Coarse ellipse and circle defintion

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DeltaFoxtrot
Posts: 21
Joined: Fri Jan 13, 2017 8:46 pm

Coarse ellipse and circle defintion

Post by DeltaFoxtrot »

I am trying to design an engine cowl using FreeCad and I have made this using 4 or 5 sketches to define the shape at various stations. The sketches are made up from lines, ellipses and circles and the cowl is made by lofting between these sketches. This produced a good cowl shape for me apart from the rather coarse definitions of the circles and ellipses which seem to be made up of a small number of straight lines. At first I thought this was simply a rendering problem, but when I print out the cowl these are there in the final print. I can see these in the STL and, on close inspection, in the CAD file. Is there a way to increase the resolution of these features to smooth out the cowl?

I have attached the STL file as the FreeCad file is too large (apparently) to attach. I also attached a screen grab of one of the sketches showing the issue with the ellipses and circles.

I would be grateful for any help with this as I am very new to CAD.

Regards
DF

OS: Windows 7
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.16.6706 (Git)
Build type: Release
Branch: releases/FreeCAD-0-16
Hash: f86a4e411ff7848dea98d7242f43b7774bee8fa0
Python version: 2.7.8
Qt version: 4.8.7
Coin version: 4.0.0a
OCC version: 6.8.0.oce-0.17
Attachments
Capture.JPG
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Turbulent_Cowl_v3.stl
(1018.15 KiB) Downloaded 47 times
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sgrogan
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Re: Coarse ellipse and circle defintion

Post by sgrogan »

DeltaFoxtrot wrote:I can see these in the STL and, on close inspection, in the CAD file. Is there a way to increase the resolution of these features to smooth out the cowl?
For export, switch to the Mesh Design WB, then EDIT>Preferences..., Import-Export panel, Mesh Formats tab.
This is independent from the on screen rendering in FreeCAD, so you can have lightweight/responsive FreeCAD on-screen rendering and a fine-grained .stl export.

OS: Windows 7
Word size of OS: 64-bit
Word size of FreeCAD: 32-bit
Version: 0.16.6706 (Git)
Build type: Release
Branch: releases/FreeCAD-0-16
Hash: f86a4e411ff7848dea98d7242f43b7774bee8fa0
Python version: 2.7.8
Qt version: 4.8.7
Coin version: 4.0.0a
OCC version: 6.8.0.oce-0.17
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DeltaFoxtrot
Posts: 21
Joined: Fri Jan 13, 2017 8:46 pm

Re: Coarse ellipse and circle defintion

Post by DeltaFoxtrot »

Thanks for your response sgrogan, I will give this a try. Probably be Friday before I get the chance. I assume there some obvious settings in preferences to refine the mesh.
DeltaFoxtrot
Posts: 21
Joined: Fri Jan 13, 2017 8:46 pm

Re: Coarse ellipse and circle defintion

Post by DeltaFoxtrot »

view in slic3r
view in slic3r
Capture2.JPG (23.44 KiB) Viewed 2197 times
mesh deviation settings
mesh deviation settings
Capture.JPG (23.38 KiB) Viewed 2197 times
mesh settings
mesh settings
Capture3JPG.JPG (26.21 KiB) Viewed 2197 times
sgrogan,

I tried following your advice and changed the maximum mesh deviation, but I still have a coarse looking cowl in slic3r. I tried this a couple of times finally using 1 micro metre mesh deviation. When I create the mesh using the default option of netgen, FreeCad hangs so I tried using the standard option with surface deviation set to 0.001 mm to create the stl file (now too large to attach).

it appears to me that the features on the top of the cowl are present in the model and refining the mesh is not removing them.
not sure what I m doing wrong here, any suggestions gratefully received.

DF
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sgrogan
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Re: Coarse ellipse and circle defintion

Post by sgrogan »

DeltaFoxtrot wrote:it appears to me that the features on the top of the cowl are present in the model and refining the mesh is not removing them.
not sure what I m doing wrong here, any suggestions gratefully received.
Can you post the .FCstd file?
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DeltaFoxtrot
Posts: 21
Joined: Fri Jan 13, 2017 8:46 pm

Re: Coarse ellipse and circle defintion

Post by DeltaFoxtrot »

When I try I get a message saying the file is too large
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sgrogan
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Re: Coarse ellipse and circle defintion

Post by sgrogan »

switch to the Part WB then, EDIT>Preferences PartDesign panel Shape view tab. Set Maximum deviation to a value to 0.5% or higher, then save the .FCstd file?
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DeltaFoxtrot
Posts: 21
Joined: Fri Jan 13, 2017 8:46 pm

Re: Coarse ellipse and circle defintion

Post by DeltaFoxtrot »

Thanks! I will give that a go tomorrow.
DeltaFoxtrot
Posts: 21
Joined: Fri Jan 13, 2017 8:46 pm

Re: Coarse ellipse and circle defintion

Post by DeltaFoxtrot »

I have tried. I raised it in steps up to 10% but the file is apparently still too large (1.7 Mb).
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DeepSOIC
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Re: Coarse ellipse and circle defintion

Post by DeepSOIC »

DeltaFoxtrot wrote:I have tried. I raised it in steps up to 10% but the file is apparently still too large (1.7 Mb).
Then do this: select the final shape, and export it in ".brep" format. If the resulting brep file is still too big, zip it. If still to big, use file sharing service like dropbox or google drive, and post a link.

---
I haven't really investigated, but from my experience the setting in mesh export doesn't work. I have set it to my preference some day, 30um. Then I noticed that the exported mesh for another 3d print looked too coarse, and went back to using my old macro. The macro adjusts Deviation property of selected object to give 30um accuracy, and forces a re-meshing by hiding-showing the object (was necessary before, now in 0.17 mesh is updated immediately).
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