Multiple Defects

[The Rookie]

Hi all! I hope all is well.

I was doing a study today to see the effect of process parameters on a “bubble” defect in PET tubes. I say “bubble” because I’m not sure that I can call it trapped gas or a void yet...It is too small to test with a heat gun to check for expansion or collapse.

Anyways....With pack and hold off, I noticed that a bubble was in the same direction as a flow mark. Not sure what to classify this mark as, but maybe one of you might :)

In one picture attached, I Sharpied over the bubble and traced the line I observed so it’s easier to see.

The same mark is on each tube, and I can actually feel it when I run my finger along the surface of the tube.

Any ideas on how to resolve this or what the cause might be?

[Joel JS]

Hey,

Without knowing all the juicy details, here's some thoughts:

What happens when you short it enough that you can see the short...... does it look like the melt flow will likely trap gas in this same location? (then they are likely bubbles)

Do "bubbles' get worse/bigger/more numerous with no pack pressure? (then they are voids)

Can you move them around with fill speed? (if so, then likely bubbles)

Joel