Cleaning Screws
Cleaning Screws
Cleaning Screws
Introduction
When it comes to maintaining screw and
barrels, the most common question asked is,
What is the best method to purge and clean
our screws and barrels?
Figure 1
Figure 2
Hot gloves
Brass putty knife
Brass gauze
A round wire brush about the
diameter of the barrel bore mounted
on long rod
Stearic acid flake
Electric drill
Several cotton rags
Figure 4
Figure 3
Purging should continue until the extrudate
has completely transformed from the
processing resin to the purging resin.
Once the die has been completely purged,
the screw rotation can be completely
stopped so that the die on the extruder or the
endcap on the injection molding machine
can be removed and the end of the screw can
be exposed.
With the die or endcap
removed, the screw can be restarted and
rotated at about 10 rpm to allow the
remaining HDPE purging resin to be
pumped out of the remaining portion of the
screw.
Tools and Cleaning Materials (Figure 4)
The tools and cleaning materials needed to
pristine a screw and barrel are very few and
simple. They consist of the following:
Figure 5
Once the hoses, rotary union, and piping are
removed from the back of the extruder, the
screw extractor mechanism can be attached
to the extruder gearbox. Using the screw
extractor, the screw can be pushed down
most of the distance of the barrel. (See
Figure 6)
Figure 8
As the exposed portion of the screw has the
HDPE removed, then another 4 to 5 turns of
the screw can be pushed forward using the
screw extractor, and the cleaning process is
continued.
Once the large amounts of HDPE are
removed with the brass putty knife and wire
brush, the stearic acid should be sprinkled
onto the root of the hot screw, and the brass
gauze should be used to remove the
remaining HDPE residue. (See Figure 9)
Figure 6
The screw should now be pushed forward
until about 4 or 5 turns of the screw can be
exposed for cleaning. (See Figure 7)
Figure 9
Figure 7
Figure 10
Once the screw has been completely cleaned
it can be set aside (Figure 11) until the barrel
Figure 12
With the barrel temperatures still set at the
purging temperatures, the barrel is ready for
its cleaning process.
Figure 11
Figure 13
Figure 14
Once the brush/gauze assembly is inserted
into the bore of the barrel, the electric drill is
used to rotate the brush/gauze assembly in
and out of the barrel bore until the
brush/gauze assembly moves easily in and
out of the bore. It may be necessary to use
additional stearic acid before the bore
cleaning process is thoroughly completed.
Once the brush/gauze assembly is removed
from the barrel bore, a bundle of cotton rags
needs to be pushed back and forth the (See
Figure 15) length of the barrel bore to swab
Figure 15