Cutting 11ga P&O, dross poroblem

I have a project that I need to finish! I have been using 11ga Hot rolled but today I had a Boo Boo happen and lost the last part needed to finish. All I could find in a hurry was 11ga P&O. I can’t get it to cut properly. I am getting major dross. I have tried all I know in trying to fix the problem. 1. feed rate, 2. amps, 3. air pressure, 4. new consumables, 5. a combination of all above. It seems that the metal is too soft. I have not had any problems with Hot rolled. I may have to finish with 10ga Hot rolled bc I have a sheet of that but would rather not. Any help would be appreciated.

I might be a idiot but what is P&O?

Pickled & oiled. It’s a preservative treatment applied to prevent rust.

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Never seen it before in my life. My dom tubing comes oiled but just wipes off with brake clean.

Still! Can someone tell me why I have the dross problem! Do I need to clean the material first?

You should be able to get cleaner cuts at faster speeds than HR steel.

I clean before with mineral spirits or acetone or alcohol. That way the pores in the metal aren’t absorbing the oil when I cut & it heats up. Embedded in the steel it can cause adhesion problems or orange peel when painting or powder coating.

I’ve not cut it without cleaning so don’t know if that’s your problem.

We need pictures, and I forget what your setup is.

I get plenty of dross with my 11 gauge cuts, but I can pick it off with my fingers and the cut is perfect.

I believe P&O is just hot rolled that’s been bathed in acid (pickled) and then oiled to prevent rust. I cut 10ga P&O without cleaning and it cuts perfect so I kind of doubt its the metal.

Im still a newb to this so I am not sure what it could be… Air line maybe not putting out enough pressure?

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I have plenty of air, I maintain a steady flow of air with pressure steady at 100# but I am set from 60 to 80# depending on material thickness. The air is clean and dry. I have been watching videos on cutting 10ga P&O metal. I have used P&O for other projects but not for Plasma Cutting. It seems that I am not able to cut fast enough. On each part there are 32 rectangles measuring .27" wide x 1.25" long and 48 rectangles measuring 1.5" wide and 1.25" long. I am working on lowering my lead in rate and increasing the cutting rate so I can get a clean lead in. I am set at 30amps, 40 ipm lead in and 70 ipm cut rate and have cut at 120 IPM and still have dross that I have to knock off with a hammer and flat bar. I have tried up to 40amps and multiple feed rates. I will try to get a picture of part of the part so others can see what I mean. Icecactus, Will you tell me what settings you are using?

I am using a miller 625 extreme. 40 amp tip. 40 amps on the dial. I used 60 ipm.

What’s funny though is that I thought I used what the miller manual said…I couldn’t remember what that was, so I looked it up. Its 218 ipm…I knew there was no way I cut that fast. So I looked in my fusion file, it was set it to 60 ipm which is what the manual says to cut 1/4" at…apparently I misread the manual and took the value for 1/4" not 1/8". It cut really well at 60 ipm though and will probably continue to use that.

For reference I am using an HTP Microcut 875 and cutting the following:
12ga @ 45amps, 120IPM
10ga @ 45amps, 110IPM

This is on HRPO material.

Those are small pieces. Are you cutting right next to each other? Spread your cuts way apart. Don’t cut each one right next to the last cut.
Aldo 45 amps and SLOW your cut down. Don’t speed it up.
Let us know what you end up doing.

It is my understanding that brake clean is not a good cleaner for parts that will be plasma cut or welded due to the possible poisonous fumes that will be released when heated.,hydrogen%20chloride%20and%20possibly%20phosgene.%E2%80%9D

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Phosgene gas is the same stuff they used to clear / wipe out the trenches in WWI. Nasty stuff - definitely stay clear of any chlorinated products when welding. Non chlorinated brake clean is better / safer, but I use acetone or mineral spirits or alcohol and avoid brake clean. It’s too easy to pick up a chlorinated can by mistake.

