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inventor simulation testing counter balances on fabrications

21 REPLIES 21
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Message 1 of 22
safiredesignengineers
1827 Views, 21 Replies

inventor simulation testing counter balances on fabrications

hi group

 

in inventor 2013 simulation what is the way to test a fabrication for counter balanced weight stability?

if you see the enclosed rough assembly. I have been playing with variouse stuff and not getting the results i want.

the idea is to work out how much weight the arm will hold without tipping over. and then by increasing the base size and weight  or arm length i can then work out the ultimate design for my needs.

 

the way i want it to work is so that the base is just sitting on the floor as in real life with gravity and weight keeping it there and then as i apply weight to the arm see the tipping or load effect.

 

this upload is simple and i constrained the base via an axis on the edge put as soon as i run the symulation it just tips over and it shouldnt?

 

I have tried many other things but get a variety of results like the base suddely flying off and a thousand miles an hout due to the contacts used ?

 

any help on the best way to do this type of set up?

 

regards Adrian

21 REPLIES 21
Message 2 of 22

I might have my software mixed up (Mech Sim vs Inventor Sim), but I would think "soft-springs on the base corners. As soon as you get a negitive result on a spring it's begining to lift up and tip over.


Inventor 2020, In-Cad, Simulation Mechanical

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Message 3 of 22

I think I would use Spatial and 3D Contact rather than Revolution or Cylindrical joints.


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Message 4 of 22

I guess that as soon as the CG moves beyond the edge of the base it should become unstable and start to tip over.


Inventor 2020, In-Cad, Simulation Mechanical

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Message 5 of 22

Hi Blair

 

but the centre of gravity is set low in the centre of the base?

 

regards Adrian

Message 6 of 22

Hi JD

 

using spatial can have funney effects on a test like this, like the base entering the floor, or the assembly suddenly flying off.

I have played with settings to adjust this but it should be simpler.

 

regards Adrian

Message 7 of 22

I think the key will be to get to correct properties for the 3D Contact.

It looked to me like your direction of Gravity was backwards.

3d contact.PNG

 

For the Cylindrical joint to act appropriately (if even possible) I think you will need to edit the Joint Torque Properties.

Cylindrical.PNG

 

Similar problems have come up here in the past (perhaps by you?), but I don't recall the solution.  Perhaps a search would turn up discussion the "Desker".


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Message 8 of 22

Hi Jd

 

Yes sorry i did have the gravity the wrong way! this is just a quick test file that i could upload.

and yes the similer problem has come up posted by me, but this time i thought by uploading a simple assembly it might provoke a simple method by somone.

 

there must be a simple good solution as anyone that fabricates stuff usining inventor will want to run tests like this on the potential work.

 

A

 

Message 9 of 22

Is this a static item, where the unit is not moving, if so then there is not a stability triangle required for unit. As soon as the C/G moves beyond an edge or hinge point the unit will tip. If this is a dynamic unit that is in motion as the C/G moves outside of the stability triangle then the unit will become unstable and tip.


Inventor 2020, In-Cad, Simulation Mechanical

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Delta Tau Chi ΔΤΧ

Message 10 of 22

Might be a bad time to ask questions like this.
There seems to be reduced participation here by the Deskers between AU and Christmas.

Maybe try over here http://beta.autodesk.com

or

bump this thread after the new year if they don't come along and respond before then.

 


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Message 11 of 22

So is this the best way to work out the limits of an object tipping over with counter balanced weights etc..?

I want to have a definitive way to solve issues like this, I am not keen on fudging controls to make it work, it needs to be simple but definitive.

 

regards Adrian

Message 12 of 22

Any time the C/G moves outside the base of a stationary object, it will tip over unless the base is fixed.

 


Inventor 2020, In-Cad, Simulation Mechanical

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Delta Tau Chi ΔΤΧ

Message 13 of 22

Hi Blair

 

thanks for your reply, This makes sense and i had a good play last night. and when playing with the weights / COG and then seeing the results in the simulation i found that when the COG was outside the base i then added a extension leg that went past the COG and it stabalised again, But I still don't like the fudging of the settings in simulation.

to stop strange things happening I have to apply friction, increase stiffness and damping also i found that when my floor plate was thin say 50mm thick then the test davit assembly started to sink into the floor when it tipped? if i increased the floor thickness it resisted more?

 

Surley for a static weighted object that is being looked at for tipping purposes the friction, damping and stiffness should not be relevant? and it should not have effect unless there are other forces as well?

 

Now i don't mind increasing and adjusting these figures to make it more stable in my test as long as this has no effect on my test and this is what i don't trust and would like to know more on.

 

Also solid objects should never be able to sink into each other!! this must be a simple rule to apply?

 

regards  Adrian

Message 14 of 22

I would be using Mech Sim and attached "soft springs". I can then graph the forces of the soft springs and anything with a positive displacement would mean that the unit base is lifting up.

 

Yes for a static object you can really simplifiy your simulation.


Inventor 2020, In-Cad, Simulation Mechanical

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Delta Tau Chi ΔΤΧ

Message 15 of 22

Hi Blair

 

what is mech sim? is this the same as inventor sim?

 

or is it the 2d autodesk mechanical?

 

regards Adrian

Message 16 of 22

the full name is: Autodesk Mechanical Simulation 2013

 

It used to formally be: Aglor Mechanical Simulation


Inventor 2020, In-Cad, Simulation Mechanical

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Delta Tau Chi ΔΤΧ

Message 17 of 22

 

 

I've got product design suite unltimate 2013 but i dont have "Autodesk Mechanical Simulation 2013" ?

is this a higher level than normal? or am i missing somthing?

 

I am simulating in inventor.

 

 

Message 18 of 22

It is a stand-a-lone separate software package.


Inventor 2020, In-Cad, Simulation Mechanical

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Delta Tau Chi ΔΤΧ

Message 19 of 22

sorry i have a million questions:

is it better than inventor simulation?

and worth the extra cost?

what does it cost?

 

I guess in inventor i can add some soft springs and get feed back with the grapher on, i assume this needs some aditional  bits drawn on the assembly etc to attack the springs to?

 

regards Adrian

 

 

Message 20 of 22

Each release of IV the FEA portion gets better but it's still lacking features such as Hydrostatic (I use alot). We've been using the Algor software since 1994/95.

 

Guess I'm just old-school and like some of the features and used to the software.


Inventor 2020, In-Cad, Simulation Mechanical

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