I get holes in a solid object after sweeping

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71GA
Posts: 49
Joined: Mon Mar 27, 2017 10:03 pm

I get holes in a solid object after sweeping

Post by 71GA »

I have been learning FreeCAD using online Youtube tutorials and I am currently stuck for the first time. In this tutorial https://youtu.be/tDg9tXB_7hg?t=29m45s author of the videos sweeps a triangular sketch along a helix and gets a nice screw (it starts at 29:45) while I get holes in my screw:

Image

Here is the file:
2017-03-27 -- outer threads -- v3.00.fcstd
FreeCAD - outer threads
(515.96 KiB) Downloaded 37 times
I decided to ask about this after trying this for the 3rd time and online search didn't return any results. My FreeCAD info is:

Code: Select all

OS: Linux
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.16.Unknown
Build type: Release
Python version: 2.7.13
Qt version: 4.8.7
Coin version: 3.1.3
OCC version: 6.9.1
and I am on Arch Linux:

Code: Select all

Linux ziga-laptop 4.9.9-1-ARCH #1 SMP PREEMPT Thu Feb 9 19:07:09 CET 2017 x86_64 GNU/Linux 
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DeepSOIC
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Location: used to be Saint-Petersburg, Russia

Re: I get holes in a solid object after sweeping

Post by DeepSOIC »

Hi!
Recomputing the last cut in this freecad version repairs the hole:
OS: Windows 10
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.17.10647 (Git)
Build type: Release
Branch: master
Hash: 7901cf7ad28952173ec8e2a55c39e8eb5c441e3c
Python version: 2.7.8
Qt version: 4.8.7
Coin version: 4.0.0a
OCC version: 7.0.0

You can try rotating the sweep by a few degrees. It will move the terminations off seam edge, and it may help.
chrisb
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Re: I get holes in a solid object after sweeping

Post by chrisb »

It looks like overlapping threads. it works if you change the height of the sweep's triangle from 3.1 to to 3.09.

Edit: translated to English.
Last edited by chrisb on Tue Mar 28, 2017 1:50 pm, edited 1 time in total.
A Sketcher Lecture with in-depth information is available in English, auf Deutsch, en français, en español.
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NormandC
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Re: I get holes in a solid object after sweeping

Post by NormandC »

ENGLISH PLEASE.
Montoya88
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Re: I get holes in a solid object after sweeping

Post by Montoya88 »

[quote="71GA"]sweeps a triangular sketch along a helix and gets a nice screw while I get holes in my screw: [quote]

I've done this before and it really slows the computer down when I send it drawing or drawing dimensioning.

Have you've tried fasteners? It is a third party add-on.
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71GA
Posts: 49
Joined: Mon Mar 27, 2017 10:03 pm

Re: I get holes in a solid object after sweeping

Post by 71GA »

DeepSOIC wrote:Hi!
Recomputing the last cut in this freecad version repairs the hole.

...

You can try rotating the sweep by a few degrees. It will move the terminations off seam edge, and it may help.
Hey I tried to recompute the drawing using this method: https://www.freecadweb.org/wiki/Std_Refresh but it didn't help. Rotating a sweep by some degrees? Isn't that cheating? I am not very happy about this idea...
chrisb
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Re: I get holes in a solid object after sweeping

Post by chrisb »

NormandC wrote:ENGLISH PLEASE.
I am sorry, I had searched for unread topics and didn't go down the forum tree. Since the original post was in german I didn't even take a look at the subforum and answered in german. :oops: :oops:
I will edit my post.
Last edited by chrisb on Wed Mar 29, 2017 8:29 am, edited 1 time in total.
A Sketcher Lecture with in-depth information is available in English, auf Deutsch, en français, en español.
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Willem
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Re: I get holes in a solid object after sweeping

Post by Willem »

Hi, did you add the macro Force recompute to your freecad from this page https://www.freecadweb.org/wiki/Macro_ForceRecompute.

It happens regularly that when the sketch for the rotation and the sketch for the sweep are drawn in the same plane you get an error like you did. The cause of this problem is in the OCC Cad kernel. Rotating the sketch is an easy job as you can see in the images. First click on the three tiny dots in the placement settings. Next fill in the rotation with incremental values set on.
One.png
One.png (59.63 KiB) Viewed 1916 times
Two.png
Two.png (37.65 KiB) Viewed 1916 times
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71GA
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Joined: Mon Mar 27, 2017 10:03 pm

Re: I get holes in a solid object after sweeping

Post by 71GA »

Willem wrote:Hi, did you add the macro Force recompute to your freecad from this page https://www.freecadweb.org/wiki/Macro_ForceRecompute.
I did install the macro now but if I just use it to redraw my model I still get holes in my model.
Willem wrote:Hi, did you add the macro Force recompute to your freecad from this page https://www.freecadweb.org/wiki/Macro_ForceRecompute.
It happens regularly that when the sketch for the rotation and the sketch for the sweep are drawn in the same plane you get an error like you did.
I tried all over again and I followed this advice of yours. I put sketches on separate planes, but now boolean cut doesn't even show up.
Image


Here is the file:
2017-03-27 -- outer threads -- v3.00.fcstd
another failed attempt
(442.53 KiB) Downloaded 27 times
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NormandC
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Re: I get holes in a solid object after sweeping

Post by NormandC »

DeepSOIC wrote:Recomputing the last cut in this freecad version repairs the hole:
That's odd, it doesn't work with the latest OCC.

OS: Ubuntu 16.04.2 LTS
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.17.10646 (Git)
Build type: None
Branch: (detached from 732bd85)
Hash: 809758b7395f8e591a8a196459bf5a014a864aaf
Python version: 2.7.12
Qt version: 4.8.7
Coin version: 4.0.0a
OCC version: 7.1.0
71GA wrote:Rotating a sweep by some degrees? Isn't that cheating? I am not very happy about this idea...
It's not cheating, it's working around the geometric modelling kernel (OCC)'s flaws. One of these flaws is failed Boolean operations when one of the solid sits flush to a cylinder seam edge.

Here's what I find puzzling: in 0.16.6707 with OCC 6.8.0, the sweep rotation fixes the Part Cut. It doesn't anymore in OCC 7.1.0. :?
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