Autodesk Robot Structural Analysis
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instabilit y type 3 RX direction
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When I calculate my modell i get the following error: instability of type 3 in RX direction
I have looked at the node but everything seems to be correct. I the releases box I have tried to tick off RX, but that did not help.
Solved! Go to Solution.
Re: instabilit y type 3 RX direction
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Open calculatin Report , find there Max min values on stiffeness matrix diagonal and write here these two values.

Rafal Gaweda
Product Support
Autodesk, Inc.
Re: instabilit y type 3 RX direction
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Min/Max after decomposition: 7,463808e+006 6,847539e+019
precision: 1
Re: instabilit y type 3 RX direction
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if the difference between these values is greater than 1e11 \ 1e12 program reports instability number 3.
It is related to big differences in stiffenes of elements for example very short elements exist in model = some inaccuracies.
You can check it this way: on dummy model select everything, make intersection, then open Bars table on View tab. Find shortests bars. Then locate nodes \ places on original model and correct location of nodes.
If it is not the case. Send me model. You already know how.

Rafal Gaweda
Product Support
Autodesk, Inc.
Re: instabilit y type 3 RX direction
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I don't understand how to do what you told me to do
Re: instabilit y type 3 RX direction
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I'm sending the file![]()
Re: instabilit y type 3 RX direction
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Example below
If not - send me the file.

Rafal Gaweda
Product Support
Autodesk, Inc.
Re: instabilit y type 3 RX direction
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Inacurracies in your model:

Rafal Gaweda
Product Support
Autodesk, Inc.
