Extrusion Sizer Design

[basenxuser]

Hi all,

Presently i am working on a polyolefin pipe extrusion vacuum sizer design. Let me eloborate the problem to get a proper guideline

1. Our die size is 5mm
2. Our sizer entry size is 5.5mm and exit size is 5.3mm

I am able to achieve the ID and OD of the requirement.

Problem:
I am getting a continuous dotted line on the outer surface of the pipe. no matter whatever processing tweaks i do, it persists.

Observation:
1. I observe that while the pipe is entering into the sizer, due to the vaccuum suck, some air is trapped around the profile of the tube ( since the parison size is smaller compared to die )
2. I believe the sizer should be smaller than the die size.Since the die should have the shrinkage added to it.

But my current situation is to manage a better sizer without changing the die..

Is there any hope to make this happen..Pleas guide me folks..

Thanks in advance..

 

[patprimmer]

Is the vacuum tank water filled.

Is there a rubber ring to act as a water seal. If so is its finish smooth and clean and uniform.

Regards
Pat
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[basenxuser]

Hi,

Sorry for the delayed reply..can you suggest me a design for simple sizer to achieve OD and ID?

 

[patprimmer]

A water filled vacuum tank with a rubber seal made from old inner tube and vacuum adjusted to pull the tube to size. It is really very simple.

Regards
Pat
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[basenxuser]

Hi pat,

Thanks for the reply. wish to share the success of my sizer design. As you said we do have a vacuum tank setup in our extruder. Actually the problem was the slight ovality in the sizer ID which has created the air gap in the vacuum tank. so came the dotted line on the surface of the extrudate.

Ovality gone..now things are fine..