sketch constraints

JYZMT · ‎01-17-2018

Can some one tell me why parameter Test_B can not be changed? I can't see why its being constrained?

Anonymous · ‎01-17-2018

Isn´t that very similar to the problem you posted here?

https://forums.autodesk.com/t5/fusion-360-design-validate/sketch-problems-over-constraint/td-p/76854...

To quote your last entry there: "....It seams ok with circles, as suggested earlier, but not with semi circles...".

That´s exactly the same problem here (I tested it with circle/tangent -> no problems). I suppose that it might be a bug in the sketch-solver.

Maybe you should post this example in the "support" area with a more specific description (like your quote "works with circles, but problems with arcs") - you might have a better chance to get a feedback from Autodesk.

Just an idea.

Manfred

TheCADWhisperer · ‎01-17-2018

I couldn't find what exactly was wrong with the sketch - so I tried to reproduce the issue in Autodesk Inventor Professional.

Everything worked as expected in Inventor.

If you are a student - you can download Autodesk Inventor Professional for free from Autodesk Education Community.

JYZMT · ‎01-17-2018

Thats funny, I thought I had posted it in the support forum??? I'm sure it was their earlier because I was looking at it against the other topics, which are still in there? strange. Either I'm losing it or it was moved.

I tried posting again (my intention within the support forum) because last time we put it down to an old rouge file, but this was a new fresh one and it still went wrong.

Thanks for checking this @TheCADWhisperer I also can't understand why its not working, and this is the point. this is a simplified version of models I need to build, and I really need to understand what is wrong with my methodology, so I can build it differently. If there is a problem in the way I've defined in terms of logic, then I just need to know... but as far as I can see, it should work?

The circles method is also going wrong when I tried a few things, so that's not the solution. BUT I have had success with defining the circles (and arc) using a radius dimension, as opposed to a point to point dimension used in the file. Its as if it gets stuck when it tries to change the overall width.

HughesTooling · ‎01-17-2018

Drawn and constrained in a slightly different way seems to work. File's attached.

Mark

Mark Hughes
Owner, Hughes Tooling
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HughesTooling · ‎01-17-2018

Just experimenting with your original sketch and just dimensioning the arcs with a radius rather than from an edge fixes it. After deleting your dimensions I needed to try and drag an arc centre which made the sketch jump and correct itself then add the radius dimension.

Mark

Mark Hughes
Owner, Hughes Tooling
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jeff_strater · ‎01-17-2018

Thanks, @HughesTooling for the suggestion. I will pass the original design to our sketch team to investigate more fully why it fails. It could be a bug. Thanks for sharing the design, @JYZMT.

Jeff

[edit] the bug on the original model has been filed as FUS-37937

Jeff Strater
Engineering Director

JYZMT · ‎01-17-2018

Thanks, this does seam to work. But Its made me really question the robustness of sketches, which should be super stable for confidence in this software. I can't see any errors in the logic of what I was doing before, and Its made me very nervous as I define new models and sketches. Basically I feel like I'm designing on eggshells; I'm testing every parameter with gritted teeth to see if it glitches, and I've lost loads of time unpicking models I thought were working. Thanks for your help.