q] - universiti teknikal malaysia...

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UTeM Library (Pind.l/2005)

UNIVERSITI TEKNIKAL MALAYSIA MELAKA

BORANG PENGESAHAN STATUS TESIS*

JUDUL: QUALITY STUDY OF PARTS PRODUCED BY 3D PRINTER SESI PENGAJIAN: 2/2006-2007

Say a KEVIN JOK SAGENG

mengaku membenarkan tesis (PSM/Sarjana/Doktor Falsafah) ini disimpan di Perpustakaan Universiti Teknikal Malaysia Melaka (UTeM) dengan syarat-syarat kegunaan seperti berikut:

1. Tesis adalah hak milik Universiti Teknikal Malaysia Melaka. 2. Perpustakaan Universiti Teknikal Malaysia Melaka dibenarkan membuat salinan

untuk tujuan pengajian sahaja. 3. Perpustakaan dibenarkan membuat salinan tesis ini sebagai bahan pertukaran

antara institusi pengajian tinggi. 4. **Sila tandakan (~)

D SULIT

D TERHAD

Q] TIDAK TERHAD

(Mengandungi maklumat yang berdarjah keselamatan atau kepentingan Malaysia yang termaktub di dalam AKTA RAHSIA RASMI1972)

(Mengandungi maklumat TERHAD yang telah ditentukan oleh organisasi / badan di mana penyelidikan dijalankan)

Disahkan oleh:

(TANDATANGAN PENULIS) (TANDATAN N PENYELIA)

Alamat Tetap: N0.1452, LORONG E7,TAMAN SATRIA JAYA, BDC,

93350 STAMPIN, KUCHING, SARAWAK

Tarikh: 14 MEl 2007

Cop Rasmi: RUlY HARYATJ BINTI HAMBAU

Pensyarah Fakulti K!!JUruteraan Pembuatan

Unrv&rsiti Tekmkal Maliys1a Melau Karung BerkUI'ICI 1200. Aytr Keroh

75450 Melakd

Tarikh: _ _ I....;..Cf-_m_€_1 _~_o_Df+--·--

* Tesis dimaksudkan sebagai tesis bagi ljazah Doktor Falsafah dan Sarjana secara penyelidikan, atau disertasi bagi pengajian secara kerja kursus dan penyelidikan, atau Laporan Projek Sarjana Muda (PSM). ** Jika tesis ini SULIT atau TERHAD, sila lampirkan surat daripada pihak berkuasa/organisasi berkenaan dengan menvat akan sekali sebab dan t empoh tesis ini perlu dikelaskan sebagai SULIT at au TERHAD.

UNIVERSITI TEKNIKAL MALAYSIA MELAKA

Quality Study Of Parts Produced By 3D Printer

Thesis submitted in accordance with the requirements of the Universiti

Teknika1 Malaysia Melaka for the Degree of Bachelor of Engineering

(Honours) Manufacturing (Design)

By

Kevin Jok Sageng

Faculty of Manufacturing Engineering

Apri12007

DECLARATION

I hereby, declare this thesis entitled "Quality Study OfParts Produced by 3D Printer"

is the results of my own research except as cited in the reference.

Signature

Author's Name

Date

Kevin Jok Sageng

13th April 2007

APPROVAL .. . ,

This thesis submitted to the Faculty of Manufacturing Engineering ofUTeM and has

been accepted as partial fulfillment of the requirement for the degree of Bachelor of

Manufacturing Engineering (Honours) (Manufacturing Design).

·· · ······· · ··~-~·-·········· Main supervisor

Faculty ofManufacturing Engineering RUZV HARYATI BINTI HAMBALI

Pensyarah Fiiikulti Kejuruteraan Pembuatan

Univers1ti Teknikal Malaysia Meliilka Karur!! lierltunci 121)(', Aver Keroh I 'q /osf:ur)J .

75450 Meta.... -,

II

ABSTRACT ~

. (

The "Quality Study of Parts Produced by 3D Printer" is based on Rapid Prototyping (RP)

concept where RP model named Master Pattern is designed by Computer Aided Engineering

(CAD) modeling software. The Master Pattern consists of shape and features of triangular

and circular protrusion as well as triangular and circular hollow cavity and also part features

consists of sections with draft angle were designed by using Solidwork CAD software.

