Shutoff Nozzles

[zshupe]

We are having issues with CP Pryme (N66, high glass filled) drooling. The drool is so excessive, we constantly get short shots from this 'mega cold slug' landing in our gates. I used to think the issue was a worn barrel, however I have recently shot this material in another, newer, press and have had the same issues. I have dropped melt temp to the point of no-melt (still drooled with no melt) and tried many combinations of melt temp and back pressure, nothing seems to work.

I recently ordered a cheap ~$200 mechanical shutoff nozzle tip. Although it didn't completely shutoff during recovery, it was enough resistance to stop the drooling. It worked amazingly until the 3rd run when it completely stopped shutting off (yes I got the hardened version).

I am now looking for a shutoff nozzle body; whether it be pneumatically or mechanically actuated. Do you guys have any experience with these? Anything else you would recommend I try to deal with the drool before going this route? I am worried about contamination when changing jobs, seems like a shutoff nozzle body will have a lot of areas for material to hang up.

Thanks!
EDIT: We also have a throughput of material through our dryers of 10 hours, and moisture checks show the material is plently dry.

[rickbatey]

The best I've used is Herzog. Not cheap but OEM on many brands of IMM's. You should use the air actuated version as air leaks are easy to repair but the oil units can start a fire when they leak. Used them in a plant that ran interior parts, low gloss, molded in color w/o painting. No issues with color bleeding out after color changes. They make them for highly filled resins too.
Rick.

[zshupe]

Thanks for the input! I'll see if I can convince mgmt to invest in that, sadly I think it will be worth more than this old machine I'm on, haha.
Any other methods you have used to deal with excessive drooling? I'm using a smaller sized RT tip, low nozzle and front barrel temps (bottom of material spec), I'm on the lower end of backpressure, and the process is almost screw dependent to keep dwell time down.

[chrisprocess]

I'm guessing you already tried increasing decompression after screw recovery? No luck?

[TWood]

Thanks for the input! I'll see if I can convince mgmt to invest in that, sadly I think it will be worth more than this old machine I'm on, haha.
Any other methods you have used to deal with excessive drooling? I'm using a smaller sized RT tip, low nozzle and front barrel temps (bottom of material spec), I'm on the lower end of backpressure, and the process is almost screw dependent to keep dwell time down.

Before you go to the expense of a shutoff nozzle, you may want to try this, it has worked well for me in the past to prevent drooling of LCP's: http://molderschoice.com/catalog-2016/Page%2021%20E%20UNIVERSAL%20TIP.pdf