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Author Topic: Plasma Kerf Angle  (Read 7088 times)

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Plasma Kerf Angle
« on: January 20, 2010, 03:33:30 PM »
I'm wondering if anyone has had an issue like this.  When cutting a square object in 1/4" plate I notice that the first Y and first X cut are square, but the second X and Second Y are cutting at about  a 20* angle.  I tried rotating the torch in the holder and got the same results.  Fiddling with cut speed, height and amperage didn't help much.  When I cut a circle all sides of the circle cut square.  I usually only deal with sheet metal so I've never noticed this before.  Has anyone ever experienced anything like this?

Re: Plasma Kerf Angle
« Reply #1 on: January 20, 2010, 05:44:22 PM »
I would guess either consumables or speed. It doesn't take much of a nick on an orifice to deflect a flow of air/plasma. Turn the cup 90 degrees and check again.....maybe.

Bill C.
Re: Plasma Kerf Angle
« Reply #2 on: January 20, 2010, 06:40:01 PM »
I tried that.  I think it may have something to do with this...

"Most plasma torches use a clockwise swirling flow of plasma gas, which produces a straighter cut on the right hand side of the kerf with respect to forward torch motion. Typical bevel angles for conventional plasma torches range from 1-3 degrees on the "good" side of the cut and 3-8 degrees on the "bad" side of the cut. High tolerance plasma cutting systems can achieve even lower bevel angles."

From this article on cut troubleshooting...

Re: Plasma Kerf Angle
« Reply #3 on: January 21, 2010, 12:11:26 AM »
Good info!

Offline stirling

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Re: Plasma Kerf Angle
« Reply #4 on: January 21, 2010, 05:53:06 AM »
The undercut edge of the kerf caused by the CW swirl should be on the metal you don't want and the straight(er) kerf edge should be on the metal you do want.

So if you want the square, cut round it CW but if you want the square hole then cut round it CCW.

i.e. the kerf (which is always in the bit you don't want) should allways be to the left of the bit you do want with respect to the direction of travel. (if that makes sense  ;D)

That said, I don't think this is why your kerf changes in angle. I reckon it's more likely to be explained by the paragraph "Irregular bevel (positive and negative bevel on the same piece" a tad lower down in your article.

(I'm assuming you're using THC ?)