ZCorp ZPrinter 310 Plus 3D Printer Apparatus is used to produce three Master Pattern's

physical prototype. This study investigates the surface finish, dimensional accuracy, flatness

and straightness of the three Master Pattern samples produced using 3D Printer apparatus by

using appropriate measuring equipment for quality testing namely the Digital Caliper,

Coordinate Measuring Machine (CMM) and Portable Surface Roughness SJ-301 Measuring

Instruments. The result of the study shows that the 3D Printer has a process capability to

produce parts with a dimensional tolerance of ± 0.1000 to ± 0.2000mm and the surface

roughness, Ra is correlated to the flatness and straightness. The findings shows that shape,

surface and dimensional irregularities as the main defects and problem to parts produced by

3D Printer and the problem can be reduced by ensuring the process parameter such as part

orientation, part hardening period, post processing method and curing time is properly

adhered to produce parts with the highest quality.

Ill

ACKNOWLEDGEMENT

First and foremost, I would love to extend my prayer and thanksgiving to God for the

wonderful blessings and spiritual guidance that matures and strengthens me as each

days passes along the implementation of this study.

I would also like to express my deepest gratitude to my thesis supervisor, Pn. Ruzy

Haryati Binti Hambali for the guidance and advice through out the process of this

thesis writing. God bless you for your sincere thought and assistance.

Special thanks also to Mr. Shajahan Bin Maidin acting as my Second Panel for the

time and commitment in assessing my thesis writing and also for being a caring and

understanding person in regards to difficulties in concluding this thesis work.

My greatest gratitude also goes to Universiti Teknikal Melaka Malaysia (UTEM) for

the privileges to complete my thesis proposal implementation and providing the

platform and eager assistance in providing the technical apparatus and advice

especially the technician, Mr Fairuz at Rapid Prototyping Lab.

Most of all, my heartfelt thank to my family for their continuous love and support

through good and bad times. Last but not least, my fellow peers Petrus Ak. Japong,

Nur Wadiah bt. Mohd Andai, Nor Fairuz Hayati and Mobd. Hafiq Ikhwan; I would

like to say thank you for your friendship, encouragement and motivation.

IV

TABLE OF CONTENTS

Abstract

Acknowledgement

Table of Contents

List ofFigures

List ofTables

1. INTRODUCTION

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1.1 Objectives ofthe Study

1.2 Scope of the Study

1.3 Problem Statements

LITERATURE REVIEW

2.1 Rapid Prototyping Background

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2.2 Rapid Prototyping Process Advantages and Disadvantages

2.3 Classification ofRapid Prototyping

2.4 Basic Processes ofRapid Prototyping

2.4.1 CAD Model Creation

2.4.2 Conversion to STL Format

2.4.3 Slicing ofthe STL file into thin cross sectional layers

2.4.4 Construction ofthe model one layer atop another

2.4.5 Finishing and clean editing the model

2.5 STLFile

2.6 3D Printer Apparatus

2. 7 3D Printer Components

2.8 Basic Process of 3D Printing

2.9 3D Printing Process Capabilities

2.10 Quality of Parts Produced by 3D Printing

2.11 Protective Coatings

2 .12 Advantages of3D Printing Machine

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2. 13 Disadvantages of 3D Printing Machine

2.14 3D Printer Materials Systems

2.14.1 Powder Materials

2. 14 .1. 1 High Performance Composite Material

2.14.2 Casting Materials

2.14.2.1 Investment Casting Material

2.14.2.2 Direct Casting Material

2.14. 3 Specialty Material

2.14.3.1 Snap Fit Material

2.14.3.2 Elastomeric Material

2.15 Epoxy

2.15.1 Resin

. . (

2.15.2 General Characteristic and Advantages ofResin

2.15.3 Adhesive Properties ofResin

2.15.4 Mechanical Properties of Resin

2.15.5 Micro Cracking ofResin

2.15.6 Fatigue Resistance ofResin

2.15. 7 Degradation from Water Absorption

2.15.8 Typical Applications ofResin

2. 16 Hardening (Infiltration) Material

2.16.1 Physical and Chemical Properties

2.16.2 Stability and Reactivity

3. METHODOLOGY

3.1 Sample Manufacturing

3.2 ZCorp ZPrinter 310 Plus 3D Printer Operating Mechanism

3.3 ZCorp ZPrinter 310 Plus 3D Printer Technical Specifications

3. 4 Experimental Methodology

3.5 Methodological Procedure

3. 6 Virtual Prototyping Introduction

3.6.1 Virtual Part Design ofMaster Pattern

3.6.2 Solidwork CAD Model Creation

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3.6.2.1 Numerical Information for Master Pattern

