# How can I fix this error?

**URL:** <https://prepomax.discourse.group/t/how-can-i-fix-this-error/1646>\
**Category:** General Questions\
**Created:** [March 29, 2024, 12:46am UTC](https://prepomax.discourse.group/t/how-can-i-fix-this-error/1646 "2024-03-29T00:46:04Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Majid](https://avatars.discourse-cdn.com/v4/letter/m/13edae/32.png) [@Majid](https://prepomax.discourse.group/u/Majid)\
**Post date:** [March 29, 2024, 12:46am UTC](https://prepomax.discourse.group/t/how-can-i-fix-this-error/1646/1 "2024-03-29T00:46:04Z")

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Hello everyone,

I am doing powder compaction forming by PrePoMax. I get this error when I define a rigid body constraint in my simulation. Does anyone know how I can fix this problem? (Please see the attached figure)

 ![photo_2024-03-29_09-41-02](https://global.discourse-cdn.com/free1/uploads/prepomax/original/2X/f/fce413eb9bfda14754c4fc59743e791d53c7c31f.jpeg)

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**Author:** ![FEAnalyst](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/feanalyst/32/688_2.png) [@FEAnalyst](https://prepomax.discourse.group/u/FEAnalyst)\
**Post date:** [March 29, 2024, 7:54am UTC](https://prepomax.discourse.group/t/how-can-i-fix-this-error/1646/2 "2024-03-29T07:54:27Z")

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Are you using shell or 2D elements ? Currently, they don’t work with rigid bodies in explicit dynamics: [Rigid body constraint doesn't work with shell, axisymmetric and plane stress/strain elements in explicit dynamics · Issue #59 · Dhondtguido/CalculiX · GitHub](https://github.com/Dhondtguido/CalculiX/issues/59)

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**Author:** ![Majid](https://avatars.discourse-cdn.com/v4/letter/m/13edae/32.png) [@Majid](https://prepomax.discourse.group/u/Majid)\
**Post date:** [March 29, 2024, 9:10am UTC](https://prepomax.discourse.group/t/how-can-i-fix-this-error/1646/3 "2024-03-29T09:10:54Z")

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@FEAnalyst Thank you so much for your reply. Yes, I am using a shell part.

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**Author:** ![FEAnalyst](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/feanalyst/32/688_2.png) [@FEAnalyst](https://prepomax.discourse.group/u/FEAnalyst)\
**Post date:** [March 29, 2024, 9:12am UTC](https://prepomax.discourse.group/t/how-can-i-fix-this-error/1646/4 "2024-03-29T09:12:33Z")

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> [@Majid](#):
>
> Yes, I am using a shell part.

Then I would replace it with a single layer of a solid mesh. Shells in CalculiX are expanded to solids anyway.