Contact between part and part-inserts

[riomilo]

Hello,

Suppose we are dealing with multi-component simulations (part + part inserts) and each component is meshed independently.

Suppose also that there is not perfect contact between the meshes of the different components, how does MoldFlow tackle the spaces between the parts? Does MoldFlow suppose that this space is Mould material?

Is it required a perfect matching between the meshes of components that are in contact? Is it required that nodes on contact surfaces have the same space-coordinates for both components?

If not, what is the recommended meshing procedure that guarantees a correct heat and stress transfer between components?

Thank you in advance.

[nishit78]

This answer is based on my understanding and for AMI-2012.

Perfect mesh matching at the contact faces is most certainly preferred. That being said, if the matching is not perfect you can expect to see some inaccuracies in the analysis as a result.

If there is a space between the 2 mating surfaces, i'd assume that moldflow assumes mold steel in that space, but i can't say that for sure.

As for the best-practices, if you have MDL, the best is to directly import the solid cad geometry assembly in Moldflow (using MDL) and then the mesh settings offer an option for "Mesh on Assembly Contact Faces" under the "CAD" tab.

If you dont have MDL or you can not import CAD assembly then the other thing that i do is break up my CAD assembly into a seperate surfaces (eg. interfaces surfaces, remaining 1st body surfaces, remaining 2nd body surfaces, etc). I then mesh them all individually and finally create a single study file stitching everything together as necessary. As you can imagine this can be a very tedious process but without the MDL you have no other choice as far as i know, other than accepting the inaccuracies.

Hope this helps

Nish

[nordhb · Accepted solution]

Hi,

Regarding contact, of course it is ideal to ensure precise match on contact interfaces, but not always achievable.
One might have to put a lot of effort to make a precise match depending on cad model quality.
Each node on interfaces will have a corresponding node on the other side, and it makes data communication between adjacent bodies easier during analysis.
However, this is not the only way to transfer data from one body to its neighbors. The Moldflow solver development has proved that this can be done without this limitation of precise matching, so the solvers of Moldflow Insight 2012 are more capable to deal with not precise match.
So, it is good if nodes are matched on interfaces. If CAD model is clean, "precise match" is a good option, but not compulsory.

Regarding Autodesk Moldflow Design Link:
From the release Autodesk Moldflow Design Link 2012, you can install the default version that
will operate with *.ipt, *.iam, and *.sat files, with no license required.
You can use Autodesk Inventor Fusion 2012, to import various cad formats, and save in .sat-format.

Regards,
Berndt

[riomilo]

Thank you so much for your answer.

Just one additional clarification, if there is not perfect match between two surfaces, does Moldflow suppose that the interphase is Mold material?

Best Regards,

Camilo

[nordhb]

You are welcome.

The solvers of Moldflow Insight 2012 are more capable to deal with not precise match, and is able to transfer data at surface interface even if not perfect match.

Do you mean having a big gap between surfaces?
If too large, and in for example Cool FEM, you can look at Temperature, mold-insert difference (averaged) result the large difference in temperature between the mold and the insert may indicate an air gap between the two.
Otherwise, it has contact with mold block.

Does this answer your question?

Regards,
Berndt

[riomilo]

Thank you again for your answer.

Suppose a plastic part and a metallic insert whose surface meshes do not match well (for Filling and Packing simulations). If those surfaces have a big gap, does MoldFlow suppose air (or other material) between them ? Or, if I have assigned previously part and insert contact to those materials, Moldflow solver always transfer data between those surfaces ?

Best regards,

Camilo

[nordhb]

Hi,

having a gap between plastic part and insert due to mesh facetting, there will be a transfer of data at interface when doing a Fill+Pack, and in Advanced settings, tab Core shift, insert temperature set to
Calculate transient temperature during flow for all part inserts and cores

The interface conductance and heat transfer coefficient will influence the heat transfer from plastic part to insert.
If the gap becomes too large, the part insert will keep initial temperature.
Looking at temperature by time (rescale temperature to be reasonable) you should be able to see this for your study.

Hope this clarifies.

Regards,
Berndt

[teopado89]

Excuse me, where is the "Mesh on Assembly Contact Faces" under the "CAD" tab ? Thanks

[nordhb]

Hi,

it is under tab "CAD", and the study need to have a CAD Body.

Surfaces has the "NURBS" option.

Regards,

Berndt

[teopado89]

Please can you explain me how to import it to have the "CAD" tab?
I have a Catia R19 file with solid geometry (part + insert).
Thanks

[nordhb]

Hi,

after selecting Import, and Open of selected cad file with solids an Import dialog opens.

Tick "Direct Import using Autodesk Simulation Design Link".

If a watertight solid geometry it will become a CAD Body in Synergy. (then tab CAD in mesh settings)

If you use "Process using Autodesk Simulation Moldflow Design Link", and in Advanced... selected Translate surfaces, you will get CAD surfaces of the solid geometry. (then tab NURBS in mesh settings)

Regards,

Berndt

[teopado89]

Thanks a lot nordhb! Tomorrow i'll try your method.

I'm trying to solve a problem of intersections.

When are intersections critical?

Is it a problem of which the intersect elements are (i.e. meshes of 2 parts (1st and 2nd shot) meshed not simultaneously, or mold insert mesh and beams cooling circuit, part insert and part meshes...), or does it depend of the type of analysis? 

I'm a bit confused.

Thanks in advance.

Matteo

[nordhb]

Hello Matteo,

how to deal with intersections depends on mesh type and type of analysis. Have no overview as such, but generally:

Review this article:

Is precise mesh matching needed at interface for cavity and insert

"It is recommended to use similar element edge length when meshing components, to get similar edge length at components interface. "

If cooling circuits passing mold boundary or mold inserts modeled as surface blocks (not 3D tetra), you normally remove triangles at surface intersections with beams.

Often you see strange temperature if having intersections.

If 3D mesh, you need to model the holes in CAD in mold block for cooling circuits or mold inserts.

For meshing in general, you can review this AU2014 presentation:

SM5706-P: Purging Old Misconceptions: Best Practices for Meshing in Simulation Moldflow Insight  at Autodesk University online.

(You might need to log in to review.)

Reagards,

Berndt