Deflection in Faces

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MRx
Posts: 319
Joined: Wed Jul 08, 2020 5:59 am
Location: Tainan / Taiwan

Deflection in Faces

Post by MRx »

https://streamable.com/41savt

look at the X coordinate of the first face, look at the Z coordinate of the side face.
Those faces were created with normal pocketing, half of the object is okay the other one isn't.
I have had those issues with all previous freecad versions too (currently I'm using FC 0.20)

Is there any way to fix those faces manually via Python?

Currently the only way to fix it would be to cut out the entire affected area (hoping that it will work), and redraw / fuse it. I just did that and that face is the result of it.

----

I have figured out that it makes a difference from which side the pocket operation comes from if I do a pocket from the right side of the model the entire model seems to invert (outside vs inside), if I cut the model at that part from the left side it seems to work (I'm still experimenting here).
Heck those issues should not be in a CAD program.
chrisb
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Re: Deflection in Faces

Post by chrisb »

Can you upload the file? Sometimes we see such rounding issues, which cannot be fixed by setting Refine=True.
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MRx
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Location: Tainan / Taiwan

Re: Deflection in Faces

Post by MRx »

I would call it arcbug?

It's not the actual model but something I put together within 2 minutes and it has several rounding issues inside. Maybe even the refine created those issues?

freecad shows up nanometer rounding issues, they should not be there.
Attachments
arcbug.FCStd
(72.89 KiB) Downloaded 26 times
chrisb
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Re: Deflection in Faces

Post by chrisb »

I wouldn't call it terrible, I see some deviation in the range of the 6th decimal.
This effect happens more in XZ and YZ and here it vanishes if you map the first sketch to XY plane.
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MRx
Posts: 319
Joined: Wed Jul 08, 2020 5:59 am
Location: Tainan / Taiwan

Re: Deflection in Faces

Post by MRx »

chrisb wrote: Mon Nov 08, 2021 1:44 pm Can you upload the file? Sometimes we see such rounding issues, which cannot be fixed by setting Refine=True.
Those rounding issues are caused by the tolerance settings of Vertexes, Edges and the Shape object itself.
It's all coming down now to the way how tolerances are handled in FreeCAD.
kisolre
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Re: Deflection in Faces

Post by kisolre »

Maybe those coordinates are derived from the tessellated representation and not the actual surface?
user1234
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Re: Deflection in Faces

Post by user1234 »

kisolre wrote: Wed Jan 19, 2022 8:56 am Maybe those coordinates are derived from the tessellated representation and not the actual surface?
Yes, like very CAD in this world. But often in commercial CADs the representation coordinates are "smart" (i hate that word) rounded, to represent it better.

If you want to measure it, you must measure it with measure tools. I measured some points and get with measure tool a precision of 10e-15.

Code: Select all

distance = 1.1mm    unit distance = 1.1000 mm
solution count: 1
   solution 1:
      point1 106.12323   -9.881584656241131e-15   -8.086107999999996
      point2 106.12323   -1.10000000000001   -8.086107999999994
      DeltaX 0
      DeltaY 1.1
      DeltaZ 1.77635683940025e-15
      shape type on object1 is: Vertex
      shape type on object2 is: Vertex
@MRx: just asking, you blame the loading time. How fast (or slow) opens it for you? For me it is instant open.
MRx
Posts: 319
Joined: Wed Jul 08, 2020 5:59 am
Location: Tainan / Taiwan

Re: Deflection in Faces

Post by MRx »

Vertices: 810
Edges: 1196
Wires: 510
Faces: 409
Shells: 1
Solids: 1
CompSolids: 0
Compounds: 0
Shapes: 2927

it takes around 10 seconds to load the file now, before it took 50 and very long time on operations (with a single BREP file in FCStd)
The Geometry check now shows up 0 errors, touching the flexed faces resulted in a garbled object back then. This issue is resolved a long time ago already - but it now just matches up with the other issues.

I must have had the tolerance issue for a long time. The part was designed with multiple freecad versions, it's hard to say what has modified the tolerance of the solid itself.
user1234
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Re: Deflection in Faces

Post by user1234 »

MRx wrote: Wed Jan 19, 2022 10:26 am it takes around 10 seconds to load the file now, before it took 50 and very long time on operations (with a single BREP file in FCStd)
That is waaay too long. What OS and processor do you have. Have you compiled it yourself? Do you use a virtual console?

A while ago we argue about the tessellation setting. What they are atm? Just said, FreeCAD needs on too high precise settings (they are only visual, not for the geometry itself) much more time to tessellate as for any other operation itself. This is a known weakness. For example a cut of 5000 holes in an array can vary from 20min (or more) to 5 seconds! Also it needs unnecessary much more RAM.

When checking the geometry, all tolerances are 10e-7, but the geometry is much more preciser.

As i said, it opens for me really instant. I cut a hole and made a pad on it. I do not notice any loading time.

Greetings
user1234
MRx
Posts: 319
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Location: Tainan / Taiwan

Re: Deflection in Faces

Post by MRx »

It's a macbook pro 2012 (with SSD)

Small objects load instantly, my working object takes 10 seconds, I still need to see how things perform over time... the discovery from last week how to fix damaged models has changed everything here.
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