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Problems with GAS

10 REPLIES 10
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Message 1 of 11
biricio
669 Views, 10 Replies

Problems with GAS

Hi, I have to fill a simple hull with the gas (only the contour).
However the gas doesn't follow the path (overflow well beam) and he stops before. Why?!?

Thanks a lot
10 REPLIES 10
Message 2 of 11
DimitarV
in reply to: biricio

This happens when the gas pin is placed at the end of fill, which is almost the case here.
The key is to move the gate closer to the gas pin or vice versa, thus allowing the gas to penetrate in the flow channel near to where the injection begins and then continue to displace the material in front of it until the cavity is filled 100%, then continue packing.

You will need to experiment with your short shot volume, the delay time and gas pressure in order to optimize the process, i.e. avoiding blow outs, fingering, etc (see picture).

Hope this helps,
Dimitre
Message 3 of 11
biricio
in reply to: biricio

Thanks DimitarV for the help.

I have followed your indications.
When I put the &volume filled at 85% or 90%, MPI it stops and signals me an error. How do I do?!?

In addition, the time increases so much after the phase of V/P.

Thanks
Message 4 of 11
nordhb
in reply to: biricio

Hi,
the basic reason is that melt does not reach the node where you want to inject gas.
Gas is injected in cavity with no effect on melt.

After switchover, the melt has not reached the node where you want to inject gas:
the packing is 0 time and 0 pressure, so what you see is melt decompression, which makes time long.
And the decompression of melt does not reach gas injection node, resulting in the error.

The recommendations from DimitirV is a good starting point, and still valid for what you see.

What I suggest is in that direction too:
Make sure that melt will reach the gas injection node either in filling phase, or a packing phase,
by moving gas inlet or injection location or change process settings.

So to get some initial results, fill the cavity, switchover automatically, and pack until cavity is filled.

The gas delay time is the time from velocity/pressure switch-over to when injection of gas into the mold begins.
If you want to inject the gas to be immediately at the time of velocity/pressure switch-over,
enter a delay time of zero.

Regards,
Berndt


Berndt Nordh
Message 5 of 11
biricio
in reply to: biricio

Hi.
If I have understood well, the only solution is to move the gas inlet or injection location. Correct?

Because if I change the process settings hardly change something. I have only to move the gas inlet or injection location.
Now, I try.
Thanks
Message 6 of 11
biricio
in reply to: biricio

The situation is now improved (see image).
But I would want the gas followed the perimeter instead now he stops.
Message 7 of 11
DimitarV
in reply to: biricio

After looking at your images again I think you may also have geometry issues:

First of all get rid of the 1d elements and use only the 3D mesh.

Modify the part by adding a flow channel on the inside perimeter edge (chamfer or round bead). The gas likes to form an oval X-sec coring, and trying to core a somewhat thin rectangular wall is not the best approach.

Add radii at the four inside corners - the gas takes the path of the least resistance when makes turns (the inside corner). Adding radii there will prevent thinning down the walls.

Regards,
Dimitre
Message 8 of 11
biricio
in reply to: biricio

Hi, I've modified the geometry and ri-launched the analysis. Later I tell you.

I ask you a thing.
If I increase the time and the pressure (in the Gas Pressure Controller Settings) it changes something.
For example: I increase the pressure up to 10MPa. Does the gas filling improve?

Thanks
Message 9 of 11
biricio
in reply to: biricio

Hi, this is the result with the upgrade model.
The situation is improved (see image) but the gas doesn't make the whole perimeter.
What must I do?

thanks
Message 10 of 11
DimitarV
in reply to: biricio

Reduce you shot size (V/P switch-over).
Place the gas pin into the chamfered edge (gas channel).
Continue optimizing the process... delay time, gas pressures, time...
You may also consider thinning down the other walls to reduce fingering.
Keep the two gas channels apart, i.e. eliminate the chamfer at the end of fill for a short distance. You may need to adjust this later on depending on how far the gas will go, but don't try to have a one continuous cored out section all around.
Message 11 of 11
MOLDES-2010
in reply to: biricio

Hi, please help me, I am peruvian and for me not easy speak or write english, but I will try ok.
I am new user in it program, but need make design gas, it in midplane or 3d, also only put gas input or inlet in node, not is necesary desing the path for run the gas, also tell me the parameters, check please my model of example.
Very thanks for help me.
Regards

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