posted December 05, 2001 02:15 AM            

Stray air currents of cooler air (than the
extrusion area ambient temp) can upset
some barrel zone controllers- causing them
to overshoot their set point. This gives a
change in output.It's rare that this would
happen, but not unknown.
And of course, blown film processors could
find stray air currents upsetting their
bubble stability.

posted December 07, 2001 06:42 PM            

Thanks for your reply, the surging problem that I was dealing with has mysteriously disappeared. I think I had it down to two factors, either a material change, or the fact that we added a chiller to cool throat temp, being an experienced extruder operator has taught me most of what I know, have you heard of Griff extrusion seminars? I attended one this year, but I would appreciate it if anyone could recommend any good books dealing with general extrusion process, single screw process troubleshooting etc.

posted December 08, 2001 02:51 PM            

Allan is very good with the practical aspects of extruders- I organized two seminars for him, here in New Zealand in August.

I would strongly recommend that you join the nearest SPE section to you (if you are not already a member)

As far as books go:

Film Extrusion Manual- Process,Materials,Properties
tappi press 1992

the SPE guide on
Extrusion Technology & Troubleshooting
spe 2001

Extrusion Coating Manual 4th Ed
tappi press 1999

The Dynisco Extrusion Processors Handbook
dynisco corp

Extrusion Solutions- the SPE Extrusion
Division NewsLetter compilation is excellent too

(Dynisco very generously donated copies
of this last one to give to attendees, I
think if you contact your Dynisco Rep you'll be able to buy one)
The first and third choices are available
from www.tappi.org - SPE's web addy is www.4spe.org
Don't be put off by the titles- they contain lots of general information-
what sort of extrusion are you involved with?

posted December 08, 2001 04:11 PM            

I've found that with PS the optimum feed throat temp is 38-45C. If you're chilling
the throat, you could cause moisture
problems from condensation- what material/s?
were causing you grief?
email me at Evros_Extrusion@xtra.co.nz if you
prefer.

posted November 17, 2010 12:39 AM            

Blown Film- The Plastic Bag Company

Cast Film- Ristrom Packaging