research on the torsional strength of composite products manufactured from the plastic injection molding process

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MINISTRY OF EDUCATION AND TRAINING

HO CHI MINH CITY UNIVERSITY OF TECHNOLOGY AND EDUCATION FACULTY FOR HIGH QUALITY TRAINING

RESEARCH ON THE TORSIONAL STRENGTH OF COMPOSITE PRODUCTS MANUFACTURED FROM

THE PLASTIC INJECTION MOLDING PROCESS

LECTURER: PhD. NGUYEN VAN PHUCSTUDENT: TRAN MINH DAT

CAO NGUYEN HOANG TIEN NGUYEN MINH DUC

S K L 0 1 2 6 3 7

GRADUATION PROJECT

MECHANICAL ENGINEERING TECHNOLOGY

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MINISTRY OF EDUCATION & TRAINING

HO CHI MINH UNIVERSITY OF TECHNOLOGY AND EDUCATION FACULTY OF INTERNATIONAL EDUCATION

GRADUATION PROJECT

Ho Chi Minh City, March 2024

RESEARCH ON THE TORSIONAL STRENGTH OF COMPOSITE PRODUCTS MANUFACTURED FROM THE

PLASTIC INJECTION MOLDING PROCESS

Advisor: Ph.D Nguyen Van Thuc

Students: Tran Minh Dat 19144065

Cao Nguyen Hoang Tien 19144330

Nguyen Minh Duc 19144063

Major: Mechanical Engineering Technology

Year of Admission: 2019 – 2023

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HCMC UNIVERSITY OF TECHNOLOGY AND EDUCATION

Faculty of International Education

THE SOCIALIST REPUBLIC OF VIETNAM Independence – Freedom – Hapiness

----o0o----

Ho Chi Minh City, October 01, 2023

GRADUATION THESIS PROJECT TASKS

Instructor’s full name: Mr. Nguyen Van Thuc

Full name of student: Tran Minh Dat Student ID: 19144065 Nguyen Minh Duc Student ID: 19144063 Cao Nguyen Hoang Tien Student ID: 19144330 Major: Mechanical Engineering Technology

Forms of training: Formal training Year of Admission: 2019 – 2023 Class: 19144CLA

Date of delivery: 01/10/2023 Task complete date: 14/03/2024

I. THESIS NAME

Investigating the torsional strength of composite products manufactured through the plastic injection molding process.

II. INITIAL FIGURES AND DOCUMENTS

− Figure trial: according to torsion strength standards, or a specific product. − Material: composite plastic substrate (PLA, TPU).

− Prototyping method: plastic injection molding.

III. CONTENT OF IMPLEMENTATION

− Overview of plastic injection molding technology.

− Overview of materials used for flexible moment-resistant structures.

− Manufacturing prototypes corresponding to various components of composite materials. − Torsional durability testing, statistical analysis and synthesis of results

V. EXPECTED PRODUCTS:

− Realistic product model. − Analysis report.

IV. PRESENTATION LANGUAGE

INSTRUCTORS

(Sign and write full name)

AUTOMATIC CONTROL DEPARTMENT

(Signed & stamped)

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HCMC UNIVERSITY OF TECHNOLOGY AND EDUCATION

Faculty of International Education

THE SOCIALIST REPUBLIC OF VIETNAM Independence – Freedom – Hapiness

----o0o----

Ho Chi Minh City, October 1, 2023

ASSESSMENT FORM OF INSTRUCT LECTURER

Full name of student 1: Tran Minh Dat Student ID: 19144065 Full name of student 2: Nguyen Minh Duc Student ID: 19144063 Full name of student 3: Cao Nguyen Hoang Tien Student ID: 19144330 Major: Mechanical Engineering Technology

Year of admission: 2019 – 2023 Class: 19144CLA Full name Instructor: Mr. Nguyen Van Thuc

Through The Plastic Injection Molding Process.

COMMENT:

1. Regarding the topic content and implementation volume:

... ... ... 2. Pros:

... ... 3. Cons:

... ... 4. Recommend for defend graduation thesis or not?

... 5. Type rating:

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HCMC UNIVERSITY OF TECHNOLOGY AND EDUCATION

Faculty of International Education

THE SOCIALIST REPUBLIC OF VIETNAM Independence – Freedom – Hapiness

Student 2 Student 3

Nguyen Minh Duc Cao Nguyen Hoang Tien

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ACKNOWLEDGEMENT

I would like to extend my sincere appreciation and gratitude to Mr. Pham Son Minh, Mr. Tran Minh The Uyen, Mr. Nguyen Van Thuc and all the professors in the faculty committee for their invaluable support and guidance, which have been instrumental in helping our team successfully complete our graduation project to the best of our abilities.

