topic Re: Help with Dynamic Simulation in Inventor Forum

Help with Dynamic Simulation

Anonymous — Fri, 16 Jan 2015 11:41:19 GMT

Hi guys,

I'm relatively new to Dynamic Simulation (although I've been using Inventor for years!) and I'm trying to set up an assembly to calculate the force generated by a press. I've attached a screen shot of the set-up. What I'm mainly wanting help in is:

What joints should I use to create the assembly?

What function should I use to calculate the force exerted by the press?

At the moment, my setup results in a force of about 19N, which, from real-life examples, is about 24,980N shy of what I was expecting!!

Any help would be greatly appreciated.

Re: Help with Dynamic Simulation

JDMather — Fri, 16 Jan 2015 11:46:00 GMT

Revolution Joints

Prismatic Joints

Point-Line Joints

Unkown Force - Jack Force

Re: Help with Dynamic Simulation

Anonymous — Fri, 16 Jan 2015 11:48:21 GMT

Thanks for the reply. Could you elaborate a little with your joints answer? Where would you apply the joints you've described?

Re: Help with Dynamic Simulation

JDMather — Fri, 16 Jan 2015 11:52:22 GMT

I would use the joints between your components.

What book are you using to learn Dynamic Simulation?

Have you gone through the Tutorials?

You have asked a very complex question without attaching your assembly here.

I can re-model all of you assembly just from the pictures - but I will be guessing the dimensions and it might take me a couple of weeks to get it done.

Can you attach your assembly here or upload to A360?

Re: Help with Dynamic Simulation

JDMather — Fri, 16 Jan 2015 11:58:33 GMT

Actually, I don't need the modeled parts, but I would need a part with a line representing each linkage and the assembly of the schematic linkages.

Something like this

Re: Help with Dynamic Simulation

Anonymous — Fri, 16 Jan 2015 12:04:34 GMT

Sorry for the complexity of the question without supporting dataset. I can post a dropbox link if you would like? Dataset is 12mb.

I've been using the 2010 Dynamic Simulation books to create my assembly. I've gone through some tutorials but nothing of this type of assembly.

Re: Help with Dynamic Simulation

JDMather — Fri, 16 Jan 2015 12:05:30 GMT

@Anonymous wrote:

...I can post a dropbox link if you would like? Dataset is 12mb.

.....

A360

Re: Help with Dynamic Simulation

Anonymous — Fri, 16 Jan 2015 12:18:12 GMT

@Anonymous wrote:
@Anonymous wrote:
...I can post a dropbox link if you would like? Dataset is 12mb.
.....
A360

When I log in to A360 I get stuck at an administrator approval page.

Dropbox link: https://www.dropbox.com/sh/arimqy5z7e47ocy/AABYP6Ed9ZRegoxfIHOizNpla?dl=0

Re: Help with Dynamic Simulation

JDMather — Fri, 16 Jan 2015 17:45:54 GMT

I get stuck at that dropbox site requiring the creation of an account (which I have no desire to do).

I try to keep my main working machine very clean and am cautious of sites like that through prior bad experience.

I will try to make up a wireframe example sometime tomorrow.

Re: Help with Dynamic Simulation

JDMather — Sat, 17 Jan 2015 15:07:50 GMT

I only had your image to go by - no files - so I guessed dimensions for the linkages.

Open the Cam Press Master.iam assembly file.

Go to Environments>Dynamic Simulation.

Click Uknown Force and Enter.

I get maximum force of about 10 times your stated expectation.

Please check my results and be aware that the dimensions of the linkages may need to be adjusted to match your assembly dimensions (in the master part file sketch blocks).

Re: Help with Dynamic Simulation

JDMather — Sat, 17 Jan 2015 15:16:09 GMT

For those not familiar with using Sketch Blocks -

all I needed was a few lines to represent the linkages for the kinematic diagram. (the circles aren't technically needed, but help to visualize the points of revolution DOF)

Re: Help with Dynamic Simulation

JDMather — Sun, 18 Jan 2015 15:14:38 GMT

I should point out that I did not assign any friction values to the joints.

Re: Help with Dynamic Simulation

Anonymous — Mon, 19 Jan 2015 08:55:03 GMT

Thank you so much for having a go at this simulation for me! I will have a good look through the model you've created.

Much appreciated!!

Re: Help with Dynamic Simulation

JDMather — Wed, 21 Jan 2015 11:52:58 GMT

Keep in mind that the calculated results assume perfect links that don't bend and perfect joints with no clearance.

View the spike in the calculations with caution.

Re: Help with Dynamic Simulation

Anonymous — Mon, 02 Feb 2015 11:24:45 GMT

I have used your workflow and it works perfectly to produce the results anticipated. Obviously I had to play around with the friction settings, but I have found a resonable answer to the original query.

Thanks again for your help on this issue. Very much appreciate it!

P.s. Maybe you should speak to Autodesk about consultation on dynamic simulation...

Re: Help with Dynamic Simulation

JDMather — Mon, 02 Feb 2015 18:18:20 GMT

@Anonymous wrote:

...

P.s. Maybe you should speak to Autodesk about consultation on dynamic simulation...

Not sure who at Autodesk I would speak to. What should I ask them, "When will this functionality be in Fusion 360?"

BTW, another consideration in your problem -

Inventor treats the elements as though they were perfectly rigid and with perfect joints.

No bending of the elements and the joints don't reflect manufacturing tolerances and clearance.

Think of it like a lumberjack on a log in the river.

The lowest energy condition is for the lumberjack to go into the water.

For this reason - if you have a very sharp spike in the unkown force - take it with a grain of experience realizing that the mechanism is treated as though perfect kinematic diagram.

Re: Help with Dynamic Simulation

Anonymous — Tue, 03 Feb 2015 08:54:18 GMT

@Anonymous wrote:
@Anonymous wrote:
...
P.s. Maybe you should speak to Autodesk about consultation on dynamic simulation...
Not sure who at Autodesk I would speak to. What should I ask them, "When will this functionality be in Fusion 360?"

Haha! No, no, just that they should contract out dynamic simulation work to you - you seem to be pretty switched on with the whole process!!

Dynamic simulation - parent frame poorly oriented

danielstastny — Sun, 22 Feb 2015 16:51:40 GMT

Hey

I am working on a Project and i had some problems with the dynamic simulation in INventor 2014.

I am designing a simple engine for my work and currently i am doing the valvetrain. But when i come to the point of choosing a joint for the rocker arm and the valve as well as the camsahft and the rocker arm a problem like "parent frame of loop joint slidin cylinder curve is poorly oriented. rolling or sliding must be in XZ plane of this frame. X tangent. Z normal.

Well i have no idea how i can change this.

If anybody had a similar problem or has any experience with dynamic simulation regarding the sliding or rolling joints i would be very glad.

If needed i can send my file.

Re: Dynamic simulation - parent frame poorly oriented

admaiora — Mon, 23 Mar 2015 13:16:45 GMT

Just curious, how did it was justified the difference in the results between the 24980 N and 241562 N?

Which is the correct result?

thanks!

Re: Dynamic simulation - parent frame poorly oriented

danielstastny — Mon, 23 Mar 2015 13:29:19 GMT

what has this to do with my problem?