First Post - Cutting Question

[dwolanski]

Hello All,
I recently re-purposed some unused tools I had lying around. I had a CNC CO2 laser I no longer used and Harbor freight Plasma cutter and thought it would be a good project to make CNC Plasma Cutter.

I made the mods to the table and software and got it to work just fine. I do not have THC. After I make a few $ with the setup I want to move up to THC and a Hypertherm.

The issue I seem to be having is bevel. It can be seen here when I make little tabs on a square part. The bevel on the edges is also quite pronounced and when you go to mate two pieces edge to edge there is a sizable (say .040") gap from the bevel.

I am looking to reduce the bevel...

Here is my setup..
Harbor Freight 62204 IPT 40 cutter
Standard .9 mm tips
Cutting Clockwise around part
Gap .063
Shown in 1/4" A36 Steel
Cutting around 30 ipm (17 mm /second)
80 psi
Nice no dross zone

Suggestions????

[weldguy]

Welcome to the site, this is a common issue for many.

Hard to see from the pic but is your bevel on all 4 sides or just on 2 parallel sides?

[dwolanski]

All 4 sides. Bevel starts out sharp then kinda wanders. Corners are worse.

I am making a tool to ensure the head is perpendicular but I did put a square next to it and it seemed pretty close.

[Charlie10]

That's an issue you will always fight to some degree with plasma, it's just the nature of the technology unfortunately, especially with a harbor freight torch and no THC. You can minimize it though. It looks like you have a negative bevel, assuming that part is laying with the top side up, which means your torch height is too low. That may be a product of no THC if it's only in some spots, but you may want to raise it a little if it's all the way around.

[mdwalker]

When troubleshooting issues like this you first need to make absolutely certain the torch is square to the table. If it is not then nothing else you do is going to matter. Second you need to make sure your consumables are in new condition. The slightest damage to consumables can affect cut quality. Next make sure you have clean dry air at proper pressure for your machine. Once all of these conditions are met then start experimenting with cut speed and torch height.

[acourtjester]

One thing you can try now is a better support for the torch, just a ring around the tip is not enough. Move out to the handle section to stop any pivoting of the torch. I prefer the torch cable separate from the cable chain grouping. I use a cable boom as a way to support the cable from above.
As stated above anything that changes the plasma stream with effect the cut. High volume of air through a small orifice with a very small defect with move the stream. Look at both sides of the cut the plasma stream looks like a candle flame (inverted) so torch height can have a effect with a bevel.

[dwolanski]

Thank you all for the great suggestions.

I do have a condensater on my air supply. See pic.

I just built a tool with my CO2 laser that fits the cup and ensures the torch is perpendicular. Can't wait to try all the suggestions out to improve my parts! Thanks again!