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Active Member
rrindhe
Posts: 6
Registered: ‎01-27-2014

warpage which is occurring in post shrinkage

921 Views, 8 Replies
02-03-2014 09:14 PM

Warpage Problem to be shared with Autodesk People, they stated that this Warpage is occurring in post shrinkage. Moldflow does not show the Warpage which is taking place in post shrinkage. Except center warpage, all over warpage pattern is matching with Moldflow.

 

As per my experience, MoldFlow shows warpage which is occurring in post shrinkage also.

I would like to confirm from all experts if my statement is True. Please revert back.

 

Problem:-

(please check attachment)

 

Except center warpage, all over warpage pattern is matching with Moldflow

 

As per Moldflow, center area is sagging towards Z Plus,

In Actual condition, part is sagging towards Z minus.

  At the time of ejection, part looks ok. After 24 hrs it is sagging by 3.0mm in Z minus direction.

Now Moldflow is helpless to find out the way to arrest the Warpage.

For the future products/analysis, there is no way to check if your part will warp in post shrinkage. It means there is no assurance in Moldflow results for Warpage.

 

History:-

Fusion mesh was used for analysis with 90.3% mesh match and 88.7% reciprocal.  We also used 3D mesh to cross-check.

 

Material used for analysis is different than actual, but it is equivalent. All results are matching with actual.

 

Cooling lines and feed systems used as per the mold design which are actual in mold.

 

Mold temperature, melt temperature and all boundary conditions are as per used for trial. Mold temperature is matching with actual within 5Degree Difference.

 

Carried out all fine tuning/ difference in boundary conditions to match with  practical conditions. Also cross-checked all boundary condition as per the trial parameters, but there is no significant result showing the Warpage pattern or values.

 

Trial was attended by Molding experts. They done lot of tryouts as they can do to improve the Warpage condition but every thing is useless.

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Contributor
KaindlJ
Posts: 20
Registered: ‎01-03-2014

Re: warpage which is occurring in post shrinkage

02-04-2014 05:09 AM in reply to: rrindhe

What material are you using in Moldflow, and does it have CRIMS data? Another consideration would be, how are you storing your parts? If they're stacked or are in a warm environment this could be normal and not really predictable by Moldflow unless you export the residual stresses and run them through Simulation Mechanical or similar software.

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Active Member
rrindhe
Posts: 6
Registered: ‎01-27-2014

Re: warpage which is occurring in post shrinkage

02-04-2014 05:19 AM in reply to: rrindhe

 Plastic raw material is PA6,30% Glass Fiber Filled:- Technyl C 218 V30 Natural used for analysis.

Working on AMI 2013.


rrindhe wrote:

Warpage Problem to be shared with Autodesk People, they stated that this Warpage is occurring in post shrinkage. Moldflow does not show the Warpage which is taking place in post shrinkage. Except center warpage, all over warpage pattern is matching with Moldflow.

 

As per my experience, MoldFlow shows warpage which is occurring in post shrinkage also.

I would like to confirm from all experts if my statement is True. Please revert back.

 

Problem:-

(please check attachment)

 

Except center warpage, all over warpage pattern is matching with Moldflow

 

As per Moldflow, center area is sagging towards Z Plus,

In Actual condition, part is sagging towards Z minus.

  At the time of ejection, part looks ok. After 24 hrs it is sagging by 3.0mm in Z minus direction.

Now Moldflow is helpless to find out the way to arrest the Warpage.

For the future products/analysis, there is no way to check if your part will warp in post shrinkage. It means there is no assurance in Moldflow results for Warpage.

 

History:-

Fusion mesh was used for analysis with 90.3% mesh match and 88.7% reciprocal.  We also used 3D mesh to cross-check.

 

Material used for analysis is different than actual, but it is equivalent. All results are matching with actual.

 

Cooling lines and feed systems used as per the mold design which are actual in mold.

 

Mold temperature, melt temperature and all boundary conditions are as per used for trial. Mold temperature is matching with actual within 5Degree Difference.

 

Carried out all fine tuning/ difference in boundary conditions to match with  practical conditions. Also cross-checked all boundary condition as per the trial parameters, but there is no significant result showing the Warpage pattern or values.

 

Trial was attended by Molding experts. They done lot of tryouts as they can do to improve the Warpage condition but every thing is useless.


 

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Active Member
rrindhe
Posts: 6
Registered: ‎01-27-2014

Re: warpage which is occurring in post shrinkage

02-04-2014 05:24 AM in reply to: KaindlJ
Material has CRIMS data.
you mean it is not possible with moldflow,
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Valued Contributor
HugoHerrera7042
Posts: 62
Registered: ‎07-07-2009

Re: warpage which is occurring in post shrinkage

02-05-2014 02:37 PM in reply to: rrindhe

Hi,

 

sounds like a very interesting problem.

 

It's important to acknowledge that warpage is a final consequence of maybe a bunch of different things. These things are the ones I would focus on to try and understand the real problem.

 

As for the MoldFlow duplication, per your comments, it looks that it is very complete, my 2 questions are:

1. Is the mold shrinkage you are taking out of your warpage animation (different in X, Y, Z) is the real one in the mold?

2. are the parts being measured on a free state? as to not needing anchor planes to simulate the measuring method?

