Plasma cutting air mix

[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]

Air plasma torches and consumables are designed for use with air.....which is roughly 80% nitrogen and 20% oxygen. Since most shops already have a compressed air system, this makes for an inexpensive way to provide gas for a plasma cutter. The oxygen content provides a bit of an exothermic boost on steels, and even helps remove dross on stainless and steel as compared to using pure nitrogen. Using pure nitrogen on steel will make for an ugly, drossy cut at lower speeds.

First though....definitely do not put pure oxygen in any plasma torch that is not specifically designed for oxygen use. There are components in the air flow control system, the torch leads, the consumables and the torch body that will burn in the presence of pure oxygen......and oxygen fire can easily destroy the torch, the leads, the power supply and possibly your shop! Just don't do it!

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?

Contrary to popular belief, industrial plasma systems that use oxygen as the plasma gas (and air as the shield gas) create faster cuts with better edge angularity and lower cost per foot of cut as compared to an air plasma. The lower cost can be traced to: 1. longer consumable parts life (liquid cooled consumables with highly accurate gas flow controls) 2. Faster cut speeds 3. Better cut quality resulting in less secondary operations (grinding, dross removal, weld edge preparation, etc.). You will pay more to buy these systems, and pay less on a day to day basis to use them.

Oxygen plasma cutting is typically used on industrial cnc operations, many are the latest technology high definition class plasma systems (such as Hypertherm's HPR130XD through HPR800XD) and all have liquid cooled torches and consumables, microprocessor controlled gas flow circuits and power supplies.

Jim Colt Hypertherm

 

[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


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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