constant velocity not working when using outside offset

Wolfes Metal Fab · Post by **Wolfes Metal Fab** » Fri May 23, 2014 5:11 am

I am trying to figure out why constant velocity is not working in mach 3, and a mach technician told me that my g code file is producing arcs in the corners instead of just a 90 degree angle, so it is not doing CV. This happens when using outside offset, because it offsets the cut to the outside, which means the plasma cutter makes a small arc while hugging the shape, but this evidently cancels any potential to use CV.

Any ideas Les?

Thanks again for the wonderful program, customer support and addition of features!

Brian

rikduk · Post by **rikduk** » Fri May 23, 2014 9:28 am

Wathever the shape you cut, cv (constant velocity) will work.
it just keeps the speed constant, wich means Inside corners are rounded, because of the accel. decel. of your machine

Are you talking about the feature cv stop on angle?
If so, it works, even if you have a small radius.
But i dont think it works on outside corners

Or you can try instead in the same menu, stop cv on distance:
then you enter how far from a corner you start to turn.

Post by **Les Newell** » Fri May 23, 2014 9:38 am

CV should work on arcs but try this: In your cut operation turn on 'triangle' in the 'loop sharp corners' box. Set the loop size and angle threshold sliders fully to the left. Corners will now be sharp angles rather than being rounded.

Wolfes Metal Fab · Post by **Wolfes Metal Fab** » Fri May 23, 2014 2:41 pm

No, not talking about stop CV, just trying to induce some corner rounding so i can find what is ok to improve cut cleanliness and speed and compromise between sharp and smooth CV corners.

I had the checkbox on none, so i didn't think it implemented that, so I overlooked that. I changed it like you said, and the gcode came out how we want for test the cv setting. I will have to wait till my drive is fixed to actually run a test, but that should solve that problem.

Thanks Les

Wolfes Metal Fab · Post by **Wolfes Metal Fab** » Fri Jun 13, 2014 1:55 am

Well all that fooling around, and i think it was just a bug in my install/version of mach. I had emailed a mach 3 tech, and then asked for your help with what he was talking about, and in the end, you are right, it doesn't matter it works either way the post is made. That is after i updated to the latest version of mach. I was able to cut a 3" star at 500 ipm with .05 tolerance and it was perfect, .1 and it was borderline for what i want, 672 ipm and 1.0 for tolerance and it was massively rounded even at 75 accel. Just what i wanted it to do though, so i can see the results and find what is ideal for me. Thanks guys for your help!