Skip to main content
MB_84522303-Newcomer
3-Newcomer
Apr 20, 2023 6:19 AM UTC
Solved

Creo Mechanism - Ridiculous force

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.

 

 

 

ChrisKaswerAnswer
16-Pearl
Apr 20, 2023 6:39 PM UTC

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".

View in thread

6 replies

SweetPeasHub17-Peridot
17-Peridot
Apr 20, 2023 2:46 PM UTC

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?

Translate
MB_84522303-NewcomerAuthor
3-Newcomer
Apr 20, 2023 6:15 PM UTC

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

I am using slider connection with shown dynamics properties. 

MB_8452230_0-1682014192545.png

MB_8452230_2-1682014246578.png

 

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:

MB_8452230_3-1682014362908.png

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 ?

 

Translate
ChrisKaswer16-PearlAnswer
16-Pearl
Apr 20, 2023 6:39 PM UTC

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".

Translate
    Terms & ConditionsAccessibility statement