# Create MPC for 3D element

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Hi everyone, Now I have a problem deal with create MPC for 3D element.

My components include 2 parts fix together (bolt and plate). At thread match position, I want to create MPC connection between thread and hole

But it apprears error " DOF on grid 704 appears twice in equation, please modify dof selections". Whether I made MPC connection rightly or not?

Thanks guys

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What's your final goal of using MPC?

Alex Nguyen likes this

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He is doing homework about mpc, i think so!

Alex, Could you take photo of mpc definition? Dofs & nodes?

Alex Nguyen likes this

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Dear Mr. Tinh and Mr. Q.Nguyen Dai

I have a assembly structure between bolt and hole. My mission has to connect them together by match node and MPC node. (green line in below figure)

Weight factor of Dependent node= -1 and Weight factor of Independent = +1 for each DOF

But after I create mesh bolt and hole (ensure match node), then I create MPC, and MPC warn that " DOF o﻿n grid 704 appears twice in equation, please ﻿modify dof selectio﻿ns﻿"﻿

I also wonder why need create MPC while these nodes ( between bolt and hole) were matched together (coincident node). Or maybe because these nodes were matched together so MPC can not created?

Thank so much Mr. Tinh and Mr. Q.Nguyen Dai

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Yeah, i understand.

2 nodes are concident => so you cannot pick them separatedly.

You pick n704 as dependent, and then pick overlapped one as independent but hypermesh catches n704 so n704 was selected for both dep and indep=>

Press O to enter panel Options>graphics> activate "concident picking" and try again.

Are you sure there are 2 nodes ? In case you equivalenced them (shift F3), you have to detach (panel 3d>detach)

If you shared nodes (equivalenced), you don't need mpc because there's only 1 node.

You did not answer question of @Q.Nguyen-Dai ?  I want to know your goal, too.

Alex Nguyen likes this

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Thank you Mr.Tinh

Yeah, I understood.

I'm very sorry for forget answer question of @Q.Nguyen-Dai. My goal of using MPC is calculate Nonlinear Static Structure( stress, displacement, deformation). Really I also only know that much.

I'm be grateful Mr.Tinh so much. I remember this is third time you support me about MPC problem. Thank you so much

Best regard @tinh and @Q.Nguyen-Dai

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On 5/24/2019 at 4:24 AM, Alex Nguyen said:

Dear Mr. Tinh and Mr. Q.Nguyen Dai

I have a assembly structure between bolt and hole. My mission has to connect them together by match node and MPC node. (green line in below figure)

Weight factor of Dependent node= -1 and Weight factor of Independent = +1 for each DOF

But after I create mesh bolt and hole (ensure match node), then I create MPC, and MPC warn that " DOF o﻿n grid 704 appears twice in equation, please ﻿modify dof selectio﻿ns﻿"﻿

I also wonder why need create MPC while these nodes ( between bolt and hole) were matched together (coincident node). Or maybe because these nodes were matched together so MPC can not created?

Thank so much Mr. Tinh and Mr. Q.Nguyen Dai

Hey. I'm experiencing the same problem. I was trying to resolve it somehow, but I wasn't lucky.

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On 5/24/2019 at 4:24 AM, Alex Nguyen said:

Dear Mr. Tinh and Mr. Q.Nguyen Dai

I have a assembly structure between bolt and hole. My mission has to connect them together by match node and MPC node. (green line in below figure)

Weight factor of Dependent node= -1 and Weight factor of Independent = +1 for each DOF

But after I create mesh bolt and hole (ensure match node), then I create MPC, and MPC warn that " DOF o﻿n grid 704 appears twice in equation, please ﻿modify dof selectio﻿ns﻿"﻿

I also wonder why need create MPC while these nodes ( between bolt and hole) were matched together (coincident node). Or maybe because these nodes were matched together so MPC can not created?

Thank so much Mr. Tinh and Mr. Q.Nguyen Dai

oh... I have the same problem. really. I don't know what to do

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As above tutorials, You should not equivalence "couple nodes". Make ensure that One node in number ID is "a", and another node which number ID is "b" .

You let try. I had finish it.

Thank you everyone

Best Regards

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