Extrusion Process Purging Procedures

Cleaning The Screw For Extrusion

When cleaning screws for extrusion, you need the right product and process for purging that’s fast-acting and thorough, but that also avoids costly damage. The wrong chemicals or tools, such as scrapers, are ruinous to screws and lead to serious production problems.

Use the appropriate grade of ASACLEAN for cleaning the screw for extrusion: a resin-based purging compound containing no harmful chemicals.

Purging Instructions For Cleaning The Screw For Extrusion

Follow these step-by-step instructions when using an ASACLEAN purging compound for cleaning screws during the extrusion process:

  1. Check that all zones are in the proper temperature range for the grade of ASACLEAN purging compound being used.
  2. Run the barrel empty. Wipe the hopper and feed throat.
  3. For unfilled grades of ASACLEAN, screens and dies may be left in place for purging (consult your ASACLEAN technical representative for mesh size and minimum die clearances required). If the machine is heavily contaminated and using our glass-filled grade (EX, PX and NF) – remove the screen pack to prevent plugging. Remove the die as well, if necessary.
  4. Feed one to two barrel capacities of ASACLEAN into the extruder.

    Note: Feed ASACLEAN into the barrel at a rate which allows for filling the flights of the screws as best as possible.

  5. Start purging at low screw speed; after material begins coming out from the head, increase the screw speed to the maximum safe level. Periodically, stop the screw and allow ASACLEAN to sit for a few minutes. Resume screw rotation at maximum screw speed.
  6. Continue until most of the ASACLEAN is purged from the barrel.
  7. Visually inspect the purge pile. The machine is clean and purging is complete when ASACLEAN coming from the machine is visually free of contamination.
  8. Repeat steps 4 through 7 if contaminants are still visible.
  9. Displace the ASACLEAN with the next resin, again, at the maximum safe screw speed.

Purging Process Tips For Cleaning The Screw For Extrusion

  • ASACLEAN mechanical grades do not depend on chemical reactions.
  • For maximum performance, ASACLEAN should not be diluted with other materials.
  • ASACLEAN is most effective when pressure within the barrel is maximized.

Temperature Ranges:

Grade °F °C
U 355-625* 180-330
EX 390-625* 200-330
UP 340-570 170-300
HP 340-570 170-300
SX 570-700 300-370
NH 355-625* 180-330
E 340-570 160-330
NC 355-625 180-330
PX2 535-790 280-420
PF 535-790 280-420
NF 355-625* 180-330
NB 355-625 180-330

*If processing between 330˚C-360˚C(625˚F-680˚F), local ventilation is required.

Tips Targeting Specific Areas Of The Extruder

The following techniques should be used after performing the above procedures.

Vented Barrels: Special procedures may be required to effectively clean extruders with vented barrels. If you cannot plug the vents, contact a Purging Process Expert at ASACLEAN to discuss the most appropriate method for your situation.

Dies: Raising the temperature of the die to approximately 15-30°C (30-55°F), while remaining within the service temperature range for both the resin and ASACLEAN grade being used, may help remove material deposits more quickly. If purging a heat-sensitive resin, do not exceed the safe processing temperature of the material. If using a highly polished or textured die, contact us before running the glass-filled ASACLEAN grade.

For further insight into our recommended purging procedures, visit the Purging Process Resource Center. This page offers you training videos, guidelines, technical documentation and more to help answer your purging compound questions.

Ready to learn even more about ASACLEAN purging compound products and services? Click here to schedule your free, 10-minute consultation with a Purging Process Expert at ASACLEAN.

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