Pressure Drop Study in LCP

[brentb]

Accepted mold design with LCP calls for what would be horribly small sprue, runner, and nozzle orifice sizes if any other resin was being used. The LCP flow path size would make Bob Hatch (and many other Molders) cringe.
Say I have a job that is using half my available pressure to fill and pack the part, do I need to do a pressure drop study? I can't see it unless I am near pressure limited processing. I can't increase gate, runner sprue and orifice sizes anyway, since nasty things could happen.

I would like other opinions on this, remember it is LCP V...ra.

KOM

brent

[Suhas]

Hi Brent,

1. I would not do a full Pressure Drop study if you are no where being pressure limited.
2. I would only be concerned if you see degradation from shear or the parts not performing to the requirements. If the parts test out OK, you are good.
3. If possible, you should do a melt flow on the pellets and then the parts and see the difference.
4. I have also thought of a new idea as I was writing this: The degradation can be from the barrel heats, screw shear, etc. So when the machine is cycling, get ready with a clean purge plate, stop the machine and slowing purge the built shot on the purge plate and right way try to see if you can make the purge small enough to be pellet size. Do a Melt flow on this purge. So now, you have pellets (base line), purge (degradation in the barrel), parts (degradation in the runner and gate).

Hope this helps.

Suhas