We are humbled and honored to have had the opportunity to work under your guidance and supervision throughout the 5-month project implementation. Your dedication, passion, and commitment to our academic growth have made a lasting impact on our development as aspiring professionals.

We would also like to express our gratitude to the entire faculty for providing us with a conducive learning environment and the necessary resources to carry out our project effectively. Your unwavering support and commitment to fostering our academic growth have been invaluable.

Once again, we extend our heartfelt thanks to Mr. Pham Son Minh and all the professors in the faculty committee for their invaluable assistance and support throughout our journey. We are truly grateful for the opportunity to learn from your expertise and for your unwavering belief in our abilities. Your guidance has shaped us into better individuals and has prepared us for future endeavors.

Ho Chi Minh City, March 2024 Executed student

(Sign and write full name)

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ABSTRACT

This graduation project focuses on measuring the torsional strength of composite plastic products through injection molding and blending two different types of plastics (PLA, TPU) with various injection parameters. Subsequently, the torsional strength of the products is measured. Finally, based on the experimental measurements, we can determine the final conclusions.

The objectives of the topic are: - Overview of the concept of CTJM

- Overview of plastic injection molding technology - Experimenting with molding products

- Measuring the torsional strength of the products - Synthesizing and analyzing the results

With this project, "Research on the torsional strength of composite products manufactured through the plastic injection molding process," under the guidance of Mr.Nguyen Van Thuc.

The accomplishments achieved by the group in the project are:

- Molding sample products by blending two types of plastics, PLA (100% → 60%) and TPU (0% → 40%)

- Researching the compliant mechanism called constant-torque joint mechanism (CTJM). - Conducting experiments to measure the torsional strength of the products.

- After completing the measurements, we proceeded to plot the torque moment force chart, comparing the results of different types of plastics for analysis.

- Comparing the torsional strength measurement results of the products among different scenarios and drawing the final conclusion of the topic.

After completing the project, the team has learned and gained more insights into the field of plastic injection molds, mechanism design and analysis of torsional moment, a better understanding of plastic molding machines and the parameters for molding various types of plastics, measuring and analyzing torsional moments with compliant mechanisms, and teamwork skills. Through this knowledge, it will establish a foundation for personal development and gain more experience in the future.

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TABLE OF CONTENTS

GRADUATION THESIS PROJECT TASKS ... I ASSESSMENT FORM OF INSTRUCT LECTURER ... II GUARANTEE ... III ACKNOWLEDGEMENT ... I ABSTRACT ... II LIST OF ABBREVIATIONS ... VI LIST OF TABLES ... VII LIST OF CHARTS AND IMAGES ... VIII

CHAPTER 2: THEORETICAL BASIS ... 3

2.1. Overview of constant torque joint mechanism (CTJM) ... 3

2.1.1.Definition... 3

2.1.2.Operational principle ... 3

2.1.3.Characteristics and properties of the constant torque joint mechanism ... 3

2.2. Classification and comparison constant-torque joint mechanisms ... 4

2.2.1.Classification of constant-torque joint mechanisms ... 4

2.2.2.Comparison of constant-torque joint mechanisms ... 5

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2.3. Actual product size ... 6

