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COE DISCUSSION FORUM
Forums > COE Forums > CATIA V5
Subject: Flexible assembly

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Author Messages
mohammad101


08 Aug 2008 12:08 PM

hi every one

I have a problem. does anyone knows about assembling and simulating springs and other flexible parts like belts ? I have a mechanism that includes some flexible parts and I have to

simulate the mechanism . I know it is easy to assemble and manipulate flexible parts in solidworks  . but does CATIA do these works ? did anyone ever simulate mechanisms like this in CATIA ?
::: Try to fly with CATIA :::
MBERRY

08 Aug 2008 01:59 PM
I think you are out of luck with deformable items like springs. As for belts you can do it thru a simulation with laws. Assuming the belt moves over pulleys, the radius values are known, so it easy to define the rotation angle of all other pulleys based on the first one's rotation. Setup all of them to be revolute joints where the angle of each may be specified in the law.

Mike
TX520

08 Aug 2008 02:47 PM
It seems that it would be possible to make a law to modify a helix (I'm assuming your made your spring by ribbing a circle along a helix).
mohammad101


28 Aug 2008 01:37 AM

hi guys

did you ever try the simulation with laws  about springs ? I trid it and it does'nt work .

 the lenght and the pitch of the spring is defined by a formula and when I simulate with

laws the spring must be updated at any step .I think it is a bad way to simulate the springs .
::: Try to fly with CATIA :::
MBERRY

28 Aug 2008 06:39 AM
I think the recommendation regarding laws was just a way to model different states of the spring within a single part, so you could visualize the deformed shapes. However, when you use kinematics at the product level, it assumes all parts are rigid and just moves them during the simulation. The simulate with laws capability is meant to drive the mechanism commands according to some rules rather than you entering values for the motion. With kinematics there is no update of each part at each time step - this would slow the simulation to a crawl and you would have to manage update problems if they occur in the parts as well.

Mike
mohammad101


28 Aug 2008 07:49 AM
hi dear MBERRY
with your comments I can't simulate the spring motion !
tell me :
* can you really simulate a mechanism in CATIA that includes a spring ?!!!!
if yes tell me the step by step scenario !!
if not , tell me what I have to do ? perhaps I have to use solidworks !!!! because CATIA is
unable to do this work !!!

* is CATIA unable to simulate the spring motion ?
if yes , the engineers of dassault systems must resignate and go home and never produce softwares like CATIA !!!!!

* do you know why the simulation of flexible parts in CATIA is impossible ?

I think the programmers of dassault systems can solve this problem but I dont know why
they dont do this !
::: Try to fly with CATIA :::
MBERRY

28 Aug 2008 08:49 AM
Harsh comments...Anyway, I think I already answered your questions. I don't know of a way to simulate kinematic motion in an assembly AND deform parts during the simulation. Maybe the CATIA CAE analysis workbenches can do it, but I have no experience in that area so I can't comment - anyone else?

Mike
GLAURENCE

28 Aug 2008 10:36 AM

If you are just simulating the kinematics, you need to split the spring into two parts/halves and let them move independently along a common vector. It is a great way to "fake" it.

If you really need to simulate the spring and need to see elastic movement, you need to use a CAE kinematics package like ADAMS for CATIA.
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Forums > COE Forums > CATIA V5 > Flexible assembly



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