The cleaning of a hot runner should always be carried out one step at a time in the correct order:
housekeeping, screw and barrel, manifold and finally tips.
Housekeeping
Always start from the beginning and it always starts with housekeeping; ensure hoppers, granulators and conveying
systems are immaculately clean. This should never be taken lightly especially when using purging compounds. The
faster results expected from a purging compound can be seriously hampered by reintroducing colour from poor
housekeeping.
Screw and Barrel
The screw and barrel are sometimes
mistaken as being clean when colour
changing hot runners because
purging the screw and barrel is done
at low and constant pressure and
low speed (Fig 2). This can give a
purging that looks clean yet can show
up in your mouldings as is depicted
in c, d and e (Fig 1). Aquapurge’s
mechanical purging compounds like
Barrel Blitz Universal that use the
natural compression of the screw to
clean can be effective to clean under
low pressure and speed conditions
especially when encountering colour
plate-out (Fig 2) or carbon.
Visit the Aquapurge Ltd website for more information on Tips for colour changing Hot Runners