Part Design Subtractive Helix fails with construction line as reference

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drmacro
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Part Design Subtractive Helix fails with construction line as reference

Post by drmacro »

If an attempt to make a thread with Part Design Subtractive helix using a construction line as reference it fails.

But works if the base axis is selected.
Snip macro screenshot-aa45a7.png
Snip macro screenshot-aa45a7.png (111.76 KiB) Viewed 622 times
In attached file select Sketch001
Select Subtractive helix
Select Reference as Horizontal sketch axis
OK

In attached file select Sketch001
Select Subtractive helix
Select Reference as Construction line 1
Fail, resolve the cut, but completes.

If the sketch is not at global origin and the construction is used, the the recompute fails.

I am using source from today of 0.20.

The user who found this is also using 0.20, but the release version.

He and I are using different versions of OCC. He is using what is required by 0.20 release. I'm using 7.7.
Attachments
Helix_Constructionline_fail.FCStd
(15.22 KiB) Downloaded 13 times
Star Trek II: The Wrath of Khan: Spock: "...His pattern indicates two-dimensional thinking."
chrisb
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Joined: Tue Mar 17, 2015 9:14 am

Re: Part Design Subtractive Helix fails with construction line as reference

Post by chrisb »

Works here with the pitch left at default 4.45mm and direction reversed.

Code: Select all

OS: macOS 10.16
Word size of FreeCAD: 64-bit
Version: 0.20.29177 (Git)
Build type: Release
Branch: (HEAD detached at 0.20)
Hash: 68e337670e227889217652ddac593c93b5e8dc94
Python 3.9.13, Qt 5.12.9, Coin 4.0.0, Vtk 9.1.0, OCC 7.5.3
Locale: C/Default (C)
Installed mods: 
  * FC_SU
  * DynamicData 2.46.0
  * FeedsAndSpeeds 0.4.0
  * fcgear
  * Manipulator 1.4.3
  * fasteners
  * sheetmetal
  * ExplodedAssembly
  * Curves 0.3.0
  * Assembly4 0.11.12
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drmacro
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Posts: 8866
Joined: Sun Mar 02, 2014 4:35 pm

Re: Part Design Subtractive Helix fails with construction line as reference

Post by drmacro »

I've tested on three slightly different git versions and the guy who discovered, with the results I described.

When it succeeds, is the thread actually cut? I was seeing the lines on the surface but no thread depth. Similar to coplaner issues. But, no errors.

And by switching to horizontal sketch axis the user fixed it as well.
Star Trek II: The Wrath of Khan: Spock: "...His pattern indicates two-dimensional thinking."
chrisb
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Re: Part Design Subtractive Helix fails with construction line as reference

Post by chrisb »

Very strange: I tried again and it failed here too. The secret lies in the sketch of the section: If I add dimensions to the sketch ...
SnipScreenshot-e326f0.png
SnipScreenshot-e326f0.png (14.65 KiB) Viewed 532 times
... It works, as you can see in the section view. Another good reason to fully constrain sketches.
A Sketcher Lecture with in-depth information is available in English, auf Deutsch, en français, en español.
drmacro
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Re: Part Design Subtractive Helix fails with construction line as reference

Post by drmacro »

This is a peared down version of the original file with the problem.

In his sketch it was fully constrained.

I'll be digging at it more in the morning.
Star Trek II: The Wrath of Khan: Spock: "...His pattern indicates two-dimensional thinking."
chrisb
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Re: Part Design Subtractive Helix fails with construction line as reference

Post by chrisb »

For the sake of completeness: I didn't change any of the measures. The horizontal distance didn't fix anything, only the vertical.
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drmacro
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Re: Part Design Subtractive Helix fails with construction line as reference

Post by drmacro »

Definitely something going on.

Here is can be seen in wireframe. In the top image using the sketch horizontal, in the bottom using construction line.
Helix_snip_merge.png
Helix_snip_merge.png (243.66 KiB) Viewed 431 times
But, all is good if the sketch is rotated away from the seam line of the hole. (Using either construction line or horz sketch axis)
(As we know seam lines are evil. ;) ) But, this seems inconsistent. I suppose it could be that the construction line may be effected by computational tolerances differently...
Attachments
Helix_test.FCStd
(16.29 KiB) Downloaded 7 times
Star Trek II: The Wrath of Khan: Spock: "...His pattern indicates two-dimensional thinking."
NHSA_Rainer
Posts: 104
Joined: Mon Aug 30, 2021 3:37 pm

Re: Part Design Subtractive Helix fails with construction line as reference

Post by NHSA_Rainer »

Hi,

Interesting problem. I do not understand why does he use a construction line exactly on the X,Y,Z origin point.

I made a test with a body outside of the origin point and used a construction line as revolving center for a subtractive helix and it worked trouble free.

Maybe there is a conflict between the origin and the construction line being on the origin ¿?
drmacro
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Re: Part Design Subtractive Helix fails with construction line as reference

Post by drmacro »

NHSA_Rainer wrote: Mon Jun 27, 2022 2:04 pm Hi,

Interesting problem. I do not understand why does he use a construction line exactly on the X,Y,Z origin point.

I made a test with a body outside of the origin point and used a construction line as revolving center for a subtractive helix and it worked trouble free.

Maybe there is a conflict between the origin and the construction line being on the origin ¿?
The construction line isn't necessary in this case. I suspect the user just didn't realize it.
Star Trek II: The Wrath of Khan: Spock: "...His pattern indicates two-dimensional thinking."
NHSA_Rainer
Posts: 104
Joined: Mon Aug 30, 2021 3:37 pm

Re: Part Design Subtractive Helix fails with construction line as reference

Post by NHSA_Rainer »

drmacro wrote: Mon Jun 27, 2022 3:07 pm
NHSA_Rainer wrote: Mon Jun 27, 2022 2:04 pm Hi,

Interesting problem. I do not understand why does he use a construction line exactly on the X,Y,Z origin point.

I made a test with a body outside of the origin point and used a construction line as revolving center for a subtractive helix and it worked trouble free.

Maybe there is a conflict between the origin and the construction line being on the origin ¿?
The construction line isn't necessary in this case. I suspect the user just didn't realize it.
Right. I was all the time asking myself why did he add a construction line on top of the native X,Y,Z origin ¿? That is redundant.

I admit being a Newbie myself too, that sometimes we tend to overthink things
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