Need some help with my circles if possible.

[Williams Hydraulics]

Hey guys, I have a torchmate2 4x8 cnc table with a hypertherm 105 plasma. The problem i'm having is that when I cut out circles they are not coming out a true circle and I am just wondering if it's a setting in CAD I need fix or what. I'm kinda new to all this we just got the table up and running about 2 months ago now. I'll try and get a pic on here in a little bit of one of the parts I cut out so y'all can see what it's doing.

[HaasMetalDesigns]

your best bet is call torchmate they will tell you what to do

[acourtjester]

You may need to re-calibrate your X & Y axis steps per inch you can tell by the position on the table. Which axis has a problem or both check by measuring the hole in both directions compared to you drawing. Remember how you set the cut up in Sheetcam if you used inside or outside offsets weather you look at the hole of what dropped out for the correct measurement.
The CAD will give you a correct DFX size output if you say 2" it will be 2" unless you use the wrong SheetCam offsets.
If you want a 2" hole you need to use inside offsets with the correct kerf values these are in the hypertherm manual for each tip size. If all setting are correct and the hole is not correct then the table movement is the problem.

[Metriccar]

Is the top of the hole round but the bottom of the hole is not?

If neither the top or bottom are round, that's one set of problems. It is more likely slag building up preventing a proper cut, especially if it's thicker material. Welder's anti-splatter spray really helps with this. I went from 65% good hole yield to 100% good hole yield just by spraying anti-splatter on the sheet before cutting. OR, lead in length, pierce height or a THC issue.

If the top is round but the bottom is not, that's another set of issues.
The machine should slow down about 30% on smaller holes. The machine should overcut to prevent ridges left at the lead in.

I figured I am getting about as good as a hole as I can get with an air plasma, but it took some time. Small holes are about the most challenging thing to make on an air plasma table. The general rule is the smallest hole should be 1.5x the thickness of the metal. In other words, if you are cutting 1/4" thick metal, you can expect to get a 3/8" hole to come out nice. Smaller than that, taper seems to be an issue.

I always go back and redrill smaller holes to make my product more professional looking. I could just oversize the hole to account for the taper, but prefer a better looking product.

[Williams Hydraulics]

this is a pic of one of the holes i cut out its got almost a squared shape to it

[RGR]

Im not 100% sure, but i would verify that your gantry is squared up..on both sides..I can pick mine up and set it "1" tooth off on the gear rack and get funky oval circles. It could be what you have going on. Also, might check your belts on your motors and make sure they dont have excess "slack". Mine are nice and tight. Hopefully its that simple.

[srp]

Looks mechanical to me. Loose drive system pulley maybe. If the cutting is slow acceleration probably not a factor but maybe. Something in the left-right movement.

[Williams Hydraulics]

Just wanted to say thanks for all the help i tightened my belts on up and cut the same piece out and it come out a whole lot better

[RGR]

Cool! Also watch your gear track if you have one. Sometimes slag can do this by binding up the gears

[Nacs Fab]

Yes I also agree, mine had a pinion that would slip on the X-Axis and it would do that. I would check there first, if it were not re-intersecting, I would guess it was on the Y axis. There should be absolutely ZERO slack on the table when powered up. A local business has a torchmate and theirs was flat used up - they replaced all the pinoins and bushings and it was good as new.

[Williams Hydraulics]

Yea i keep the gears cleaned out everyday and that was also one of my problems one of the gears had slack in it i guess it just worked lose thanks