Question on plasma cutter

[charlz]

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]

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]

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]

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]

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]

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]

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]

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]

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

 

[alltoys]

J J

Are building your own computerized Plasma cutter from scratch??

 

[J_J]

J J

Are building your own computerized Plasma cutter from scratch??

No, I had ordered this computer cutting table about a year ago. It has to be put together and when finished it will look similar to the one below. All I have to do is add the plasma cutter and learn about G-CODE, and I have a spare computer. When finished, I should be able to copy a pattern, clean it up, and convert it to code and tell the machine to cut it. My Lincoln Pro-Cut 55 will cut up to 3/4 in, but as you go larger, there is a slight bevel. Laser is better and gives a more vertical cut.

The other pictures are the kind of things I would like to do. plus of course to build my own attachments.

I can also set my table up as a 4 ft table or an 8 ft table.

 

[Scooby074]

You should get yourself a decent Dessicant filter. Toss those hose end things. Put it on your main line then put a "toilet paper"(motor guard) type filter on your machine as a last chance unit. I doubt those cheapies will flow the necessary CFM. Good dry air with appropriate flow is essential to plasma.

http://www.airtekltd.com/watts_13.htm
http://www.motorguard.com/air_2_6.html

 

[Skyco]

I'm using those $8 HF desicant things without issue on my HF 40A plasma cutter, I actually have two in series so the restriction can't be too bad. I did have one break at the threads. BTW they are discontinuing those units, they aren't online at the regular HF website, the store website linked still shows them. In my experience if the disappear from the main site they usually disappear form the store site as well as soon as they sold 'em all.
They do show a $40 metal one that is much larger on their website now. I've been pondering making a big one with about 2 or 3 inch pipe and just filling it with silica gel.
My HF plasma cutter came with a flowmeter contraption to set the actual CF airflow out the cutter torch.

 

[Scooby074]

I'm using those $8 HF desicant things without issue on my HF 40A plasma cutter, I actually have two in series so the restriction can't be too bad. I did have one break at the threads. BTW they are discontinuing those units, they aren't online at the regular HF website, the store website linked still shows them. In my experience if the disappear from the main site they usually disappear form the store site as well as soon as they sold 'em all.
They do show a $40 metal one that is much larger on their website now. I've been pondering making a big one with about 2 or 3 inch pipe and just filling it with silica gel.
My HF plasma cutter came with a flowmeter contraption to set the actual CF airflow out the cutter torch.

The larger HF one will work alot better than the hose end ones. If your having luck with them then good, but i wont recommend one for any serious air usage.

I bought a similar one to the large HF one at princess auto here in NS. It worked ok, BUT it wont flow much more than 10-12CFM, no matter what the website says(princess auto says 18CFM HF says 17). If you intend on using it for any high flow purpose like sandblasting or HVLP painting than you should spend the cash for a purpose designed dessicant filter like a Watts or a Motor Guard and not a piece of pipe with some pipe caps.Been there, done that. Size it to your compressors output. Ebay can help out alot. A watts dryer new is in the $200 area, Yeah its alot, but your airtools will thank you. and its cheap insurance if you do any painting.

 

[charlz]

I just got the compressor a few months back and the plasma the other week so I was trying to put something together quickly to provide dry air and see how the plasma worked. Reading some of welding boards indicated some people were using the the HF units with success. I am still not ruling out technique, until I get some more cuts under my belt it's possible I am going to slow/fast/whatever

I saw the exact same desiccant cartridge at Lowes but for about $5 more than HF is selling them for. I noticed you can take them apart to dry the desiccant. I may go buy another one and try it in parallel, their pretty cheap and it can't hurt much.

I am pretty familiar with desiccant, we used cartridges on the planes I worked on in the military to provide dry air to the electronics. The F-4's you could take it apart and dry the desiccant, the F-18's were throw-aways.

 

[J_J]

I just got the compressor a few months back and the plasma the other week so I was trying to put something together quickly to provide dry air and see how the plasma worked. Reading some of welding boards indicated some people were using the the HF units with success. I am still not ruling out technique, until I get some more cuts under my belt it's possible I am going to slow/fast/whatever

I saw the exact same desiccant cartridge at Lowes but for about $5 more than HF is selling them for. I noticed you can take them apart to dry the desiccant. I may go buy another one and try it in parallel, their pretty cheap and it can't hurt much.

I am pretty familiar with desiccant, we used cartridges on the planes I worked on in the military to provide dry air to the electronics. The F-4's you could take it apart and dry the desiccant, the F-18's were throw-aways.

I would put a large bleed type water separator at the compressor, and put one or several desiccant filters just before the plasma cutter, and change them out when they change color. You don't have to throw them away, just put them somewhere there is heat and they will dry out. and of course you can make yourself a customized unit, but you have to keep the little beads from getting into the plasma intake line.

One of those 1 gal sealed paint cans with the turnbuckles would make a good large desiccant absorber/drier filter.

As far as the air volume, the plasma cutting nozzle is very small and can not pass a lot of CFM. A cheap air compressor that will push at least 90 psi will work fine, with some filtering. I believe you can also use nitrogen and maybe some other gases.

 

[Skyco]

I've reactivated my HF dryers in the toaster oven.....shhh don't tell the wife

 

[RWolf]

Skyco, I've got the same plasma cutter and really like it. I've used it for about a year off and on doing quite a bit of cutting and haven't used up my first tip. The previous one was from Homier and would go through a tip about every other cutting job.

J-J, I've been looking at that same table but haven't convinced myself yet to part with the money and besides that I've told myself that until I clean out my shop I can't have any more toys.

 

[charlz]

Got some time to work on this today. Left the desiccant inline but turned the regulator on the plasma all the way up. Same result, 90psi static turns into about 40 psi dynamic. Removed the desiccant and 90psi static only drops to about 70psi dynamic. Didn't get to make any test cuts but it should work a lot better. Looks like it is time for a different filter and/or desiccant setup. Thanks for the input guys!

 

[JoeL4330]

Plasma Air Filters