Mystery displayed offset location/orienation of tube resulting from sweep

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otoien
Posts: 87
Joined: Sun Aug 13, 2017 2:38 am

Mystery displayed offset location/orienation of tube resulting from sweep

Post by otoien »

In the attached file, the curved tube should have been located with the short end facing the hollow cylinder, however it does not; on my system running the latest 0.19 development version both location and orientation is displayed incorrectly.
Try the following:
1. Mark the curved tube, right click and recompute object. Location does not change.

2. Check out the two sweep that the tube is cut from and notice no offset or orientation change.

3. Mark both the tube and the hollow cylinder and export as step file. Open the step file. Now the tube is at the correct location in the new file. So FreeCAD knew all along where the tube should be.

4. It is a bit suspicious that placement has such fractional numbers with angle at 180.221 and two of the axis also have odd numbers. I usually do transforms with rotation in 15° increments. However several other tubes in the rather large project the tube is copied from have similar orientation placement and displays correctly. This tube and some others that were affected also displayed correctly over a number of file versions but at some point (possibly with some later 0.19 FreeCad updates) they were suddenly at the the wrong location after reloading the file and would not correct itself.

5. So to correct it, under placement set angle at 180° and x component to 0.707 and the z component to -0.707. It is still not displaying correctly, but after right clicking in the model tree and recompute object, the tube is at correct location facing the hollow cylinder as in the loaded step file. (I have currently been able to fix all the offending tubes in my project this way).

I wonder what is going on here and if there is a way to avoid it in the future?
(I never know when a new offset of a tube may show up...)

Incorrect-location-orientation-Cut-sweep-001.FCStd
(15.83 KiB) Downloaded 35 times

Code: Select all

OS: Windows 7 SP 1 (6.1)
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.19181 (Git)
Build type: Release
Branch: master
Hash: 2504247d65271b937dd5f033a0efff9c0d7bf375
Python version: 3.6.8
Qt version: 5.12.1
Coin version: 4.0.0a
OCC version: 7.3.0
Locale: English/United States (en_US)
otoien
Posts: 87
Joined: Sun Aug 13, 2017 2:38 am

Re: Mystery displayed offset location/orienation of tube resulting from sweep

Post by otoien »

A little bump since this scrolled off the screen without any responses. Can anyone reproduce this with the supplied file?
Below are screen shots of the incorrect location, and the correct location after step export and reopening the step file.

Curved-tube-001.jpg
Curved-tube-001.jpg (4.37 KiB) Viewed 444 times
Curved-tube-002.jpg
Curved-tube-002.jpg (4.82 KiB) Viewed 444 times
User avatar
papyblaise
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Location: France

Re: Mystery displayed offset location/orienation of tube resulting from sweep

Post by papyblaise »

it more easy to do the draw in the right place immediatly because it's very paintfull to change all parameter at the same time
otoien
Posts: 87
Joined: Sun Aug 13, 2017 2:38 am

Re: Mystery displayed offset location/orienation of tube resulting from sweep

Post by otoien »

papyblaise wrote: Fri Jan 10, 2020 4:09 pm it more easy to do the draw in the right place immediatly because it's very paintfull to change all parameter at the same time
Thanks for the response. In this case the curved tube was copied to appear at multiple locations, so I would not want to repeat the sketch for each location. I only needed to change the vertical z-offset under position in the different copies, so I do not understand what is painful (except the position error that sometimes appears). And if the part is relocated and reoriented (some of those tubes where to slope downwards), it is very painful if there is an offset to the original location. But you are right in that I could have oriented the sketches correctly in the first place to avoid the initial need to change orientation when using the transform. Interestingly only one of several of those copied/relocated tubes ended up at an incorrect location.

Do you see the same as in my description and images above when you open the file?
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