topic Re: GAIM - through nozzle in Moldflow Insight Forum

GAIM - through nozzle

Anonymous — Fri, 30 Apr 2021 11:51:56 GMT

For a gas injection through the nozzle as explained here:

Gas Injection Methods

is there a way to set this up automatically (without having to create a sprue)?

i.e. after setting the plastic injection point, how can I place the gas nozzle inline ?

Thanks!

cheers,

dave

Re: GAIM - through nozzle

bernor_mf — Fri, 07 May 2021 06:48:11 GMT

@Anonymous

Hi Dave,
there are different methods to inject gas, like the picture shows, through the nozzle, or with a local gas nozzle direct in to a position in the cavity.

If you intend to inject gas through the nozzle the use a full runner system is needed to consider the how melt and gas will travel.
It has one gas entrance.

If you want to simplify for some pre-studies, you could put injection location and gate entrance boundary condition on the same node.
Then it could use same controller for the gas entrance.
This then assume the melt and gas is balanced through the hot runner system.

The injection location will close end of injection/packing to avoid backflow.

Suggest you create a simplified model (midplane) to test what makes sense for the studies you want to do.

Hope this helps, somewhat.

Regards,
Berndt

Re: GAIM - through nozzle

Anonymous — Fri, 07 May 2021 16:04:07 GMT

Thanks for the advice Berndt!

I'm able to pick the same the same node for both the injection and gas entrance - so it's good now. 😅

Do you have a suggestion on how to increase the wall thickness?

I've been experimenting with delaying the gas start time - isn't it equivalent to increasing the velocity/pressure switchover % (by volume filled)?

Or perhaps cooler tool temperature, to encourage freezing faster?

Now I'm trying reducing the gas pressure, to slow down the gas bubble.

So many options...

Thanks again for the help.

cheers,

dave

Re: GAIM - through nozzle

bernor_mf — Mon, 10 May 2021 09:53:08 GMT

@Anonymous

Hi David,

well, putting the injection location and gas inlet direct on cavity will create a thinner thickness in that area.
Suggest to add a piece of the runner in the gate area.
It increases wall thickness close to gate in simulation.

From on-line help, about gas delay time:
"The gas delay time is the time from velocity/pressure switch-over to when injection of gas into the mold begins.
If you want the gas to be ejected immediately at the time of velocity/pressure switch-over, enter a delay time of zero."

You then could move your velocity/pressure switch-over, to control amount of melt going in to cavity, hence thickness.

Not sure where you need to increase thickness.
Usually it becomes thicker at end of gas bubble.

Cooling or a waiting time to build up a frozen layer could help.

Regards,

Berndt

Re: GAIM - through nozzle

Anonymous — Wed, 12 May 2021 07:10:27 GMT

Hi Berndt,

thank you again for your help and insight.

Good point with setting the delay time to zero - then I have one variable less to play with - can focus on the V/P switchover as you suggested.

I'm trying to create a hollow section, but need a certain wall thickness overall for structure. Currently the walls are very thin so just trying to increase it:

You're right - the area just after the injection/gas entry point did turn out quite thinner t:

I'm not too worried about it for now.

Is there a convenient way to measure this? I can make a cross-section and measure to "nearest node", but the arrow disappears as soon as I rotate to verify:

Thanks again and have a good day!

cheers,

dave

Re: GAIM - through nozzle

bernor_mf — Wed, 12 May 2021 08:33:27 GMT

Hi Dave,
thanks, happy to help. 😊

Pretty difficult to measure node to node when result plot is turned on.
Find that hard too.
Sometimes turning on mesh display for plot helps to navigate, and sort out how to measure.

To control thickness as such is difficult when coring out with gas.
As you might have noticed it is also shape dependent, as inner corner will have thinner thickness than outer corner.
A rounder shape will give a more uniform thickness.
Material melt viscosity also play a role.
As the melt viscosity increases, the gas channel wall thickness will increase.
As the melt temperature decreases, the viscosity increases, increasing the wall thickness.
Might be worth trying?

Regards,
Berndt

Re: GAIM - through nozzle

Anonymous — Sat, 15 May 2021 15:59:53 GMT

Hi Berndt,

Is it possible to show the mesh with the gas core result? Seems I can only activate one or the other.

Otherwise good tips on the wall thickness - more parameters to play with but I'm getting there!

Thanks again and have a nice weekend 😊

cheers,

dave

Re: GAIM - through nozzle

bernor_mf — Sun, 16 May 2021 12:00:36 GMT

Hi Dave,
there is a nice and useful script you could use, that comes with the software.
On the command line type: ExportGasCoreSTL
and click Go.
This command is for 3D mesh type and GAIM.

'@ This command will produce a new study (new_study(_x)) with the following
'@ The Geometry will be exported as defined in the original study
'@ The Elements wholly enclosed by gas will be removed
'@ An STL file of the gas core surface.

You could import the generate gas core stl-file to Synergy.
If needed create surface mesh on gas core stl-file.
You could add stl-file to cored out study file.

Hope this helps.
Regards,
Berndt

Re: GAIM - through nozzle

Anonymous — Sun, 16 May 2021 13:16:57 GMT

Hi Berndt,

That's a pretty cool script, it's definitely simpler versus this method I found create stl file

Since I'm using Creo, I use the first part of the instruction to make the fdx file, then use an online service to convert to an stl that I can import.

I tried your script - it does as it should and saves me the conversion step. The stl file opens fine on its own, but for some reason disappears when added to an assembly - more a problem with Creo than Moldflow though.

Thanks!

cheers,

dave

Re: GAIM - through nozzle

bernor_mf — Mon, 17 May 2021 06:51:38 GMT

Hi Dave,

the disappearing when importing to assembly could be a unit issue.

The STL file from ExportGasCoreSTL are in SI units, hence in meters.

If importing in mm, it will be very small, and "disappears".

When you import the STL-file to Creo, check if you could change units before actual import takes place,

from mm to m.

Maybe need to import separately first, and save in Creo native format , then add to assembly.

Regards,

Berndt

Re: GAIM - through nozzle

Anonymous — Mon, 17 May 2021 19:04:01 GMT

Kudos Berndt!

That was exactly it - I just scaled up the gas core by 1000 and voila - it appeared 😊

Thanks again and have a great day 👍

cheers,

dave

Re: GAIM - through nozzle

bernor_mf — Tue, 18 May 2021 05:51:07 GMT

Thanks, Dave!

Happy to help. 😊

Good to see that issues are resolved and you could move forward. 👍

Wish you a nice day.

Regards,

Berndt