and seem to do OK, but want to make sure that there isn't something I'm missing.

The first thing is that I have been using my non adjustable auto darkening welding helmet. It works pretty good but almost seems too dark. What shade should I be using for plasma cutting?

What air pressure should I be using? So far I've been cutting sheetmetal, and a little 1/8" steel (Also played around with a little aluminum, and Stainless Steel). Should the incomming air pressure be changed based on the thickness of the metal I'm cutting?

Is there some sort of guideline for the current that I'm using also? I've noticed that sometimes there is a bit of slag on the backside of the cut. Should I be reading this as too much or too little of something?

Once in a while When I start to cut, the arc starts, runs for about a second, then turns off. (I also have the post flow on for about 5 seconds, I don't know if that's needed).

When cutting the sheetmetal, I found that sometimes, the material was cut away, but then the slag cooled back together so I had to cut it again. Does this mean that there's not enough air pressure to blow the steel away? current too low? too High?

Thanks for any help you guys can give.
Steve

[brucer]

i use a speedglas auto darkening helmet, i cut with the filter turned off, i think its a shade 5 or shade 6... a tinted face shield works good also, i like a tinted face shield better.. i also have a pair of tinted glasses my brother give me that come off the railroad, i think they are some kind of torch goggles actually but they work good also..

on my longevity 40i i would run around 50 psi air pressure on 3/16 steel, probably would run the same on 1/8" also.. i would probably start around 30amps and be moving fairly fast..

you want your post flow long to cool the consumables, i think i set mine at like 8 seconds, it might be 10.. you want post plow to cool the consumables..

The arc should exit the material at a 15- to 20-degree angle opposite the direction of travel. If it's going straight down, it means you're going too slow and, you'll have an unnecessary build-up of slag. If you go too fast, it will start blowing up.

most people that are starting off with a plasma run too slow.. its seemingly kind of unnatural as to how fast you can cut with a plasma..

[KHK]

I use a Longevity auto darking hood. usually set on the lowest setting.
Ditto on Brucer's post.
On the 160pi that I had, the Arc Force knob had to be at least 50% of the dial for consistency cutting. This was on one of the first machines, so not sure that this is still true for your machine.

[norcalvp]

Thanks guys! I really appreciate it. I'll try to bump up the air pressure a little. I cut a piece of 2X2 .120 wall steel tubing this weekend and noticed that when i'm cutting it appears as though the cut is closing then the steel cools, so I have to go over parts of it 1-2 more times. Could this be because I have the air pressure a little too low?

I may go down to the welding shop and see what kind of torch goggles, hoods they have....

STeve

[LONGEVITY-Support]

Hello norcalvp,

Set the helmet to the lowest setting possible, also try to keep your air pressure between 50-60 psi's to get the best cut possible, to much air pressure can cause the arc to shut off when torch head gets close to the metal or cause the arc to sputter in and out, if cutting 1/8" you can set your base currents to about 30 amps, post flow can also be set between 1-3, these settings should help you produce more precision cuts and also help save consumables.

Best,

DP

[Gadget]

If you move too slow the metal can puddle in behind the cut sometimes. Try going as fast as you can with the cut.

[Nick]

I cut a piece of 2X2 .120 wall steel tubing this weekend

Bit of a tube frame race car build? (Sorry, one track mind.)

Plasma is fantastic as a time saver for general roughing out at worst, decent to spec work at best. (For the average user) If you're doing precision joint work, a chop saw might be an option - especially on .120.

The problem you may be running into is the sheer fact that the plasma has to exit the cut piece somewhere, and it's depositing on the outside wall of the .120.

I'd save it for cutting my 1/4"-1/8" brackets / gusset plates.

Best of luck boss, and keep the shiny side up. ^_^

[norcalvp]

no, building a crankshaft pully removal tool for my wife's Honda Odyssey. Had to do a timing belt. one day maybe a racecar..... got to get the kids out of the house first.....

[tigqk]

If you get yourself a helmet get a few welding beanies to because sparks fly in and burn your hair and it will keep the grinder dust and smoke out.I don't use a welding helmet with the plasma cutter to cumbersome but I do use a tinted pair of form fitted welding googles that are vented, and have had sparks unexpectedly come back and hit me right in the face cutting tubing...it happens, but they fit well.Some settings are user preference, post flow don't need a whole lot, hit slag with a chipping hammer from the side, and try lifting the torch abit to see if that helps with it closing in on you refusing.You want to keep your amperage down because your consummables last longer, their is a good article on plasma cutter use on this site but don't remember url.