3.6.3 Conversion to STL Format

3. 7 3D Printer Preparation

3.8 Virtual Prototyping with ZPrint Software

3.8. I Orientation ofMaster Pattern

3.8.2 Checking the Build Settings

3.9 Physical Prototyping

3. 1 0 Post Processing

3.1 0.1 De-powdering of the Master Pattern

(

3.1 0.2 Removal of Master Pattern from Build Box

3.10.3 De-powdering Process in the Powder Recycling Unit

3.1 0.4 Drying the Master Pattern

3.1 0.5 Application of Resin Glue to Master Pattern

3.11 Sample Preparation for Testing

3 .11 .1 Product Quality

3. 12 Dimensional Accuracy Measurement

3.12. I Dimensional Accuracy Measuring Information

3.13 Surface Roughness Measurement

3.13.1 Surface Roughness Measuring Information

3. 14 Flatness and Straightness Measurement

3 .14.1 Flatness and Straightness Measurement Information

3.15 Validation

RESULTS AND ANALYSIS

4.1 Introduction to Dimensional Accuracy Result and Analysis

4.1.1 Dimensional Accuracy Measurement Result

4.1.2 Dimensional Accuracy Graph and Analysis

4 .2 Introduction to Flatness and Straightness Result and Analysis

4.2.1 Flatness and Straightness Measurement Result

4.2.2 Flatness and Straightness Graph and Analysis

4.3 Introduction to Surface Roughness Result and Analysis

4.3. 1 Surface Roughness Measurement Result

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4.3.2 Surface Roughness Graph and Analysis

5. DISCUSSIONS

5. 1 Introduction

5.2 Detailed Analysis for Dimensional Accuracy Measurement

5.3 Detailed Analysis for Flatness and Straightness Measurement

5.4 Detailed Analysis for Surface Roughness Measurement

6. CONCLUSIONS

6.1 Conclusions

6.2 Suggestions and Recommendations

REFERENCES

APPENDICES

A Detail Projection Sketching for Master Pattern

B Dimensional Accuracy Measurement Data Table

C Theoretical Equation for Calculation for X Control Chart Tolerance Limit

D Data Table for X Chart Tolerance Limits

E Calculation For X Control Chart Tolerance Limit

F Compatibility Data for Tolerance

G Straightness and Flatness Measurement Data Table

H Straightness and Flatness Printed Measurement Data Sheet

I Surface Roughness, Ra Measurement Data Table

J Surface Roughness, Ra Printed Measurement Data Sheet

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K Measuring Instruments for Dimensional Accuracy, Surface Roughness and

Flatness and Straightness

L Table for Measurement Standard for Ra according to TIS B0601-1994

Standard

M Gantt Chart for Thesis Report Writing

Vlll

LIST OF FIGURES

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2.1 3D Printer Main Unit ,.

