Hot runner balance evaluations

[maruggi2008]

Hello,

i have analyzed a complex hot runner (144 cavity), and the main requirement of my customer was to evaluate possible unbalance. 

The customer did the hot runner and after that, he compared the numerical and sperimental results.

The comparison IS NOT GOOD.

I know that the reason can be numerous but i think that one of the main is that in the real hot runner (in particular with very short cycle time: 2-3 seconds like this) THE TEMPERATURE IN THE HOT RUNNER AT THE BEGINNING OF THE CYCLE IS NOT UNIFORM BECAUSE OF SHEAR HEATING EFFECTS COMBINED WITH HOT RUNNER GEOMETRY.

SO MY QUESTION IS: IT IS POSSIBLE TO CONSIDER THE UNEVEN MELT TEMPERATURE, DUE TO THE SHEAR HEATING EFFECT, THAT IS PRESENT, AT THE BEGINNING OF THE MOLDING CYCLE, IN THE HOT RUNNERS WITH SHORT CYCLE TIME?

IN NORMAL FILL ANALYSIS THE MELT TEMPERATURE AT THE BEGINING OF THE CYCLE IS PERFECTLY UNIFORM AND THIS IS A BIG SEMPLIFICATION, IN THIS WAY WE SIMULATE THE MOLD STARTING AND NOT WHAT HAPPEN WHEN THE HOT RUNEER REACH THE STEADY STATE!!!

Thanks in advance

Marco Salvador

[madhukeshwart]

1.  when running analysis with multiple cavities like 144 cavity. surely there will be difference in temperature of different cavities due to shear imbalance 

2. If temperature variation is <10 deg C, there will not any any issues 

3. 'THE TEMPERATURE IN THE HOT RUNNER AT THE BEGINNING OF THE CYCLE IS NOT UNIFORM'.

it will be the beginning only   & may be after couple of shots it becomes stable and uniform. 

[timothy_vanast]

Hello Marco,

Quick question for you: Is the hot runner system modeled in beams or 3D tetras?

Thanks,
Tim

[mppkumar]

Hi @maruggi2008

Is it possible for you share the hot runner layout?

yes, you can change the melt temperature by changing the outer heater temperature locally as shown in the image (you should know the temperature locally on those hot runner regions)

Meltflipper concept used in hot runners to avoid the shear induced imbalances, refer the below link

http://www.beaumontinc.com/meltflipper/meltflipper-options/opti-flo-hot-runner/

[maruggi2008]

3D.

I'd like to import the initial temperature of each node of the Hot runner from a previous analysis. 

Is it possible?