2.4. Applications of constant torque joint mechanism ... 6

2.5. Domestic and international research ... 7

2.5.1.Domestic research ... 7

2.5.2.International research ... 8

2.6. Compare the CTM compliant mechanism with traditional mechanisms ... 9

2.7. Plastic materials used in the injection molding process ... 10

2.7.1.Overview of PLA and TPU plastics ... 10

2.7.2.The reason for choosing composite plastic ... 14

2.7.3.Definition of composite plastic ... 16

2.8. Overview of injection molding technology ... 16

2.8.1.Definition of the injection molding process ... 16

2.8.2.Advantages and disadvantages of the injection molding technology ... 17

2.8.3.Applications of injection molding in daily life ... 18

2.9. Introduction to Haitian injection molding machine ... 18

2.9.1.Haitian injection molding machine ... 18

2.9.2.The process of using the Haitian plastic injection molding machine ... 20

2.10. Mold Technology ... 23

2.10.1.Definition... 23

2.10.2.Classification of plastic injection molds ... 23

2.10.3.Overview of two-plate mold ... 24

2.10.4.Technical requirements and quality control ... 25

2.11.Torque strength testing machine ... 26

2.11.1.Introduction to Torque Strength Testing Machine ... 26

2.11.2.The functions of the main components on the torque strength ... 27

2.11.3.Main Components of a fixture ... 28

2.12.Introduction to MATLAB ... 31

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2.12.1.Definition... 31

2.12.2.Application ... 31

2.13.Introduction to artificial neural network (ANN) in MATLAB ... 32

2.14.Introduction to Origin software ... 32

CHAPTER 3: EXPERIMENT ... 33

3.1.The implementation process ... 33

3.2.Injection molding parameters ... 33

3.3.Perform torque measurement ... 38

CHAPTER 4: EXPERIMENTAL RESULTS ... 41

4.1.The steps of data processing ... 41

4.2.Proceeding with data processing ... 41

4.3.Using artificial neural network (ANN) in MATLAB. ... 54

4.4.Comparing results between ANN and the experiment. ... 57

CHAPTER 5: CONCLUSION AND DEVELOPMENT DIRECTION ... 64

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LIST OF ABBREVIATIONS

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LIST OF TABLES

Table 2.1: Physical properties of PLA ... 11

Table 2.2: Physical properties of TPU ... 13

Table 2.3: Table of plastic mixing ratios and plastic weights for each case ... 15

Table 3.1: Injection molding parameters for Case 1 ... 34

Table 3.2: Injection molding parameters for Case 2 ... 35

Table 3.3: Injection molding parameters for Case 3 ... 36

Table 3.4: Injection molding parameters for Case 4 ... 36

Table 3.5: Injection molding parameters for Case 5 ... 37

Table 3.6: The result table after completing the torsion torque test process ... 40

Table 4.1: Table illustrating the constant-torque and TFA of the product in Case 1 ... 43

Table 4.2: Table illustrating the constant-torque and TFA of the product in Case 2 ... 45

Table 4.3: Table illustrating the constant-torque and TFA of the product in Case 3 ... 47

Table 4.4: Table illustrating the constant-torque and TFA of the product in Case 4 ... 49

Table 4.5: Table illustrating the constant-torque and TFA of the product in Case 5 ... 51

Table 4.6: Table illustrating the constant-torque and TFA of the product in all Case ... 53

Table 4.7: Table of 8 input variables ... 55

Table 4.8: Table of input variables ... 56

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LIST OF CHARTS AND IMAGES

Figure 2.1: Real-world products applying the CTJM mechanism ... 3

Figure 2.2: Diagram of distributed compliance model (Type I) [1] ... 4

Figure 2.3: Diagram of the distributed compliance model (Type II) [1] ... 5

Figure 2.4: Actual product size ... 6

Figure 2.5: Applications of the Constant Torque Joint Mechanism (CTJM) Product [1] ... 7

Figure 2.6: Concept of a CTM in domestic research [2] ... 8

Figure 2.7: Concept of a CFM and CTM of china research [3] ... 9

Figure 2.8: Polylactic Acid (PLA) [4] ... 10

Figure 2.9: Applications of Polylactic Acid (PLA) [4] ... 12

Figure 2.10: Thermoplastic Polyurethane (TPU) [5] ... 13

Figure 2.11: Applications of Thermoplastic Polyurethane (TPU) [5] ... 14

Figure 2.12: Weighing and mixing PLA and TPU plastics ... 16

Figure 2.13: The operating principle of plastic injection molding [7] ... 17

Figure 2.14: Plastic Machine Haitian MA 1200III ... 19

Figure 2.15: The structure of the 5 basic systems of the Haitian plastic injection molding machine [8] ... 20

Figure 2.16: Imagine clamping mold ... 20

Figure 2.17: Simulation image of the injection molding process [9] ... 21

Figure 2.18: Haitian Plastic Dryer (Real-Life Image) ... 22

Figure 2.19: Haitian Plastic Shredder (Real-Life Image) ... 22

Figure 2.20: Images of PLA plastic before and after using the HAITIAN plastic shredder . 23 Figure 2.21: Real-life and Software-Based mold images ... 24

Figure 2.22: Structure of a two-plate mold [10]... 25

Figure 2.23: Torque strength testing machine (Real-Life Image) ... 26

Figure 2.24: Real-life image fixture components for testing torsional moment ... 29

Figure 2.25: Components of a fixture (3D and real life imagines) ... 29

Figure 2.26: Assembly of the fixture in the Inventor assembly environment and reality ... 30

Figure 2.27: Complete clamping device along with the standard sensor ... 31

Figure 3.1: Image of 5 injection molding parameters ... 34

Figure 3.2: Image of injection molding parameters in case 1 ... 35

Figure 3.3: Image of injection molding parameters in case 2 ... 35

Figure 3.4: Image of injection molding parameters in case 3 ... 36

Figure 3.5: Image of injection molding parameters in case 4 ... 37

Figure 3.6: Image of injection molding parameters in case 5 ... 37

Figure 3.7: Actual products of the 5 cases ... 38

Figure 3.8: Actual images of the product and the fixture ... 38

Figure 3.9: Installation and fixation of torque testing machine ... 39

Figure 3.10: The interface of the TIA Portal software and torque strength testing machine. 39 Figure 4.1: Graph illustrating the deformation of the product in Case 1 ... 42