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Hello everyone! OK! I have used any and all suggestions that I have received in response to my dilemma and am very grateful . So thank you very much. This is what I have tried to no avail.

  1. Cleaned with Lacquer thinner, wiped clean, both sides and allowed to dry completely.
  2. 30amps, 25ipm. No help
  3. 30amps, 15ipm. No help
  4. 33amps, 40ipm. No help
  5. 35smps, 65ipm. No help
  6. 27amps, 28ipm. No help
  7. 45amps, 30ipm. No help
  8. 45amps, 100ipm. No help
  9. 45amps, 90ipm. No help
  10. 45amps, 65ipm. No help
  11. If I slow down below 50ipm I may as well pay the customer for letting me run there parts. LOL!! I don’t drink but I may start…
  12. I give up. No help! With good metal it takes 25 minutes to finish 1 part. The program spaces the rectangles apart. IE; Top row, bottom row, center row, next to top row, next to bottom roe and so on and this works on the Hot rolled. I wrote the program in 4 separate profiles. This way the part can cool for about 1 minute between cuts.
    I do think the metal is too soft. I ran into something like this when I was working. When we tested the metal with a hardness tester it tested below the range of where it should have been. when welded it would burn through very quickly. In another instance we had metal that came in so hard that after it was welded and galvanized it broke like glass. I do have a picture of the dross but can’t post it yet. When I have the permission I will post it at that time. I have permission to switch to 10ga Hot rolled to finish this project. So that is what I am left with for now. We have 11ga Hot rolled coming in next week. Thank you to everyone…

All the same results with all those different speeds? What’s your normal speed for HR or CR?
I cut 11g at 120 to 160ipm at 45 amps depending what I’m cutting out.

I know it sounds far out! But it is what it is. This is the only material that I have had a problem with. I normally cut at 33amps @ 65ipm. Please remember that I am cutting out a lot of material; probably about half of the part is cut away. The part is 15" wide x 31.5" long. I can’t show a picture bc at this time it is Proprietary information. I have been cutting 10ga Hot rolled at 33 to 40amps and 50 to 70ipm depending on the size of the cut outs. I cut 12ga Hot rolled at 35amps and 75ipm. On these I have very minimal dross, easy to clean off with wire brush. Some times need a little more persuasion. On the 11ga hot rolled the set up was fine. 30 to 33 amps and 50 to 65 ipm. I can cut the profile a lot faster but the slots not so fast. I do not have much room for lead in. About .15" is the longest I have used so far. I have tried selecting each small slot with a start point to increase lead in but that isn’t much better. On larger parts and profiles I am using about what you (Fortifyfabworks) are using. I have lowered the water level thinking that the splash up was cooling too fast. No help. I am lost on this material? It just seems that it is too soft. I have had better luck cutting Aluminum. Would it make a difference if I change the cutting height? I am @ .060" most of the time. I use similar set ups between Cold and Hot rolled. I have some extra material that I will do some test cuts to show. Those I can post.

any marking on the sheet regarding the steel grade or composition? Something like A36. Does the place you got it from know any details about how it was made (other than p&o)? I’m thinking maybe it’s some alloy mix - it should still cut, though, but it may be a mix that as you say is too soft to cut or weld without a specific process. Perhaps it needs nitrogen vs air or something like that? Interesting.

Must be from china lol

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I am back with good news! We got 1 sheet of Hot rolled today and were able to finish our project with one day to spare. WooHoo! I have a picture of a piece of the drops. You can see the difference. Both were cut at 33amp at 65ipm. I am still confused about that metal. It did have some markings but I didn’t think to write it down. The seller took back the one full sheet that we were NOT going to use. We traded for the Hot rolled. And they apologized for bad experience. We showed them the cut outs and they were confused too. They said that they were going to check into it. We got the first two sheets off the bundle. The left is the Hot rolled, the right is the P&O…bad%20dross%201 bad%20dross%202 They are the same size, 1.5" x 1.25"