Cutting Out items - Endmill getting stuck?

Hi,

several times now i had the issue that when i try to cut out some shapes, the carving goes wrong because (I think) the bit gets stuck.

For example in the attached picture, I used the #111 in Meshcam, and used a a Roughing Cycle, Margin of 0.1260, disable surface limit. Used ‘Cut X then Y’, Waterline and Pencil Cleanup. I always used the defaults that CarbideMotion recomends.

at around 50% or so (i have not continuously watched the process) it must have gotten stuck from how it looks like on the picture, but not sure.

All I know is that this happened before when i was trying to cut out a shape. When the endmill goes into the ‘trench’ it cuts to make it deeper, it sounds like its hitting the sides of the trench.

The wood was firmly fixed on the table and did not move. I used soft Redwood (which was also not cupped or bowed).
Since I cannot upload .nc files (and even packed its too big), here is a link to it if somebody wants to try: https://www.dropbox.com/s/wb1hm3jmb7lekuw/49ers.nc?dl=0
Can anybody shine light on this? Either this is happening because i am doing something wrong, or because Meshcam does something wrong (at this point i don’t think its the Nomad because i also had the circuit board replaced which fixed the old ‘double vision’ issue i experienced).

Since MeshCam has the parameters for #111, shouldn’t it build the paths in a way that things like this don’t happen?

Have you watched it when it fails to know specifically what’s happening when it fails, or does it fail when you leave it alone and do something else while it mills and then you hear the disaster and come back to survey the damage?

Asking because I had several complete fails that looked like yours and it never happened while I was on the computer; always when I left the room. It was my computer putting itself to sleep. I turned that off and haven’t had any failures since…

Oliver, I ran your gcode through CutViewer Mill and coordinate-wise it runs fine.

Perhaps the machining parameters (stepdown, stepover, speed) were set too agressively in the wizard…from your photos it looks like the Nomad severely skipped around during the machining, which would tend to support stalling of an axis during the machining, and then resuming after the next retract and plunge.

Hi,

my Mac stayed on the whole time, and i had lots of other jobs that i ran that were all fine. The Mac is running Caffeeine which keeps it from going to standby.

I was not there when it happened, it also kept cutting, it was just off on the X axis by half the width of the workpiece.
I always seems to happen only if i run jobs that try to cut out something when meshcam is set to ‘geometry only’.

The settings is used were the default settings in Meshcam for ‘Wood - Soft’ and since i was using very very soft Redwood, i dont think thats the case.

But otherwise it makes sense with the stalling and retracting you mention, i just dont know WHY it would do that with such soft wood, and a new sharp cutter. Plus i have cut very hard Jatoba wood before with no issues like this, however i usually use the ‘Whole Stock’ option and not ‘geometry only’.

Geometry Only vs Whole Stock will not make any difference in the toolpath generation, other than saving a whole lot of unnecessay machining. :wink: I use Geometry Only probably 99.44% of the time (and if you get that reference you are probably as old as I am…)

I have seen other instances on the forum here where the preset machining parameters (stepdown/over and speed) seem to my eye to be overly agressive. But that is probably just me.

I have been running open-loop stepper driven machines for about 15 years now, and probably run them more conservatively than I need to. But my viewpoint is if an open-loop machine loses step anywhere in the job, the workpiece is ruined, so I’d rather take more time than might be necessary, than to waste the stock and time and need to do something a second time (backing off parameters the second time to be sure…)

In my experience, the spindal only stalls if I have entered too aggressive a feed speed, a depth per cut, or both.

Also, in your photo it looks like the wood chips are quite thick and really caked in the machining grooves. It’s possible the cutter is getting stuck on the chips. So even though it’s a softer wood, it looks like you need to be less aggressive with feeds and speeds.

Hi Randy!

99.4? Thats pure as ivory! :wink: Anyways, I have used the Geometry only too a dozen times at least without issues, but the issue like above happens ONLY at ‘Geometry only’ for some reason (could be type of job i run though too that needs this).

The settings worked fine in this very hard jatoba wood, and like i said this redwood is very very soft (I can almost mill it with a pencil ;)).

I am currently looking into Vcarve, to see if i get similar issues. Plus Vcarve has nicer settings and better visualization (i think), plus calculates the paths way faster it seems from my limited testing. I have not actually used it yet to carve something since I was hoping that somebody here has some ‘known-good’ settings for the 101,111,112 and 102 tools so i can enter them correctly and most importantly, the correct Export settings.

but thats another topic… (literally here: VCarve Pro settings and definitions)

OK, we’ve both established our decrepitude now… :slight_smile:

Oliver, I’m not a woodworker so my perceptions are colored by machining aluminum, brass, plastic which make discrete chips that clear nicely out of the kerf.

Could it be that your wood is fibrous and the cut fibers are wrapping around the cutter and jamming it? In that case a solution might be to increase the “+” value to maybe the cutter diameter to give a larger kerf around the workpiece.

Sounds like it :smile:
The chips were in fact collecting in the groves, but not wrapping around the cutter at all, when i stopped the job, the cutter was totally clean.

They don’t need to wrap around the cutter to get stuck and stall it - if the cutter is hitting too much kerf, it can get stuck or skip a step and then it will hit a wall and stall.

interesting, maybe thats the cause then. Seems to happen with softer (cheaper) wood more often that with expensive and dense hardwood.