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 MAN
Trang 1MINISTRY 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
Trang 2MINISTRY 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
Trang 3HCMC 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)
Trang 4HCMC 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:
Trang 5HCMC 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
Trang 6ACKNOWLEDGEMENT
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)
Trang 7ABSTRACT
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
Trang 8TABLE 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
Trang 92.3 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
Trang 102.12.1.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
Trang 11LIST OF ABBREVIATIONS
Trang 12LIST 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
Trang 13LIST 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
Trang 14Figure 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
Trang 15CHAPTER 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
Trang 16− 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
Trang 17CHAPTER 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:
Trang 18CTJM 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]
Trang 19b 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
Trang 202.3 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
Trang 21Figure 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
Trang 22constant-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
Trang 23mechanisms, 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
Trang 24wear, 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]
Trang 25Table 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
Trang 26products 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
Trang 27commonly 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
Trang 28The 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
Trang 29properties 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
Trang 30Figure 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
Trang 31Figure 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
Trang 32designs 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
Trang 33Figure 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
Trang 34Clamp 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
Trang 35control 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]
Trang 36Figure 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)
Trang 37A 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
Trang 38- 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
Trang 39the 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:
Trang 40• 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