g02 not working for small circles

[netdude]

Testing out how small my plasma can cut, I created small test to cut holes 0.1 in, 0.2 in, 0.3 in, and 0.4 inch. When I first ran with UCCNC it just did a single pierce at each circle start point but did not cut the circle. I turned off the torch and played with commands at MDI line using "G02 J0.1". I had made a part before with a 1 inch circle so I incremented the J value up and it started working after about .5 inch. I then tried same thing using G03 and it worked fine at all sizes using G03. I went back into sheetcam, told it to reverse direction for those cuts, and ran again and it cut all circles fine.

Is there something I'm missing? Why is it acting differently cutting in one direction versus another? Attached is test file.

small test.tap

(1.48 KiB) Downloaded 609 times

[cncdrive]

A circle can't be interpreted as a circle if it is smaller than one step of your axis.
And even if the circle is larger, but still have a similar size as only a few steps then it will not be a circle shape, but it will be only a few steps around, not a circle looking shape, because the axes resolution is not high enough to nicely form a circle.

The 1/steps per value is one step distance of your axis. So, for example you have 100 steps per value setup then one step is 1/100= 0.01 units.
This means that your stepper or servo motor can step on 0, 0.01, 0.02, 0.03 etc.
If your circle is then 0.01 size then the machine can onlystep one to interpolate it, because the circle has a size of a single step,
and it is then physically impossible for your axis to make smaller steps than 0.01 units with this example 100 steps units.

It is the same as when you drawing a circle in a drawing program. If your circle is so small as a single pixel then it will be not shown as a circle.
And even if it it 2x2 pixels size it will still show up as a square and not as a circle.

[netdude]

I understand the first "hole" won't do much so I'm not worried about that one. But the core issue is it doesn't work using G02 commands but works fine with G03 commands. I simply changed in sheetcam to reverse the path and that triggered G03 commands and it cut just fine (again the first hole will just be a quick pierce and no movement). And just issuing G02 and G03 command in MDI box exhibits the issue. That is what I'm trying to figure out as an issue with UCCNC as a bug or configuration issue. I have x/y configured for inches and using 564 steps per unit.

[cncdrive]

OK, I think I know what the problem is, but give me a few days to verify. Will post as soon as I've checked it out.

[netdude]

cncdrive - thanks for the info. On your previous post, you were looking at the wrong scale. The circles are 0.1 inch, 0.2 inch, 0.3 inch, 0.4 inch. On my machine an inch is 564 steps so .1 inch should be about 56 steps in a linear move. I get 0.1 is too small so it just does pierce. Again, when I reversed direction in sheetcam it worked fine. I have also tried same commands on mach3 machine and works fine using either g02 or g03.

[cncdrive]

This issue was fixed in test release 1.2103, details of the issue in the release notes.