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DEVELOPMENT OF BOTTOM CAVITY OF 4 LITER BOTTLE WAN AHMAD SMFUL BIN WAN MUHAMAD SUKERI A report submitted in partial fulfilment of the requirements for the award of the degree of Bachelor of Mechanical Engineering Faculty of Mechanical Engineering Universiti Malaysia Pahang NOVEMBER 2007 PERPUSTJ4KAAN UVERSm MALAYSIA FHAWG No. Peroehan: 037939 A Pang rp Tarikh \Icb O2Ju&74j YIL
Transcript
Page 1: Wan Ahmad Saiful Bin Wan Muhamad Sukeri

DEVELOPMENT OF BOTTOM CAVITY OF 4 LITER BOTTLE

WAN AHMAD SMFUL BIN WAN MUHAMAD SUKERI

A report submitted in partial fulfilment of the

requirements for the award of the degree of

Bachelor of Mechanical Engineering

Faculty of Mechanical Engineering

Universiti Malaysia Pahang

NOVEMBER 2007

PERPUSTJ4KAAN UVERSm MALAYSIA FHAWG

No. Peroehan:

037939A

Pang rp

Tarikh \Icb

O2Ju&74jYIL

Page 2: Wan Ahmad Saiful Bin Wan Muhamad Sukeri

ABSTRACT

Four liter plastic bottle always use in chemical industry. A good of mold will

need to produce a high quality of four liter plastic bottle. Actually the mold for this

bottle is dividing into three parts. They are top cavity of bottle, main cavity of bottle

and bottom cavity of bottle. This project will show how and what are the processes

that involve developing the bottom cavity of four liter bottle. These projects start

with initially in design stages, material selection for bottom cavity mold and fabricate

the mold. The latest technologies that use to fabricate the mold are Master Cam

software and CNC milling machine. Another processes are use to ensure no defect

and follow the characteristics from actual specification.

I'4

Page 3: Wan Ahmad Saiful Bin Wan Muhamad Sukeri

ABSTRAK

Botol plastic 4 liter sememangnya banyak digunakan dalam indusfri kimia.

Acuan yang baik diperlukan dalam menghasilkan botol plastic 4 liter yang bermutu.

Pada dasarnya acuan mi terbahagi kepada tiga iaitu acuan pada bahagian atas botol,

bahagian tengah botol dan juga pada bahagian bawah botol. Di dalam projek mi akan

ditunjukkan bagaimana dan apa proses yang terlibat dalam menghasilkan acuan

bawah botol.Projek mi melibatkan proses reka bentuk, pemilihan bahan yang sesuai

sehingga kepada pembentukan acuan menggunakan technology terkini iaitu perisian

Master Cam dan CNC milling machine.Untuk menghasilkan produk yang bermutu,

acuan tadi perlu melalui beberapa proses lain supaya produk yang dihasilkan tidak

mengalami kecacatan dan menepati spesifikasi sebenar.