14 . Powder Recycling Unit

(

2.2 14

2.3 Build Box 15

2.4 Resin Binder 15

2.5 The 3D Printing Layering Principle 16

2.6 The 3D Printing Operating Principle 16

2.7 Strength of Part in Regards to Part Orientation 18

2.8 Comparative Tensile Strength and Stiffness ofResins 30

2.9 Typical Fibre Reinforced Plastic Stress/Strain Graph 31

2.10 Typical Resin Stress/Strain Curves (Post Cure 5hrs @80°C) 31

2.11 Effect of Periods of Water Soak at 1 00°C on

Resin Inter-Laminar Shear Strength 32

3.1 Experimental Design of the Experiment 39

3.2 Master Pattern Isometric View 43

3.3 Master Pattern Isometric View with Dimension 44

3.4 Master Pattern Sample 1, 2 & 3 (Top View) 48

3.5 Master Pattern Sample 1, 2 & 3 (Bottom View) 48

3.6 Soft Horsehair Brush and the Polypropylene Scraper 50

3.7 Plaster Ceramic Powder 50

3.8 Powder Recycling Unit 52

3.9 AirBrush 52

3.10 Cyanoacrylate Resin Glue 53

3.11 Dimensional Element of the Master Pattern 56

3.12 Surface Roughness Measurement Information for Top Surface 60

3.13 Surface Roughness Measurement Information for Bottom Surface 60

3.14 Surface Roughness Measurement Information for Top Surface 62

3.15 Surface Roughness Measurement Information for Bottom Surface 62

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4.1 Tolerance Limit Line Indicator 66

4.2 Graph for Master Pattern Length, Dl versus Number of Samples 68

4.3 Graph for Master Pattern Width, D2 versus Number of Samples 69

4.4 Graph for Master Pattern Height, D3 versus Number of Samples 70

4.5 Graph for Protrusion Length, D4 and the Triangular Protrusion Width, D5

versus Number of Samples 71

4.6 Graph for Triangular Protrusion Height, D6 versus Number of Samples 72

4 .7 Graph for Triangular Hole Length, D7 and Triangular Hole Width, D8


4.8 Graph for Circular Protrusion Diameter, D9 versus Number of Samples 74

4.9 Graph for Circular Hole Diameter, D 10 versus Number of Samples 75

4.10 Graph for Protrusion Circular Protrusion Height, D 11


4.11 Graph for Master Pattern's Overall Average Major Diameter


4.12 Graph for Flatness & Straightness for Left and Right X-axis andY-axis


4.13 Graph for Flatness of Top and Bottom Surface


4.14 Graph of Surface Finish, Ra (!lm) for Top Side (A) X andY-axis


4.15 Graph of Surface Finish, Ra (!lm) for Bottom Side (B) X andY-axis


4.16 Graph of Surface Finish, Ra (!lm) for Top and Bottom Side


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LIST OF TABLES

2.1 Physical and Chemical Properties for Cyanoacrylate 34

2.2 Stability and Reactivity Properties for Cyanoacrylate 35

3.1 Technical Data Specifications for ZCorp ZPrinter 310 Plus 37

3.2 Drying Time for Parts 52

3.3 Data for Surface Roughness, Ra Measurement Parameter 59

4.1 Data for Flatness of Top and Bottom Surface Testing 79

4 .2 Data for Average Surface Roughness, Ra value for A and B Side 85

Xl

CHAPTER 1!

INTRODUCTION

3D Printing process is a techruque which used the resin binder as the main medium to

cure the powder ceramic material compound. In this study, a mixture of powder

material will be cured using the resin bonding curing technique in 3D Printing

method. The method of construction is of layer by layer construction of which a layer

or powder will be resurfaced by a layer of binder or bonding agent on top and the two

layer will bond together to form a solid surface and the process is repeated by the

application of a new layer of powder and binder from bottom until the top of the

design. Recently, there is a high demand in faster development time for parts and

product before manufacturing substituting conventional methods thus scientists and

engineers is turning their attention to Rapid Prototyping (RP) method to initiate the

Rapid Tooling (RT) application to produce the physical prototype of a part which is

then to be examined and analyzed for further improvement to the part design with the

aim of high quality finish.

The selection of Quality Study of Parts Produced by 3D Printing Application for

study is because of the necessity to understand its importance in terms of product

development especially in tooling where the accuracy, surface finishing and the

reliability of parts that can be produced in multiple production process especially in

terms of the ability in holding close tolerance can affect the production in a whole.

3D Printer is the most effective means of tooling production which integrates RP and

RT application for faster product development. The process offers lots of advantages

compared to the conventional technique in production tooling such as by

Stereolithogrpahy (SLA). It seems that 3D Printer application is fast gaining

recognition and popularity as a modern technology and starts to stirs up the interest

1

of product manufacturer, developer, scientists and engineers to develop a study on

the effectiveness of the method in RP and RT field in aid to manufacturing. Thus, it

is the right time to study and understand this technique and hopefully it can

contribute to the improvement and promote better understanding to the 3D printing

process. . (

The extensive use ofRP and RT technique can help to reduce a products production

time using the 3D Printer prototyping process. Besides that, the print bonding curing

is a process which utilizes the epoxy resin to increase the viscosity of the powder

ceramic material thus produced a strong bond among the molecules of the material to

hold each interlinked layer of surface together achieving a hard molded compound.

