FILL TIME -RAM POSITION VS RAM SPEED

[ktr.mech]

Hello moldflow user ,

Could please any one explain about FILL TIME , ram position vs ram speed

i want to match result  , actual injection mold machine and moldflow result.

and meanwhile The actual injection machine in HOLDING SETTING  ram position, ram speed and injection pressure is there but in moldflow holding setting its not available, what is the reason?  

[bernor_mf]

Hi,

the fill time is a result of the injection, velocity phase.

Ram speed vs ram position setting gives the flow rate.

You need to set machine parameters, like screw diameter, to get this correct.

Pack/holding control is there.

Pressure vs time.

This set up is not in Filling control.

Hope this helps.

Regards,

Berndt

[PascalGosset · Accepted solution]

Hello,

Applying the real speed settings of a screw to a simulation is not easy.

Often, the compressibility of the material is poorly estimated.

Thus, in simulation, the filling ends too soon or too late.

Then, Moldflow does not always succeed to match your speed profile.

Look at the summary table. Adding intermediate results does not solve everything.

But in reality, the machines do not follow the requested speed profiles either.

If you want to make a comparison, copy the effective  screw speed curve.

Good luck...

[bernor_mf]

Hi Pascal,

thank you for the comment and sharing your experience.

In terms of compressibility : Modelling the nozzle and part of screw for runner system:

Have you tried that, to see the effect on compressibility?

I find it difficult to get the machine data for this.

Also, if having a mechanical filter in nozzle how that effects compressibility..

Regards,

Berndt

[PascalGosset]

Hello Berndt,

Effectively, when you make such comparisons, you have to take into account the material in the feeding system and in the machine nozzle.

Take a look this image. It's a good sample of what I often observe.

The 1st plot represents the Flow Rate in the press nozzle. Blue curve: reality; black curve: simulation.

At injection beginning, Moldflow did not succeed to match to the real speed (as I wrote previously).

Then, it ends the filling too soon:  at 3.8 s instead of 4.4 s.

I guess it is because of an underestimation of the compressibility.

The 2nd plot represents the Pressure in the press nozzle. Red curve: reality; black curve: simulation.

You can see I took into account the material in front of the screw, in the press nozzle, in the hot and the cold runners.

As often, the real pressure is clearly underestimated: 25% (920 bars instead of 1230 bars).

However, the material injected is classified Gold (Hostaform C9021 from Celanese).

An underestimation of the compressibility can also explain this defect.

If you try to compare real speed and pressure to simulations, you will probably meet these troubles.

[bernor_mf]

Hello Pascal,

thank you for shedding light over this.

Much appreciated.

Beside compressibility effect on pressure, mechanical losses in machine to be considered.

To understand this pressure loss, which Moldflow does not take in to account yet, typically

an air shot is made at machine.

Regards,

Berndt

[bernor_mf]

Hi,

will be interesting to see how this works when released:

Simulation combined with the real world

Sounds a bit similar to Moldflow Plastics Expert, MPX.
MPX was a bit ahead way back then, and maybe market more matured now.

Some history notes:
K98
MOLDFLOW LAUNCHES PLASTICS XPERT (MPX)
K95
At K'95, Moldflow introduced a product called Intelligent Process Control.
IPC was intended to set up, then actually control an injection press using Moldflow's CAE data.

MPX import for Moldflow Insight is still there.

Ok, a little bit out of scope for this topic, but interesting as coupling of simulation and injection molding machine.

Regards,

Berndt