Weird Sketch behaviour

[Helmi74]

Hi,

i don't know if this is a known problem already but additionally to the "sketch geometry is over constrained" problem (see other thread in this forum) i currently see some weird stuff while sketching.

First of all this only lead to dimension lines jumping to another position that i placed it after hitting the last mouse button to create it. Not nice but not that crazy that you couldn't live with it for the moment. But now i see geometry moving around when i change some dimensions of other objects.

For example i have a circle 5mm big created within a rectangle. After resizing the circle later to 4,5mm the rectangle underneath it moved away about 15mm.

Maybe hard to describe but see this video: http://screencast.com/t/EELCcGyz

This currently makes me unable to continue my design and leaves me a bit lost.

[innovatenate]

Thanks for posting!

Watching the video it looks like the 25.4 mm dimension is "flipping" datums. Is there any chance you could uplaod an F3D or share the design with me? Nathan (Dot) Chandler (At) Autodesk (Dot) Com. 

One thing that may help is to start with a "fixed" item and then build the reset of the sketch from a fixed piece of sketch geometry. For example, if you add a Fix constraint to the reference lines in the center of the rectangle, does this help with the dimension flipping?

Thanks,

[Helmi74]

Hi Nathan,

thanks for your reply. I've used invite -> share on the file to invite you which seems to have invited you to my complete project. Don't worry about the mess - this is my "general project" for everything that doesn't fit in anywhere else. The latest Design ("BFB0512...") is the one we were talking about.

[innovatenate]

Frank,

I was unable to reproduce the issue with the file. Instead, I made a quick video that I hope will demonstrate some strategies that may help prevent this type of issue from occurring in Fusion 360.

The strategy I used to happened organically as I was recording and may be a bit odd, but it gets the job done. There are many ways to accomplish outside of this one method.  I hope the video illustrates how to better define sketch figure's degrees of freedom by using sketch projection, constraints, and dimensions to prevent unwanted or unexpected movement in the Fusion 360 sketch environment. 

Video:

https://screencast.autodesk.com/main/details/c3a26eaa-4e93-4277-9f4d-d4cee9cd6538

I hope that this is helpful and I welcome any questions or feedback you may have.

Thanks!

[Helmi74]

Hey Nathan,

sorry for my late reply. Last days have been a bit busy.

Thanks so much for your screencast - that helps much more than you could even think. Not only regarding this issue but as it gives a bit of an insight to your workflow. Whenever i see such a practical screencast i realize that i only use a part of the features that Fusion360 already offers.

Thanks for sharing!

[Oceanconcepts]

I second Frank's comments- this sort of conversational look at work flow really helps to explain and clarify the Fusion sketch interface. 

[Anonymous]

That was an extremely useful video, thanks.