- Extruders are the final machine of any scraps
- Because it is the last one, it should handle all
the problems the previous machines didn't solve.
- Special extruders can handle materials with some
contamination, moisture, etc. but don't relay on this
machine to solve the problems left behind by other machinery.
- The better quality flakes you feed the higher quality
- Pelletizing lines starting
from recycled materials need a chapter
by its own because the matter is pretty
complicated and not easy to explain
in a short way.
part of the line is the extruder.
are hundreds of companied around the
world manufacturing extruders with very
different characteristics but not many
somehow specialized for handling plastic
scraps, specially coming from washing
and separation lines.
- Extruders in this case MUST have
at least a venting unit, two better,
and a good mixing action while melting
- Single screw or twin ?
- This the main question for everybody
that doesn't have an answer yet.
- Of course it is easy to say a long
co-rotating twin screw extruder with
two venting makes a perfect job but,
on the other side, what about investment,
operating and maintenance costs ?
- Does a twin screw extruder build
pressure enough for effective filtration
- Should extruder have barrel
with anti-wearing steel coating or it's
a waste of money ?
- Which is the ratio power/Kg of single
versus twin screw extruders ?
- After you answer all these questions,
you got the right machine.
- Actually there is not a fix answer
to all this, meaning the choice is different
case by case because a lot depends on
the material you are dealing with, the
characteristic of the incoming material
and which quality you're trying to get
at the end or, in other words, the final
application of the pellet itself.
- Because of the high level of competition
in this field, technology is going forward
quite fast and new developments are
achieved very often.
- On the other side, do not expect
any miracle even from the very best
extruder around because if you feed
garbage, in the very best case, you
get a nice looking pellet that's still
garbage anyway and doesn't have any
- The meaning of this is to not complain
with the extruder manufacturer if your
pellet is not good as you expected but
check what you're feeding into first
and try to get a better quality chip
- As far as Polymer
Filtration, there is another dedicated
- Few words about die-face cutters
- A good die-head of both die-face
cutters and flat head for pelletizers
make a lot of difference in production
rate so this is another important choice
- Be careful !