over constrained design

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shorthauler
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Joined: Sun Jul 03, 2022 12:49 pm

over constrained design

Post by shorthauler »

Dear Community,
I have been working with FreeCAD for quite a while and I though I were familiar with overconstrained designs. I have attached what I am working on now, it is telling me that it is overconstrained, and I cannot even pad this sketch. I have been trying for two days - I give up and resort to the forum hoping for some help.

- shorthauler
Attachments
A320 FCU Case_Side Plate_2.FCStd
(13.58 KiB) Downloaded 20 times
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Forthman
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Re: over constrained design

Post by Forthman »

Hi,
There are several things wrong with your sketch.
- the massive use of dimensional constraints (especially those at 90°)
- intersections in the lines of the sketch

I don't know the original dimensions of your model, and you'll probably have to find other origins for the dimensions, but the Pad is doing well
always remember to place all possible geometric constraints before placing dimensional constraints ;)
A320 FCU Case_Side Plate_2 v2.FCStd
(27.18 KiB) Downloaded 7 times
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hammax
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Re: over constrained design

Post by hammax »

... that was pure Sketcher torture.
It's still like that in the reconstruction: therefore => 1st the pure rib => 2nd the cut outs.
Check the dimensions!
Attachments
A320 FCU Case_Side Plate_3.FCStd
FC.20
(14.15 KiB) Downloaded 8 times
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papyblaise
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Re: over constrained design

Post by papyblaise »

I erased all the constraints and the lines in the center and in 1/2 hour it's done
Attachments
A320.FCStd
(20.29 KiB) Downloaded 12 times
A320.JPG
A320.JPG (15.28 KiB) Viewed 770 times
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thomas-neemann
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Re: over constrained design

Post by thomas-neemann »

shorthauler wrote: Sun Jul 03, 2022 12:54 pm ...
here is the result of an "automatic" repair in a few minutes, if you wish i can link a video about it
1735.FCStd
(40.44 KiB) Downloaded 10 times
Bildschirmfoto_2022-07-03_17-37-07.png
Bildschirmfoto_2022-07-03_17-37-07.png (11.18 KiB) Viewed 732 times
Gruß Dipl.-Ing. (FH) Thomas Neemann

https://www.youtube.com/@thomasneemann5 ... ry=freecad
chrisb
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Re: over constrained design

Post by chrisb »

shorthauler wrote: Sun Jul 03, 2022 12:54 pmI have been trying for two days - I give up and resort to the forum hoping for some help.
Hi and a late welcome to the forum!
I highly appreciate that you try on your own and don't leave every minor obstacle to the forum regulars. But two days is too much and you are welcome to ask a bit sooner.
A Sketcher Lecture with in-depth information is available in English, auf Deutsch, en français, en español.
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Shalmeneser
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Re: over constrained design

Post by Shalmeneser »

:idea: (check my dimension)

* Do not do everything in the same sketch
* use Sketcher_RemoveAxesAlignment on rectangle
* use the axis (should be better to rotate everything)
Attachments
A320 FCU Case_Side Plate_SHALM.FCStd
(78.52 KiB) Downloaded 8 times
shorthauler
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Joined: Sun Jul 03, 2022 12:49 pm

Re: over constrained design

Post by shorthauler »

Thanks a lot for all your very helpful answers. I have downloaded and looked at all the files - I have learnt a lot from every one of them.

@Forthman: Am I understanding righ that you are using parallel constraints in order to avoid the 90 constraints? I was under the assumption that both are constraints. So parallel constraints are easier to digest for FreeCAD?

@Forthman: What do you mean by intersections in the lines of the sketch?

@Hammax: I understand what you mean by 1st the ribs and 2nd the cutouts. I wanted to make sure that I have a closed shape, so I started with a rectangle and split the edges. I will try to do an excercise and follow your method.

@Papyblaise: Merci beaucoup, mon ami! Unfortunately, I need the slot in the middle to insert another part.

@thomas-neeman: Danke, Thomas! I don't want to push you to make a video, but maybe you can simply give me a good search word, so I can read up on the automatic repair.

@Shalmeneser: After looking at your design, I read up on the pocket tool. Very helpful! Why do you discourage from putting everything into one sketch?

@all: This is only one part of what will be a case for a A320 FCU (home cockpit). For those who are not into aviation: The FCU is the uppermost panel of an A320, above the screens and below the windshield. There are several providers for these FCUs, but they only offer the dials and faces, but no casing. Once it is finshed and I can be sure that everything works, I will upload the final result.

Greetings to all of you, especially to those in Douce France, how blessed you are being there during this time of the year!

- shorthauler
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thomas-neemann
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Re: over constrained design

Post by thomas-neemann »

shorthauler wrote: Sun Jul 03, 2022 6:23 pm ... Danke, Thomas...
no problem, I just had to cut the recording

https://www.youtube.com/watch?v=ztaDsy5---c

phpBB [video]
Gruß Dipl.-Ing. (FH) Thomas Neemann

https://www.youtube.com/@thomasneemann5 ... ry=freecad
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Shalmeneser
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Re: over constrained design

Post by Shalmeneser »

Why do you discourage from putting everything into one sketch?
KISS : keep it stupidly simple (to be able to understand / modify it quickly)
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