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warpage

261 Views, 5 Replies
01/12/2018 3:53 PM

My question is about warpage after injection.

 

I have a study, dual domain, coll+fill+pack+warp, and the results for Moldflow show the correct deflection, but after injection, in reality, the deflection of the  part hapeens in other direction. This is because the thickness.After extraction the part continue to deflection but in other direction.

 

How to analyse this situation in Moldflow?

 

Material is PA6+50% GLASS FIBER.

 

 

 


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Message 1 of 5 ( Views: 261 )

Re: warpage

01/12/2018 4:55 PM

Hi Nilza,

 

there was a video presentation by Jim McGuire called "Net Shape Injection Molding Warpage Prediction-Based Mold Correction"

at the Autodesk University 2010 where Jim reported exactly this behavior that in DD Simulation warpage is reversed (sometimes).

 

Funny - his customers (BASF customers) knew that, but BASF doensn't knew about the effect.

 

The video is not available anymore (why?) - I have it on my HD though.
Maybe we get something managed.

 

Conclusion:

Since I saw the video I run every DD warpage simulation usually as a 3D Simulation also, just to ensure warpage goes in the same direction.

 

It might depend on your part - I guess it is sufficient for DD? So no "chunky" part?

With 50% GF a PA 6 should show to much warpage at all... What material do you have exactly?

Could you show the part (at least partly) so we get an idea of the problem?

 

Best regards

Harald


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Message 2 of 5 ( Views: 256 )

Re: warpage

01/25/2018 8:22 AM

@harald.goetz

 

Hi Harald,

I use similar approach, depending on part and material, and run DD and 3D to ensure warp trend in same direction, but magnitude might be different.

 

From your experience: if you find 3D warp opposite DD warp, which result do you hold as "right"?

 

And for 3D warp : do you use residual stress model or generic shrinkage model?

 

I am in a project where this appears, (PA66+35GF) and I probably need to run additional studies on different materials...

(Cannot share results.)

 

(Noticed AU presentations is from 2011 and forward, Would have been interesting to take part of AU 2010 video presentation by Jim McGuire called "Net Shape Injection Molding Warpage Prediction-Based Mold Correction")

 

Regards,

Berndt

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Message 3 of 5 ( Views: 204 )

Re: warpage

01/25/2018 8:47 AM

Hi Berndt,

 

the good thing for me: So far I did not see a single part the bends in the other direction...
So I can't help too much here.

 

I use now the residual stree model now with MRD- sometimes with RSC and "internal" values for it - which gives slightly
higher numbers in 3D warpage compared to MRD std.

 

I compared a lot of parts to older 3D simulations with the generic shrinkage model and usually it fits quite well.

When doing simulations for suppliers we often see strong deviations due to extrem slow filling.

Might be an issue for you? (If you use 4-7 s instead of 1,5s the deviations can be big :))

 

We also try just to use models with measured data (not the red ones) in the mechanical section.

 

Best regards

Harald


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Message 4 of 5 ( Views: 201 )

Re: warpage

01/25/2018 10:00 AM

Hi Harald,
thank you for prompt reply. Much appreciated. Smiley Happy

 

The fill time is relevant for part, 2s, in this case.

 

Material data seems to be the issue here.


The grade I used had measure mechanical properties and shrinkage data (CRIMS).
Pretty well characterized.

 

I got result for a similar grade. Same manufacturer, but better characterized material data.

A main difference is that the "suspicious" grade with opposite warp DD vs 3D has single point thermal properties.
And manufacturer provided data sets, so some unknowns regarding testing.

 

Same manufacturer, and grade tested by Moldflow Plastics Lab, and known and better data set:

The result shows same trend for DD and 3D warp where DD is some 1.5-2x higher in magnitude
(MRD and 3D warp residual stress model.)


3D warp: residual stress model vs DD warp is more symmetric in trends compared to 3D warp generic shrinkage model.

 

Conclusion:
If DD vs 3D warp shows opposite trends, check material data (too...). Even if measured mechanical properties and shrinkage data (CRIMS).
Run comparative simulation with equivalent material with well charachterized data set "gold quality" in all instances.

 

Will do a study using RSC-model, as a reference, how it affects warp magnitude.

 

Thanks!

 

Best Regards,
Berndt

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