LINK TẢI LUẬN VĂN MIỄN PHÍ CHO AE KET-NOI
Nghiên cứu khả năng chế tạo kết cấu mềm tuân theo mômen bằng phương pháp ép phun nhựa
Researching the manufacturing capability of moment-compliant soft structures using plastic injection molding method
ACKNOWLEDGEMENT
We could not have successfully completed our graduation project without the support of everyone around us. Thanks to the dedicated and passionate teaching of our instructors, who imparted knowledge and supported us throughout our learning journey. With deep appreciation, we sincerely thank:
✓Assoc. Prof. Ph.D. Pham Son Minh - our main project supervisor, who patiently guided and provided favorable conditions for us during the project implementation. He always took the time to make detailed corrections and give instructions to achieve the best results.
✓Ph.D. Nguyen Trong Hieu - project leader for his dedicated guidance in the process of researching, designing and manufacturing plastic injection molds to create soft moment structure models.
✓Ph.D. Tran Minh The Uyen - for providing equipment and tools that made our graduation project more efficient.
✓ We would also like to acknowledge the faculty members at Ho Chi Minh City University of Technology and Education for their dedication to teaching and their contributions to our academic development.
✓Lastly, we extend our gratitude to the Board of Directors of the university for creating a conducive environment that supports students and learners in their research and projects.
In conclusion, we wish to express our heartfelt appreciation to all the instructors for their dedication and tireless efforts. We wish them good health, happiness, and youthful spirits as they continue to educate future generations.
Author
v
SUMMARY
Topic: “Researching the manufacturing capability of moment-compliant soft structures using plastic injection molding method”.
Summary: Continuing the research process of previous students. In this topic, the team focuses on designing and manufacturing plastic molding dies for soft moment- resistant structures, laying the groundwork for subsequent groups to use the molds to create products for future research and storage purposes.
Target: Apply and maximize the knowledge learned in the field molds in particular and mechanics in general. The group has researched, designed and manufactured a set of plastic injection molds for soft moment structures.
Content:
• Knowledge of injection molds.
• Knowledge of moment-compliant soft structures.
• Fabrication and assembly.
• Testing injection mold.
Conclusion: After completing the project. The resulting product is a complete set of injection molds and can be used in research and production with high automation. Besides, our team has gained more practical knowledge in the mold making process, thereby helping us to have more confidence when entering the actual work later. However, in the process of making, there are many mistakes due to lack of experience, leading to repeated corrections and time consuming.
vi
TABLE OF CONTENTS
MISSION OF THE GRADUATION THESIS ..........................................................i ASSESSMENT FORM OF INSTRUCT LECTURER.............................................ii ASSESSMENT FORM OF DECIPATION LECTURER...................................... iii GUARANTEE ...........................................................................................................iv ACKNOWLEDGEMENT ..........................................................................................v SUMMARY................................................................................................................vi TABLE OF CONTENTS .........................................................................................vii LIST OF TABLES ....................................................................................................xi LIST OF F IGURES ............................................................................................... xiii LIST OF ABBREVIATION....................................................................................xvi CHAPTER 1: OVERVIEW .......................................................................................1
1.1 Overview of moment-resisting soft structure. ...................................................1 1.2 Overview of the Constant-Torque Joint Mechanism (CTJM)...........................1 1.3 Reasons for choosing the topic ..........................................................................3
1.3.1 Why choose the CTJM structure .................................................................3 1.3.2 Why choose moment-resisting soft structures using the plastic injection
molding method?..................................................................................................4 1.4 Topic objective ..................................................................................................5 1.5 Research methods ..............................................................................................5 1.6 Research scope...................................................................................................5
CHAPTER 2: THEORETICAL BASIS ....................................................................7
2.5 Choose soft structures........................................................................................7 vii