VI

Page 4: Wan Ahmad Saiful Bin Wan Muhamad Sukeri

TABLE OF CONTENTS

vii

CHAPTER

1

TITLE PAGE

DECLARATION OF THESIS

DEDICATION

ACKNOWLEDGEMENT iv

ABSTRACT v

ABSTRAK vi

LIST OF FIGURES x

LIST OF TABLES xii

LIST OF APPENDICES xiii

INTRODUCTION I

1.1 Project background 1

1.2 Problem Statement 2

1.3 Objectives 2

1.4 Scopes of Project 2

LITERATURE REVIEW 4

2.1 Intoduction S 4

2.2 The principle of blow molding 4

2.2.1 Parison formation 5

2.2.2 Parison dimension 5

2.2.3 Extrusion blow molding 6

2.2.3.1 Wall thickness 9

2.2.3.2 Blow up ratio 10

Page 5: Wan Ahmad Saiful Bin Wan Muhamad Sukeri

viii

3

2.2.3.3 Wall thickness and melt 10

Temperature

2.3 Main characteristic of the bottom bottle design 10

2.3.1 Main characteristic of bottom mold 11

2.3.2. Mold materials 12

2.3.3. Important of fast mold cooling 13

2.3.4. The pinch off 14

2.3.5 High quality undamaged mold cavity 14

Finish

2.4 CNC milling 14

2.4.1 Cutting speed 18

2.4.2 Spindle speed 20

2.4.3 Feed rate 21

2.5 Overview of polymer material 22

2.5.1 Types of polymers 23

2.5.2 Chemical end use requirement 23

2.5.3 Shrinkage 24

METHODOLOGY 26

3.1 Introduction 26

3.2 Project methodology 27

3.2.1 Literature review 28

3.2.2 Bottle design 28

3.2.3 Survey 28

3.3 Design concept 29

3.3.1 Material selection 29

3.4 Flow of fabrication process 30

3.4.1 Square part 31

3.4.2 Surface grinding 31

3.4.3 Simulation by Master Cam 32

3.5 Machining by CNC milling 34

3.5.1 Set the tooling height 34

Page 6: Wan Ahmad Saiful Bin Wan Muhamad Sukeri

ix

4

5

3.5.2 Spindle speed and feed rate calculation 35

3.6 Surface finish 36

3.6.1 Air grinding 36

3.6.2 Polishing 37

3.6.3 Sand blasting 37

3.7 Summary 38

RESULT AND DISCUSSION 39

4.1 Introduction 39

4.2 Statistic from survey 39

4.3 Final design of bottle 41

4.3.1 Final design of bottom cavity 42

4.4 Data from machining 42

4.5 Discussion 43

4.5.1 Cutting tool fracture 44

4.5.2 Programming 45

4.5.3 Unsmooth surface 46

4.6 Cost analysis 47

4.7 Bottom cavity of 4 liter bottle 48

4.8 Summary 49

CONCLUSION 50

5.1 Conclusion 50

5.2 Recommendation 51

REFERENCES 52

APPENDIX A 53

APPENDIX B 56

APPENDIX C 57

APPENDIX D 58

Page 7: Wan Ahmad Saiful Bin Wan Muhamad Sukeri

LIST OF FIGURES

FIGURE NO. TITLE PAGE

2.1 Injection of air in blow mold 6

2.2 Parison programming with die orifice 7

2.3 Die with variable orifice 8

2.4 Various blow molding process 9

2.5 Bottom cavity mold 11

2.6 Three axis milling machine 15

2.7 Feed drive for work table 16

2.8 Work piece clamping for milling 16

2.9 Tooling system milling 17

2.10 Tool dimension milling. 18

3.1 Design methodology flow chart 27

3.2 Flow of fabrication 30

3.3 Conventional milling machine 31

3.4 Grinding machine 32

3.5 Simulation process 33

3.6 CNC milling 34

3.7 Air grinding 36

3.8 Polishing by sand paper 37

Sand blasting machine 38

x

Page 8: Wan Ahmad Saiful Bin Wan Muhamad Sukeri

xi

4.1 Survey analysis 40

4.2 Finalize design of bottle 41

4.3 Finalize design of bottom cavity 42

4.4 Tool fracture 45

4.5 Unsmooth area before surface finish 46

4.6 After surface finish 47

4.7 Bottom cavity 48

4.8 Assembly with main cavity 48

Page 9: Wan Ahmad Saiful Bin Wan Muhamad Sukeri

LIST OF TABLES

TABLE NO. TITLE PAGE

2.1 Cutting speed for varians material 19

2.2 Recommended feed per tooth 22

2.3 Shrinkage various material 25

3.1 Process in simulation 33

3.2 Tool height 35

3.3 Spindle speed and feed rate 35

4.1 Data collection from student 39

4.2 Data collection from staff 40

4.3 List of machining time 43

4.4 Machining time after tool fracture 44

4.5 Cost 47

xli

Page 10: Wan Ahmad Saiful Bin Wan Muhamad Sukeri

LIST OF APPENDICES

APPENDIX NO TITLE PAGE

Al Full geometry of bottom cavity 53

A2 Full geometry of half bottom cavity 54

A3 Location of cooling channel and guide screw 55

B Tool list of machining 56

Cl Sample of survey 57

Dl G codes for CNC programs 58

xli'

