Shaping Processes For Plastics Extrusion

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Shaping Processes For Plastics - Extrusion
1. Introduction
Extrusion is a compression process in which the
material is forced to flow through a die orifice
to provide long, continuous product whose
cross-sectional shape is determined by the shape
of the orifice
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Shaping Processes For Plastics - Extrusion
1. Introduction
Screen pack
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Shaping Processes For Plastics - Extrusion
2. Analysis of Flow Rate
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The goal of the engineering analysis
Find the flow rate with respect to various
parameters in the system. These parameters
include parameters of the screw, the clearance
between the screw and the inner surface of the
barrel.
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The goal of the engineering analysis
1. Flow rate (volume) inside the extruder ?
2. Flow rate (volume) through the die ?
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Flow rate of the extruder not include the die
2. Analysis of Flow Rate
Drag flow
w
Screw surface
v
d
Barrel
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Shaping Processes For Plastics - Extrusion
2. Analysis of Flow Rate
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Shaping Processes For Plastics - Extrusion
2. Analysis of Flow Rate
Back pressure flow
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Shaping Processes For Plastics - Extrusion
2. Analysis of Flow Rate
Back pressure flow
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Shaping Processes For Plastics - Extrusion
2. Analysis of Flow Rate
Net forward flow Qx
(3)
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Shaping Processes For Plastics - Extrusion
The design parameters those that define the
geometry of the screw and barrel.
The operating parameter those that can be
changed during the process to affect the output
flow
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Shaping Processes For Plastics - Extrusion
2. Analysis of Flow Rate
Maximum pressure and maximum net flow rate
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Shaping Processes For Plastics - Extrusion
2. Analysis of Flow Rate
Extruder characteristic
Qmax
pmax
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Shaping Processes For Plastics - Extrusion
3. Determination of the operating point
Pressure and Flow rate
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Shaping Processes For Plastics - Extrusion
3. Determination of the operating point
Die characteristic
Qx
Qmax
Operating point
Extruder characteristic
pmax
p
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Example Given diameter D120 mm
length 3.0 m
channel depth 8.0 mm pitch
95 mm viscosity 75 pas
head pressure 4.0 Mpa
Find the rotational speed of the screw
required to achieve a
volumetric flow rate of 90 cm3/s
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Solution to be filled in the classroom