Sawtooth edges

[sspowdercoat]

Hi all. I have a hypertherm 85 on a water bed table. I was cutting 10mm plate and I was getting weird edges on the cuts. Any ideas on what caused it?

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The rest of the cuts were all fine and the top of the cut is good.
Cutting at 70amps on an 85 tip, 12mm/s, I have really dry clean constant air.

Thanks!
Stuart

[adbuch]

How often does this happen? How close it your water level to the torch? I have seen something very similar in a recent post, but have not heard back from the OP. Have you checked your gears/belts for wear or play? This almost look like you have some slop in the table, and much more pronounced it one direction than the other at 90 degrees.
David

[acourtjester]

First off I would look at a motion problem due to the repeating of the pattern. Since it seems to go in 2 directions (X and Y) so motions on those axis would be out too. Another thing is air flow as that has an effect on the plasma stream, but the pattern would throw that out.
Best guess from me is torch bounce from the THC.

[adbuch]

That is a great suggestion. Perhaps check your cut height as the machine follows the cut path. Can you see any up-and-down motion of the torch with respect to the work piece? Have you replaced the consumables lately?
David

[sspowdercoat]

Thanks for the replies!

So I dreaming about this all last night, I think adbuch & acourtjester are onto something. We have had the machine for about a month now and someone else did mention the water being a bit high and may be creating gasses under the table. It was the last few sheets that cut weird and the water was getting pretty warm.

Using the same parts its cutting fine so far in the cold morning. Im going to turn my THC off and on for the last few plates to see if its the gasses changing the voltage somehow or if its just the gas changing the cut profile.

Ive got 3 more sheets of 10mm to cut out, I'll keep you posted.

[sspowdercoat]

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[sspowdercoat]

Three sheets done, didn't change anything but the water lvl has droped from 14mm to 22mm. Im guessing it was too high

[adbuch]

Did you get rid of the saw tooth edges and are now cutting smooth edges?
David

[sspowdercoat]

Yeah back to normal.

[adbuch]

That's great to hear!
David

[acourtjester]

very interesting hope it is the solution, Thanks for posting the follow up it will help other in the future too.