[SOLVED] Poor toolpath trajectory for pockets

[Giulio Buccini]

I want to mill a bracket out of an aluminum plate. Quite soon I have detected strange toolpaths when trying to carve some pockets to make the bracket lighter.

I discovered different "strange things": some arc-paths starts with a straight line, while others does not follow the profile of the pocket walls.
This poor accuracy affects many of the pockets of my object:

Selection_7574.jpg (45.94 KiB) Viewed 1383 times

Only TagSlots 1 and 2, as well the circular/hex pockets, seems ok to me. The other pockets have all small or big problems.

For example, SmallSlot 1 and 2 have some "humps" ad the corners:

SmallSlot 1.jpg (15.56 KiB) Viewed 1383 times

I tried to increase the size of the slots and/or to decrease the endmill diameter (from 3 mm down to 2 mm) but the problem is still noticeable.

Any idea how I can mitigate/reduce this "distortions"?
I don't need a big accuracy on such stuff, since the most important pockets seems ok(holes and hex and TagSlot 1,2). At the same time, I would make this problems on the remaining pockets hard to be detected at naked eye.

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OS: Ubuntu 16.04.7 LTS (XFCE/xfce)
Word size of FreeCAD: 64-bit
Version: 0.20.25943 (Git) AppImage
Build type: Release
Branch: master
Hash: a65464b722a846bd2999aa2fecdff1132b15b297
Python version: 3.9.7
Qt version: 5.12.9
Coin version: 4.0.0
OCC version: 7.5.2
Locale: English/United States (en_US)

[bmsaus4ax]

Any idea how I can mitigate/reduce this "distortions"?
I don't need a big accuracy on such stuff, since the most important pockets seems ok(holes and hex and TagSlot 1,2). At the same time, I would make this problems on the remaining pockets hard to be detected at naked eye.

The Dogbone Dressup seems to be causing this.

Did you intend to apply Dogbone to all operations as it seems by the tree view?

If you deactivate all operations, then reactivate all but the Dogbone Dressup on Profile operation, execute a simulation the "bumps" disappear.
Reactivate the Dogbone and Profile again after this ; rerun the simulation and all operations remain as desired. (no bumps)

I do not know specifically why this works, but it seems to decouple the Dogbone Dressup.

[Giulio Buccini]

Hi, thanks for your reply.

No. I do not want to apply the dogbone to all pockets. I've applied just to one pocket (the one with the hexagonal shape) and I'm fine with it.

The problem of misaligned toolpath trajectory, and strange "humps", arise with all of the remaining pockets but three.
In other words, these are the pocket with poor toolpath:

SmallSlot 1
SmallSlot 2
Slot 1
Slot 2
Slot 3
Slot 4
Slot 5

For example, here the problem with SmallSlot 1 and 2 (I switched to a black blackground to make the image more clear):

Selection_7576.jpg (19.52 KiB) Viewed 1187 times

The toolpath is not parallel to the packet walls on both of short edges. Furthermore, there two abnormal "humps" at the two opposite corners.
I tried to reduce the tool diameter, change the offset parameter, deactivate the cutter compensation with no success. The path is enlarged/shrinked but stay wrong.
Seems that the two short sides of the rectangular shape are made by two arcs, instead of a straight path with two arcs at the ends...

[Giulio Buccini]

Well... after looking carefully, I noticed that there are some minor issues even with TagSlot 1,2.
There is a straight path at the beginning of the curved edges (look image below).

Selection_7577.jpg (31.84 KiB) Viewed 1148 times

In can live with that. Is hardly noticeable at naked eye. Anyway, I suppose that this would be unacceptable if you need a certain degree of accuracy for precise parts.

[Giulio Buccini]

SOLVED!
SOLVED!
SOLVED!

This was a problem related to the accuracy settings of the Path workbench (i.e. the number of decimals used - quite important for small segments in the model).

After applying the suggestions from Sliptonic, (and recomputing all of the paths: dropdown menu -> "Recompute object") everything has worked at the first shot.