Today's KNOWLEDGE Share:Area under pressure curves

Today's KNOWLEDGE Share:

Area under pressure curves

If you are lucky to have pressure transducers in a cavity, as depicted in the figure, you will be able to observe different pressure curves decay over time during the packing phase.

Pressure drives the packing flow.

The longer you apply pressure the more material you push in the cavity.

So the Area under a pressure-time curve after packing starts and until pressure decays to ambient is a decent measure of how much melt you have pushed under a given transducer (assuming no back-flow and a proper frozen gate).

In the above picture, for instance, one can immediately say that the part will suffer from differential shrinkage, because the area under the three transducers is very different.

The part région near the first transducer close to the gate will be far more packed than the downstream region close to the transducer near the end of flow, showing the smallest area under the pressure curve.

Simulation will of course process all this information, with the help of PvT data, and translate that into a volumetric shrinkage distribution, showing less shrinkage near the gate and more at the end of flow.

By programming the packing pressure profile, one can minimize the difference in area under the three curves, which will lead to much more uniform packing and thus lower warpage in general.

I am not saying you need pressure transducers in your cavities, but studying the process this way, at least once, allows you to thoroughly understand how the molding process really works and how to make the best plastic parts.

Source:VITO LEO

Visit MY BLOG http://polymerguru.blogspot.com

 #plastics #injectionmolding #polymerindustry #polymerprocessing #polymers #polymerscience #transducers #shrinkage

#moldflow #moldex3D #sigmasoft #cadflow #simulation