Figure 4.2: Graph illustrating the constant-torque and TFA of the product in Case 1 ... 42

Figure 4.3: Graph illustrating the deformation of the product in Case 2 ... 44

Figure 4.4: Graph illustrating the constant-torque and TFA of the product in Case 2 ... 44

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Figure 4.5: Graph illustrating the deformation of the product in Case 3 ... 46

Figure 4.6: Graph illustrating the constant-torque and TFA of the product in Case 3 ... 46

Figure 4.7: Chart Showing The Deformation Of The Product In Case 4 ... 48

Figure 4.8: Graph illustrating the constant-torque and TFA of the product in Case 4 ... 48

Figure 4.9: Chart Showing The Deformation Of The Product In Case 5 ... 50

Figure 4.10: Graph illustrating the constant-torque and TFA of the product in Case 5 ... 50

Figure 4.11: Chart Showing The Deformation Of The Product In All Case ... 52

Figure 4.12: Graph illustrating the constant-torque and TFA of the product in all case ... 52

Figure 4.13: Product and experiment in Taiwan research ... 54

Figure 4.14: Input data ... 55

Figure 4.15: Output data ... 56

Figure 4.16: Training ANN ... 57

Figure 4.17: Results after running with input and output parameters ... 57

Figure 4.18: A chart illustrating the results of the experiment and the ANN in case 1 ... 58

Figure 4.19: Graph illustrating the constant-torque and TFA of the ANN and experiment in Case 1 ... 58

Figure 4.20: A chart illustrating the results of the experiment and the ANN in case 2 ... 59

Figure 4.21: Graph illustrating the constant-torque and TFA of the ANN and experiment in Case 2 ... 59

Figure 4.22: A chart illustrating the results of the experiment and the ANN in case 3 ... 60

Figure 4.23: Graph illustrating the constant-torque and TFA of the ANN and experiment in Case 3 ... 60

Figure 4.24: A chart illustrating the results of the experiment and the ANN in case 4 ... 61

Figure 4.25: Graph illustrating the constant-torque and TFA of the ANN and experiment in Case 4 ... 61

Figure 4.26: A chart illustrating the results of the experiment and the ANN in case 5 ... 62

Figure 4.27: Graph illustrating the constant-torque and TFA of the ANN and experiment in Case 5 ... 63

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CHAPTER 1: INTRODUCTION

1.1. Reasons for choosing the topic

In the modern industrial era, machinery and composite products are playing increasingly crucial roles. Composite products are commonly used in industries such as robotics, healthcare, and various other fields, all of which have high demands for torsional strength. This issue not only affects the quality of service and products but also their performance and safety during usage. To meet the escalating demands for accuracy and durability, research on the torsional strength of composite products has emerged as a significant research direction. Therefore, the team has decided to select the topic “Research on the torsional strength of composite products manufactured from the plastic injection molding process”, specifically mixing two types of plastics PLA and TPU to create a new composite plastic with superior properties compared to the original plastic in order to enhance the torsional strength of the product.

− Researching the Constant-Torque Joint Mechanism (CTJM).

− Research on the blending ratio of two types of PLA and TPU plastics to create a new composite plastic.

− Experimenting and evaluating the torsional strength of different composite plastic cases.

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− Utilizing ANN tool to predict outcomes and compare them with experimental results.

1.4. Approaches, Research Methods 1.4.1. Approach method:

− Theory of Constant-Torque Joint Mechanism (CTJM), theory of plastic injection molding technology, overview of PLA, TPU and composite plastics, theory of ANN prediction algorithm, etc.

− Approach by applying the above theories to conduct experiments and evaluate data from various composite cases.

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CHAPTER 2: THEORETICAL BASIS

2.1. Overview of constant torque joint mechanism (CTJM) 2.1.1. Definition

A constant-torque joint mechanism (CTJM) provides a nearly constant torque over a specific rotation interval. Instead of using sensor control, CTJMs passively maintain a constant torque. Potential applications include dynamic and static balancing of machines, human joint rehabilitative devices, and human mobility-assisting devices[1].

Joint mechanism of

2.1.3. Characteristics and properties of the constant torque joint mechanism

Some main characteristics of the Constant Torque Joint Mechanism (CTJM) include important factors related to its capability and performance in specific applications. Below are some of the main characteristics of CTJM:

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CTJM is an adaptable mechanism with the potential to customize its features and applications according to specific needs and criteria, particularly in Robotics, Medical, Automation, and industry.

