Ok. So I was carving a desk top sized(~6"x11") American flag for a customer last night. After 6ish hours, this happened right at the end of the carve.
I have done this design several times. And I used @fenrus’s stl tool, which I have also used several times. I was running the finish pass with a 1mm ball nose at a 0.006" stepover.
Created it with @fenrus’s tool, ran it on Carbide Motion Build 513, on my XXL. The only variable that I changed on this one from the last 3 or 4 I carved was that I moved it from .004" step over to .006" to save time.
Perfect, as I expected. The only think I can think of is that the .006" combined with the chunk of stock left, just didn’t allow it to clean out and forced the endmill off course. But at the end of the routine the endmill was still in the area of the error rather than at the end of the run like one would expect. Like instead of running a final profile cut, it bounced around in this one spot.
.006mm? That’s 2 ten thousandths of an inch (0.00023622047 "). The machines doesn’t have that kind of resolution, features this small won’t impact anything.
It just really blows my mind that everything else was done cleanly. The piece didn’t shift at all, and the router and endmill are still tight. Something just caused it to cut a random wavy line, then proceed to clean out a pocket. It wasn’t just an errant line, but something very weird.
The simple version is you lost steps, machine lost position, but continued to try to follow your instructions.
Looks like you ran into stock that wasn’t planned for in the gcode.
It cut cleanly for the first 9ish inches along the line, then went haywire. I can cut my stock down to size better next time. I just haven’t had this issue before, on this same carving. I just wanted to run it by y’all before I ruin a nice piece of mahogany and have to change my delivery date again.
the gcode generator uses the roughing bit to do a full clearing round around the stock to make sure there is space for the finishing bit… and F&S are pretty conservative generally as wll