Plasma cutting air mix

[J_J]

Since the plasma cutter should use clean, dry, oil free air.

Do you think a mix of 25 psi oxygen/50 psi air would give a cleaner and deeper cut?

How about any of the other gases?

For mild steel use oxygen plasma and air shield for the best cut quality, lowest dross levels, minimal rework, excellent weldability and highest cutting speed/productivity.

Illustrated Guide to Plasma Gas Selection - How to Choose the Best Gases

 

[muddstopper]

JJ, I am by far no expert. By reading thru the link you provided, it would appear that adding O2 to your air supply should work well. Not sure how you plan on mixing the air and O2 to the torch. I assume thru the use of a pair of flow regulators. I do think that you might see a pretty significate increase in the cost per cut if you do decide to use O2. Plasma cutters take a lot of air and would very quickly empty even a large bottle of O2. I would suspect that the use of O2 would increase the temperature and allow for a faster travel speed during cut. Most likely allow for deeper cuts as well. I dont know if you are aware of this or not, but when using oxy/acet for cutting, that it is possible to turn off the acet, once the cut is started, and continue cutting just using O2 to blow the molten metal out of the cut. O2 is a oxidizer and will cause the molten metal to burn as the fuel source for the flame. I suspect that the fact that O2 is a oxidizer that that is why it isnt recommended to use when cutting stainless or aluminum, and I certainly wouldnt want to use it on metals such as magnesium.


What is it you are trying to cut that you feel the need to add O2 to your plasma cutter?

 

[J_J]

I was thinking cleaner and better cuts without having to grind the dross off some parts.

I have a plasma cutting table that I need to assembly and a Lincoln Pro-cut 25 and 55, and was just curios for hobby type work.

 

[muddstopper]

Again, I am no expert, but I believe excessive dross has more to do with proper amperage settings, travel speed, and standoff of the work piece than it does with air. Jim Colt made a post somewhere in this forum about using a plasma torch properly, you might do a search. I think his comments might be buried in another thread about plasma cutters

Found one post you might find useful,, http://www.tractorbynet.com/forums/...cutters-why.html?highlight=plasma#post3854936

 

[Fifelaker]

The plasma table at school is very clean when set up correctly. Muddstopper is on the right path with amps, travel speed, standoff and air pressure. I have a home made track torch that is used with A/O if I get every thing set correctly there is very little clean up if any.

 

[muddstopper]

I use a straight edge, as my track torch. One of these days I am going to build a plasma cutting table, but to many irons in the fire right now

 

[blueriver]

I'm new to the plasma and CNC table world ... Have made a lot of practice cuts and wasted a few 5x10 sheets of 14 gauge .. I added a water pan which made a world of difference next step is THC and Floating head .. I have found for my situation 70 lbs of air and proper amps and speed are key elements for smooth cuts and minimum dross ... Here's a piece today cut from 14ga 70 lbs 30 amps. 80 imp

 

[Mark @ Everlast]

Do not! Not unless you have a torch rated for it. That's a good way to get hurt. They use 02 on Hi Def systems but they are specially designed for it. IF you want to use an alternative gas, use Nitrogen with a regulator. It'll make a good, clean cut if used by itself.

 

[Reverser]

I'm new to the plasma and CNC table world ... Have made a lot of practice cuts and wasted a few 5x10 sheets of 14 gauge .. I added a water pan which made a world of difference next step is THC and Floating head .. I have found for my situation 70 lbs of air and proper amps and speed are key elements for smooth cuts and minimum dross ... Here's a piece today cut from 14ga 70 lbs 30 amps. 80 imp

Looks good.
What plasma cutter do you have?

 

[blueriver]

Looks good. What plasma cutter do you have?

I have 2 ... A longevity 62i that is dedicated to the table and a longevity 80i that's on the welder cart

 

[J_J]

Do not! Not unless you have a torch rated for it. That's a good way to get hurt. They use 02 on Hi Def systems but they are specially designed for it. IF you want to use an alternative gas, use Nitrogen with a regulator. It'll make a good, clean cut if used by itself.

Do not, what.

You do know that air has oxygen in it and it is logical that adding about about 25 % more should add to the cutting power.

Maybe thicker and cleaner cut and less dross.

Do you not believe anything in the charts posted above?

 

[muddstopper]

I just started reseaching this and ran across this, You can plasma cut it, but can you weld it? - TheFabricator.com

It would seem that O2 would be the preferred choice or cutting carbon steels, but not so good for stainless or aluminum. I have also ran across agruments, that I wont post links to, that suggest that their is a difference in how the torch body is made if using O2 instead of shop air. I havent been able to confirm this thru a reliable source so I think it would bear a little more investigation before one tries it. Is some of the arguments, it was suggested that O2 would burn up a regular plasma torch, but again, I havent been able to confirm this.

