I made a jig to hold coasters in place while I cut designs into them. I created pockets into the material to place the coasters into but the toolpaths cut in a very strange way. On the outside pockets instead of clearing the pocket area in successive parallel cuts the cutter does small cuts and then does a full pass as expected. The end result is as expected but the cutting is strange.
I recreated the design and toolpaths thinking there might be something there I couldn’t see but I got the same thing.
Probably not a good explanation so here’s the file. Have a look at the simulation on very slow speed and see what you think is happening.
Pocket toolpaths generally follow the shape of the perimeters of the pocket. 3D Roughing toolpaths use a more rasterized clearing strategy.
The only concern I see in your file is that the inner/shallower pocket of the square design is not large enough - needs to overlap the outer/deeper pocket area to avoid material being missed by the endmill.
If you change the inside pocket to use only the outside boundary & cut down to 8mm
Then the outside pocket to cut starting at 8mm & down to 12 mm, you get a cleaner cut.
I agree that the toolpath does seem a bit erratic. I tried adjusting the stepover to 2.95mm & that seemed to result in a smoother/consistent toolpath. It may be the half-diameter default stepover is causing the function some weird left-over value that it then tries to clear up.
One more improvement you can make to your toolpath settings is to start the 2nd outer pocket at the end depth of the 1st pocket - since now your 1st pocket is clearing all the area above to that depth.
@Chaotica Yeah I just slapped the toolpaths together to show the erratic cutter movement.
I’ve already cut the jig and used it…worked perfect for the coasters I carved into today.
I guess my whole point to this is …why is the toolpath so strange. Is it a dimensional thing? There’s lots of room for a .25 endmill so I’d think it should be able to do consistent passes around the pocket without backtracking multiple times
Sometimes the step-over settings result in the function thinking it has some weird left-over bits of area it hasn’t cleared. I don’t know if the programming team has looked into this more closely - but it is something that comes up every once in a while.
If you select both circles and offset them inward 3.175mm, you will see the same thing.
This is how the pocket path calculates where it needs to cut. Even changing the stepover to 3.1 eliminates it.
Welcome to computer math, where everything makes sense, until it doesn’t.
Looks like you are running into rounding errors, so that sometimes the paths seem to overlap (so nothing else needs be done), and sometimes they don’t (all the weird little areas).
In general, if your stepover exactly divides into the width of the pocket, there’s a good chance you will run into this problem.
Since it’s human nature to make things ‘round numbers’, what I have done is to change the stepover to be some slightly ‘not round’ number. If the stepover was 0.125" (1/8"), I’ll change that to 0.126" instead. The tiny difference won’t affect performance, but it will break up all those times when it would divide evenly into what we think of as round numbers.
Yeah I just slapped the toolpaths together to show the erratic cutter movement.
