Plasma Dross

[thkoutsidthebox]

Hi,

I was able to try out a Thermal Dynamics Plasma the other day using a hand torch. Unbelieveable piece of equipment. Anyway, three of the pieces I cut are shown below, I wasn't using it for long so didn't really develop any technique, just messing with it to see what it could do.

Im just wondering if the dross shown is normal with plasma, or can it be much cleaner?

If it is normal, that would lend to a lot of time spent on cleanup of large parts....

Thanks.

[tyler774]

Hello,

That is what is termed slow speed dross, hard to avoid when hand cutting. Your torch is probably capable of much cleaner cuts. I get nice cuts by hand if I use a staight edge and crank the power up, (with a drag shield). Decorative cutting usualy looks ugly when I 've tried it, usualy means getting out the die grinder to clean it up.

Later

Tyler

[thkoutsidthebox]

Thanks Tyler. The torch was only a 40amp unit, not much power and it didn't really get through the 6mm mild steel well. I moved it at different speeds to see how fast it could cut since I've heard people on this site mentioning 300ipm for a cnc plasma, but it didn't cut well at a fast pace, just burned the surface. When I eventually get my own unit I'll be using a machine torch with it cnc'd, and hopefully it'll be more powerful that the 40Amps of this one.

Are you saying that with my prospective cnc setup I won't have to worry about cleanup as much?

Most of my stuff will be 'artsy'. I don't like the thought of having to grind out this on pieces meters in length.

Thanks.

[tyler774]

Hi

Clean up would be less for sure with CNC, the dross will not disapear completly though. If your settings are all goood it chips off with a tap from the chisel or chipping hammer. anywehere there is sharp corners it will stick more.

I hav'nt added pictures before, hope it works. Took maybe 15 minutes to chip dross from the back side of this, it's about 3 x 3 feet,perhaps 18 gage? can't remember. Cut on a Torchmate machine with a Hypertherm Powermax 1000 , & THC.

Tyler

[Scratch]

You use a chipping hammer? I use a grinder. I use a 4.5" angle grinder with a hard wheel on it and just lightly skim the edge. It seems like the vibration of the grinder, helps to wipe it off very easily.
I then take a 6" 60 grit flap wheel on another grinder to clean up any smoke residue or anything else that happens to be on there. Then I flip it over to the front side and hit the entire piece with the flap wheel to get off the little tiny "spatter-dross" (my term...) that is around some of the edges on the front side.
That whole process on a piece like the one pictured above would take me about 5 to 7 minutes.
Sometimes, if needed, I'll wipe some acetone or laquer thinner on it if there's any oil on it, otherwise it's ready for paint.

I'm using a Thremal Dynamics 151 on a practical table.


By the way Tyler... I really like that piece.

[massajamesb]

That is about right for a first-timer cut by hand.
Some plasmas are better than others when it comes to dross, but there are a number of factors that will decide how much dross you get.
Height of cut, constant cut height, travel speed, amperage, etc. will all play a factor.
I haven't uploaded all my new pictures yet, but I have one in my member photo gallery of a 1/4" thick plate bracket I cut on my cnc. It was cut with oxy/acetylene (I now use plasma or oxyacet). I ground the top and bottom edges of the plate to remove rust,but no slag. The picture is a little fuzzy, but I can tell you, it was CLEAN. Swarf was minimal, and what I did have fell off easily.
This is because you are keeping all the variables optimal, and you are not trying to move your torch around with a shaky hand.
Plasma will work the same, for the most part, except most plasma cuts will be cleaner,depending on material thickness. Overall, I use oxyfuel for anything over 3/8 and plasma anything below. My plasma is a 40 amp Thermal Dynamics cutmaster 50.

Attachment 29388

Attachment 29389

Tyler, that is nice. I like

[thkoutsidthebox]

Thanks folks. There is so much experience on this site. I really appreciate the replies. Tyler I can't see your pic, but it seems everyone else can so it might be a problem at my end....

[fractaledge3]

Hi,

You can finally have no dross cutting, but I can tell that there is no dross free cutting from the first shot(run), because there are a lot of parameters:
-Type and thickness of the material
-Torch Height (should be constant along cut)
-Cutting speed
-Amperage(depend upon material type and thickness)
-Air pressure
-Plasma gas used(air ,N2 ...)
-Type of the torch used and its nozzle.
My plasma machine is hypertherm (powermax 600), with machine torch, also I use the fine cut nozzle in cutting small parts.
Here are some photos for unfinished work and other finished work on a deferent materials.

[Scratch]

Ahh... Curlz MT. One of my favorites!

[Graybeard]

Hi,

We are all haunted by dross problems from time to time. I have my best luck using the settings recommended by the torch manufacturer. Mine is a Powermax 600, using fine cut consumables on 16 and 14 gauge mild steel. Also do some on 1/8" and 3/16". I use air and have a CandCNC MP-1000 torch height control. I have added a water tray to my table and set the water level even with the steel or slightly above. I get very nice cuts with virtually no dross except on sharp points. Most dross comes off easily when hit with a chisel or angle grinder.

A couple of tricks I've come accross:

A quick squirt of welders anti-spatter or your wife's Pam cooking spray will keep a lot of dross from sticking. It also helps keep your nozzles clean.

I mix muriatic acid with water (1 gal. acid to 45 gal. water) and hang my cut pieces in it overnight. By morning the dross, mill scale, oil, rust, etc. will be gone. I rinse with plain water and dry the piece. It's ready to paint. However, if you don't paint it immediately you will get flash rust and if you let it set too long it will get extremely rusty. Avoid the rust problem by soaking the piece in soda water (1 cup washing soda in 5 gal. water).

It all sounds complicated, but it sure beats grinding, sanding and polishing.

[DSL PWR]

What the heck is washing soda?

[Graybeard]

Washing soda is just that - wasing soda - I use the Arm & Hammer brand. I get mine in the laundry detergent section of my local supermarket.