Hole quality on backside of parts

Hi everyone,

I’ve been testing my plasma (Hypertherm 30XP, finecut consumables) with pretty good results so far on Aluminum.

I’ve noticed that while I get pretty good small hole features, the backside isn’t so pretty. See video in link below. This is on 1/16’’ 6061/5052.

Just wondering if this is normal for plasma or not. I’m assuming it is…and actually am guessing that the nicks you see on the backside are caused by the dross/slag that gets removed with our grinder.

If it’s not normal, any tips would be appreciated! For reference, the holes go from 10mm in diameter down to 3mm, and the smallest hole is a pierce only hole.

Are you using Fusion? If so, are you using the feed optimization program for the holes? I usually run it on all the holes first, then run a new operation for the outside cut. I cut my aluminum parts with Nitrogen instead of air. I realize you can’t do that. I also put a coating of mig gun tip slim on the torch nozzle. It keeps the molten aluminum from sticking to the tip and screwing up the THC reading to FireControl.


Approximately how many seconds or minutes of cutting does the nozzle gel ward off the sticking of molten aluminum?

Pretty long time. My parts rarely exceed about half the size of the table. The nitrogen gives a much cleaner edge and keeps the edge oxidation down. I do set the cut height to .015 for aluminum.


It isn’t cheap to say the least. Locktite make a ceramic nozzle spray. The best I have ever seen. Would say it would work on a plasma as well.


I just put some nozzle gel on my finger and apply it to the entire end of the nozzle and cup. I have not tried the Loctite spray, but I will now. I just ordered some. I’ll report back when it gets here. $31 is not that bad. It should last a long time. It’s much cheaper than a sheet of 5052.


Best stuff ever to use on nozzles. Spatter will wipe off by hand.
At work we had demo of a line boring machine with a welder. He brought some of that spray. It was the best part of the demonstration.

I am eager for all suggestions with aluminum. That is one thing that my family keeps requesting of me: aluminum plant identification stakes. I spend 30 seconds cutting each one out and up to 5 minutes smoothing the edges for each one. Thank you Phillip and BigDaddy.

See BigDaddy, even in your impaired state you are helpful (not grumpy at all)! :grin:


@Bigdaddy2166 his reply is when you got it. You got it.

Phillip, are you suggesting that BigDaddy is exaggerating a bit?

1 Like

Haha, and yes, I set myself up for that one.
I am still grumpy.

1 Like

Not at all. We had a neighbor at the shop. When you would brag on him that is what he would say.

1 Like

Not to get off the subject. Anybody that tells you that is probably driving an H1 Hummer for apparent reasons.


@leonhart88, I only have experience cutting 14 gauge aluminum. Sometimes my cuts have no dross but always a very rough edge. Even during the same cut job, I will have some major bottom-side dross issues but I blame that on the warping of the panel. So 90% of the plant stakes have virtually no dross and 10% have terrible dross. So I can’t blame it on a particular direction or speed.

Moral of the story: I think you can strive for minimal to no dross (mostly with the cut height coupled with the exacting amount of amperage) but you will still have a rough edge. It is never is as smooth as mild steel.

I turned off the feed optimization for my aluminum cuts to try to minimize the dross on the curves but I did not have any holes that required any precision. If you need the precision with the holes, use feed optimization and realize you are going to get more bottom-side dross.

1 Like

Yup using Fusion 360.

I’ve looked at feed optimization but haven’t really set it up yet. I am using different speed settings on the holes first though vs the outside.

I was running at 1000mm/min on the holes and 2000mm/min on the outside (sorry it’s in metric, I’m Canadian :sweat_smile:)

And yes, running an air plasma.

The top side of the holes looks pretty good, it’s just the bottom side that doesn’t look that great.

Can you shoot a link to this “mig gun tip slim” you’re talking about? I haven’t experienced a THC fail so far :crossed_fingers:

Forney 37031 Nozzle Gel For Mig Welding, 16-Ounce , White Amazon.com

If you get an aluminum spatter on the nozzle, it will conduct voltage, and the THC will try to compensate for the new reading.
By the way, I’m an old fart and hate the metric system. I know "it’s so much easier ":grin:


Thanks for the tips. The amount of dross I’m seeing isn’t too bad…I’m actually getting more dross on mild steel (see video below)…although the holes on mild steel seem to come out a bit nicer after deburring.

I’m using fine cut, 1/16’’ 6061, and a cut height of 0.03’’ with THC. 0.03’’ seems best, and was suggested by Jim Colt in another forum for the 30XP + finecut.

At this point I’m assuming this is just a limitation of the system I have running and/or a limitation of cheaper air plasma. I think it should be fine for our needs, but I just wanted to get an idea of what is reasonable to expect since this is the first time we’re really dialing in our plasma across multiple materials.

In terms of dross for mild steel - is below normal? This is 16Ga CRMS, same setup, 30XP + finecut, 0.03’’ cut height. Running at 1500mm/min holes and 4500mm/min outside. It does seem like running faster results in less dross. I haven’t tried faster than 4500 yet.

Aside from a link to the coating you guys put on for Aluminum…any suggestions on what abrasive wheel to use for mild steel dross? Aluminum dross comes off really easy with a maroon rolec disc, but mild steel is harder so I think I need to get something different for that. Links appreciated!

Thanks for all the help :pray:

It looks to me like you should speed it up just a touch. Do some testing with circles or squares.


Haha - sorry :joy: growing up in Canada it’s just what I’m used to…although I know the machining world still operates in imperial and I will be setting up our MR1 soon so I might need to switch gears a bit.

Thank you for the link. Do you just rub this on the outside of the nozzle, avoiding the orifice itself? Or do you just dunk the hole tip in there like in the Amazon picture?

I’ll get a tub and see what it’s all about.

1 Like

Get yourself a good burnishing tool. Here is an example.

This is a cheap piece of junk, but you will get the idea.