Generally, the liquid resin material is coated onto the surface inducing a chemical

process that causes the liquid to undergo a phase transition to a solid state once it is

bonded with the powder ceramic material. Traditionally, this process has been

accomplished by conventional heating in oven which involves extra cost and time.

The resin material to be deposited is printed and applied to atop the surface of

powder layer and cured layer by layer to finally construct a full physical prototyping

model of the part.

This study emphasizes on the quality study of the parts produced using 3D Printer in

RP and RT application. The quality study is based on criterion such as the

dimensional accuracy, surface finish, flatness and straightness. Further study is

conducted to investigate and to analyze the effect of the design in relation to the

process capability of the 3D Printer machine in order to maximize the overall surface

finish of the part.

2

1.1 Objectives of the Study

The purpose of this investigative study is to achieve the following:

(1) To identify the quality study includjng the dimensional accuracy, surface

finish, flatness and straightness ofthe resulting parts by metrological means

(2) To study the effect and causes of the 3D Printing process in relation to

constructed part' s quality in order to maximize dimensional accuracy, surface

finish, flatness and straightness of each resulting part

1.2 Scope of the Study

( 1) Design the virtual part which ts the Master Pattern using the Soljdwork

software

(2) Convert the CAD drawing file into STL data file format recognized by the 3D

Printer

(3) Produce the part using the 3D Printer Machjne

( 4) Produce three Master Pattern samples using the 3D Printer Machine

(5) Study the dimensjonal accuracy of the three Master Pattern samples

(6) Study the surface finish of the three Master Pattern samples

(7) Study the flatness and straightness of the three Master Pattern samples

(8) Analyzed the results and make future work recommendations

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1.3 Problem Statements

Manufacturing and production has evolved into a competitive and challenging

proposition to produce the best tooling product with the best design and cost effective

with high function ability. The needs for fast and productive manufacturing

production must be synchronized with the utilization of rapid prototyping

development in manufacturing to enhance design function and workability to the

maximum.

Rapid Prototyping (RP) is one of the tools that utilize the CAD concept to create the

mechanical structure of the part in visual prototyping. The 3D Printer Machine

manages the manufacture process of the physical prototype as an application of

Rapid Tooling (RT) concept under the Direct Tooling classifications. 3D Printer

production operation uses the STL format to program instructions that controls the

layer by layer construction of the 3D Printer machine and subsequently produced the

complete designed part.

Tooling now days IS very important m product development. The accuracy,

durability, finishing and the amount of parts that a tool can produce affect the

production. Tool manufactured by conventional methods usually offers good quality

of the product but the cost of these tolls could be up to hundreds pound and the time

required for their manufacture up to months.

This study investigates the surface finish, dimensional accuracy, flatness and

straightness of the parts produced using 3D Printer in rapid tooling application.

4

CHAPTER2

LITERATURE REVIEW

2.1 Rapid Prototyping Background

Rapid Prototyping (RP) is a fast tracked and advanced manufacturing tool which

relies on the Computer Aided Design (CAD) and Computer Manufacturing

Application (CAM) to produce prototypes by using various advanced manufacturing

apparatus and method. Prototype part is usually in the form of solid and cost effective

physical model which can be produced in a fast production steps. Parts produced are

highly precise and detailed with good dimensional stability and tolerances that

resembles the actual concept of the designed product.

Rapid Prototyping in general is referred to as "Fabrication of a physical, three

dimensional part of arbitrary shape directly from a numerical description typically a

CAD model by a quick, highly automated and totally flexible process." (Rapid

Prototyping Report, October 1992)

RP is an excellent tool for communicating and interacting ideas among the personnel

involved in the design of the part and also the research and development personnel

right up to the management. RP presents as visual aids to enable the relaying and

conveying of vital information between the product development phase and the full

production run of which data are obtained through design testing and production test

run of the prototype model of the part.

