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Post molding warpage

296 Views, 9 Replies
03/20/2018 6:57 AM

Hello,

 

As i understood that warpage analysis in MF predicts results after the part temperature goes below transition till room temperature.

But say material has CRIMS data and fiber filled, can we predict the post molding warpage? i.e, say after 24hrs or 48 hrs post molding..

The other way we do is export residual stress to a structural simulation software for analysis, but i want to know can this be done in MF itself?

 

Thanks,

Madhan.


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Message 1 of 9 ( Views: 296 )

Re: Post molding warpage

04/04/2018 2:41 PM

Hi @madhan_rm

 

That's basically not possible. Actually, the warp simulation finish at the ejection time, not at the room temperature. Hence, the warp produced from the ejection temperature to the room temperature is not considered, as Moldflow does not know the Boundary Conditions of the post-molding cooling process.

 

I hope it helps!

 

Cheers,

Javier


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Javier Jubierre

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Message 2 of 9 ( Views: 232 )

Re: Post molding warpage

04/05/2018 12:41 PM

@Javier.Jubierrewrote:

 

That's basically not possible. Actually, the warp simulation finish at the ejection time, not at the room temperature.

 

 

Really?

I was thinking that the warpage considers cooling up down to room temperature (otherwise it wouldn't make any sense alt all, or?)

The main boundary condition that is not taken into account is the tool itself - "just" its thermal behavior (like hot spots etc.).

 

So what we miss so far are the restriction to warpage due to the tool, as well as the fact that we (Moldflow Users) do not - or can not -
differ between warpage and post molded warpage.

 

Am I wrong? Then please correct me.

 

Best regards

Harald


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Message 3 of 9 ( Views: 219 )

Re: Post molding warpage

04/05/2018 4:57 PM

Hi,
CRIMS is using material shrinkage data, to create the CRIMS coefficients.

 

The shrinkage data is obtained from a tag die with etched grid lines in it.
The grid lines are measured after the parts are molded and cooled for several days.
So not possible to get measured data at different time in hours.
In such case you need to do special testing, I think.
Asking for plastics lab to measure at specific hours. Not sure it can be done.

 

Using the grid lines, shrinkage is measured parallel and perpendicular to flow.
Parts are molded with a matrix of different conditions including changes in melt temperature,
mold temperature, injection rate, part thickness, pack pressure and pack time.


Moldlfow is using initial stresses for warp.
In-cavity residual stresses result plot are stresses before Warp (DD and Midplane).
So initial stresses for Warp or other software.

 

Initial stresses includes stresses arising from thermal shrinkage during cooling to room temperature.
Hence Warp deflection result is at room temperature or ambient temperature.

 

You can export In-cavity residual stress result in patran or xml format.

 

There are also some scripts for this such as mpi2xxx.

 

About exporting models and files

 

Makes sense?

 

Regards,
Berndt

( If my comments are accepted, provide "Kudos" as appreciation. If your request is answered/resolved, please click the "Accept as Solution" button. Thanks.)

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Message 4 of 9 ( Views: 212 )

Re: Post molding warpage

04/06/2018 3:05 AM

Thanks for your reply.

 

My worry is, component am dealing with has to be 3D meshed, in this case how do i transfer internal stress to other simulation software?

 

Best Regards,

Madhan.


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Message 5 of 9 ( Views: 203 )

Re: Post molding warpage

04/06/2018 4:56 AM

Hello @madhan_rm,

 

You can transfer the internal stress for 3D mesh to other analysis programs and now have some options available.

 

The below link may be helpful for understanding these options.

 

Moldflow: How to export the process induced material properties from a flow simulation

 

Please let me know if you have any questions.

 

Thanks,

Tetsuya

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Tetsuya
Support Specialist
Product Support
Autodesk, Inc.



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Message 6 of 9 ( Views: 200 )

Re: Post molding warpage

04/06/2018 7:15 AM

Hi @madhan_rm,

 

From the other point of view, it might be interesting to try annealing analysis with "viscoelasticity" function.

 

This is implemented only in Moldflow Insight 2018 (Beta) on Project Scandium 2018 by Autodesk Labs.

https://beta.autodesk.com/welcome/key/V8223H37LQSB5PHJ

 

(Sorry that it's my first thought since I don't try it yet.)

 

Regards,
Mayumi

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Mayumi O

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Message 7 of 9 ( Views: 194 )

Re: Post molding warpage

04/09/2018 5:08 AM

Hi,

Residual stress model (3D) shows the initial strain have calculated from Tg to room temperature. Please refer below;

Residual Stress Model.pngRegards,
EThaya


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Message 8 of 9 ( Views: 179 )

Re: Post molding warpage

04/09/2018 7:29 AM

Hi all,

Thanks all for your comments on this post.

 

I see this is a hot topic so I went and ask the developer for feedback. As I said, we do not know the cooling dynamics, from the ejection temperature to the room temperature, so it is not possible to iterate over it. Instead, we simulate the warp from ejection to room temperature in one single step.

 

Here I copy the statement of the developer: (sorry, I cannot copy the full text)

In the commercial code,  we do not calculate the transient shrinkage/warpage after ejection to room temperature. We just simplify the calculation from after-ejection to room temperature in one-step.

I hope it helps!

Cheers,

Javier


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Javier Jubierre

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