How to properly create rotation

Iwona Wyrębska_20318
Iwona Wyrębska_20318 Altair Community Member
edited November 2023 in Community Q&A

Hi Everyone,

my project is to model a planetary ball mill, and I have some big problem with the rotation of the disk and cylinders. 

These elements should rotate in the opposite direction (as in the picture); however, if the speeds of the disk and cylinders are close to each other, the movement of the cylinders slows down or stops altogether. 
This problem does not occur when I change the rotation to the same direction. I think there's something wrong with the reference system but I can't find the error.
I will be grateful for help.

Iwona
1.png 241.6K
2.png 233.3K
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Answers

  • Stephen Cole
    Stephen Cole
    Altair Employee
    edited November 2023

    Hi Iwona, it looks like you have the kinematics setup as 'parent child' where the child geometry will follow the parent then also apply it's own kinematics. The setup looks OK however it's difficult to tell from the images.

    I would recommend trying to setup the rotation of the cylinders as two kinematics and removing the parent - child relationship.  For the cylinders you can setup 1 motion to rotate around the centre of the domain, and a second kinematic setup to rotate around the CoM of the cylinder.  For this second kinematic you'll need 'moves with body' to be selected to ensure that you are always rotating around the CoM of the cylinder, even though this is moving.

    Regards

    Stephen

     

  • Iwona Wyrębska_20318
    Iwona Wyrębska_20318 Altair Community Member
    edited November 2023

    Dear Stephen, 

    Thank you very much for your reply; I appreciate it. 

    I did what you advised, but it's the same result; in this case, there is a problem with rotating around the centre of the domain. When I set it (just this one move), it also begins to turn around its own axis in the same direction.  I see two vectors, but the gray one is generated automatically, and I can't remove it.

     

    Best regards

    Iwona

    3.png 259.2K
  • Stephen Cole
    Stephen Cole
    Altair Employee
    edited November 2023
    Iwona Wyrębska_20318 said:

    Dear Stephen, 

    Thank you very much for your reply; I appreciate it. 

    I did what you advised, but it's the same result; in this case, there is a problem with rotating around the centre of the domain. When I set it (just this one move), it also begins to turn around its own axis in the same direction.  I see two vectors, but the gray one is generated automatically, and I can't remove it.

     

    Best regards

    Iwona

    Hi Iwona, could you share the input files?  if you zip them at time = 0 s and include the simulation_data folder we can review the settings.


    Regards

    Stephen

  • Iwona Wyrębska_20318
    Iwona Wyrębska_20318 Altair Community Member
    edited November 2023

    Dear Stephen, 

    The file is attached; thank you for your time.

     

    Best regards

    Iwona

  • Stephen Cole
    Stephen Cole
    Altair Employee
    edited November 2023
    Iwona Wyrębska_20318 said:

    Dear Stephen, 

    The file is attached; thank you for your time.

     

    Best regards

    Iwona

    Hi Iwona,


    Is this the motion you were looking for (Attached).  I created a new square geometry to just rotate around the centre point while maintaining it's original orientation.  Then as a child of this rotating the rectangle and associate disks around their own axis.  I checked the rotations first then linked them together.


    Regards

    Stephen

  • Iwona Wyrębska_20318
    Iwona Wyrębska_20318 Altair Community Member
    edited November 2023

    Dear Stephen,

    that's the motion!:)

    You helped me a lot, I fought it for a long time... Thank you!

     

    Regards

    Iwona

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