Beginner problem with Part Design

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purehunter
Posts: 59
Joined: Fri May 24, 2019 5:45 am

Beginner problem with Part Design

Post by purehunter »

Hi,

I started my first "real" project for a 3d object and did not choose the way to draw a 2D sketch first and extrude it, but directly went into the part design with the combination of the simple 3d forms. After a few steps I encounter always the same problem and I'm not sure, if it is a FC error or it is my fault.
I started with a wedge, placed it on the xy plane and entered all data to define it. Next I placed 3 identical cylinders with the same thickness as the wedge around, about 2/3 of the cylinders outside of the wedge, looking like mickey-mouse-ears. Then combined all objects into one. In the next step the error occurred: I selected the vertical line (part thickness) where one "ear" touches the wedge and added a fillet. This works for the 2 fillets of one ear, but when doing the same with the 3rd fillet the part looked destroyed with some "rays" into the room.
Now I'm asking myself, is this a program error, or is my approach "wrong"?

Code: Select all

OS: Windows 10 Version 2009
Word size of FreeCAD: 64-bit
Version: 0.20.1.29410 (Git)
Build type: Release
Branch: releases/FreeCAD-0-20
Python 3.8.10, Qt 5.15.2, Coin 4.0.1, Vtk 8.2.0, OCC 7.6.3
Locale: German/Germany (de_DE)
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microelly2
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Re: Beginner problem with Part Design

Post by microelly2 »

welcome to the forum

IMPORTANT: Please click here and read this first, before asking for help
https://forum.freecadweb.org/viewtopic.php?f=3&t=2264
chrisb
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Re: Beginner problem with Part Design

Post by chrisb »

Hi purehunter, welcome to the forum.
You most probably are facing a limitation of the fillets - I wouldn't call it a bug. It sounds as if you may have a very sharp angle where the ears touch the center, and those can be a problem for filleting. Please attach your file to the post, so we can have a look.
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purehunter
Posts: 59
Joined: Fri May 24, 2019 5:45 am

Re: Beginner problem with Part Design

Post by purehunter »

Hi chrisb,
I'm using FC 0.18
here I have the drawing.
Next steps were adding fillets with 10mm to the sharp corners between the ears and the wedge.
Thanks for having a look into.
Lufteinlass_real_02_base.FCStd
(23.36 KiB) Downloaded 33 times

Code: Select all

OS: Windows 10 Version 2009
Word size of FreeCAD: 64-bit
Version: 0.20.1.29410 (Git)
Build type: Release
Branch: releases/FreeCAD-0-20
Python 3.8.10, Qt 5.15.2, Coin 4.0.1, Vtk 8.2.0, OCC 7.6.3
Locale: German/Germany (de_DE)
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Roy_043
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Re: Beginner problem with Part Design

Post by Roy_043 »

The problem is related to the fact that a cylindrical face has a seam. Fillets that consume this seam are not possible. If you change the Angle of FahneLu to -90° and that of FahneLU001 to 90° you should be able to apply the required fillets.
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meme2704
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Re: Beginner problem with Part Design

Post by meme2704 »

Hi
I redid your picture described, with a cylinder smaller than the triangle, an equal, and a bigger one
if I radius the short one, the connection with the face is not pretty, and can only be 1mm, with the one that is equal, and provided you select all sides one by one we can not go beyond 0.5mm, after there is overlap in the blue circled part, for the big, no problem provided you do not go beyond the radius of the cylinder (minus 0.001mm) or the available height above the triangle
So there are limits in the realization of the rays, or the chamfers
Attachments
mikey1.PNG
mikey1.PNG (44.35 KiB) Viewed 973 times
mikey2.PNG
mikey2.PNG (25.3 KiB) Viewed 973 times
mikey.FCStd
(305.26 KiB) Downloaded 17 times
chrisb
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Re: Beginner problem with Part Design

Post by chrisb »

Roy has already described the cause of the problem and given a solution. In general a fillet cannot completly consume an adjacent face, which would happen here. The image shows a 4.5mm fillet, a larger radius would make it fail:
Bildschirmfoto 2019-05-24 um 19.29.03.png
Bildschirmfoto 2019-05-24 um 19.29.03.png (25.96 KiB) Viewed 951 times
If fillets fail it is good practice to retry with a very small radius which you can increase if it succedes.
A Sketcher Lecture with in-depth information is available in English, auf Deutsch, en français, en español.
HBC0
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Re: Beginner problem with Part Design

Post by HBC0 »

Hi

Another way to apply a fillet to this example is to change the refine value of the last fusion (Fusion002) from false to true. ;)


fillet_ 0.png
fillet_ 0.png (54.14 KiB) Viewed 938 times
purehunter
Posts: 59
Joined: Fri May 24, 2019 5:45 am

Re: Beginner problem with Part Design

Post by purehunter »

Hi guys,
thanks a lot for your great help and suggestions. I will play around a soon as I have time again. Don't wonder that I will not answer in the next days, as I'm not at home...
I think it will take a little to "understand" these hidden "features".

cheers Purehunter

Code: Select all

OS: Windows 10 Version 2009
Word size of FreeCAD: 64-bit
Version: 0.20.1.29410 (Git)
Build type: Release
Branch: releases/FreeCAD-0-20
Python 3.8.10, Qt 5.15.2, Coin 4.0.1, Vtk 8.2.0, OCC 7.6.3
Locale: German/Germany (de_DE)
chrisb
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Joined: Tue Mar 17, 2015 9:14 am

Re: Beginner problem with Part Design

Post by chrisb »

As others may search for similar issues: Please rename the subject of the first post to something more descriptive such as "Beginner problem with Part Design fillet".
A Sketcher Lecture with in-depth information is available in English, auf Deutsch, en français, en español.
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