classification of solidification processes. principle of the process structure/configuration process...

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

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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