Help needed with simple Dynamic Simulation

[nick_parry]

Hi

I'm new to the Dynamic Simulation and have been trying to use it to justify the force required by the cylinder to rotate the arm. It seems such a simple assembly but having watched all the You Tube video's I can find, I can't understand why I have joint errors.

The assembly has no constraint errors and behaves as expected when dynamically dragged.

I have set a time of 2 sec and the cylinder moves from 100mm (extended) to 0mm (retracted)

I keep having a joint error which I can't seem to fix, which I think is preventing me from selecting a Joint for a Jack within the Unknown Force command.

If anyone could take a look and point me in the right direction it would be appreciated, as i'm out of idea's

Data is Inventor 2020.

[WHolzwarth]

DS is more critical than Inventor's constraint solver.

Constraining of the cylinder sub-assy is better with an insert constraint at the top (right now), but the other should be changed to only a mate between the axis of the arm's end and the center point of the rod end.

This is transferred as a Point-Line Joint in DS, and seems to work better now.

[nick_parry]

I've altered the assembly constraint as suggested

I've locked the d.o.f 2 (R)  in the new Point Line Joint - That now runs & appears to be stable - So thanks for that.

I can now apply an Unknown Force - Jack.

I've used a face on each Hex Nut at each end of the Cylinder - So the Arrows Appear opposed in the direction of the Cylinder.

How do I obtain a predicted force required from the cylinder.

The Output Grapher result is a constant force. The cylinder force will vary over the path.

Do I have to use the Unknown Force command can it be read from the force plot on one of the current Joints.

[WHolzwarth]

I didn't test it with your files, but perhaps this link can shed some additional light:

https://forums.autodesk.com/t5/inventor-forum/graph-hydraulic-cylinder-load/td-p/2547428

[JDMather]

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@nick_parry wrote:

I've altered the assembly constraint as suggested

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Can you Attach the altered assembly?

[nick_parry]

I've attached the updated data.

I notice you recommend a book by Wasim Younis - I think this will be a valuable read.

[j.palmeL29YX]

Notwithstanding some possible (and to recommend) improvements: 

Running your Simulation2 I get >>this<<. 

The result seem to be plausible. What is your problem? 

(The locked Rotational degree of freedom MAY cause problems. In your model it doesn't)

[nick_parry]

Thank you Jürgen

I couldn't find where to display the force results for that joint.

Lack of experience with D.S

Your screen grab helped greatly.

[j.palmeL29YX]

>>Here<< some suggestions how to improve the quality of your DS. 

(One of the basic rules in DS: While defining joints use origin planes, origin axis' and/or origin points of the components as often as possible)

If my reply solves your problem, click the "accept as solution" button. This can help others find solutions faster

[WHolzwarth · Accepted solution]

I wouldn't change the Cylindrical Joint in DS to Prismatic, Jürgen.

The piston rod normally moves cylindrical versus the cylinder's body, and placed at it's end is a ball joint system.