2.2. Classification and comparison constant-torque joint mechanisms 2.2.1. Classification of constant-torque joint mechanisms

The design of Constant Torque Joint Mechanism (CTJM) using a distributed-compliance model can be classified into two types:

a. A distributed-compliant limb parameterized by using five segments (Type I):

This type utilizes five symmetrically placed segments (lengths ranging from L2 to L6) surrounding the design space in an arc-shaped configuration. Each segment can bend and stretch, divided into six nodes (n2–n7). The optimization objective is to adjust the values of

Figure 2.2: Diagram of distributed compliance model (Type I) [1]

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b. A distributed-compliant limb parameterized by using three segments (Type II)

It also uses five symmetric segments (from L2 to L6), but simplified with two curved segments (L2 and L4) and one straight segment (L3). The optimization goal is to minimize shape variation and optimize the flatness of the constant-torque region[1].

Figure 2.3: Diagram of the distributed compliance model (Type II) [1]

2.2.2. Comparison of constant-torque joint mechanisms

The choice between Type I and Type II of the constant-torque joint mechanism (CTJM) depends on specific factors of the application as well as design requirements. Here are some important points to consider when determining when to use each type:

Type I (Five-Segment Limb):

• This type is more complex than Type II as it utilizes five limb segments.

• Type I is suitable when there is a need to distribute stiffness and compliance of the mechanism across the entire limb.

Type II (Three-Segment Limb):

• This type is simplified with only three limb segments, reducing the complexity of the mechanism.

• Type II is suitable when you want a simplified model with good performance and easy adjustment.

Since the project aims for applications requiring flexibility and evenly distributed stiffness, Type I is chosen.

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2.3. Actual product size

The detailed dimensions of the CTJM moment structure model are as follows: it has a diameter of ϕ 90mm and a thickness of 5mm. This structure comprises 4 legs, each with a thickness of 0.9mm capable of clockwise bending. The model includes 4 fixed holes and 1 square hole in the middle with dimensions of 9mm and a 3mm fillet, connected by a spline curve designed to securely hold the product for torsion strength testing. The product was designed using Inventor software.

Figure 2.4: Actual product size

2.4. Applications of constant torque joint mechanism

This mechanism can be found in many application including technological or medical services and daily life products.

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Figure 2.5: Applications of the Constant Torque Joint Mechanism (CTJM) Product [1]

Figure A Robotics: CTJM is integrated into robot arms to balance loads and maintain

equilibrium positions while performing specific tasks. This helps improve the accuracy and efficiency of the robot.

Figure B and C Medical: CTJM can be used to create constant torque angles in

applications such as knee support devices or artificial limbs. This helps reduce pressure and increase comfort for users.

Figure D Automation and Industry: In automation and industrial systems, CTJM can

be used to maintain stable torsional stiffness in joints and moving shafts.

Additionally, in the field of research and development, CTJM can be used to explore aspects of compliant mechanisms and precise torque control[1].

2.5. Domestic and international research 2.5.1. Domestic research

Medical or healthcare devices assisting in the rehabilitation of human joints often rely on functional mechanisms that could provide stable output torque. To achieve this target, available equipment usually uses motorized mechanisms combined with complicated sensor control systems. This paper presents a novel design concept of a monolithic compliant

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constant-torque mechanism (CTM). It could produce an output torque that does not change in a prescribed input rotation. Thanks to the monolithic nature of the compliant mechanism, the device is more compact, lightweight, and portable regardless of sensors or actuators. However, to be used in rehabilitation equipment, the mechanism must produce a stable output torque over a sufficiently wide range of operation. The design methodology of this compliant CTM uses genetic algorithm shape optimization. After obtaining the optimal configuration, finite element analysis is used to verify the design. This chapter also proposes a general design formulation to find the CTMs with a certain constant output torque within a specified input rotation range that can be used for human joint rehabilitative devices or human mobility-assisting devices[2].

Figure 2.6: Concept of a CTM in domestic research [2]

2.5.2. International research

− China research

The working principle of conventional compliant mechanisms is based on Hooke’s law. The reaction force of the structure is proportional to its deformation. Thus, if a compliant mechanism is required to generate a large displacement, a large driving force is the precondition. This phenomenon causes the challenge of achieving a large stroke by using an actuator with limited driving force. To overcome this problem and to meet the demand of some applications, the compliant constant-force mechanism (CFM) or statically balanced compliant mechanism has been proposed. Different from conventional compliant

