Extrude shape to 3D produces strange geometry
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Extrude shape to 3D produces strange geometry
Hello,
I'm just making my first steps with FreeCAD. My current playground is a wood construction that I want to build. It'll be a separator wall that I can stand in my room behind me to serve as a webcam background and that'll be filled with rock wool to improve acoustics.
So I started by creating two sketches, one for the back wall and one for the border. Both shall be layered on top of each other. The back wall is a simple rectangle, extruded to 3 mm thickness. I guess that worked well. But the next layer, a frame of four wood bars, produced strange results. I can't even describe that rendering error. I've attached the source file and a screenshot of it.
I'm working in the Part workbench. The sketches should be fixed and complete. The sketch "Rahmen" (frame) was made from 4 rectangles.
What have I done wrong?
OS: Windows 10 Version 2009
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.24291 (Git)
Build type: Release
Branch: releases/FreeCAD-0-19
Hash: 7b5e18a0759de778b74d3a5c17eba9cb815035ac
Python version: 3.8.6+
Qt version: 5.15.2
Coin version: 4.0.1
OCC version: 7.5.0
Locale: German/Germany (de_DE)
I'm just making my first steps with FreeCAD. My current playground is a wood construction that I want to build. It'll be a separator wall that I can stand in my room behind me to serve as a webcam background and that'll be filled with rock wool to improve acoustics.
So I started by creating two sketches, one for the back wall and one for the border. Both shall be layered on top of each other. The back wall is a simple rectangle, extruded to 3 mm thickness. I guess that worked well. But the next layer, a frame of four wood bars, produced strange results. I can't even describe that rendering error. I've attached the source file and a screenshot of it.
I'm working in the Part workbench. The sketches should be fixed and complete. The sketch "Rahmen" (frame) was made from 4 rectangles.
What have I done wrong?
OS: Windows 10 Version 2009
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.24291 (Git)
Build type: Release
Branch: releases/FreeCAD-0-19
Hash: 7b5e18a0759de778b74d3a5c17eba9cb815035ac
Python version: 3.8.6+
Qt version: 5.15.2
Coin version: 4.0.1
OCC version: 7.5.0
Locale: German/Germany (de_DE)
- Attachments
-
- Trennwand.FCStd
- (10.03 KiB) Downloaded 17 times
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- freecad-screenshot.png (147.1 KiB) Viewed 699 times
- papyblaise
- Veteran
- Posts: 7876
- Joined: Thu Jun 13, 2019 4:28 pm
- Location: France
Re: Extrude shape to 3D produces strange geometry
we've said it a hell of a lot of times , [edited out by mod]
NO T-PROFILE
do for example the top and the bottom, then the left and the right
Edit by mod (PrzemoF): please keep this forum professional and nice. Insulting other users will not be tolerated. If you're not sure if you're crossing the line - do not post!
NO T-PROFILE
do for example the top and the bottom, then the left and the right
Edit by mod (PrzemoF): please keep this forum professional and nice. Insulting other users will not be tolerated. If you're not sure if you're crossing the line - do not post!
- Attachments
-
- cloison.FCStd
- (13.05 KiB) Downloaded 9 times
-
- cloison.PNG (18.15 KiB) Viewed 695 times
- Shalmeneser
- Veteran
- Posts: 9475
- Joined: Wed Dec 23, 2020 12:04 am
- Location: Fr
Re: Extrude shape to 3D produces strange geometry
No 3-lines vertex (T-junction) ! The border line of a surface need to be just a line
- Shalmeneser
- Veteran
- Posts: 9475
- Joined: Wed Dec 23, 2020 12:04 am
- Location: Fr
Re: Extrude shape to 3D produces strange geometry
2 versions : Part or PartDesign wb.
- Attachments
-
- Trennwand _Shalm.FCStd
- (28.07 KiB) Downloaded 9 times
Re: Extrude shape to 3D produces strange geometry
Hi fellow wood worker
MacOS Big Sur / Win 10
Designer | Faculty
Wayne State University
Interior - Industrial Design
Designer | Faculty
Wayne State University
Interior - Industrial Design
Re: Extrude shape to 3D produces strange geometry
This topic has already been fully explained in terms of FreeCAD. However, there is a difference in the experiences of a woodworker and a metalworker. (I do both.)
If I gave the attached sketch to a metal worker the response would be "What do I do with this?
A woodworker might respond "How tall should the strips be?"
Gene
If I gave the attached sketch to a metal worker the response would be "What do I do with this?
A woodworker might respond "How tall should the strips be?"
Gene
Re: Extrude shape to 3D produces strange geometry
@papyblaise that's inappropriate.
