[billy]

Anyone interested in starting a project to develop a Foam application to simulate the injection molding process (polymers) with the following capability:

- Two-phase flow (based on interFoam)
- Non-isothermal
- Compressible (?)
- Viscoelastic flow


Post here.

[hsieh]

Hi, Billy,

I am interested. What do you have in mind?

Pei

[n_sathya]

thanks billy for opening this topic.
just yesterday i expressed my interest in related topics and its good to see we have some interest in this.
in addition to the list of capabilities, i'd like to add the use of a 3D model.
hele-shaw approximation for 2.5d is reaching its limitation as part these days are bulkier.
if anyone is interested in taking this up, i have a paper that walks through implementing 3d flow simulation process.

[hsieh]

Hi, Sathya,

Could you please email me the paper?

pei

[billy]

Which paper is that?

[yeblod]

Sathya, I'd be interested in seeing that paper. I have some experience in this issue as I used to develop commercial code in this arena.

[n_sathya]

here is the reference: "three-dimensional finite element method for the filling simulation of injection molding"
Geng Tie, Li Dequn, Zhou Huamin.
Engineering with computers (2006) 21: 289-295

[billy]

In my opinion, this reference is closer to what we want since OpenFOAM uses the finite volume method.

"Numerical simulation of mold filling in injection molding using a three-dimensional finite volume approach"
CHANG Rong-Yeu & YANG Wen-Hsien
International journal for numerical methods in fluids
2001, vol. 37, no2, pp. 125-148

[yeblod]

Once upon a time I used to have access to the original papers, but now I'd have to pay for these citations. Here's a couple of *free* papers from guys at Moldex3d who've referenced Chang and Yang
http://w3.moldex3d.com/en/services/techpapers/0401.pdf
http://w3.moldex3d.com/en/services/techpapers/0402.pdf
(The second paper looks more useful)
Its time to consider what you want the system to deliver i.e. is it an academic research analysis tool or a practical molding tool. I know even now that there are a large number of small molders for whom the cost of Moldflow type system is too great. However when you start reaching into the realms of visoelasticity and compressibility (and temperature and pressure specific heats and so on..) you will find that you'll spend most of your time in materials characterisation and modelling and not in doing the fun stuff. But from my experiences in Hele-Shaw (2.5D) I'd suggest the following development strategy.

1. Steady-state isothermal, newtonian flow solution. I'm not an expert in OpenFOAM but this looks like an out of the box solution.

Now there's two options
2a. Isothermal, newtonian transient flow with flow front advancement. Most systems use FVM with a fractional volume of fill model modelling the frontal location - some are using ficticious liquids to model air evacuation. This is unlikely to model "jetting" - is this a requirement?
2b. Develop non-newtonian model for viscosity - keep it isothermal as the temperature terms can be loosley coupled later. Do you need viscoelasticity or just 3d viscous terms? In a practical sense viscoelastics terms may be locally significant near "gates" and other sharp discontinuities but in a "real" large component are they needed? From my past, the most significant impact of viscoelasticity is in calculating the free surface die swell in extrusion. Transport models that incorporate "wall slip" aka "plug flow" are notoriuosly difficult to handle.

3. Add the temperature terms to develop a non-isothermal flow. Again if you use compressibility and other temp,pressure dependent properties these will complicate the solution. Then consider temperature evolution and local velocities at the flow front - "fountain flow effect" - also used in fibre orientaton models. Then there is the issue of cooling and the buildup of frozen layers - I used to handle this with a generic no-flow temperature and a psuedo high newtonian viscosity but there are probably more recent ways of modelling this effect. Freezing has the effect of reducing the flow channel resulting in increased pressure drop.

4. Look a the effect of mold wall temperatures, cooling channels etc (I never quite got this far <grin>). We did enable the mold temps to be profiled over different areas, but just used a high heat transfer cooefficient to model the mold wall boundary condition.

Enjoy

[billy]

I added a new solver based on interFoam for non-isothermal flow. So it has a temperature transport equation and CrossWLF viscosity model.



