I am often asked which method is the best way to purge. Unfortunately there are so many different types of compounds and applications that there no specific method which is best, but most procedures include the following aspects.
Preparation: One of the most important aspects of purging is the preparation. This includes obtaining and mixing your materials, acquiring the processing parameters, and reviewing the recommended procedures.
Initial Cleaning: The old material must be vacuumed and wiped out to avoid cross contamination.
Initial Purge: The purging material must be run through the machine to remove the old material from the barrel, screw, nozzle, and hot runner system.
Final Cleaning: A second cleaning operation is typically needed to clear out the purge form the hopper and material delivery system.
Final Purge: The final material is run through the barrel, screw, nozzle, and hot runner system to push out the purging compound.
Production: The last step involves getting the machine back into production mode while making acceptable product.
I understand there are many purging products which have specific requirements, but you will find these steps involved in most purging procedures you encounter.