In addition to prototypes, RP techniques can also be used to make tooling which can

be referred to as rapid tooling. For small production runs and complicated objects,

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(5) A production tool used to examine manufacturing methods offabricated parts

and assembly processes and procedures to obtain the best and most effective

manufacturing methods.

(6) A communications tool for internal design reviews and also for design

reviews with the customer

(7) RP is a design verification and optimization tool to qualify the form, fit and

function of individual parts and assemblies where its physical visualization

concept enables verification of design details as a mean to gain internal

design acceptance and justification.

However, RP also have several disadvantages where part may have s1ze and

geometry limitation for example a part volume is generally limited to 0.125 cubic

meters or less, depending on the RP machine. Metal prototypes are difficult to make

and for metal parts with large production runs, the conventional manufacturing

techniques are usually more economical. RP generated tools may not easily be

modified or corrected using typical tool making or conventional techniques.

2.3 Classification of Rapid Prototyping

Generally, there are five main RP processes most commonly used in the industry.

These processes are described and listed as the following:

( 1) 3D Printer

3D design built using 3D CAD is converted into cross section or slices and

the printer then prints the cross sections one atop another from bottom to top

of the design. The printer spreads a layer of powder based material and the

print head applies a mixture of resin solution to the powder causing powder

particles to bind to one another to the printed cross section one layer below.

The process is continuous with new layer of powder and resin binder applied

to complete the shape design.

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(2) Stereolithography Apparatus (SLA)

Selective curing of a photopolymer resin by an ultraviolet laser, built on a

descending platform, in a vat.

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(3) Selective Laser Sintering (SLS)

A laser traces the shape of the part to be modeled in a thin layer of powder.

The laser softens and bonds the powder particles together. This process is

repeated over layers of powder.

(4) Laminated Object Manufacturing (LOM)

A laser cuts the outline of a cross section ofthe CAD file into an ultra thin

layer of modeling material. A new layer of material is then indexed, bonded

to the previous layers, and cut. This process is repeated using very thin layers

of material.

(5) Fused Deposition Modeling (FDM)

Fused Deposition Modeling Process (FDM) Thermoplastic modeling material

such as ABS plastic, polycarbonate is fed into the temperature-controlled

FDM extrusion head and heated to a liquid state. The head extrudes and

deposits the material in ultra thin layers onto a fixtureless base.

(6) Solid Ground Curing (SGC)

CAD model of the part is created and it is sliced into layers using Cubital's

Data Front End® (DFE~ software and the flat work surface is sprayed with

photosensitive resin in the beginning of each layer. For each layer, a

photomask is produced using Cubital's proprietary ionographic printing

technique. The photomask is positioned over the work surface and a powerful

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UV lamp hardens the exposed photosensitive resin. After the layer is cured,

all uncured resin is vacuumed for recycling, leaving the hardened areas intact.

The cured layer is passed beneath a strong linear UV lamp to fully cure it and

to solidify any remaining particles. Then, wax replaces the cavities left by

vacuuming the liquid resin. The wax is hardened by cooling to provide

continuous, solid support for the model as it is fabricated. In the final step

before the next layer, the wax/resin surface is milled flat to an accurate,

reliable finish.

2.4 Basic Processes of Rapid Prototyping

There are numerous rapid prototyping techniques commonly used. Each of these

techniques can be simplified by five basic step processes that define the rapid

prototyping concept in a whole. These steps are listed as the following:

( 1) Creation of a CAD model of the intended design and features of the part

(2) Conversion of the CAD model to STL format

(3) Slicing ofthe STL file into thin cross sectional layers

( 4) Construction of the model one layer atop another

(5) Finishing and clean editing the model

The above step processes can be briefly described in this following section:

2.4.1 CAD Model Creation

The part is modeled using a Computer Aided Design (CAD) software package such

as Solidworks or Catia. The Solidwork software is specifically used in the design of

the part because Solidwork is solid modelers that represent the part in 3D features

with more precise details and characteristic of the assemblies and sub assemblies of

the part. Solid modeling concept is important because of its high accuracy in defining

the surfaces of the part to be produced in rapid prototyping. Wire frame modeler such

as AutoCAD is deemed not suitable for the CAD model creation simply because

Solidwork is a better option in generating a solid model of the part with all the design

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parameters such as surface curves or geometry specification of the part 1s fully

represented as 3D Solid modeling.

