posted January 20, 2003 10:59 PM               

I need your help regarding our extruded acrylic sheets (2ft x 4ft size).

We use a downstream single screw extruder and the sheet output is fine. After some time, we discovered the acrylic sheets that had been stacked flatly had warped.

I am wondering if moisture had anything to do with the warping - or is there something wrong with the extrusion process.

Our practice is to wrap the sheets (in 20pcs) with 2 layers of thick kraft paper, as soon as the sheets come out of the extruder.

The sheets are stored in an enlosed warehouse with ambient temperature.

Thanks,
Allen

posted January 21, 2003 05:02 AM               

I don't think your problem is being caused by moisture- My guess is the tempatures you're running on your roll stack.

What temps, linespeed, chill roll diameter and configuration of chill rolls are you using?

posted January 23, 2003 12:09 PM               

In addition to checking the roll-stack temps also check the material. Prehaps somthing there has changed. (Such as too much regrind, slightly different formula, prehaps wrong grade.)

Good luck and let us know!

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Brian And Elizabeth Richard

posted June 17, 2003 09:24 PM               

Is the warping threw the machine direction?
Try the old school way:
Fans, Fans, Fans.........

Throw a fan underneath the sheetline and see what happens. Or above it.

You stated you packaged the product in 20
sheets/Kraft.
Kraft paper holds alot of heat in, heat = moister. You might want to let the skids
of product breath for a while, they could
hold heat for many days.

Most acrylic is so stiff the memory would be comming from the roll nips.
Line tension is another problem.
Streching the piss out of it is easy to do,
especially on heavy quage.

Do you run your roll process water on a chiller system?