Best Purging Compound

[Joel JS]

Hi,

What's everyone's best purging compound.

I have two applications that have given us a lot of trouble..... going from black PP to a light grey PC and we get black specs...... color change from black abs to a light beige abs and we get little black swirls by the gate.......both jobs are hot manifolds, I purged both jobs with Asaclean through the manifold at higher temps with poor results.

Looking for something that will work the first time.

Thanks - Joel

[iautry1973]

I have used Asaclean before with good results, but they have a ton of different grades. I know they have some specifically geared to hot runners etc. Might be good to send them an email and see what they suggest. Usually they will send you a free sample of whichever grade you think may be the best. I have used Dynapurge as well. Not bad either, but the boss didn't like the smell so out the door it went LOL.

[tbramel]

I have been doing tests recently with various brands. My best results so far have been with Purgex. Base my testing on a Hot Runner Valve Gated tool. The trials are with Black ABS to White ABS in a 240T, 490gr barrel. Shut down to producing good parts in White took 35 minutes and 2kg of Purgex.

[rickbatey]

How did you purge the manifold clean? There may be room to improve that part of the process. Changing colors is pretty easy until you throw in high and low heat resins into the mix. Plus a hard look at your scheduling will go a long way toward easing your color change pains!!
Rick.

[rickbatey]

BTW- What brand and type hot runner? Most companies don't tell the OEM supplier that they'll be changing colors and that will make all your hair turn gray!! The manifold has to be built with special attention to allow faster color changes.
Rick.

[CM8787]

I've used Ultrapurge when changing color on PET machines and changing from PET to Poly... Have not used it through a manifold though. I've heard it can void warranty. But it seems to work well on our lines that we add high amounts of color to. Cleans the screw pretty well.

Not sure how old your hot runner is, but I've noticed that older hot runners that have sharp corners in them can "catch" material, then it degrades and breaks loose..... Maybe it needs "softer" corners tooled inside?

[Joel JS]

BTW- What brand and type hot runner? Most companies don't tell the OEM supplier that they'll be changing colors and that will make all your hair turn gray!! The manifold has to be built with special attention to allow faster color changes.
Rick.

I don't know the brand, but it was made for color changes and the inner diameter smaller so as to help with color changes..... the only thing I am sure of is the fact that my machine is pressure limited on this job!

Thx - Joel

[Joel JS]

I have used Asaclean before with good results, but they have a ton of different grades. I know they have some specifically geared to hot runners etc. Might be good to send them an email and see what they suggest. Usually they will send you a free sample of whichever grade you think may be the best. I have used Dynapurge as well. Not bad either, but the boss didn't like the smell so out the door it went LOL.

Good advice..... will check it out.

thx - Joel

[Joel JS]

Thx for this valuable info. Will get a sample.

Joel :D

[JayDub]

color change from black abs to a light beige abs and we get little black swirls by the gate.......both jobs are hot manifolds,

Joel - does this tool have valve gates?

[rickbatey]

Exactly how do you purge this manifold? It could be there's room for improvement with your technique.
Rick.

[Joel JS]

Yes Jaydub, the tool does have valve gates.

[JayDub]

Yes Jaydub, the tool does have valve gates.

Try raising the manifold temps in the region of the gates by 10 or 15 F. Valve pins can interfere with material flow causing excess shear and burning that shows up as "smoke" off the gate. I haven't seen it in ABS (I don't think I've run ABS in a hot runner tool) but have seen it with PC and PSU.

[Joel JS]

Fyi - after doing a sampling of various purging compounds, Purgex worked the best so far, and was the cheapest. We are ordering 200 lbs to continue to try.

Joel