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mechanisms, the CFM does not obey the Hooke’s law. The CFM has been a hot research topic and many kinds of constant-force devices have been developed in the literature. For instance, compliant microgrippers with constant gripping force constant-force robot end-effectors and micro-positioning stages with constant driving force have been proposed. However, all of these designs provide linear output motion. They are not suitable for use in some cases (e.g., joints and rotation platform), where the CFM with a rotational motion is needed. Such a kind of CFM is called a constant-torque mechanism (CTM). This paper aims to develop a novel compliant rotary positioning stage with constant output torque and a simple structure. Similar to CFM, a CTM can be realized by different structure design strategies, such as combining positive-stiffness and negative-stiffness beams or using curved beams directly. In this paper, a new constant-torque rotary stage is devised by only adopting straight beams to yield a simple structure. As compared to existing designs using complex curved beams the proposed design is much easier to be fabricated owing to the use of straight beams[3].

Figure 2.7: Concept of a CFM and CTM of china research [3]

2.6. Compare the CTM compliant mechanism with traditional mechanisms

Compliant mechanisms are devices that can transform motion or force through the deformation of their own structure. Compared to conventional mechanisms, compliant mechanisms offer several advantages. They can mitigate issues like backlash, friction, and

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wear, which are common in traditional mechanisms. Additionally, compliant mechanisms are often more cost-effective and compatible with vacuum environments. These advantages have led to widespread adoption of compliant mechanisms in precision engineering applications, enabling ultra-high precision motion in devices such as micropositioning stages, microgrippers, microinjectors, and others.[3]

2.7. Plastic materials used in the injection molding process 2.7.1. Overview of PLA and TPU plastics

− Polylactic Acid (PLA) plastic

Polylactic Acid (PLA) plastic is a thermoplastic polymer that softens when heated and hardens when cooled. It is made from renewable resources, such as cornstarch and sugarcane. It is also biodegradable under the right circumstances, which would be a facility where plastic scraps are turned into fertilizer by microbes, which must reach 140 degrees for 10 days, in order to compost the material. PLA cannot be composted in your typical compost heap. PLA plastic is commonly used as filament in 3D printing to create 3D-printed parts.[4]

Figure 2.8: Polylactic Acid (PLA) [4]

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Table 2.1: Physical properties of PLA

Glass transition temperature – Tg

The chemical properties of PLA

− PLA is typically made from fermented plant starch such as from corn, beets, sugarcane,

or coconut husks.

− PLA is considered biodegradable and depends on various factors such as

temperature, moisture, and the presence of specific enzymes.

− PLA dissolves in many solvents, including chlorine solvents and some esters. − PLA can undergo photodegradation when exposed to ultraviolet (UV) light.

Application of PLA plastic:

− PLA plastic is often used in the production of biodegradable packaging materials,

including films, boxes, and trays.

− PLA plastic is used to produce disposable items such as cups, plates, and bowls. These

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products can decompose after use, reducing environmental impact compared to traditional petroleum-derived plastics.

− In the garment industry, PLA is becoming popular as it is used in the production of

environmentally friendly fabrics. These fabrics are commonly used in clothing, bed sheets and other textile products.

− PLA is a popular material for 3D printing filaments due to its ease of use, low toxicity,

and biodegradability. It is commonly used in 3D printers for prototyping and creating a variety of objects.

− PLA films and coatings are used in many applications, including in the production of

biodegradable bags, agricultural films and coatings for paper products.

Figure 2.9: Applications of Polylactic Acid (PLA) [4]

− Thermoplastic Polyurethane (TPU)

Thermoplastic Polyurethane (TPU) is a type of polymer belonging to the elastomer family of thermoplastic materials. It is known for its combination of flexibility and resilience

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commonly found in rubber, with the processing and molding characteristics typical of thermoplastics. It is soft to the touch but extremely durable and strong. It offers high abrasion resistance and is capable of resisting oils, greases, and solvents well.[5]

Figure 2.10: Thermoplastic Polyurethane (TPU) [5]

Table 2.2: Physical properties of TPU

Maximum Operating Temperature without Load

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The chemical properties of TPU

− TPU typically has resistance to oils, greases, and some chemicals. − TPU can withstand the impact of ultraviolet (UV) radiation.

Applications of TPU plastic

− TPU is used in the production of sporting goods such as athletic shoe soles, swim fins, sports equipment handles, and protective gear due to its flexibility, lightweight, and durability.

− TPU is suitable for medical applications, including tubing, hoses, and other flexible medical devices. It is body-friendly and can be easily sterilized, making it a reliable choice for many medical applications.

− TPU is used in the automotive industry to manufacture various components such as seals, gaskets, hoses, and interior trim due to its resistance to oils, chemicals, and abrasion.

