Extrusion Blow Molding – Resin or Color Change: Suggested Purging Procedures

The following are suggested purging procedures for extrusion blow molding as it applies to resin or color change applications.

Changeover Procedure

  1. Maintain temperature and RPM settings for resident resin.
  2. Disconnect or shut-off auxiliary feeding equipment and thoroughly clean the hopper.
  3. Begin to empty barrel and, when resident resin is below the feed throat, introduce Appropriate Dyna-Purge grade for resident resin (1 to 2 times barrel capacity) into empty hopper or side port.
    Note: actual amount needed depends on machine conditions.
  4. If allowable, a reduction in head gap clearance should increase back pressure, allowing for improved results.
  5. Begin to purge. Short bursts of high agitation (RPMS) will loosen build-up. Subsequently slowing the speed or stopping the screw allows the purge to expand and then push out the loosened contamination. Continue to alternate this process until the purge is clean and free of contamination.
  6. Thoroughly clean the hopper and adjust temperature settings for your next production resin.
  7. Using your next production resin, flush out the remaining Dyna-Purge.
  8. Thoroughly clean the head surface to remove any contamination and, if applicable,
    install new screen pack and make adjustments to head clearance.
  9.  Start production run.

Safety First

Before performing any procedure, it is the machine operator’s responsibility to be aware of their company’s safety policy, to wear the appropriate personal protective equipment, and to make sure that only authorized personnel are in the area.


Important! The information presented herein, while not guaranteed, was prepared by competent technical personnel and is true to the best of our knowledge. NO WARRANTY OR GUARANTY, EXPRESS OR IMPLIED, IS MADE REGARDING PERFORMANCE, SUITABILITY OR OTHERWISE. This information is not intended to be all-inclusive as to the manner and conditions of use, handling or storage. Other factors may involve other or additional safety or performance considerations. While our technical personnel can respond to questions regarding safe handling and use procedures, safe handling and use remains the responsibility of the customer. No suggestions for use are intended as, and nothing herein shall be construed as, a recommendation to infringe any existing patents or to violate any Federal, State or local laws.

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