Sketch on body face flipping problem

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yakirsh4
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Joined: Sat Jul 31, 2021 11:29 am

Sketch on body face flipping problem

Post by yakirsh4 »

Hello,

I am new to FREECAD and I have a peculiar problem when attempting to create a sketch on a body face.
I am attempting to create a sketch (to create a "hole" in the body) on this face:
Image
When I click the face and then click "Create a new sketch" the created sketch is "flipped":
Image
I can go along with this flipping and create the sketch I want (and it's working fine) but this is pretty annoying working like this.

I would like to know if I am doing something wrong here or if there is a way to flip the sketch again.
Just to clarify, I don't want to flip the display with the cube in the right top corner but to flip the entire sketch.
The difference is that with the "flipped" configuration the horizontal and vertical lines are also flipped.

Thank you.
drmacro
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Re: Sketch on body face flipping problem

Post by drmacro »

Did you try the "Reverse" setting when creating the new sketch?

And, be aware attaching sketches to generated geometry is not recommended:

Topological naming problem
Advice for creating stable models
Basic Attachment Tutorial
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chrisb
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Re: Sketch on body face flipping problem

Post by chrisb »

You didn't do anything wrong, it's a matter where FreeCAD places the origin. Better control of the attachment as drmacro has pointed out can help. If vertical/horizontal is flipped, you can also turn the sketch by ±90° in the AttachmentOffset properties.
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Shalmeneser
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Re: Sketch on body face flipping problem

Post by Shalmeneser »

Try not to sketch on face but on regular plane (eg XY). Less flipping (and TNP) will occur.
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M4x
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Re: Sketch on body face flipping problem

Post by M4x »

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Cekuhnen
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Re: Sketch on body face flipping problem

Post by Cekuhnen »

The problem of lines horizontaly or vertically inverting i noticed a lot in FreeCAD also with normal sketches that were even dimensioned
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yakirsh4
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Re: Sketch on body face flipping problem

Post by yakirsh4 »

Wow, Thank you so much.
I had so much trouble with sketches moving around in my document that I ended up starting a new one, it's so good to know that this can be avoided.
I will try to use the suggestions here and in the "Advice for creating stable models" as much as possible.

I have 2 follow up questions:
1. for Dealing with the TNP problem in my current project (which I already working on), can I use the "reorient sketch" feature to change the sketches base to one of the plains to avoid future TNP problems or should I just open a new document and create everything from scratch?
2.In the "Advice for creating stable models" there is a reference to a "master sketch", there is more information on the subject anywhere?

Thank you.
drmacro
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Re: Sketch on body face flipping problem

Post by drmacro »

Cekuhnen wrote: Sat Jul 31, 2021 3:03 pm ... sketches that were even dimensioned
A technical point. Sketches are not dimensioned. They a constrained. It just happens that the vehicle for describing dimensional constraints looks like a traditional drafting dimension.

Constraints meet no particular dimensioning standard (ANSI, ISO, etc.) and, in general, are intended to constrain the shape of sketch geometry. They don't, for example, indicate anything about how the result of the sketched shape is to manufactured (i.e. tolerance, etc.).

This may be a minor point to some, but, using terms loosely can lead to misunderstanding and confusion. Especially when a forum is read by a large number of non-native English speaking folks...not to mention when people use things like Google translate.
(Agreed, this is not as bad as the blind men describing an elephant... :mrgreen: )
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Cekuhnen
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Re: Sketch on body face flipping problem

Post by Cekuhnen »

Ok point taken.

The sketches were fully constraint yet still elements mirror flipped on their own position which I found unusual
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M4x
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Re: Sketch on body face flipping problem

Post by M4x »

Can you share some examples? It never happened on me and I've seen it in this forum only on very rare corner cases. Usually in combination with an assembly which had some freedome to move somehow.
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