2.4.2 Conversion to STL Format I .

Various CAD software package uses different algorithms to represent solid object

modeling. The STL format has been adopted as the benchmarking format in rapid

prototyping. It is the standard format used universally in the rapid prototyping

industry. The next process involves the conversion of the CAD file into STL format

which can where the 3D printer machine will read and process the data file

specifically as STL format. STL format defines a 3D dimensional surface is made of

an assembly of planar triangles. The file contains the coordinates of the vertices and

the direction of the outward normal of each triangle. However, the STL files cannot

represent curved surfaces to the exact detail because it uses planar elements. While

increasing the number of triangles improves the approximation, the size of the file

also increases requiring more time to process and build the part design. Therefore, it

is important to balance the accuracy with manageability to produce a useful STL file

in terms of development time effectiveness.

2.4.3 Slicing of the STL file into thin cross sectional layers

In the third step, a pre processing program prepares the STL file to be built. The size,

location and the orientation of the model is adjusted by the user according to the

types of programs used. Build orientation of the model is very important considering

the fact that properties of rapid prototypes vary from one coordinate direction to

another. The part orientation partially determines the time required to build the model

because it will define the number of layers needed to construct the model. An

example of this is when placing the shortest dimension in the z (vertical) direction

reduces the number of layers thus shortening the model build times. The pre

processing software slices the STL model into a number of layers from 0.01 mm to

0.7 rnm thick depending on the build technique. The program may also generate an

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auxiliary structure to support the model during the build. Supports are useful for

complex features such as overhangs, internal cavities, and thin-walled sections.

2.4.4 Construction of the model one layer atop another

The actual construction of the part occurs during this stage. The RP machines will

build the model one layer at a time from constructing materials such as polymers,

plastic or powdered metal. The process is an auto run by the RP machine needing

minimum human supervision. The most common and advanced RP machine used in

building the actual model is the 3D Printing and Stereolithography (SLA) machine

which will be described in the next section. There are also other types of RPO

machine such as the Selective Laser Sintering (SLS) or the Fused Deposition

Modeling (FDM) machine.

2.4.5 Finishing and clean editing the model

The final step involves the post processing of the model where the model is taken out

of the RP machine and removed the model from its supporting base and support

structure. Minor cleaning is done and some heat treatment process may be applied to

the model for extra strength and durability. Sanding, sealing or painting the model

will improve its overall appearance to be presented as high quality surface finishing.

Some photosensitive materials need to be fully cured before use.

2.5 STL File

The .STL file format has bec.ome the Rapid Prototyping industry's standard data

transmission furmat and is the format required to interact with 3D Primed parts. This

format approximates the surfaces of a solid model with triangles. The more complex

the surface. the more tiiangles produced in the STL file format. AJI modern CAD

software system such as So1idworks, CA. TIA and Pro Engineers can generate STL

file to be applied to any Rapid Prototy-ping (RP) machine.

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2.6 3D Printer Apparatus

3D Printing is a rapid prototyping process which produces a physical parts which

embodies the three dimensional conception of an object or product in design. It is an

advanced manufacturing technology method that can produces high quality product

with good surface finish and high dimensional accuracy.

3D Printing in general is a process where a visual conception of a product is

produced from a 3D computer modeling which is then generated into a physical

geometry from the data derived in the 3D modeling. 3D Printer allows the creation of

solid, plastic and 3D objects in CAD drawings in a short time. 3D Printing method

involves building plastic parts layer by layer at a time using a resin binding agent to

cure plaster ceramic powder to finally create the solid physical as conceptualized in

the 3D drawing.

2.7 3D Printer Components

3D Printer apparatus consists of two main important components. These are:

(1) 3D Printer Main Unit

3D Printer Main Unit as shown in Figure 2.1 consists of main components

such as the Binder Cartridge which supply and print the bonding agent on top

the layer of powder, the Feed Piston that moves up to supply powder for

printing, the Build Piston that moves down once a layer of powder resin

material is bonded to initiate a new layer, a roller attached to the Gantry

which spreads the powder and lastly the Build Box which is filled with

powder ceramic material as the main material for construction of model.

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