Question on plasma cutter

charlz · Mar 31, 2009

I picked up a Powermax 600 at an auction, local trailer manufacture going out of business. Just under $600 out the door which I thought was a pretty good deal considering what these sell for new.

I don't have a good moisture trap system so I put one of these HF dessicant cartriges on the back http://www.harborfreightusa.com/usa/itemdisplay/displayItem.do?itemid=94733

Rated at 90psi max, (the inlet on the plasma says 120 psi max) so I ran at 90 psi. Cutting some 1/4 it seemed like it wasn't clearing the cut out. Could be technique, this is my first plasma. I noticed the pressure gauge on the unit drops to about about 40 when the trigger is pulled. Am I just not getting enough air across the desiccant or is that pretty normal based on how much air these units consume? I have an 80 gallon 175psi compressor so air supply really isn't an issue.

OlderToday · Mar 31, 2009

Check to see if the top of your trap adjusts the air pressure as well. I don't have the same unit, but my trap allows me to adjust pressure by pulling up on a valve, rotate to new pressure, then push the valve down to lock it.

charlz · Mar 31, 2009

OlderToday said:
Check to see if the top of your trap adjusts the air pressure as well. I don't have the same unit, but my trap allows me to adjust pressure by pulling up on a valve, rotate to new pressure, then push the valve down to lock it.

It does, I had it cranked up to about 80psi. The manual recommends about 72 psi for the length of torch I have on there.

kennyd · Mar 31, 2009

Two things come to mind:
1. What is your compressor rated for? (CFM @ 90 PSI) You NEED 6 CFM minimum I think.

2. If your compressor is up to the task, then take out that HF trap and see if it works...I bet it can't pass enough air and that is why you have the pressure drop. It gives a max pressure, but no flow rating-typical of HF crap.

sld · Mar 31, 2009

Do you have the ground cable clipped to what you are cutting?

Don't ask me how I know that doesn't make a clean cut.http://www.tractorbynet.com/forums/images/smilies/biggrin.gif

RonMar · Mar 31, 2009

What Kenny said. It sounds to me like you do not have enough flow. You could put a "T" and a gauge after that filter and I bet you will see a significant drop in pressure when you trigger the cutter. It would probably be quicker to just take the filter out of circuit for a quick test.

Another indication can probably be heard, or even seen using a sheet of paper. Hang a sheet of paper by the top edge, then holding the torch up an inch or two from the paper, pull the trigger. The airflow out of the torch will blow the paper away from the torch with the initial blast. The paper will then fall back toward the torch as the flow/pressure drops off. You may also be able to hear the hiss at the torch diminish from the initial turn on level.

charlz · Mar 31, 2009

My compressor is a Curtis rated at 18cfm @ 175 psi so I know its not the compressor (a craigslist gem). I'll try taking the desiccant cartridge out of the circuit for a few test cuts. If it performs better maybe I can get away with putting two in parallel? The unit has a gauge on the front and that is where I am seeing it drop from static 80psi to 40psi when the trigger is pulled/held.

J_J · Mar 31, 2009

charlz said:
My compressor is a Curtis rated at 18cfm @ 175 psi so I know its not the compressor (a craigslist gem). I'll try taking the desiccant cartridge out of the circuit for a few test cuts. If it performs better maybe I can get away with putting two in parallel? The unit has a gauge on the front and that is where I am seeing it drop from static 80psi to 40psi when the trigger is pulled/held.

charlz,

I have two Lincoln plasma cutters, and the way to adjust the air is to pull the trigger and rotate the air adjust for the 75 psi called for. When you let off the trigger, the air pressure will go up higher. While you are cutting, you want about 70 to 75 psi, at least that is how mine is set. That HP filter will absorb water real fast, and is no good after the crystals turn color. You can put it on the top of your water heater and the water will eventually dry out, so you can use it again. You can also buy those crystals and make your own water absorbing filter. You definitely need dry and oil free air. One day soon, I hope to get my computer plasma cutter system operational.

J_J · Mar 31, 2009

charlz said:
My compressor is a Curtis rated at 18cfm @ 175 psi so I know its not the compressor (a craigslist gem). I'll try taking the desiccant cartridge out of the circuit for a few test cuts. If it performs better maybe I can get away with putting two in parallel? The unit has a gauge on the front and that is where I am seeing it drop from static 80psi to 40psi when the trigger is pulled/held.

Your plasma cutter is reading static pressure when connected. When you are cutting, you are seeing dynamic pressure, and that is what you adjust by rotating the knob, and lock it in place. Good luck. Check your tips and swirl chamber often. There are several dealers that make circle cutters and guide wheels for straight line cuts.

Plasma Cutting Guide

http://www.flangewizard.com/circle_wiz.html