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How to get extrusion barrels aligned perfectly

by Editor123

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The operation of extrusion barrel alignment
is perhaps the most important aspect in the efficient operation of an
extrusion process. It matters little whether it’s an extruded sheet
process or a blown film line or the process of injection molding, it is
the relationship that exists between the two centers that are most
vital. These two centers are those of the gearbox’s thrust shaft and the
screw. If there is a misalignment it’s liable to cause both barrel wear
and screw wear. In case of excessive misalignment there maybe a
premature failure of the screw on account of fatigue. This fatigue is
caused due to the cyclic bending of the screw while it rotates inside
the barrel. There may also be significant system efficiency loss due to
the clearance between the barrel and the flights of the screw. The task
of extruder barrel alignment involves the positioning of the extruder
barrel in a way so that there is concentricity between the rotational
center of the gearbox thrust shaft and the mechanical center of the
barrel. This task is not the easiest to accomplish. There are three
methods of alignment of the extruder barrel to the gearbox thrust shaft.
These methods involve the use of a level, a borescope or a laser-based


A laser-based barrel alignment system results in improved accuracy
and the measurement and reporting is also faster. The accuracies
achieved are typically 0.001”. Though the system is expensive the
accuracy and speed makes it well worth the expenditure. The investment
will help in lower cost in replacement parts. The other advantages are
in reduced wear and tear on critical components, lower power consumption
and a reduction in time lost due to breakdowns. Laser alignment finds
ready use in the alignment of extrusion barrel due to the small value of
tolerance existing between the screw and the extruder barrel. Here, the
size of the extrusion screw is proportional to the importance of proper
alignment. Therefore, a misalignment of 0.060”on a 4” 24:1 screw will
require a force of more than 9000 lb on the screw in order to make it
conform to the misaligned barrel. This extra force will wear out the
screw and the barrel leading to premature failure. The result will be
apparent in terms of reduction in extruder output, line efficiency and
finally profits as well. Laser alignment of an extrusion line may take
up to 10 hours or less and this is a small investment in time. There are
technical establishments that use 2 axis laser alignment on existing
CNC as well as conventional machining centers. The collimated laser
system enables these companies to align their chucks and tool holders as
well in order to ensure perfect alignment. The use of laser alignment
system is critical to the production of extrusion die parts such as
distributors and funnel caps. Fare machine parts include Hex Head
Bushing and Pull Drive Roll. Similarly, there are precision parts for
Barmag, Reiter and Filteco.


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