Injection Molding

[kitchener2011]

Does anybody knows about a software simulation for expanded polypropylene molding injection?
I am looking for this simulation because I am working in processing expanded polypropylene (injection molding)and I want to better estimate the cooling time.Or any method to estimate cooling time for this material
Thank you!

 

[Demon3]

I would think that's hard to impossible.

For a solid PP you know the heat required as it just depends on the amount of material.

For a foamed system it will depend on that plus the influence of the foam which insulates the material. You'd need to know the insulation effectiveness of the foam (depends on cell size). Also, the foam is not even throughout the sample. There should be a skin on the outside with no bubbles in it.

As a non-expert in cycle time I'd say that sounds hard to estimate from calculations. Far better to get input from the polymer manufacturer or someone with a lot of experience molding those materials.

Chris DeArmitt PhD FRSC CChem

 

[patprimmer]

The blowing agents normally reduce cycle time, but I don't know anyone who can predict by how much to any better accuracy than rule of thumb.

Regards
Pat
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[kitchener2011]

I know that there is simulation programs for plastic injection where you can choose the material. Does any one knows about such programs for expanded propyplene mold injection?

 

[patprimmer]

Blowing agents greatly increase the variables. I have been around a long time and seen most new developments. I have never seen a simulation for predicting cycle time with PP and blowing agents. Who would do the data preparation for the simulation. The PP supplyer or the blowing agent supplier.

It would vary by apparent SG so a lot of extra data would be required.

I am sure sometimes something like this happens and I don't see or hear about it, however in this case I doubt it for the reasons mentioned above.



Regards
Pat
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[ornerynorsk]

I did a PP blown part about 15 years ago. Due to necessary heavy cross section, which was the factor in deciding to go with blown, our cycle time actually increased significantly because if we pulled it out of the mold too soon the core of the part was still hot enough to continue activating residual blowing agent, and we ended up with puffy and distorted parts.

If memory serves, we were ultimately able to hold cycle time at pre-blowing agent parameters by throwing the part into cold water upon ejection. It was neither a grand nor ideal operation, right from the beginning, but we got it to work and learned a lot from it.

You might consult with a structural foam operation for some better insight.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

 

[kitchener2011]

I have the impression that I was misunderstood.
Molding expanded polypropylene (EPP) suppose (in short) to fill the cavity with beads(pellets) of expanded propylene by means of pressure in a fill gun, steaming the mold, cooling it and then ejecting the parts(automotive parts). My question is how can I optimise all these steps(simulation programs, statistical methods, rules of thumb, etc..)
Thanks!

 

[Demon3]

Models are good when they save time by predicting something. In your case, it will be quicker to learn by experimentation.

Chris DeArmitt PhD FRSC CChem

 

[kitchener2011]

The problem here is that I have projects were I have to design the process for a molded part with a required cycle time. The cooling time represent 70-80% from the total cycle time and other than experimenting different approaches I don't have any ideea if that cycle time can be attainable.