Small pocket brakes whole model

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HDLA
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Small pocket brakes whole model

Post by HDLA »

Hello,
I've tried to make small pocket in one of the parts in the model,
but after the change some of the sketches in the other part fail and can't recreate them anymore.
I've tried to recompute everything in the document, but didn't help.
Another weird thing is that Check Geometry doesn't show any errors in the part :(

Can somebody help me understand what I am doing wrong?
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Shalmeneser
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Re: Small pocket brakes whole model

Post by Shalmeneser »

Problem with Sketch021 : not a single frontier : T-junction and multi-parts.
HDLA
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Re: Small pocket brakes whole model

Post by HDLA »

Sorry I don't understand.
Unfortunately freeCAD is really unstable software. :(
Any change in geometry brakes everything irreversible.
The idea shall be to make changes in the model easy but it is not like that.
I am playing for 2 hours already and I managed to fix this issue but if I try to change anything else in the first part the second one related to it brakes completely.

I don't give up for now but started looking for alternatives :(
drmacro
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Re: Small pocket brakes whole model

Post by drmacro »

HDLA wrote: Mon Dec 05, 2022 10:36 pm Sorry I don't understand.
Unfortunately freeCAD is really unstable software. :(
Any change in geometry brakes everything irreversible.
The idea shall be to make changes in the model easy but it is not like that.
I am playing for 2 hours already and I managed to fix this issue but if I try to change anything else in the first part the second one related to it brakes completely.

I don't give up for now but started looking for alternatives :(
This is called Topological Naming Problem.

I can be avoided. But, learning the techniques is a lot for some users.

You should look into the Linkstage3 branch where it mostly mitigated to a great degree.
Star Trek II: The Wrath of Khan: Spock: "...His pattern indicates two-dimensional thinking."
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Shalmeneser
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Re: Small pocket brakes whole model

Post by Shalmeneser »

HDLA wrote: Mon Dec 05, 2022 10:36 pm Unfortunately freeCAD is really unstable software. :(
Like any CAD program : TNP

* Do not refer to face : any modification will move your reference to an other face
* Refer to simpliest sketch instead
HDLA
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Re: Small pocket brakes whole model

Post by HDLA »

Thank you for the replys guys.

OK if I base all the sketches on other sketches instead of faces, what will happen with filets and chamfers since the are always based on edges?
chrisb
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Re: Small pocket brakes whole model

Post by chrisb »

HDLA wrote: Tue Dec 06, 2022 5:22 am what will happen with filets and chamfers since the are always based on edges?
They break as they did before. Make them as early as possible in the modeling process, and they break with less probability. This advice is sensible if and only if you avoid all references to generated geometry as far as possible.
A Sketcher Lecture with in-depth information is available in English, auf Deutsch, en français, en español.
HDLA
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Re: Small pocket brakes whole model

Post by HDLA »

chrisb wrote: Tue Dec 06, 2022 7:38 am
HDLA wrote: Tue Dec 06, 2022 5:22 am what will happen with filets and chamfers since the are always based on edges?
They break as they did before. Make them as early as possible in the modeling process, and they break with less probability. This advice is sensible if and only if you avoid all references to generated geometry as far as possible.
OK I read about TNP and the different ways to avoid problems with it.
I'll try to summarize it here:
1. Always create sketches based on origin planes and offset them to be coplanar to the plane which want to fuse the shape to.
2. When using external geometry tool always use sketches to reference to, never use this tool over edge or face.
3. Be sure that filets and chamfers are added as early as possible add them on sketch level if possible.

Am I correct until now?

Additional question for which I can't find enough info is:
How to get ShapeBinder working correctly?
I mean If I have a body which I want to use as a reference for another body(Cover for example), what is the best way to do model it?
I would like to keep the possibility to update size, shape and position of the first body without braking the model
chrisb
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Re: Small pocket brakes whole model

Post by chrisb »

HDLA wrote: Tue Dec 06, 2022 8:50 am 1. Always create sketches based on origin planes and offset them to be coplanar to the plane which want to fuse the shape to.
That's the most stable way. Not quite as but also rather stable is to attach sketches to other sketches. or to stable DatumGeometry.
How to get ShapeBinder working correctly?
It is again best to reference only sketches and not generated geometry.
A Sketcher Lecture with in-depth information is available in English, auf Deutsch, en français, en español.
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