Wearing out of the barrel

[Jendalf]

Dear colleagues,

I have question:
Do You have experience with wearing out of the barrel? Or have You ever been forced to solve problems at parts by changing of the barrel?

I have large product from PP long glass fiber (mixing 60%LGF 1,5mm pellets with Nonfilled granulated PP at gravimeter to concentration 30% in (melt) part).
The glass content in the final product is ok but problem is in its distribution where clusters of non-dispergated glass fibers appear on the surface and comes thru the whole thickness of the part. Although the part is non visible, the nondistributed glass content in some area causes that the part is scrap and can´t be used in next process.

We´ve tested a lot. Even with the changing of the screw by new special one for glass content = no change. Than put back the old refurbished = no change. Closing ring is ok, no wearing.
The last thing that had never been changed is barrel itself.

But I dont want to misslead You in decission by this, just asking about experience and possible cause of poor distribution of glass content in the part


I´v contacted supplier as well as the other IM producers - yet without clear answer.

Thanks for reading/comments in advance.

J.

[Jendalf]

Photo attached. non-disperged LGF filament on the surface of the part

[joeprocess]

We run a long fiber Stainless Steel filled PC/ABS and sometimes we experience the same thing. The root cause to our issue is hang ups of the glass in and around the check ring and tip. Are you using a free floating check ring? How aggressive is the screw tip? Does it have areas that could collect tramp glass? With the long glass fiber material I would also look at increasing the gap between the check ring and the retaining ring to allow the material to flow through easier.

[Airwinghma]

Greetings;

You need to determine if you barrel is bad/worn by measuring the zones and match to the manf specs, lots of $ need to have data. Have you tried a mixing head or section of your screw?

Scott

[Suhas]

Hi J,
It looks like the plastic is have not melted sufficiently and so the glass and the plastic are staying together. When you inject it, the long glass fiber pellet/strand is getting smeared like you put butter on bread. Have you tried increasing the melt temps and mold temps?
Suhas

[rickbatey]

I'm with Suhas. Your not hot enough to disperse the glass fibers in the melt. You should use moderate back psi and a medium screw rpm. What's the shot volume compared to press and residence time? That might be another contributor to your problem. Have you measured the actual melt temperature?
Rick.