 

that being said, I would first focus, since the material is PA6% GF, in the fiber orientation tensor result, look for molded-in-stress, residual stress result, material shear rate, frozen pressure. Then, I would focus on the material delivery system, to make sure the size is the optimal one for this tool (cycle time - time to reach ejection temperature, temperature plot, gate shearing, packing optimization based on this -part weight, etc). And on a different note, double check the drying conditions of the material.

 

Good luck!

Hugo Herrera

 

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Employee
franco.costa
Posts: 11
Registered: ‎07-25-2010

Re: warpage which is occurring in post shrinkage

02-05-2014 06:07 PM in reply to: rrindhe

Hi rrindhe,

 

whether Moldflow includes the warp which occurs during "post-shrinkage" depends on what you mean by "post shrinkage".

As others already noted, your analysis is using CRIMS. CRIMS shrinkage prediction in based on measured shrinkage values which are measured on moldings 7 days after they were molded. So yes, CRIMS will include the effect of gradual shrinkage which may occur due to slow post-molding crystallization or relaxation of stresses.

 

Regarding the center warpage being in either the positive or negative z-direction, it sounds like the outer frame of your part is shrinking more than the central arms. This is to be expected if it is center gated, due to better packing in the centre. If this is the case, the center will pop either up or down. (If you take a molded part and push the center up, are you able to pop the part into the opposite warpage shape?). Whether the free warp goes up or down might depend on some subtle differences, such as the way the parts are stacked after molding.

 

The good news is that regardless of deflection direction, using Moldflow should be able to help you minimize the differences in shrinkage between the outer rim and the central arms. It may be that decreasing the packing pressure towards the end of the packing phase will allow the center shrinkage to be a little higher (closer to the shrinkage in the outer rim) and thus reduce the amount of center deflection.

 

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Active Member
rrindhe
Posts: 6
Registered: ‎01-27-2014

Re: warpage which is occurring in post shrinkage

02-05-2014 10:23 PM in reply to: HugoHerrera7042
Hi Hugo

Thank for contributing your experience.

I have put the image just for reference.

Actually, we have considered isotropic shrinkage for making the mold. Also checked results in Moldflow with isotropic shrinkage, without shrinkage results but Moldflow is not showing this warpage trend.

For the second question- you can see the warpage visually. The Warpage checked in Moldflow with anchor plane and it is same.


Thank you
Rajendra Rindhe
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Active Member
rrindhe
Posts: 6
Registered: ‎01-27-2014

Re: warpage which is occurring in post shrinkage

02-05-2014 10:33 PM in reply to: franco.costa
Hi franco

Thank you for your reply.

As per your first statement, are there various types of post shrinkage?. For my case I have mentioned that my part is taking warped shape after 24 Hrs.

You are saying that Moldflow shows the results including post shrinkage.

As I have mentioned that Material Is PA6 30% glass fiber filled which will not pop (buckle, as per my knowledge). During the trial we kept 10 kg weight for 10 min at the centre area in opposite direction of warpage to restrict the warpage, this part also showing warpage but some lower value.
I had done some iteration with lower packing pressure and time but Moldflow is not showing any difference in centre warp. We have produced part with lower and higher part weight but warpage trend is same.

Thank You
Rajendra Rindhe

DISCLAIMER: The content of this e-mail is confidential and intended solely for the use of the addressee. The text of this email (including any attachments) may contain information, which is proprietary and/or confidential or privileged in nature belonging to Mutual Industries Limited and/or its associates/group companies/subsidiaries (Mutual Industries Ltd.). If you are not the addressee, or the person responsible for delivering it to the addressee, any disclosure, copying, distribution or any action taken or omitted to be taken in reliance on it is prohibited and may be unlawful. If you have received this e-mail by an addressing or transmission error, please notify the sender and remove this communication entirely from your system. The recipient acknowledges that Mutual Industries Limited may be unable to exercise control or ensure or guarantee the integrity of the text of the email message and the text is not warranted as to completeness and accuracy. The recipient acknowledges that the views contained in the email message are those of the sender and may not necessarily reflect those of Mutual Industries Ltd. WARNING: Computer viruses can be transmitted via email. The recipient should check & scan this email and any attachments for the presence of viruses. The company accepts no liability for any damage caused by any virus transmitted by this email. Thank you.
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Employee
franco.costa
Posts: 11
Registered: ‎07-25-2010

Re: warpage which is occurring in post shrinkage

02-06-2014 04:38 PM in reply to: rrindhe

Hello Rajendra,

 

post-molding shrinkage is definitely included in the Moldflow warp calculation if you are using CRIMS. As I explained the CRIMS models is based on shrinkage measurements taken 7 days after molding.

If someone told you that Moldflow does not include the effect of post-shrinkage, it might be because they had a different idea about the meaning of the words post-shrinkage.

When some people use that term, they might mean a change in dimensions which occurs during a subsequent heating phase (such as paint baking). If the part is heated up again, it is possible that some stress relaxation process or crystal morphology changes occur, which results in some change in shrinkage which is not recovered when the part cools back down to room temperature. I would call this an annealing process. This effect is not included in a Moldflow warp analysis.

 

best regards


Franco

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