Injection Molding – Cold Runner – Resin or Color Change: Suggested Purging Procedures

The following are suggested purging procedures for injection molding – cold runner as it applies to resin or color change applications.

Changeover Procedure

  1. Maintain temperature and RPM settings for resident resin.
  2. Retract injection unit from mold, leaving ample room for purge to exit nozzle.
  3. Disconnect or shut-off auxiliary feeding equipment and thoroughly clean material feed system, ensuring all components including blenders, hoppers, loaders, filters, magnets, hoses, and drain ports are cleaned.
  4. Empty barrel and screw of the resident resin.
  5. Introduce Dyna-Purge (1 to 2 times barrel capacity) into empty hopper or side port. Note: actual amount needed depends on machine conditions.
  6. Increase the back pressure to the maximum safe level and, with the screw in the forward position, begin to purge. Note: If unable to purge with the screw in the forward position, set machine shot size between 50% and maximum allowable setting.
  7. Continue to purge until the compound flushed out of the machine is clean.
  8. Reduce back pressure and run 2 – 4 high velocity short shots to clean the check ring.
  9. Thoroughly clean the hopper and adjust temperature and machine settings for your next production resin.
  10. With the screw in the forward position, introduce your next production resin and flush out the remaining Dyna-Purge. Note: If unable to purge with the screw in the forward position, set machine shot size between 50% and maximum allowable setting.
  11. Thoroughly clean machine nozzle and sprue bushing to remove any contamination. Caution: wear the appropriate personal protective equipment.
  12. Move injection unit forward to make contact with mold sprue bushing.
  13. 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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