Page 11: Wan Ahmad Saiful Bin Wan Muhamad Sukeri

CHAPTER 1

INTRODUCTION

1.1 Project Background

A bottle is a small container with a neck that is narrower than the body and a

"mouth." Bottles are often made of glass, plastic or aluminum, and typically used to

store liquids. Plastic bottle is commonly use in our life. There have one liter, two

liter, fourth liter of plastic bottle. Four liter bottle typically used to store liquid like

cooking oil (for both cooking and as fuel), water and other chemical substances.

These bottles are produced from polyethylene using the blow molding process.

Bottle labels consist of a printed, tight-fitted plastic sleeve. The color available for

four liter bottle is white, natural, black, and custom colors available.

Every day the demands for this type of bottle from industry are increase.

However the quantities of the product still not enough Therefore in this project, I

will develop bottle four liter which easy to handle and suitable to all liquid

especially for chemical substances. The process that uses to make bottle is blow

molding process.

In Malaysia, the number of individual that can develop mold for bottle is very

small. The mold determines the shape of the end product with all its details. It helps

Provide the end product with essential physical properties and the desired

appearance. Usually the mold maker builds the blow mold according to the molders

or the customer's specifications.

Page 12: Wan Ahmad Saiful Bin Wan Muhamad Sukeri

1.2 Problem Statement

In this project, a 4 liter bottle based on bottom cavity is developed to

overcome a few problems. The first problem is the design of the bottle now not

suitable for the certain purpose. Some of the bottle is easy to pour but very difficult

when to hold or carry it. In another word, it not agronomics to us. For the bottom

part, the design must give high stability to the bottle.

The second problem is in our country, there only a little mold maker. Usually

the mold of bottle will import from China. The price for each mold is very expensive

and high cost invests if to buy a mold from the manufacture. Beside that it can

localize the mold design in Malaysia for multi usage.

1.3 Objective

Project Objective

1). To design mold of bottom part for 4 liter bottle.

2) To assembly with a main cavity of 4 liter bottle.

1.4 Scope of Project

Project Scopes

• Design the concept of bottle.

• . Identify the suitable material properties according to the molds

• . Simulate the fabrication of the mold.

Page 13: Wan Ahmad Saiful Bin Wan Muhamad Sukeri

Fabricate blow mold (Bottom cavity).

Apply in to product fabrication and get the final product.

Page 14: Wan Ahmad Saiful Bin Wan Muhamad Sukeri

CHAPTER 2

LITERATURE REVIEW

2.1 Introduction

This chapter is discussing about the blow molding technique and extrusion

blow mold. This to element is very important to know before the mold of the bottle

can be produce. The other element that will include in this chapter is about the

polymer material consideration. The main process to develop the mold also discuss

in this chapter.

2.2 The principal of Blow Molding

A simple explanation of the principle of blow molding is a balloon. If we

blow air into a plastic tube that is closed on all side except the point which the air

enters, the tube will expand and take the shape of the mold that is around the tube.

The process begin with a plastic resin hot tube called a parison or pre-form. The

parison is placed within a split mold with a hollow cavity. The mold sides are then

clamped together, pinching and sealing the parison tube. Air is blown into the tube,

which expands the hot resin wall into the shape of the part. Once cooled the part is

ejected from the mold and trimmed. There are several methods of blow molding

plastic parts. However they all have 5 stages in common. They are plasticizing or

Page 15: Wan Ahmad Saiful Bin Wan Muhamad Sukeri

5

melting the resin, parison or pre-form production, inflation of the parison or pre-

form in a mold to produce the end part, injection of the part and finishing of the

part.

