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In Mold Constraint Simulation

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Lorena.Rivas
150 Aufrufe, 4 Antworten

In Mold Constraint Simulation

Good morning community and super experts @mason.myers @bernor_mf @PascalGosset 

 

I’ve reached a point where I’m unsure how to simulate, and I need your valuable insights and support.


Here’s the case:
The part is injected using PBT+ASA with 30% fiberglass. No mold components can be modified, and only process conditions are being adjusted to improve warpage.

Now, the client has this practice of letting the material cool for an extended period to minimize deformation as much as possible.

In my current scenario, I cannot figure out how to simulate the mold constraints affect the final result.
(To add complexity, the same model is being simulated on a different platform that includes "In Mold constraints considerations during Cooling" and predicts warpage similar to the real part)

 

I’ve reviewed many sources and am confident that this phenomenon can be simulated in Moldflow, but I’m unsure how to achieve it. (I already try DD meshes with differents warpage models, 3D with differents warpage models)


Does anyone know? It's something that we could simulate using fixed nodes?

For reference, see the images (part hidden due to confidentiality). On the left, total deflection is shown with an IPC of 11.5 seconds, and on the right, with an IPC of 70 seconds. Everything else is identical. Not big change.

 

LorenaRivas_0-1733758239325.png

I’d also like to apologize in advance if this is something "simple" to do and it’s slipping through my fingers.

 

Thank you in advance!

Lorena Rivas

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Nachricht 2 von 5
mason.myers
als Antwort auf: Lorena.Rivas

Hello @Lorena.Rivas!

 

Thank you for the kind words and I agree that @PascalGosset and @bernor_mf are super experts!

 

Moldflow should already take this into account by default.  If you extend IPC, Moldflow will assume that the part is held in the mold for a longer duration.

 

Did you isolate cause of warpage?  I am wondering if Orientation Effects and Differential Shrinkage are the leading cause of warpage.  If Differential Cooling has the least impact on warpage, extending the cooling time will have minimal impact.

 

Mason

Nachricht 3 von 5
Lorena.Rivas
als Antwort auf: mason.myers

Hi @mason.myers 

Yes, i did isolate... the main reason is orientation.
I already try ro reduce warpage doing: Changing Mold temperature (in theory higher is the best, but the customer do the opposite), Melt temperature, Pack profile (descending profile es the best), changing Injection velocity...
And that helps us with the trend... orientation effects are reduced.

BUT, at the moment to replicated the last injection made with the customer (with an specific process conditions) the results in Moldflow are 3 mm higher than the reality (and another CAE solution). So i'm trying to replicate and then work again with process variables to reduce warpage.

Material is Gold with Shrinkage, I also change the Fiber setup considered that it impact on the rheology of the polymer.. 

I'm inclined to say that the fiber orientation is the key... but I'm not sure how to replicate (or i'm working in circles and i don't see the path to follow)... so I thought that maybe the cooling conditions and the mold restrictions are impacting the fiber and the general warpage behavior.


 

Lorena Rivas

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Nachricht 4 von 5
mason.myers
als Antwort auf: Lorena.Rivas

Hello @Lorena.Rivas ,

 

The only other item that I think you could try would be a different fiber model?  We should already have preselected the best fiber model for you material however you can edit the material card to evaluate different fiber models.

 

Mason

Nachricht 5 von 5
bernor_mf
als Antwort auf: Lorena.Rivas

@Lorena.Rivas 

Hi Lorena,
thank you for your kind words.

 

I agree with @mason.myers  that extending IPC time is as keeping part in mold, and affects deflection and warpage.

 

The other result you refer to as:
"In Mold constraints considerations during Cooling" do you mean it as
"In-Mold Constraint Effect Displacement"
Total In-Mold Constraint Effect Displacement result shows total displacement under in-mold constrain considering deformation of the part inside the cavity.
The In-Mold Constraint Effect Displacement represents the deformation before ejecting.
Before the part is ejected, the deformation of warpage has been developed inside the mold.
The contact behavior will be induced between rigid mold and plastic part.
The part can’t shrink and warp freely at in-mold stage due to the rigid mold.
Besides, this contact behavior also induces the stress of part.

 

The In-Mold Constraint Effect Displacement represents the deformation before ejecting.
(Not a Moldflow result.)
(If close to real part deflection, then I am a bit puzzled... )
Cannot be directly compared with Moldflow Deflection, which is after ejection, cooled to room temperature.

 

Seems as you made a quite some runs to nail the underlying reason.

High fiber content, the fiber orientation is the driving force of the deflection.
If locked in with gate positions, hard to improve outcome, I would say.

Is the part controlled or measured as assembled or in a fixture?
Then this is another approach to review results:

Moldflow Insight Help | Adjust warp constraint positions according to the mold shrinkage allowance |...

(Also called assembly analysis.)

 

Have a look at:

Autodesk | Moldflow Summit 2024 - Session Recordings

VOLVO CARS
Shrinkage adjusted constraints: Volvo's solution to warpage challenges

 

I recently worked with a case with PP+20%GF, complete model, using this method.
Agreed quite well with measurements.

But ended up with a material change to reduce deflection.

 

Regards,
Berndt

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