Cutter velocity change on ARC feeds

[9 1/2]

After upgrading to the most recent build off of the DAK site my cutter velocity is almost stalling when encountering an arc (G02/G03) in the profile. I've noticed this only happens when my IPM is over 12. That is to say if I'm cutting at 12ipm it continues around the contour with out pause yet, if I go over 12 it slows to a crawl for the duration of the arc, then accelerating when the G02/G03 move is done.

I've been using Tcnc since version 3 some thing or other and have never encountered this issue before. Have I missed a new setting in the newest build?

Thanks to all that can offer any sort of a solution.

best regards

9 1/2

[voltsandbolts]

Hi 9 ½,

I am currently setting up a recently completed jgro stile router and trying out TurboCNC.

I have noticed that I see a major slow down in the cutting of arcs only with backlash compensation ON. If it’s OFF I can cut at 30ipm with out slowing down. But I’ll double check that tonight.

[9 1/2]

AH HA!!

Thanks Volts, that explains why the sudden change. I have only just recently turned backlash comp ON because I felt my Y axis was a little sloppy.

It was only after that did this issue crop up. I was so sure that I'd not run into this prior.

I appreciate your tip. I'll comfirm as well and post up.

9 1/2

[voltsandbolts]

Now I said I can cut faster with backlash off, but not better. Currently I am using ¼-20 all-thread as lead screws and taped Teflon blocks as nuts. With backlash off I get elongated circles. With backlash on I can cut much better….just slower. It’s the price you pay for running a machine made from hardware store parts, but hey, it’s a hobby. You can always upgrade to better lead screws (Acme, or Ball).

Make sure you have done every thing you can to eliminate the backlash mechanically and electrically first. Check for lose motor couplings, nut mounts. If your motor cables are not grounded make sure they are not bunched up together or you can get cross-talk on the cables causing gained or lost steps.

Anyone got more tips?