Figure 2.11: Applications of Thermoplastic Polyurethane (TPU) [5]

2.7.2. The reason for choosing composite plastic

In this project, we decided to use composite plastic because we can adjust the ratio and blend between two types of PLA and TPU plastics to create a material with combined

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properties of both, including the flexibility and elasticity of TPU along with the higher mechanical strength, hardness, and ease of processing of PLA. Additionally, composite plastics also have the ability to be recycled and reused, contributing to environmental protection. This opens up many application opportunities in various fields from technology to healthcare.

create composite plastics. The team will divide them into 5 specific cases: 100% PLA, 90% PLA and 10% TPU, 80% PLA and 20% TPU, 70% PLA and 30% TPU, 60% PLA and 40% TPU. For each case, the team will accurately weigh the total plastic mass in each case, which is 700 grams.

Table 2.3: Table of plastic mixing ratios and plastic weights for each case

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Figure 2.12: Weighing and mixing PLA and TPU plastics

2.7.3. Definition of composite plastic

A composite material is made up of two or more materials with different chemical and physical properties. A composite material is used to enhance the properties of its base materials.

The production process of composite plastic typically involves blending the components, then subjecting them to manufacturing processes such as compression molding, injection molding to produce final products with customized properties. Various types of composite plastics are used in a wide range of applications, including automotive, aerospace, construction materials, and industrial manufacturing.[6]

2.8. Overview of injection molding technology 2.8.1. Definition of the injection molding process

Injection molding is a manufacturing process used to produce parts or products in bulk by injecting molten material into a mold. The injection molding process can be carried out on various types of materials, primarily metals (commonly referred to as pressure die casting), glass, elastomers, composites, and most commonly, plastics. Plastics can be in the form of

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Figure 2.13: The operating principle of plastic injection molding [7]

2.8.2. Advantages and disadvantages of the injection molding technology

a. Advantages:

− Complex Shapes: Injection molded parts can retain very high precision for extremely small parts, which cannot be achieved through conventional machining processes economically. − Speed and Scale: The plastic injection process can rapidly produce large quantities of parts in batches, with a mold containing multiple cavities to produce identical products in a single injection cycle. Therefore, it is highly suitable for mass production.

− Waste Reduction: Injection molding generates minimal material waste, as excess material can often be recycled.

− Material Versatility: Injection molding supports various types of materials, including thermoplastics, thermosets, and elastomers, allowing flexibility in product design.

− Low Labor Costs: This process is largely automated, minimizing the need for manual labor in the manufacturing process.

b. Disadvantages:

− Design Limitations: Due to the need for the mold to be opened and ejected, there are

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designs that cannot be injection molded or are very difficult to mold.

− High Initial Costs: To use injection molding technology to produce a desired product in terms of size, precision, aesthetics, etc., the first step is to invest in designing a complete and precise mold. Therefore, the cost is often very high.

2.8.3. Applications of injection molding in daily life

Injection molding technology has a wide range of applications in industry and manufacturing. It also helps reduce manufacturing costs, optimize time, and enhance the ability to shape diverse products. Additionally, it plays a crucial role in recycling plastic materials, contributing to environmental protection efforts. Nowadays, the demand for plastic products is increasing, and the scope of application of injection molding machines is expanding in many fields and industries, including:

• Plastic packaging manufacturing industry: plastic bags, plastic shells, plastic bottles… • Food packaging industry: shells, candy boxes, food trays...

• Pharmaceutical industry: drug packaging, blister packs...

• Construction industry: partitions, plastic ceilings, sanitary equipment…

• Automobile manufacturing industry: wipers, control levers, door handles, control panels, sunroof shades…

2.9. Introduction to Haitian injection molding machine 2.9.1. Haitian injection molding machine

In this graduation project, the injection molding machine used by the team is the Haitian MA 1200III injection molding machine from HAITIAN company.

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Figure 2.14: Plastic Machine Haitian MA 1200III

The machine is equipped with a new motor and intelligent motion control, providing more precise processes in various wide-ranging applications such as consumer goods, toys, or construction. The Mars series (MA III) from HAITIAN represents innovation and upgrades compared to the Saturn series (SA), characterized by energy efficiency and environmental protection features.

There are 5 basic systems of the injection molding machine that operators, maintenance, and repair personnel of old injection molding machines need to know when working with the machine:

- Clamp system - Mold system - Injection system

- Injection support system - Control system

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Clamp system

Injection system

Injection pressure support system

Figure 2.16: Imagine clamping mold

Step 2: Injection Molding

When the two plates of the mold are clamped together, the injection molding process can begin. The plastic, usually in the form of pellets or granules, is melted into a complete liquid. Then, this liquid is injected into the mold. Manufacturers need to ensure stable temperature

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control throughout this step of the process.

