Problem visualizing curve of thin parabolic reflector

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PaulUK
Posts: 20
Joined: Fri Jan 19, 2018 8:43 am

Problem visualizing curve of thin parabolic reflector

Post by PaulUK »

Dear All,

I constructed a reflector that is 2.5mm thick and the edge is curved. However, over part of the reflector edge there is a strange effect. Please can someone tell me what it is or if there's a way to prevent it, or if its just some strange of bug?

My system is:
OS: Windows 10 Version 2009
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.24276 (Git)
Build type: Release
Branch: releases/FreeCAD-0-19
Hash: a88db11e0a908f6e38f92bfc5187b13ebe470438
Python version: 3.8.6+
Qt version: 5.15.1
Coin version: 4.0.1
OCC version: 7.5.0
Locale: English/United Kingdom (en_GB)

I hope that I have provided enough information to help. Note that this happens on the same version of FreeCAD on a much older computer with Windows 7. Thank you.
Image 1
Image 1
reflector_1.PNG (69.08 KiB) Viewed 1125 times
Image 2
Image 2
reflector_2.PNG (91.77 KiB) Viewed 1125 times
Image 3
Image 3
reflector_3.PNG (164.63 KiB) Viewed 1125 times
Attachments
Reflector_Template.FCStd
File for reflector example
(18.05 KiB) Downloaded 27 times
Bance
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Posts: 4190
Joined: Wed Feb 11, 2015 3:00 pm
Location: London

Re: Problem visualizing curve of thin parabolic reflector

Post by Bance »

PaulUK wrote: Thu May 06, 2021 11:16 am that is 2.5mm thick
It is not, it is of variable thickness.

Were you aiming for constant thickness?
PaulUK
Posts: 20
Joined: Fri Jan 19, 2018 8:43 am

Re: Problem visualizing curve of thin parabolic reflector

Post by PaulUK »

Bance wrote: Thu May 06, 2021 11:42 am
PaulUK wrote: Thu May 06, 2021 11:16 am that is 2.5mm thick
It is not, it is of variable thickness.

Were you aiming for constant thickness?
Initially yes, but with moving things around I'm not surprised that it is not but had not noticed. I would correct this later. This model was intended to try rounding the edge and not final. That is when I noticed this strange visual effect.

I will be wanting constant thickness. Thank you.
Bance
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Posts: 4190
Joined: Wed Feb 11, 2015 3:00 pm
Location: London

Re: Problem visualizing curve of thin parabolic reflector

Post by Bance »

I have changed some of the constraints on the sketch, most particularly the semi-circle that forms the edge should be tangent to the curves that form the dish. I have added a construction line to maintain constant thickness.
reflector.png
reflector.png (35.06 KiB) Viewed 1084 times
Attachments
Reflector_Template-1Bance.FCStd
(12.33 KiB) Downloaded 41 times
PaulUK
Posts: 20
Joined: Fri Jan 19, 2018 8:43 am

Re: Problem visualizing curve of thin parabolic reflector

Post by PaulUK »

Bance wrote: Thu May 06, 2021 12:40 pm I have changed some of the constraints on the sketch, most particularly the semi-circle that forms the edge should be tangent to the curves that form the dish. I have added a construction line to maintain constant thickness.

reflector.png
Ah I see. Thank you very much. This is what I was hoping to do. I shall check the sketch to see how it should be done. Much appreciated.
zetka
Posts: 22
Joined: Thu Oct 29, 2020 10:24 pm

Re: Problem visualizing curve of thin parabolic reflector

Post by zetka »

I am not sure what I am doing wrong, but when I try to rotate the whole part (dish), I am getting a bunch of errors:
....
13:55:19 Traceback (most recent call last):
File "D:\Program Files\FreeCAD 0.20\Mod\Part\CompoundTools\CompoundFilter.py", line 100, in execute
shps = obj.Base.Shape.childShapes()
<class 'AttributeError'>: 'App.Part' object has no attribute 'Shape'
13:55:19 Recompute failed! Please check report view.

....
Does somebody know, what that means? I am using verson 19 and 20 it appears in both.
Bance
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Posts: 4190
Joined: Wed Feb 11, 2015 3:00 pm
Location: London

Re: Problem visualizing curve of thin parabolic reflector

Post by Bance »

I have no problem rotating the dish, and Part Check Geometry has no issues with the solid, there are no compounds in the model.
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onekk
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Re: Problem visualizing curve of thin parabolic reflector

Post by onekk »

zetka wrote: Sun Oct 02, 2022 11:58 am ...
Please put you complete version info as explained in IMPORTANT: post at the top of the forum page.

There is more than a simple 0.19 or 0.20.to know to advise you for further checks, like OS and some third party libraries versions.

Regards

Carlo D.
Last edited by onekk on Mon Oct 31, 2022 8:05 am, edited 2 times in total.
GitHub page: https://github.com/onekk/freecad-doc.
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zetka
Posts: 22
Joined: Thu Oct 29, 2020 10:24 pm

Re: Problem visualizing curve of thin parabolic reflector

Post by zetka »

Hello, I am adding the problematic file. In my case it concerns the test of generating offset dish from revolving of a sketch and a intersection with cylinder. I am all time getting those errors:
"16:39:52 Traceback (most recent call last):
File "C:\CENOS\third-party\FreeCAD_0.19.24276-Win-Conda_vc14.x-x86_64\Mod\Part\CompoundTools\CompoundFilter.py", line 109, in execute
shps = obj.Base.Shape.childShapes()
<class 'AttributeError'>: 'NoneType' object has no attribute 'Shape'"

The Freecad is in older version 19.24xxx, required with the EM simulation program CENOS RF, which has some addonds to that for export and meshing.
Can somebody help me with that, where is the source of error and how to remove it?
BR,
Zetka.
Attachments
offset dish error.FCStd
(82.32 KiB) Downloaded 11 times
zetka
Posts: 22
Joined: Thu Oct 29, 2020 10:24 pm

Re: Problem visualizing curve of thin parabolic reflector

Post by zetka »

Maybe a small addition- I tried the problematic file with the Freecad 20, and the error appears too, when I try to change any from the parameters in the spreadsheet. Although the error appears, the model is correctly recalculated, based upon the parameters.
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