topic Re: Dynamic simulation closed loops and flipping normal - 2d Contact in Inventor Forum

Dynamic simulation closed loops and flipping normal - 2d Contact

lminerviniS8CTE — Thu, 24 Oct 2019 14:00:25 GMT

I am trying to model a ball detent mechanism in dynamic simulation and I am running into issues.

First, I am trying to create a 2d contact joint by making a sketch at the ball's center line and projecting it's diameter. Then I am creating a 2d sketch on a mating part of 2 indents for the ball to fall into. When I select the indent geometry in DS it tells me the sketch is not a closed loop (it is). I can then go back to the sketch and offset the geometry by a few thousandths (which tells me its a closed loop) and then it works.

Once I got that working, I can run the simulation, watch the ball ride the indent geometry as it should by pressing the play button. If the simulation runs, then go back to construction mode and hit the play button again I get an error that the 2d contact joint is impossible to solve and should be checked (normal orientation). I can flip the normal direction of one of the parts then it runs correctly again. I need to flip the normal every time simulation runs in order to avoid this error. The 2 parts only have translational degrees of freedom, so it isn't like they are flipping around.

Am I doing something wrong? I have had success with 2d contacts before.

Re: Dynamic simulation closed loops and flipping normal - 2d Contact

JDMather — Thu, 24 Oct 2019 14:53:23 GMT

Zip and Attach your assembly here.

Re: Dynamic simulation closed loops and flipping normal - 2d Contact

lminerviniS8CTE — Thu, 24 Oct 2019 17:28:52 GMT

The original model is a company design with about 100 parts, so to play it safe I simplified the section of interest.

The flipping of normals issue went away with the new assy, but I am still getting the same result on the 2d contact. It may have been some kind of bug, as my system did freeze before and was restarted. I will try to re-do the simulation from the start to see if it happens again.

I am using a sketch on the "slide" part as the detent hole geometry. I changed the color of the original geometry (what is being considered an open loop) to red and left the working geometry (after using offset command) to be default colors.

Any advice or explanation would be appreciated because I thought I conquered open loop issues about 7 years ago.

Re: Dynamic simulation closed loops and flipping normal - 2d Contact

lena.talkhina — Tue, 28 Apr 2020 15:58:12 GMT

Hello @lminerviniS8CTE !

Great to see you here on Inventor Forum.

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