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MB_84522303-Newcomer
3-Newcomer
April 20, 2023
Solved

Creo Mechanism - Ridiculous force

  • April 20, 2023
  • 1 reply
  • 2970 views

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.

 

 

 

Best answer by ChrisKaswer

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".

1 reply

S
SweetPeasHub17-Peridot
17-Peridot
April 20, 2023

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?

M
MB_84522303-NewcomerAuthor
3-Newcomer
April 20, 2023

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 ?

 

C
ChrisKaswer16-PearlAnswer
16-Pearl
April 20, 2023

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".

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