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Classification of solidification processes
Principle of the process
Structure/Configuration
Process modeling
Defects/quality control
Design For Manufacturing (DFM)
Process variation2
Shaping Processes For Plastics - Extrusion
1. Introduction
Screen pack
3
1. Introduction
Extrusion is a process in which
the material is forced to flow through a die
orifice to provide a long, continuous product
whose cross-sectional shape is determined by
the shape of the orifice
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Shaping Processes For Plastics - Extrusion
2. Analysis of Flow Rate
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Shaping Processes For Plastics - Extrusion
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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Shaping Processes For Plastics - Extrusion
The goal of the engineering analysis:
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1. The flow rate or production rate.
2. The pressure of the or product
1. Flow rate inside the extruder and at the die ?
2. Flow rate outside the extruder and at the die ?
dieThe balance between the two should lead to the flow rate as well as pressure
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Extruder
The general idea to meet the goal:
Flow rate of the extruder (not including the die)
Drag flow
Barrel
Screw surface
d
w
v
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vdwQd 5.0
ADNv cos
AANdDQ cd cossin5.0 22 (1)
dc
tan cosc fw D A A w
10
tan cosc fw D A A w
11
)(12
sin23
dl
dpADdQ cb
Back pressure flow
12
)(12
sin23
dl
dpADdQ cb
Back pressure flow
L
ADdpQ cb
12
sin 23
(2)
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Net forward flow Qx
L
ADdpAANdDQ c
cx
12
sincossin5.0
2322
(3)
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Linear relation between the net flow rate and head pressure.
Assumption: viscosity is constant.
The structure: extruder only not including die.
L
ADdpAANdDQ c
cx
12
sincossin5.0
2322
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
Variable15
Shaping Processes For Plastics - Extrusion
Maximum pressure and maximum net flow rate
L
ADdpAANdDQ c
c
12
sincossin5.0
2322
max
0
Maximum head pressure to cause no flow
2max
cot6
cd
ADNLp
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Shaping Processes For Plastics - Extrusion
pmax
Qmax
Extruder characteristic
p
Q
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Shaping Processes For Plastics - Extrusion
Determination of the operating point
Pressure and Flow rate
diepKQ sx
d
ds L
DK
128
4
Die characteristic
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Shaping Processes For Plastics - Extrusion
Determination of the operating point
p
Qmax
pmax
Operating point
Die characteristic
Extruder characteristic
Qx
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Shaping Processes For Plastics - Extrusion
Example:
Given: diameter D=120 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
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Discussion
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Shaping Processes For Plastics - Extrusion
A manufacturing process is to the material to meet requirements.
Requirements: quality, quantity, time, cost, green and sustainability.
Quantity with respect to time is called production rate.
The whole manufacturing system at the equipment level can be viewed as consisting of devices and materials.
Discussion
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Shaping Processes For Plastics - Extrusion
Both the device and material are under the manipulation from the external system that supplies energy or power and material.
There are several parameters and variables in the manufacturing system: device parameter, process parameter, product parameter.
Discussion
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Shaping Processes For Plastics - Extrusion
Device parameter also system or design parameter: the one category of parameters that describe the device, e.g., the diameter of the extruder, length of the extruder, etc.
Process parameter also operating parameter: the one category of parameters that describe the process on the material, e.g., the rotational speed of the screw bar, heat energy supply, material supply rate, etc.
Product parameter: the one category of parameters that describe or characterize the product which is the output from a manufacturing system, e.g., the flow rate, etc.
Discussion
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Shaping Processes For Plastics - Extrusion
Manufacturing system design and control:
1. Device design: to determine the device parameter.
2. Process design: to determine the process configuration and
parameter.
3. Product modification: design for process.
4. Device control.
5. Process control.
Product quality, quantity, cost, time, green and sustainability