Oil droplet residue in vents, ABS

[Joel JS]

Hi to all,

Looking for ideas on this one!

We run a dishwasher panel with ABS that, after it runs for 1 hour, develops, what looks like tiny oil droplets in the vents (see picture.) If you stop this mold at say 30 min you will see a thin gassy film in the vents that easily wipes off.

I have tried 2 other ABSes that also did the same thing (one was a little better with less droplets)

I then lowered all barrel and dme heats. I aslo probed internally temps of hot manifold and drops and nozzle and eliminated some hot areas here. The barrel and all DMEs are now on the cool side of the melt range (470F).

Material in question is Lustran ABS 288., a high flow grade, high gloss grade......not sure much else at this point of this material.

I have never seen oily droplets like this on any other jobs....its possible I didn't look close enough as they are small. Have you guys seen this before? Any Ideas?

Thx! Joel

[chrisprocess]

Looks sounds like the High Gloss component in the material is bleeding out..

I might verify the vent depths and get rid of any rough surfaces like edm finishes etc.

Wet vs Dry material test might be worth a shot - so you can rule out wet material

Anything you can do to reduce shear might also help. Slower recovery, less back pressure, slower fill speed, 'soften' up rough edges in the tool if possible.
Definitely contact the material supplier I'm guessing they've seen this before!

[Joel JS]

Looks sounds like the High Gloss component in the material is bleeding out..

I might verify the vent depths and get rid of any rough surfaces like edm finishes etc.

Wet vs Dry material test might be worth a shot - so you can rule out wet material

Anything you can do to reduce shear might also help. Slower recovery, less back pressure, slower fill speed, 'soften' up rough edges in the tool if possible.
Definitely contact the material supplier I'm guessing they've seen this before!

Thx Chris Process.... will try an ABS with low gloss and see.

Joel

[chrisprocess]

Good luck!

Another thought is to come down on the clamp tonnage since your venting at parting line - may help open up those vents. (At least so you're not over clamping it)

Let us know what you find
:)

[rickbatey]

I think it’s something added to the resin to increase the melt flow. Most likely may mineral oil. Improving venting will more than likely just extend the tim between build up and cleaning.
Rick.