Inventor Dynamic Simulation - Redundancy

[karthur1]

I need someone to explain or show me what I am doing wrong with this simulation.  I have built this in Inventor 2020 and it works fine in the assembly environment, but when I bring it over to DS, I get a single degree of redundancy.  I can't figure out how to clear this.  Nothing that I have read explains it.  I have tried all sorts of combinations of constraints/joints. When I try to run a "unknown force" it says the DOF will be temporarily locked in the initial position.

Not sure if this is a problem or not.

You should be able to open the attached "Bucket.iam" and go the the DS environment and see this conflict.

Thanks

[JDMather]

Examine the attached - Whisper assembly.

First thing I did was simplify the constraints (could leave them complex - but it was easier for me to initially diagnose by taking out extraneous constraints).

For the first Revolution Joint (Insert and Mate Point-Axis) notice that only the Insert was needed to convert to Revolution Joint.

To make this absolutely correct I should take the time to get Spherical Joint on one end and Point-Line on the other connection.  This would more closely resemble the Degrees of Freedom that would occur in the real world.  (Have a tiny bit of rotational DoF in all axis due to clearances between pins and holes in addition to the intended rotation about the main axis.)

The Piston/Cylinder set to Prismatic Joint (even though when out of the assembly the piston could rotate in addition to translate).

When assembled the rotational degree of freedom of the piston in the cylinder is (mostly) eliminated, but due to clearance with the pin it could actually have 3 degrees of rotational freedom.  That is why I did Point-Line rather than Revolution at the other end.

[karthur1]

Thanks, I see n ow that I should not have used the "Cylindrical" joint between the rod and the cylinder body, but should have used the Mate between the origin planes of both.

Is it generally better to use constraints in the assembly and let them get converted to joints in DS? I have watched several of your examples and that seems to be the way you approach it. I rarely use Joints when I am building my assemblies.

Thanks