Sanity check

[jnewmanco1]

I sampled a mold the other day that had just returned from having the cores and cavities coated with some sort of micro coating in order to tweak some dimensional issues. The project engineer tells me about the coating and said "the coating should let you fill the parts easier". I asked why he thinks that and he said it was just something in the literature of the coating material. My contention is that the coating should not have any effect on the filling speeds, times, or pressures because of the fountain flow behavior of the plastic and how it is laid down during injection. I do not think he believed me.

[Suhas]

Hi,
What a fantastic answer! You are ABSOLUTELY right. Fountain flow!
Suhas

[rickbatey]

While you are correct, many of the DLC state easier fill due to reduced surface tensions/friction. I imagine that it might be measurable when shooting highly filled resins or hard to fill cavities. We have been looking to coat several molds for release, filling issues, and even to provide contrast for vision system confirmation of inserts loaded.
Rick.

[brentb]

Then there is gravity during fill!

KOM

brent

[JayDub]

While you are correct, many of the DLC state easier fill due to reduced surface tensions/friction. I imagine that it might be measurable when shooting highly filled resins or hard to fill cavities. We have been looking to coat several molds for release, filling issues, and even to provide contrast for vision system confirmation of inserts loaded.
Rick.

Rick:
In general, resin is going to freeze – and stick - as soon as it hits the mold surface, so friction/surface tension is only important within the resin, not at the resin/mold interface. If the friction at the mold surface was reduced to the point it affected that “stickiness”, it seems to me it would allow flow discontinuities with resulting cosmetic defects something like shear splay or jetting. [This is more of an educated guess than hard knowledge, though, so if anybody has good experience, I’m open to correction.]

[rickbatey]

I understand but there is tiger striping or slip/stick as the Germans call it though it doesn't resemble splay but is a visual defect (from my experience).
I quoted the coating folks; I didn't say they were right but I'm not sure I'd call them 100% wrong either. Many times the truth is an amalgam of at least two opposing views.
Brent-funny you mention gravity. Many years ago I ran an eight cavity textile cone mold. Four parts tall in two rows. We had issue with cycle time waiting for top parts to clear mold. All sides of mood were drilled and had full clamping slots. Old tech stated parts would now shoot out into tie bars. I told him they didn't shoot up and down now!? We rolled mold over, restarted, and earned about 6 seconds for our trouble!!
KOM. Rick.

[moldptc]

they say it helps...but I see no real world measurement that backs it up...maybe off pack...it usually helps in Ejection..best I seen it do