The first four steps take place in sequence and the five step is performed

while the other four steps are cycling. Exceptions occur when a number of pieces

are produced on the same machine, simultaneously, then the four steps may overlap.

Most of the cycle time is taken up by the blowing and cooling step. The speed of the

machine that melts the resin and makes the parison must be configured to conform

to the blowing/cooling time [1].

2.2.1 Parison Formation

The parison or pre-form is formed by either of two techniques for melting the

resin, extrusion or injection molding. For small, high production clear parts,

injection blow molding would be the process of choice. For larger industrial parts

the accumulator method is the process of choice and higher volume detergent or oil

bottles would most likely be produced on a wheel machine.

2.2.2 Parison Dimension

Usually the diameter of the parison is nearly the same as the diameter of the

container finish, although this depends strongly on bottle design Containers with an

Offset neck or a handle require a wider parison. It is generally recommended that the

ratio of the container diameter to the parison diameter not exceed four to one. The

parison dimensions are not identical to the die dimensions, since the stress

relaxation and elastic memory characteristics of plastics cause the parison to shrink

in length and swell in diameter and wall thickness as it is being produced.

Page 16: Wan Ahmad Saiful Bin Wan Muhamad Sukeri

6

2.2.3 Extrusion Blow Molding

In extrusion blowing, a hot tubular is extruded continuously. The mold

halves close which seals off the open end of the parison .See in the Figure 2.1. Air is

then injected and the hot parison expands against the mold walls. After cooling, the

product is ejected. Extrusion blow molding can produce article large enough to hold

100001, of water. Blow extrusion offers strain free articles at high production rate

but scrap reprocessing is required. Controlling wall thickness is the largest

disadvantage of extrusion blow molding. By controlling (sometime called

programming) the wall thickness of the extrude parison, thinning is reduced. For a

part requiring an extremely large body yet needing strength at the corner, a parison

could be produced with the corner area much thicker than the wall [8].

Air

cooled cores

Iosing of mold halves. B) Thjcciion of air

Figure 2.1 : Injection of air in blow mold

Page 17: Wan Ahmad Saiful Bin Wan Muhamad Sukeri

(A) Picrd orficc product

0.80 torn

0.80--

0.65 tot,,

0.58 root

0.65 root

0.80 ttwtt

0.80--

(B) Programmed orifice product

0.50 nro

0.53 roct

0.58 toot

0.65--

0.75--

0.78 toot

0.80 torn

7

Figure 2.2 Parison programming with die orifice

Hot plastic is fed into an accumulator and then forced through the die. A

controlled length of parison is produced when the ram or plunger operates. The

extruder fill the accumulator and the cycle begins again. The wall thickness of tube

or parison will be controlled to suit the bottle configuration. This is done by using a

die with a variable orifice as show in Figure 2.3. The advantage of extrusion blow

molding are:

• Most thermoplastics and many termosets may be used.

• Die cost are lower than those of injection molding.

• Extruder compounds and blends materials well.

• Extruder plasticates material efficiently.

• Extruder is basic to many molding processes

Page 18: Wan Ahmad Saiful Bin Wan Muhamad Sukeri

To the Rm I head

ScrewBreaker plate

Screen pack

block ^Himg^ed --liar

Extruder

Air

imill

-.

— a 170 —0 0- ^7 101 1 WN-4 OR F, 5-A

mu Retainer rung -•--

Mandrel (movable) BushingVariable orifice

Figure 2.3: Die with variable orifice

Many different way of forming blow molded product have been developed

.Each product may have an advantage in molding a given product. On manufacture

both forms and fills the container in a single operation. Rather than compressed air,

the product is forced into the parison.

