Classification of solidification processes. Principle of the process Structure/Configuration Process modeling Defects/quality control Design For Manufacturing

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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2. Analysis of Flow Rate

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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:

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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

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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


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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pmax

Qmax

Extruder characteristic

p

Q

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Determination of the operating point

Pressure and Flow rate

diepKQ sx

d

ds L

DK

128

4

Die characteristic

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Determination of the operating point

p

Qmax

pmax

Operating point

Die characteristic

Extruder characteristic

Qx

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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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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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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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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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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

Documents

Classification of solidification processes. Principle of the process Structure/Configuration Process modeling Defects/quality control Design For Manufacturing