Injection Molding – Hot Runner Systems – Resin or Color Change Mold Open: Suggested Purging Procedures

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

Step 1: Procedure for Barrel and Screw

  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.
    Note: if necessary, reduce back pressure and run 2 – 4 short high velocity shots to clean the check ring.
  8. Thoroughly clean machine nozzle and sprue bushing to remove any contamination. Caution: wear the appropriate personal protective equipment.

Step 2: Procedure for Hot Runner System

  1. Place protective guard between mold halves to catch purge.
  2. Boost hot runner temps between 50°F (10°C) and 100°F (37°C) over set point.
    Caution: do not exceed recommended resin temperature range.
  3. Set shot size to between 50% and 75% of available shot.
  4. Move injection unit forward to make contact with mold sprue bushing and start
    purging through hot runner.
  5. Continue to use Dyna-Purge until the purge is clean
  6. If the hot runner is valve gated you can open and close the gates individually to
    improve cleanliness and purging efficiency.
  7. Thoroughly clean the hopper and adjust temperature settings for your next
    production resin.
  8. Using your next production resin, flush out the remaining Dyna-Purge.
  9. Reset shot size for part.
  10. Check gates in mold for any blockage or drool and 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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