topic Re: Over-constrained mechanism + number of joints in Inventor Forum

Over-constrained mechanism + number of joints

Anonymous — Tue, 08 Dec 2020 10:10:06 GMT

Hello everyone,

I am new on this forum and I hope that my question are relevant (and that you could help me).

I am working on a robot assembly and I have some issues. I made this assembly and then I go to environment- Dynamic simulation, the software tells me that the mecanism is "over-constraint by 4-degrees". I don't know where to find the solution (which constraints create problem) and I don't know how to change them in order to keep the same "movment" of my mechanism.
I also have another problem : I only grounded 1 element but in the assembly it tells me that many parts of my assembly are grounded. What is the problem ?
Finally I also have an issue : why are there so many standard joints ? People who work on the same project told me that they have less than 10 joints

Thank your very much in advance for your answers

Re: Over-constrained mechanism + number of joints

CGBenner — Tue, 08 Dec 2020 11:59:30 GMT

@Anonymous

Welcome to the forums! We're very glad to have you, and as long as you stick to the Inventor topic... your questions will be very relevant. I hope you can find your answers.

Re: Over-constrained mechanism + number of joints

JDMather — Tue, 08 Dec 2020 14:04:29 GMT

An assembly must, of course, include parts.

In Inventor, parts are in the form of *.ipt files.

Without the *.ipt part files, the assembly *.iam file is completely useless.

(72) DSG 421 - YouTube

If automatic conversion of assembly constraints to Dynamic Simulation Joints is turned off - you will see a much larger list of Joint types. If automatic is turned on - there is generally no need to see this expanded list of Joints.

Zip and Attach the folder of your entire project (including parts).

Re: Over-constrained mechanism + number of joints

Anonymous — Tue, 08 Dec 2020 14:15:20 GMT

Thank you for your answer

Sorry I forgot to put the parts. Here is the zip .

I just checked and the "automatic conversion of assembly constraints to Dynamic Simulation Joints" is on

Re: Over-constrained mechanism + number of joints

JDMather — Tue, 08 Dec 2020 14:33:30 GMT

@Anonymous wrote:

Here is the zip .

You cannot Attach files via email Reply. You must go to the web forum to Reply and Attach your zip folder - then double check to verify.

Re: Over-constrained mechanism + number of joints

Anonymous — Tue, 08 Dec 2020 14:36:43 GMT

Sorry for my mistake

Re: Over-constrained mechanism + number of joints

JDMather — Tue, 08 Dec 2020 14:50:32 GMT

In the real world - many of your components would be in sub-assemblies.

That is the first thing I would do with this assembly -- group components into logical sub-assemblies.

This will significantly reduce the number of Joints that have to be solved and make it easier to avoid over-constrained condition.

Re: Over-constrained mechanism + number of joints

Anonymous — Tue, 08 Dec 2020 14:52:08 GMT

Thank you I will try to do that !

Re: Over-constrained mechanism + number of joints

JDMather — Tue, 08 Dec 2020 14:57:49 GMT

Example - this should be one sub-assembly.

and this should be one sub-assembly.

Some of these sub-assemblies are probably also comprised of logical sub-assemblies.

Just like in the real world.

Re: Over-constrained mechanism + number of joints

BrendanG4AEBE — Thu, 17 Jul 2025 13:36:53 GMT

I am getting the same error.

I am used to doing FEAs where I have to define the constraints. Why does the dynamic environment tell me that I have this error as soon as I open up the dynamic simulation environment, before I have told it to do anything? I have looked at a couple tutorials on youtube for the dynamic simulation, and I'm unable to follow because I get this error before the tutorials do step #1.

Re: Over-constrained mechanism + number of joints

CGBenner — Thu, 17 Jul 2025 13:48:36 GMT

@BrendanG4AEBE

Hello. Since this is such an old post, would it be possible to elaborate on what errors you are seeing? Maybe share some screen shots? If possible, Pack & Go a small assembly that exhibits this behavior so the experts here can have a look.

Good luck!

Re: Over-constrained mechanism + number of joints

BrendanG4AEBE — Thu, 17 Jul 2025 14:22:54 GMT

Looking at the tutorials, it seems like dynamic simulation is meant for pieces that are actually supposed to move, like pistons. I am interested in a rigid body under vibration. I asked ChatGPT about this, and it says that full analysis of forced loads is not possible in inventor.

This is the first time I tried to use this environment, and I guess I didn't understand what it was actually for.