Wrong profile path (strange loops)

[julienbld]

Hi,

I draw a valid sketch containing lines and tangents arcs. I made a solid by extrusion and I tried to generate a profile path from this solid.
The result is not correct, there are some wrong "loops" in the path (where arcs join the lines)
Am I doing something wrong ? Is it a bug ? Is there a way to avoid this behaviour ?

Thank you !

[DeepSOIC]

Hi!
In the sketch, you have applied Tangent constraints the wrong way. You should do it using method 2, by selecting endpoints.
http://www.freecadweb.org/wiki/index.ph ... angency.29
You applied coincident constraint first, then tangent between edges. While that often works, it causes poor solver convergence, and consequently tangency mismatch. I believe this is the cause for the loops in path, but I think there might be another bug involved.

Unfortunately, I can't recompute your Path project in v0.17dev which I'm using.

Traceback (most recent call last):
File "C:\_vt\dev\PC\Qt\FreeCAD\Default\Mod\Path\PathScripts\PathProfile.py", line 275, in execute
self.vertFeed = toolLoad.VertFeed.Value
<type 'exceptions.AttributeError'>: 'FeaturePython' object has no attribute 'VertFeed'

OS: Windows 10
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.17.8361 (Git)
Build type: Release
Branch: DeepSOIC10
Hash: 4ac7673e543274bcae856872033a114c7b60481b
Python version: 2.7.8
Qt version: 4.8.7
Coin version: 4.0.0a
OCC version: 7.0.0

[julienbld]

Thank you !
It seems ok, now I can generate a valid path !
I don't understand why it was a problem for the solver, but this way is ok for me.

My version is 0.16. I think you can't compute the path because I didn't complete the horizontal and vertical speed fields. It might be mandatory in your version.

[herbk]

Hi,
i have the same Problem on some parts. It's not always, only if the parts a little more difficult.
Here's an example: i want to mill out this part:

loops1.jpg (52.14 KiB) Viewed 1474 times

and here the loops:

loops2.jpg (46.58 KiB) Viewed 1472 times

The loops are not on each pocket, the whole part has 34, the loops are only on this 2 pockets.
The differnt to julienbld's situation is: my part is made with the part and draft WB only, so there isn't any sketch.

[mlampert]

Hi Herbert,
Not on my computer right now, will check it out tonight. Which version are you using?
Markus

BTW: I had a quick look and you seem to have 4 of those issues, 2 on top and 2 at the bottom.

[herbk]

Hi mlampert,
you are right, there two more on the bottom..

Im using

OS: "openSUSE 13.2 (Harlequin) (x86_64)"
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.17.8577 (Git) (Packman)
Build type: Release
Branch: master
Hash: c833136cde65b90bdc2809c3022afdfa4a3a4bb6
Python version: 2.7.12
Qt version: 4.8.6
Coin version: 4.0.0a
OCC version: 6.9.1.oce-0.18-dev

Its a 17.xx, but on opensuse are some functions not available...

[sliptonic]

herbk,
It looks like you're using OCC.

I tried it again with my current version that uses libarea by default and was able to get a normal looking path. However, libarea would often fail to generate a profile at all. I got it to work by playing with the 'extra offset' value, setting it to something like -0.01. It feels like a rounding bug but I'm not sure how to track it down.

[chrisb]

It pretty sure is a rounding bug. Turning the cut before applying the path operation sometimes works, e.g. with 0.2°, and sometimes makes things even worse.

[mlampert]

Hi Herbert,

Unfortunately I can't reproduce your issue (other than in your file) with any of the builds I have of 0.17

I did notice a few things:
* it works in the newer version (sliptonic has a pull request out - doesn't help you right now though)
* I got some good results by converting your magnet wheel to a "Solid" (Part menu) and build the path around that
* I can't create the outside path with other builds. I can create the "Right" path and the "On" path, but not the "Left" - which is not entirely true. After fixing some issues it does seem to build - except that there is no outcome.

Question to the experts: Is there a limit in the size or number of properties a Feature can have ?

Stab - stab - no, still dark .... sorry

[herbk]

sorry, double post...