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Doubts in injection mould simulation (inlet conditions, temperature...)

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Old   March 22, 2015, 06:37
Default Doubts in injection mould simulation (inlet conditions, temperature...)
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Jordi Pina
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Hello!

I'm currently setting up a simulation of an injection mould process and I have some doubts.

My simulation uses the multiphase (polymer-air) and the solidification and melting models.

Let me expose my doubts:

1) What would be the appropiate boundary conditions for the inlet? In a mould process, there are three phases: filling, packing and cooling.

In the filling one the fluid is injected to the mould and I think that setting a velocity that makes the mould get filled in the desired filling time is the correct inlet condition.

However, once the mould is filled, no more polymer is injected. I think that I must control this defining a UDF in which, for example, I set that the fluid enters only from time 0 to time 2.

Next to the inlet, there is a packing function where a pressure is applied to the inlet and no more fluid enters to the cavity. How can I do this? I can't have a velocity_inlet and a pressure_inlet at the same time, can I? :S

2) During the packing phase, the polymer solidifies. I have tried to model this using the solidification and melting model. I have set that the polymer enters at 450 K, and that the walls (steel) are at 350 K. But unfortunately, when looking at the liquid fraction results, I don't see any solidification of the polymer.

I have stablished that the solidus and liquidus temperature are 415 K. However, I have no idea about the "Pure solvent melting heat" value. Where could I find this value for polycarbonate?

I will appreciate your help!
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Old   March 23, 2015, 02:52
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Paritosh Vasava
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My answers are based on my very brief experience with wax melting using the solidification-melting module in fluent.
  1. Velocity inlet or mass flow inlet is ok for inlets. For solidification you must also have a careful look at the pull velocity at the outlet. The pull velocities are only solved in the solid region.
  2. Pure solvent melting heat is the latent heat. In fluent it is J/Kg so mind the units.
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Old   March 23, 2015, 04:36
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Jordi Pina
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Dear Vasava,

first of all thanks for your reply.

I have succeed simulating solidification, even though there's no outlet in injection molding processes.

I have one question though, in fluent I can view the Liquid fraction contours. However, in CFD-Post I cannot view this results. I have selected to export them when settiing up the results... Does somebody know why I'm not seeing the liquid fraction results of the solidification model in CFD-Post?

See you!
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Old   March 23, 2015, 05:37
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Paritosh Vasava
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I tried with tutorial as well as my own case and I could see the 'mass fraction' without any additional setup. Unlike fluent in CFD-post (for solidification-melting cases) you will see only one option for 'mass fraction' and this is mass fraction of the fluid phase.
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Old   October 2, 2016, 04:17
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As5
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Hi, can anybody help me with solidification modelling of centrifugal casting...i took air as primary phase and molten metal as secondary, used mass flow inlet for type.. and also patched the fluid domain with initial metal volume fraction as 0.. still i am unable to get phase contour ..it shows 1 for the whole domain..and also while iteration vf-phase-2 is always zero... please help me!
this is the udf i am using for mass flow inlet
#include "udf.h"

DEFINE_PROFILE(inlet_mf,th,i)
{
face_t f;
real flow_time = CURRENT_TIME;
begin_f_loop(f,th)
{
if(flow_time <= 13)
F_PROFILE(f,th,i) = 0.05192308;


else
F_PROFILE(f,th,i) = 0.0;
}
end_f_loop(f,th);
}
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Old   October 3, 2016, 01:50
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Paritosh Vasava
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Can you upload your case somewhere? It is bit difficult for me to imagine based on this description.

Some pictures of results would also help.
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Old   October 3, 2016, 08:13
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This is the result, i am getting..phase 1 is metal[IMG]image hosting 10mb limit[/IMG]
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Old   October 3, 2016, 08:14
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My geometry
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