S

Page 19: Wan Ahmad Saiful Bin Wan Muhamad Sukeri

Plasticate^r ^6J Air

Form parison

!Pinch

Blow <'- :1 J

Eject

9

Figure 2.4: Various blow molding proses

The flash (Excess material) is trimmed from the bottle neck and bottom, as

well as from other areas that are pinched off, for instances to form handles or offsett

necks the marks left from the removal of the flash serve as an easy means for

identification of extrusion blow molded bottle. It typically appears as;a rough area

along the mold parting line, centered in the middle of the bottom and running half or

so of the distances to the heel of the bottle.It is also possible on careful examination,

to identify the roughness at the top of the finish, or on other areas where flash was

trimmed. The flash, after being trimmed, usually is immediately ground up and feed

back into the extruder at the controlled rate, mixed with the virgin resin [1].

2.2.3.1 Wall Thickness

The pin in the die may be activated by a timing mechanism called an

automatic timing device, which raises or lowers the pin while the parison is being

formed. This allow the resin to be extruded to form a parison that will have a more

uniform wall thickness, matching the sagging which would otherwise be thin in the

top area of the tube. When the mold closes the pin returns to its original position. It

can be seen by moving the mandrel up and down during the extrusion of the parison.

Additional resin (and increase of wall thickness) can compensate for irregular part

configurations. A further method of controlling wall thickness of the parison is

Page 20: Wan Ahmad Saiful Bin Wan Muhamad Sukeri

10

varying the extrusion pressure through a fixed die opening. Higher pressure causes

an increase in output while lower pressure will causes less resin to be extruded [7].

2.2.3.2 Blow Up Ratio

Blow-up ratio is defined as the ratio of the average diameter of the parison.

The maximum recommended blow-up ratio for the most application is 5:1 but 3:1 is

preferable and the optimum result also depends on wall thickness. With

conventional tooling the mold closing around the parison at the pinch off causes the

parison to changes in cross sectional shape [3].

2.2.3.3 Wall Thickness and Melt Temperature

The melt temperature becomes critical when extruding a parison with

varying wall thickness. Should the melt temperature be too low, the thick areas may

end up as thin areas? This can occur because of the differences in stretch ability and

heat retention in the thicker area [8].

2.3 Main Characteristic of Bottom Bottle Design

The bottom of a bottle typically only has one primary function (besides

helping hold the bottle together) and that is to provide a flat surface for the bottle to

stand upright.Boule bottoms aren't flat because they need an arched structure to

allow them to be stable on a flat surface. The bottom of a bottle is usually the

thickest part, retaining more temperature throughout the production line. Because

Page 21: Wan Ahmad Saiful Bin Wan Muhamad Sukeri

11

the bottom is hotter, it is also more fluid and has a tendency to sag, forming a shape

like a spinning top which makes it unstable on flat surfaces. Giving a bottle an

arched shape at the bottom means that if it does sag, it can do so without touching

the bottom.

2.3.1 Main Characteristic of The Bottom Cavity (mold)

The blow mold may have a number of parts, counting its various insert, but

it usually consists of two halves. When closed, these halves will form one or more

cavities which will enclose one or more parisons for blowing. The two mold halves

are usually alike. There are usually no male and female sections. Pinch off edges are

generally provided at both ends of the mold halves. A blowing pin may have the

additional function of shaping and finishing the neck inside.Both mold halves must

have built in channel for the cooling water. Set of guide pins and bushings or side

plates in both mold halves ensure perfect cavity alignment and mold closing.

Accurate guiding devices in both mold halve reduce setup

Figure 2.5 : Bottom cavity mold

Page 22: Wan Ahmad Saiful Bin Wan Muhamad Sukeri

12

2.3.2 Mold Materials

Because of the comparatively low clamping and blow pressures, the blowing

mold need not be made of a high tensile strength material, with a possible exception

of molds for very long production runs, say, hundreds of thousands or millions,

which are sometimes made of steel. The predominant raw materials for blow molds

are machined from aluminum billet, cast aluminum alloys, zinc alloys such as Kirk

site, and occasionally, bronze. Beryllium copper because of its expense and

difficulty in machining, is usually reserved for pinch inserts or cores where rapid

heat transfer is needed. All these alloys are excellent material for blow molds.