Figure 2.17: Simulation image of the injection molding process [9]

Step 3: Dwelling

During the dwelling phase, the molten plastic fills the entire mold. Pressure is applied directly to the mold to ensure complete filling of all gaps and the produced product matches the mold exactly.

Step 4: Cooling

The cooling phase is the simplest stage; the mold should be left still so that the hot plastic inside can cool and solidify into a usable product that can be safely removed from the mold.

Step 5: Mold Opening

Once the part has cooled, a clamp motor will slowly open the two parts of the mold to make the removal of the final product safe and easy.

Step 6: Ejection

As the mold opens, an ejector pin will slowly push the solidified product out of the open mold cavity. The manufacturer should then use cutting tools to remove any excess material and finish the final product for use by the customer. Excess material can often be recycled and reintroduced into the molding process for the next part, reducing your material costs.[9]

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Figure 2.18: Haitian Plastic Dryer (Real-Life Image)

The Haitian plastic dryer is a type of drying machine used in the plastic manufacturing process to remove or reduce the moisture content of plastic materials before they are fed into injection molding machines or other production processes. Before being put into use, the

Figure 2.19: Haitian Plastic Shredder (Real-Life Image)

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A plastic shredder is an industrial device used to shred, cut, and process various types of plastic materials into smaller pieces. This process helps minimize plastic waste and creates a source of recycled materials for producing new plastic products. The team used a Haitian plastic shredder to grind PLA plastic into small pieces.

Figure 2.20: Images of PLA plastic before and after using the HAITIAN plastic shredder

2.10. Mold Technology 2.10.1. Definition

Mold is a tool (equipment) used to shape products by molding method, molds are designed and manufactured for use in a certain number of cycles, which may be once or multiple times. The structure and dimensions of the mold are designed and fabricated depending on the shape, size, quality, and quantity of the product to be produced. Additionally, there are many other issues to consider such as the technological specifications of the product (angles, mold temperature, processing pressure, etc.), the properties of the processing material (shrinkage, elasticity, hardness, etc.), and economic criteria for the mold set.[10]

2.10.2. Classification of plastic injection molds

Molds are a crucial component in the process of manufacturing plastic products through injection molding. There are various ways to classify molds based on different factors such as: [10]

- According to the number of mold cavities: • Single-cavity mold

• Multi-cavity mold

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- According to the type of runner system: • Hot runner mold

• Cool runner mold

- According to the runner layout: • Two-plate mold

• Three-plate mold

- According to the number of plastic colors for the product: • Mold for single-color product

• Mold for multi-color product

In this project, we use two-plate plastic injection molds:

Figure 2.21: Real-life and Software-Based mold images

2.10.3.Overview of two-plate mold

A two-plate mold is an injection mold that utilizes a cold runner system, with the runners positioned horizontally on the mold parting line. The gate for plastic injection is located at the side of the product, and when the mold is opened, there is only one opening to retrieve both the product and the plastic runner.

For a two-plate mold, the gate can be designed in such a way that the product and the plastic runner automatically separate or remain attached when removed from the mold.

The method of using a two-plate mold is very common in injection mold systems. The mold consists of two parts: the front mold (cavity) and the back mold (core). The structure of

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the mold is simple and easy to fabricate, but two-plate molds are typically used for products with simple gate configurations.[10]

Two-plate mold has a single cavity

Two-plate mold has multiple cavities

Two-plate mold has interchangeable cores

Two-plate mold has nested interchangeable cores

Figure 2.22: Structure of a two-plate mold [10]

2.10.4.Technical requirements and quality control

Technical Requirements of the Plastic Mold:

• Ensure accuracy in product dimensions and shapes.

• Check the necessary glossiness for both the mold cavity and core to ensure the glossiness of the product.

• Ensure accurate alignment between the two mold halves. • Ensure easy product removal from the mold.

• The mold material must have high wear resistance and be easy to process. • Check the hardness of the mold during operation.

• The mold must have a cooling system around the perimeter of the mold cavity. Quality Control:

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• Product inspection: Plastic products are inspected to ensure they meet quality and size standards.

• Mold adjustment: If necessary, the mold may be adjusted to improve product quality and production efficiency.

2.11. Torque strength testing machine

2.11.1. Introduction to torque strength testing machine

A torque strength testing machine is a device used to measure and test the torque of products. The primary function of a torque testing machine is to measure the strength of the torque-applied product. This can be important in ensuring that products manufactured meet technical and safety requirements[11].

PLC CONTROL

CONNECTION WIRE TO COMPUTER

JAW CHUCK

THREE-GEAR MOTOR

GEAR SHAFT

Figure 2.23: Torque strength testing machine (Real-Life Image)

Machine specifications: − Power: 40W

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