Page 40 - 2010-2022 hose manufactureing ability and guide

Continuous Systems Extruded Tubes

To minimize handling inventory and cost For the tube extrusion process, an uncured
while maximizing throughput, the continuous rubber or thermoplastic compound ribbon or
process is common. This process combines pellets are fed into the extruder, through the
tubing, reinforcing, covering and vulcanization screw or auger with proper temperature controls
into a single process. To do this, the equipment and finally forced through a pair of metal dies,
is merely installed in a tandem fashion thereby where the cylindrical tube is formed. In the non-
enabling the hose material to flow uninterrupted continuous process, the tube is then cooled,
through each phase. Obviously the system lubricated to minimize tackiness, and stored in
controls are vitally important to minimize coils on pans, reels, or rigid mandrel poles.
downtime. Since the line output is generally Dimensional control is critical when the
limited by the reinforcement unit capacity, tube is being formed. Traditional techniques for
textile spiraling is the common approach. Also, maintaining dimensions include die selection,
since the vulcanization portion of the line is temperature, and line speed adjustments. The
often the most space consuming and expensive, latest innovations include a multi-axis laser
it is frequently not included. Hoses up to 2" ID with micrometer measuring the tube outer diameter
working-pressures up to 400 psi are the most with feedback to the extruder to provide size
probable candidates for this process. Flexible control. Ultrasonic devices, that can measure
mandrel or non-mandrel methods can be tube ID and OD, are also available. Figure 2-6
accommodated on the continuous process. shows the tube being formed as it comes
Figure 2-5 illustrates a continuous operation through the dies with a laser measurement
manufacturing textile spiral hose.
system for OD control.
Extrusion temperatures are typically
between 200°F and 275°F for rubber
compounds and 300F to 600°F for
thermoplastics. Precise temperature controls are
important to prevent scorch or partial cure of
rubber compounds or burning of the
thermoplastics during extrusion and provide
good wall gauge concentricity. The various
temperature zones of the extruder provide for a
profile that can be varied for each type of
compound to help optimize extrusion
characteristics.
For certain applications, to minimize cost or
improve flexibility, multiple tube layers may be
Figure 2-5
desirable. In these instances, a tandem or co-
extrusion may be preferred. For the tandem
PROCESS CHARACTERISTICS
method, extruders are installed in series so one
As previously mentioned, the basic hose tube may be extruded over the other. For co-
components are the tube, reinforcement, and extrusions, several extruders are mounted in
cover. In this section the process methods for such a way to feed a central die-forming point
each of these operations will be outlined. (extruder head) so that the tubing operation is
simultaneous. These extrusion advancements
TUBING OPERATION
offer a good variety of alternatives to use unique
The two common tube manufacturing polymers or to create hybrid products of
techniques are extruded and wrapped. thermoplastic and rubber.

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