Alone you go faster. Together we go farther
Please mark thread [Solved]
Want to contribute back to FC? Checkout:
'good first issues' | Open TODOs and FIXMEs | How to Help FreeCAD | How to report Bugs
Please mark thread [Solved]
Want to contribute back to FC? Checkout:
'good first issues' | Open TODOs and FIXMEs | How to Help FreeCAD | How to report Bugs
Re: Extrude shape to 3D produces strange geometry
ygoe
FreeCAD unlike other CAD apps cannot extrude from a sketch profile or sketch element selection.
it only fully extrudes everything in the sketch
If you use the RealThunder build you can make a master sketch and then from it export children
and from those extrude the parts needed.
Look here
https://www.youtube.com/watch?v=8JdwrVEKvIU&t=76s
also good
https://www.youtube.com/watch?v=jfNBfdIpzDQ&t=1s
FreeCAD unlike other CAD apps cannot extrude from a sketch profile or sketch element selection.
it only fully extrudes everything in the sketch
If you use the RealThunder build you can make a master sketch and then from it export children
and from those extrude the parts needed.
Look here
https://www.youtube.com/watch?v=8JdwrVEKvIU&t=76s
also good
https://www.youtube.com/watch?v=jfNBfdIpzDQ&t=1s
MacOS Big Sur / Win 10
Designer | Faculty
Wayne State University
Interior - Industrial Design
Designer | Faculty
Wayne State University
Interior - Industrial Design
Re: Extrude shape to 3D produces strange geometry
Oh dear, first of all thank you for the numerous replies. I'm sorry if this has been asked a thousand times before. Maybe the application isn't sufficiently clear in this regard then. (Just a guess though. I'm not feeling comfortable with the app yet, it doesn't seem to be novice-friendly.) But this all sounds complicated. I'm not really a mechanical guy, but I guess I can imagine composed objects pretty well and now just trying to find my way into CAD. I'd like to use it later for creating 3D print designs of small cases and other parts. Now I tried to use it for some wood project. Until now I simply used pen and paper for things like that.
I don't know where I made a T profile here. Maybe that means something else than I think the term means. Google for "T profile" and those images resemble exactly my interpretation of the term. At least it wasn't my intention to build that.
I understood that a sketch doesn't know what parts are meant to be filled, even though I created the object outlines in a way that should be obvious. It might be because FreeCAD doesn't remember how lines were added to a sketch. In the end there are just lines, no more rectangles. And then it wasn't smart enough to recognise that it doesn't know what it's doing and just renders garbage. This would mean that a sketch isn't all that useful, at least for designs like this.
I opened one of the provided files here but didn't understand how it was created, so unfortunately I couldn't make much use of it other than see that my intended design is actually possible (which I assumed).
The first YouTube video seemed to do something else (at least I don't see similarities here). The second about the Japanese toolbox gave me the impression that a sektch isn't a good solution here. I'll try to restart from scratch by creating 3D parts directly and positioning them in space. From what I've seen about the part manipulation tools, this should be sufficient for the project. The tutorial videos I watched first suggested that it's a good practice to use a sketch and then extrude things in the Part workbench. Now I believe this isn't always true.
I don't know where I made a T profile here. Maybe that means something else than I think the term means. Google for "T profile" and those images resemble exactly my interpretation of the term. At least it wasn't my intention to build that.
I understood that a sketch doesn't know what parts are meant to be filled, even though I created the object outlines in a way that should be obvious. It might be because FreeCAD doesn't remember how lines were added to a sketch. In the end there are just lines, no more rectangles. And then it wasn't smart enough to recognise that it doesn't know what it's doing and just renders garbage. This would mean that a sketch isn't all that useful, at least for designs like this.
I opened one of the provided files here but didn't understand how it was created, so unfortunately I couldn't make much use of it other than see that my intended design is actually possible (which I assumed).
The first YouTube video seemed to do something else (at least I don't see similarities here). The second about the Japanese toolbox gave me the impression that a sektch isn't a good solution here. I'll try to restart from scratch by creating 3D parts directly and positioning them in space. From what I've seen about the part manipulation tools, this should be sufficient for the project. The tutorial videos I watched first suggested that it's a good practice to use a sketch and then extrude things in the Part workbench. Now I believe this isn't always true.
Re: Extrude shape to 3D produces strange geometry
Look at the sketch I showed a few posts back. There are several Tees, very similar to your sketch. Three line "segments" meet at a single point.
The problem is that FreeCAD has no idea what it should do when three lines intersect at a point. If you are trying to "pad" the sketch into a solid should FreeCAD extrude both sides of the Tee line equally? Should only one side be extruded? Which one?
Some sketches are more complicated, of course, so the problem becomes worse and worse. That is why FreeCAD has strict rules on how sketches are created if those sketches are to be used for pads and pockets. (There are other uses for sketches as well, but that is beyond this topic.)
As a woodworker you will instantly know what to do. However, FreeCAD is used for many purposes, and that Tee structure is ambiguous, even to humans.
You are not the first and unfortunately will not be the last to hit this snag.
Hang in there!
Gene