Fines in Material, BlackSpecs

[Joel JS]

Hello Everyone,

Been kinda quiet here lately, so hoping I can stir the pot! :D

We have this clear lens job that has about 20% fall out for black specs... and we don't see much improvement after pulling the screw and having it cleaned.

- Acrylic
- Hot sprue
- Virgin only

What I do notice that concerns me is the amount of fines that comes in the gaylord of virgin material,..... I wonder if the fines are causing the black specs,.... has anyone had luck with a machine to clean the fines, and/or other suggestions.

Thx,
Joel

[iautry1973]

Matsui has a loader that sucks out a good chunk of the fines. I know there are other systems that do that as well. Ok not sure I have a good answer, but here are some things that you may have looked at but may be a good list of things to look at:

Is this an issue only with this lot of material? Does this material get used in other clear jobs and if so do they have the same issue? Has the heated sprue been cleaned out as well? Other thoughts would be could it be caused by shear heat from to much back pressure or to high of an inj rate? Heats to high? If you purge the material after the screw/barrel is cleaned out does the material come out clear or black specs?

I also noticed it was fairly quite lately as well. Maybe someone needs to get a big oar out to stir the pot. I personally don't have a ton to say on here as I am in MIM and most of my issues are related to the oddities associated with the sludge we shoot LOL.

[daniele_66]

I'm also interested about a system for black spot. Please could you write some url where I can find some solution.
Thanks a lot in advance

[Joel JS]

Thank Iautry!.. Your ideas are duly noted.

Has anyone used a machine that sucks out the fines? ........ it's still just way too quiet here!

Joel

[iautry1973]

You are welcome. It has been awhile and I forgot we used these at ATK. They are from Conair. They worked OK, but not sure how they would work with your system. We had a large conveying system with silos. Didn't grab all of the fines, but most of it.

https://www.conairgroup.com/product/cyclone-dust-collector/

[rickbatey]

Try a dust remover from Matsui designed for regrind. BTW what is your shut down and start up procedures? That might also be a root cause. There are resins for medical molding that are much cleaner than standard resins but you’ll have to confirm if they’re cost effective. How are you loading the drier and press? How large is the drier? What temperature are you using to dry the resin? Desiccant drier I imagine?
Rick

[douginky]

Pelletron also makes several sizes for removal of fines, dust and streamers. Some can be mounted at feed throat.