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waterline strategy mills the inside of the shape instead of the outside

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moshel
2017-10-05
2017-10-06
  • moshel

    moshel - 2017-10-05

    Hi,

    I am pretty new to this so it's probably something stupid.
    I have created a shape in openscad, exported it as stl opened it in pycam 0.61 and after some hickups (collision model was not selected so it ignored my model) it produced the right tool path for the slice removal process.
    However, the part is roundish so i wanted a waterline pass as well. when i tried to do that, the toolpath milled inside the part, not outside.

    this is the model in audodesk viewer (i don't think it allows downloads)
    this is the stl

    What am I doing wrong?

    Thank,
    Moshe

     
  • Lars

    Lars - 2017-10-05

    Hi Moshe,

    I am afraid, that you stumbled upon the instability of the waterline algorithm of pycam. I do not see a good way to fix that code (it should probably be replaced with an external library).

    I could imagine, that your model contains some interesting "interior" triangles, that could confuse the waterline algorithm. Thus maybe it could help to "simplify" the model with a 3D modelling program (I am not aware of details in this area - this is just a wild guess).

    If this does not help, then you are probably forced to use a working grid with small steps (wasting a lot of time).

    Cheers,
    Lars

     
  • moshel

    moshel - 2017-10-06

    Thanks lars... I was afraid this was the case. The docs mention a new, experimental waterline algorithm. Is there a way to try it?
    I'll try simplifying the object. Maybe remove the central hole...
    On the bright side, pycam is really the only cam i tried that can even surface this shape... So well done!
    Cheers,
    Moshe

     
  • Lars

    Lars - 2017-10-06

    The docs mention a new, experimental waterline algorithm. Is there a way to try it?

    I am not exactly sure, but I guess, the current default waterline algorithm was meant. There are better algorithms out there in other libraries - it just needs someone to integrate one of them into pycam.

    I'll try simplifying the object. Maybe remove the central hole...

    I did not intend to suggest a real change of the model :)
    I thought about a simplification of the mesh/triangle representation. Maybe you can try someting like "meshlab" or other tools that can fix geometric anomalies (not easily visible ones). Just wild guessing - I never needed to do that ...

    I am happy, that pycam is at least half-way working for you :)

    Cheers,
    Lars

     
  • moshel

    moshel - 2017-10-06

    The model is not that complicated (you can see it in the autocad viewer link) , actually. Just under 20 openscad lines... Removing the hole did not help, alas. I'll try the meshlab route. I really can't understand why my model is so difficult for all cam software... But, as i said, i am very new to this.

    Thanks again,
    Moshe

     
  • Lars

    Lars - 2017-10-06

    The number of openscad lines is not a safe indicator for the complexity of a model :)

    With the CSG modeling you will need to take care that you do not create near-infinitly small gaps between different components (e.g. by adding a bit of extra size in all dimensions).

     
  • moshel

    moshel - 2017-10-06

    I have read about that and the parts overlap. I have also did the difference of the inner hole before extruding to prevent "misunderstanding" about the faces.
    Again, i must be doing something wrong but i fail to see what.

     

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