I still don't know how to implement a boundary condition which acts as a wall for the polymer and acts as an outlet for air. Maybe there is a better approach to solve this. Maybe I can split the mesh and consider the interface an outlet. Any ideas?

[gdoura]

hi Billy,
i am interested nearly in the same problem than you: simulating the RTM process the thermomechanical problem.
i began since only 2 months, i need some bibliographical refrences that help me to understand problems involved and different models devoloped to solve that problem

[vikbergg]

Is there any updated information on this proposed project? Has anyone implemented it? If not, I'm interested in being part of this. Please let me know. Any information is appreciated!

[sradl]

Hello,

we are going to model hot melt extrusion of a polymer with OpenFOAM. However, I've not started yet but we definitely will start within this month. The flow will be non-isothermal with a high influence of dissipation on temperature and hence viscosity. So if anybody can give me a hint where to start in OF (Billy?) or want to help in the programming work is welcome.

Cheers
Stefan

[vaidy79]

Hi,

Anyupdates on this project, I'm interseted in being a part of this effort.

Any Information will be appreciated.

Regards
Vaidya

[francesco_b]

Hi All,

I'm trying to simulate molding injection in OpenFOAM, I've started playing with interFoam, then I've implemented the BC which Billy suggested and now I'm testing it. Next step is using Billy's moldFoam solver to include temperature.

If someone is interested or would like to give me any advice or suggestion about it will be a pleasure for me.

Thanks in advance

Francesco

[lzw2003]

Hi,

I have tried the molding injection application that added CorssWLF and temperature T.But it did not work correctly. I find the problem is the staintRate()(fvc::mag(grad(U_))).
Then I modified the nonNewtonianFoam (singlephase)and used CrossWLF to calculate a case . Surprisingly it worked well! That is to say the problem is in twophaseMixture.
Now I do not know where the problem is .
I will make it sure !

Does others have problems in CrossWLF ?

[awacs]

Originally Posted by lzw2003

Hi,

I have tried the molding injection application that added CorssWLF and temperature T.But it did not work correctly. I find the problem is the staintRate()(fvc::mag(grad(U_))).
Then I modified the nonNewtonianFoam (singlephase)and used CrossWLF to calculate a case . Surprisingly it worked well! That is to say the problem is in twophaseMixture.
Now I do not know where the problem is .
I will make it sure !

Does others have problems in CrossWLF ?

Dear zhiwei liu,
I have the same problem with you.
In order to simulate the filling process of injection molding,I added CrossWLF viscosity model and temperature equation to the interFoam solver.But during calculating,the courant number increased enormously after a few steps.Then the calculation stopped.

I have also tried to use the WLF model:
nu=nu0*exp(-C1*(T-Tr)/(C2+T-Tr))
It worked well in polymer filling simulation.

So,I think the problem is the staintRate(),just as you have mentioned above.
Have you solved this problem? Please give me some suggestions.

Thanks in advance.

Jitao Liu

[carlos]

Hello Foamers

i am trying to develop a solver for injection molding using interFoam considering two Newtonian fluids (polymer / air). The flow inside the cavity is assumed to be incompressible, unsteady and isothermal.

The difficult part for me is that i don't know how to specify the boundary conditions at the outlet. I want only air to leave the cavity. is that correct if i drill a hole(s) (at the opposite side of the polymer inlet) for air outlet?

Can anyone help me to solve this problem?

Thanks in advance.
Nurye

[ata]

Hi
Is there any updated information on this proposed project?
Has anyone implemented it?
I'm interested in being a part of this effort.I have done some works on viscoelastic fluids in OpenFOAM.
Please let me know. Any Information will be appreciated.
Best Regards

[KyleL]

Hello all,
I am very interested in the discussion about a moldFoam group.I would like to know if there has been any new development in this area and also would like to offer any assistance that I can as far as testing of proposed moldFOAM solver.

I have been in the Injection molding industry for 12 years now and would relish the idea of producing or helping advance the OpenFOAM project. The only solution I know of at this point is MOLDFLOW by autodesk or MOLD-3D by Moldex, both of which are very expensive and out of the financial reach of most small companies.

Thanks for your time in advance,
Kyle L