cut quality question

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03 Jul 2020 20:21 #173547 by motal2004
Hi guys.
I took a break from my table, but back at it.
I have been doing some test cuts on 3/16 mild steel, 4.7625 mm. I working on circles. I quickly CAD out a circle with in a circle, I attached 2 picture to this post of my cad designed and my sheetcam tool chart. I took several picture from different angles and i put them in my google drive folder see link below.
So my question is my circles are not coming out true circles more like an Ellipse or oval shape on parts of my cut. its at hard to tell in pictures thus the reason why i took a lot.
things i have done..
tighten every nut and bolt on my table, adjusted the height of my torch and it sits square to my table. I adjusted the tension on the belts as well. I did check my consumables and made sure they where securely fastened. Doing all this really did help get better cuts. my linear cuts are coming out true and square ,but cutting circles or larger radius cuts in thicker material is still off. I did adjust my cutting speed and reduced it by 65% That helped. I did try a few cuts with the THC disabled as well still same result. I am perplexed I am missing something? Please take a look and let me your guys thoughts.
Maybe its me and I should lower my expectations on cut quality on thicker material, as this is plasma


drive.google.com/drive/folders/1-0AK1Co4..._AU_ZXO0?usp=sharing
Attachments:

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03 Jul 2020 20:42 #173549 by tommylight
Replied by tommylight on topic cut quality question
Small circles will always be a bit off, but bigger ones should be OK.
Also the thicker material will have a bit of a slope, that depends on the torch, air supply, humidity in the air, material being cut, cut speed, and nozzle wear.
From your pictures, the torch heigh should be lowered a bit and that will help, the cut speed on smaller circles should be lowered up to the point that the THC can still maintain correct height, for bigger ones the cut speed should be 25 to 50% lower than what you use to cut straight lines.
Small is 30 to 50mm, bigger is 50 to 100mm, i do not even bother with anything smaller than 30mm, ONLY when i use one of the Hypetherm plasma sources and torches i have access to as they are big water cooled ones with very expensive nozzles.

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