Creo Mechanism - Ridiculous force

[MB_8452230]

Greetings and salutions, 

I have a mechanism which you can see in attachment. And when I do a dynamics analysis with movement. It will show me that force required to move and object which weight around 1500kg requires a force of 2 bilions Newtons. 

I am quite lost where is a problem exactly. If someone could help it would be greatly appreciated.

[SweetPeasHub]

This is an educational version file so us professionals cannot open it.

What could help us is screenshots of the model and joints and some of the key motor/force definitions you use.

Can you capture and plot the acceleration of the 1500kg mass? Is there a possible impact event like a joint at its limits, contacts, or cams with liftoff?

What is the time duration of the high force?

[MB_8452230]

So for example i wish to simulate force required for forklift to lift its forks,

I am using slider connection with shown dynamics properties. 

I set a servo motor with constant velocity of 250 mm/sec.

And when I after dynamics analysis where I use both friction and gravity.

Net load for this connection is shown as this:

And if I try to simulate it with force motor I really need to use this force for it to move with set speed. 

But why is that force such massive ? Analysis for my forks will show that they weight MASS = 1.8257271e+02 KILOGRAM 

I am honestly quite confused. And others mechanism have same problem. Am I doing somewhere some kind of mistake ?

[ChrisKaswer · Accepted solution]

You might be seeing a very high force because you've set your servo velocity to a constant speed. This means the solver is assuming that at time zero, your weight must already be moving at 250 mm/sec - this would require a very high acceleration to begin the analysis. You should apply a ramp or sine function servo speed so that you begin the servo's movement with zero velocity and increase it to your 250 mm/sec as a final speed for a time required to achieve the distance you wish to lift your forks. As SweetPeasHub already suggested - take a look at your acceleration (and velocity) and see what it is the solver used for "F=m*a".

[MB_8452230]

Ok, so i remade assembly. I used ramp but now my force is really small, it was really small force. 

And where can i found solver ? 

[ChrisKaswer]

Unfortunately, without being able to open your model, it will not be possible for most of us to provide assistance. Screen images might help, but your description sounds like we would need to see details within your model to understand where you may need to make changes.

[VR_9713318]

This thread will help you: Solved: Re: Change velocity of servo motor according to fo... - PTC Community

I would go the other way around. Knowing the capacity of my motor and hydraulic system, the system can simulate the velocity.

I often turn off friction to avoid unnecessary peaks.