Aluminum is the softest of the mold material in use and is most easily

damaged in the shop. Furthermore, aluminum molds wear easily. On the other hand,

they are easiest to machine. Aluminum and beryllium copper cast molds may be

slightly porous, and occasionally, blow molders have experienced some

permeability of such molds to the viscous resin. This may affect the appearance of

the blow part. The remedy for this problem is coating the inside of the mold halves

with a sealer This will not affect the heat transfer between the resin blown against

the mold and the mold walls.

Steel molds are heavier, more expensive, and more difficult to machine than

those made of nonferrous alloys. Higher weight will mean more setup time in the

molding shop. Moreover, the heat conductivity of steel is inferior to that of the three

nonferrous mold materials. This results in a slower cooling rate and a

correspondingly longer cooling cycle and consequently, a lower production rate for

steel molds [6].

Page 23: Wan Ahmad Saiful Bin Wan Muhamad Sukeri

13

2.3.3 Important of Fast Mold Cooling

Different materials with consequently different heat conductivity at various

point of the mold will result in no uniform cooling. This in turn might set up areas

of stress in the finished piece, which would be susceptible to splitting in use. The

blow mold halves must always be adequately cooled to solidify the part quickly,

immediately after the parison has been blown out against the mold walls.

The cooling water may be tap water. If it has a high content of minerals

which may settle in the narrow cooling channels, a closed system for circulating

purified water should be used. Usually, the cooling water is recirculated, that is,

reused time and again for along period. Sometimes it is partly recirculated and

mixed with fresh tap water to maintain the desired temperature and to economize.

Cooling channel should also be as close to the (lengthwise or other) parting

lines caused by the separation line of the two halves or by inserts. Parting lines will

practically always show along mold separation lines. Cooling these areas will result

in better finish of the piece along the parting line.

Larger molds may be equipped with several- up to three or more -

Independent cooling zones. Generally, in the top or bottom areas, that is, around a

bottleneck or the bottom pinch-off, or both, greater masses of resin are required than

along the other areas. Such areas as well as thicker wall sections, therefore, often

required additional cooling. Otherwise this section would still be viscous while the

thinner wall sections have solidified when the piece is ejected. Cooling time is

strongly affected by the extrusion melt temperature of the blow molding cycle. It

has been experienced that an increase, or decrease, of 5°C in melt temperature can

extend, or shorten, the cooling cycle by as much as one second [7].

Page 24: Wan Ahmad Saiful Bin Wan Muhamad Sukeri

14

2.3.4 The Pinch Off

Because of the comparatively high pressure and mechanical stress exerted

on the mold bottom when (in the closing step) it pinches one end off the parison

together, the pinch off in a nonferrous metal mold is frequently an insert made of

hard, tough steel. The effect on the blown part always shows in the so-called weld

line. The pinch off section does not cut off the excess parison tail.Its protruding

edges cut nearly through, creating an airtight closure by pinching the parison along

a straight line which make it easy later to break off or otherwise remove the excess

tail piece. A high quality pinch-off, of a thick walled parison is more difficult to

obtain than that of a thin- walled parison .However much depends on the

construction of the pinch off insert. The pinch off should not be knife edge, but

according to some molders, should be formed by lands about 0.1 to 0.5mm. The

total angle outward from the pinch off should be acute, up to 15 [6].

2.3.5 High Quality Undamaged Mold Cavity Finish

A high quality mold cavity finish and undamaged inside surface are essential

in polyethylene blow molding to avoid surface imperfections in the end product. If

the highest possible gloss of the end product is desired, the mold cavity should be

vacuum assists for the removal of entrapped air. If other end product finishes are

desired, the mold cavity should be finished accordingly [4].

2.4 CNC Milling machine

Milling machines have three feed axes: X, Y and Z. Two of these are

generally activated by traversing the work table while the third axis is represented


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