Mark, maybe you can supply a little inside info on why you say not to use O2 in the plasma.

 

[jimcolt]

First pic is 1/4" as cut on a low cost cnc machine with an air plasma. Second is 3/8" as cut with air plasma. Third is 1/2" as cut with air plasma. Cut at the correct cut speed and correct cut height with a good quality plasma cutter gets very nice edge quality. Samples all cut on a Plasmacam cnc machine with Powermax85 air plasma at book cutting specs using compressed air. No need for oxygen here!

Jim

 

[dragoneggs]

First pic is 1/4" as cut on a low cost cnc machine with an air plasma. Second is 3/8" as cut with air plasma. Third is 1/2" as cut with air plasma. Cut at the correct cut speed and correct cut height with a good quality plasma cutter gets very nice edge quality. Samples all cut on a Plasmacam cnc machine with Powermax85 air plasma at book cutting specs using compressed air. No need for oxygen here!

Jim


View attachment 388783View attachment 388781View attachment 388782

Jim, do you have pics you could post of various thickness steels cutting with the Powermax 30XP?

 

[blueriver]

I have 2 ... A longevity 62i that is dedicated to the table and a longevity 80i that's on the welder cart

Another... I cut today ... Just one of many... getting a bunch cut out for a special Amish sale in the area

 

[J_J]

After reading all the material that I could find and talking to reps at some of the major plasma companies, It is probably not a good idea to add more O2 than what is in the air.

It may have something to do with the oxidation of the materials in the plasma torch.

No one has said what would happen with a certain percentage of O2 plus regular air would do except a lower useful time on the torch parts.

My thoughts were to boost the O2 with the air and perhaps give a better cut with less handling on the cleanup, considering time is money also.

Air is the cheapest, but not necessarily the best gas for plasma cutting.

I appreciate the data some of you have shared.

I plan to put my cnc table together pretty soon.

 

[jimcolt]

JJ, This is what I posted a couple of days ago....and it is what will happen as you increase the oxygen content. I suspect it would be safe to 40%, beyond that there is danger of an oxygen supported fire that is almost impossible to extinguish!


I have heard of users experimenting with premixed air supplies with a higher than 20% oxygen content.....as high as about 40%. This will minimize dross on steel, likely will improve cut speeds, and will increase cut kerf width.....and probably will shorten nozzle and electrode life. I don't recommend this either....as there could be issues with the mixing of the oxygen and air that could get the oxygen supported fire started....why take the chance?

In regards to air plasma...yes it is the lowest cost gas (though, surprisingly not as low as many think.....especially when drying and filtering is calculated), but it is not the lowest cost per foot of cut....oxygen plasma systems are. Better cut speed, better cut quality, and the latest have dramatically longer consumable life as compared to their air cooled cousins. Some air plasma cutters produce incredibly nice quality with todays technology....I posted some pics a few days ago as well to show what can be expected with todays air plasma.

Jim Colt Hypertherm

After reading all the material that I could find and talking to reps at some of the major plasma companies, It is probably not a good idea to add more O2 than what is in the air.

It may have something to do with the oxidation of the materials in the plasma torch.

No one has said what would happen with a certain percentage of O2 plus regular air would do except a lower useful time on the torch parts.

My thoughts were to boost the O2 with the air and perhaps give a better cut with less handling on the cleanup, considering time is money also.

Air is the cheapest, but not necessarily the best gas for plasma cutting.

I appreciate the data some of you have shared.

I plan to put my cnc table together pretty soon.

 

[Mark @ Everlast]

Yes I am .. No second thoughts ... They are truly good machines .. Not to mention the support and backing ...maybe it's just me but I always get great service and my questions are always taken care of ... I do not like the cost of the consumables and have expressed that ... I'm placing an order soon from a supplier of (here it goes) Chinese consumables ... They appear to be right and inexpensive .. I'll know if they do the trick.

If u recall my reason for loyalty to the other brand .. You understand why I use their products and promote them

Google River-weld, if this is not your supplier. They are import and in many cases carry OEM parts. China based, but do carry good stuff and shipping is relatively fast.

 

[Big Barn]

Google River-weld, if this is not your supplier. They are import and in many cases carry OEM parts. China based, but do carry good stuff and shipping is relatively fast.

^^+1. This was a recent purchase for tig consumables I made with Riverweld /eBay. ] Terry