Learning Forum

[J.MURPHY104]

Hi,

Issue Summary:

I am trying to move ring-shaped permanent magnets (PM) and a ring-shaped weight up the shaft of a tube that contains an Iron Core on the inside. However, when I validate my simulation, I receive the following errors:

• "Moving objects touch the stationary shell."
• "Motion setup (geometry) is not valid."

I would appreciate any guidance on how to resolve these issues.

Simulation Setup:

• Moving Objects:

  • A ring-shaped permanent magnet (PM) and a ring-shaped weight.
  • These objects need to move upwards along the shaft.

• Transient Motion Band (TransBand):

  • Outer radius: 1 mm larger than the PM and weight.
  • Inner radius: 1 mm smaller than the PM and weight.
  • The TransBand fully encloses both the PM and the weight.

• Surrounding Components:

  • Iron Core inside the shaft. Not involved in motion and Ansys acknowledges this.
  • PVC Plastic Pipe surrounding the TransBand (with a 2 mm larger radius than the TransBand). Not involved in motion and Ansys acknowledges this.

• Subtraction Operation:

  • The PM and weight are subtracted along the entire height of the shaft, ensuring they maintain their ring shape throughout their motion. I did a version where the subtraction was the same height as the outside radius and got the same error messages

Observed Errors & Debugging Attempts:

• Checked that the PM and weight fit entirely within the TransBand.
• Ensured there is a gap between moving objects and the stationary shell.
• Verified motion setup settings in the Design List.

However, I still receive errors when validating.

---

Questions:

1. What does "Moving objects touch the stationary shell" mean in this case?

   • Could this mean my TransBand is incorrectly defined?
   • Do I need a larger air gap between the TransBand and moving objects?

2. Why is the "Motion setup (geometry) is not valid"?

   • Should the transient band be adjusted differently?
   • Is there a specific constraint on how motion bands should be created for ring-shaped moving objects?

3. Are there specific best practices for defining motion bands for non-solid moving objects (like rings)?

Any advice or troubleshooting steps would be greatly appreciated.

Thanks in advance for your help!

[GLUO]

Hi,

1.

Could this mean my TransBand is incorrectly defined? Yes

Do I need a larger air gap between the TransBand and moving objects? Yes

 

[GLUO]

Is there a specific constraint on how motion bands should be created for ring-shaped moving objects?

We usually require the motion band to be a connected region. For your case, since there is a stationary core inside, you could add a cylinder at the very far end of your ring-shaped motion band to make it connected.

[GLUO]

Also, if you have eddy effect turned on or have current assigned on the moving objects, you need a inner region inside the motion band. The relation is:

Motion band contains the inner region and not touching the inner region.

Inner region contains all moving objects and not touching any of them.

GL

[J.MURPHY104]

Hi Gluo,

The Trans Band is correctly defined and I have adjusted the air gap and that didn't help/make any difference.

In the image below the Transient Band I have defined is only around the blue, the green circle is stationary, which I want it to be but it is still giving me the error. I have a current assigned to the orange circle on the outside but that has no connection to the Trans Band. Can you indicate any more possible things I can do?

 

Thank you!

[J.MURPHY104]

Hi GLUO,

I do not understand what you mean by inner region and I do not understand its purpose. Can you please clarify or if anyone reading this understands, can you please help.

I appreciate the cross-sectional breakdown but I unfortunately do not understand that either. I can guarentee the stationary objects are not in contact with any objects in motion. 

Let me know if this is correct but you are saying I need an inner region inside the motion band, both of which only surround the Ring part of the set up?

Thank you for the help so far. I really need this motion setup to work. I am looking forward to your reply.

[J.MURPHY104]

Hi Gluo,

 

Thanks for the reply, can you explain what you mean by "you could add a cylinder at the very far end of your ring-shaped motion band to make it connected", I don't understand what you mean by this and how to do it.

 

Thank you

[GLUO]

Hi,

I think the main issue is lacking of inner region. A conneted cylinder at the end might not be necessary. I cannot post picture due to some forum rules, so I will use M for motion band, R for the moving rings, I for inner region, and S for stationary region. After adding the inner band and cylinder, the cross section looks like this:

S  S S S  S S  S S S

S M M M M M M M S

S M M M M M M M S

S M M M S M M M S

S M III M S M III M S

S M IRI M S M IRI M S

S M IRI M S M IRI M S

S M IRI M S M IRI M S

S M III M S M III M S

S M M M S M M M S

S  S S S  S S  S S S

Please make sure the objects in stationary not touching the motion band from outside,and the moving objects not touching the inner band from inside.

GL

 

[GLUO]

Yes. Inner region is a band smaller than motion band but still contains all moving objects.