2.1 Overview of mold ..............................................................................................9 2.2 Overview of plastic injection molding ..............................................................9 2.2.1 Plastic injection molding technology ..........................................................9 2.2.2 Overview of plastic injection machines ....................................................11 2.3 Classification of plastic injection molds..........................................................14 2.3.1 Two-plate mold. ........................................................................................14 2.3.2 Three-plate mold. ......................................................................................16 2.4 Overview of PP plastic (Polypropylene) .........................................................18 CHAPTER 3: DESIGN AND F ABRICATION OF MOLDS ................................21 3.1 Redesign product: ............................................................................................21 3.2 Shrinkage coefficient of the product................................................................23 3.3 Manufacturing the mold ..................................................................................23 3.3.1 Mold release angle.....................................................................................23 3.3.2 Calculate the number of mold cavities [6]. ...............................................23 3.3.3 Mold separation.........................................................................................26 3.4 Plastic runner design........................................................................................30 3.4.1 Sprue bushing design.................................................................................30 3.4.2 Calculate runner diameter .........................................................................31 3.4.3 The nozzle .................................................................................................32 3.5 Designing the ejection system .........................................................................34 3.6 Designing the cooling system..........................................................................35 3.7 Analysis of simulation results..........................................................................40 3.8 Selecting standard components........................................................................48
viii
3.8.1 Sprue bushing ............................................................................................48 3.8.2 Locating ring .............................................................................................49 3.8.3 Return pin ..................................................................................................49 3.8.4 Guide pin ...................................................................................................50 3.8.5 Ejector pin .................................................................................................52
CHAPTER 4: THE MANUFACTURING AND ASSEMBLY PROCESS...........53
4.1 Workpiece preparation.....................................................................................53
4.2 Manufacturing process of core plate................................................................54
4.2.1 Routing 1: Milling bottom surface, the side surface and machining holes ............................................................................................................................54
4.2.2 Rough 2: Milling top surface, 2 sides left, insert cavity ...........................61
4.2.3 Manufacturing process of cavity plate ......................................................64 4.3 Deburring and polishing ..................................................................................66 4.4 Mold assembly .................................................................................................72 4.5 Procedure .........................................................................................................75 4.6 Parameters of the molding machine used ........................................................76 4.7 Test molding ....................................................................................................76
CONCLUSION.........................................................................................................79
Conclusion .............................................................................................................79 Limitations of the project: .....................................................................................79 Development and orientation.................................................................................80
REFERENCES ............................................................Error! Bookmark not defined. APPENDIX...............................................................................................................81
ix
Milling mold cavity and machining holes .............................................................83 Manufacturing process of top clamp plate.............................................................86 Rough 1: Milling bottom surface, 2 sides surface and machining holes ...........86 Rough 2: Milling top surface and another sides surface ....................................90 Manufacturing process of spacer block .................................................................91 Rough 1: Milling bottom surface, 2 sides surface and machining holes ...........91 Rough 2: Milling top surface and another sides surface ....................................93 Manufacturing process of retainer plate ................................................................94 Rough 1: Milling bottom surface, 2 sides surface and machining holes ...........94 Rough 2: Milling top surface and another sides surface ....................................98 Manufacturing process of ejector plate..................................................................99 Rough 1: Milling bottom surface, 2 sides surface and machining holes ...........99 Rough 2: Milling top surface and another side surfaces ..................................101 Manufacturing process of bottom plate ...............................................................102 Rough 1: Milling bottom surface, 2 sides surface and machining holes .........102 Rough 2: Milling top surface and another sides...............................................105
x
LIST OF TABLES
Table 2.1: The physical characteristics of PP plastic................................................20 Table 2.2: The mechanical properties of PP plastic..................................................19 Table 2.3: Compare 2 type of soft structure................................................................8 Table 3.1: Redesign product .....................................................................................21 Table 3.2: Table caculate number mold cavities.......................................................26 Table 3.3: Create workpiece and separate mold .......................................................26 Table 3.4: Designing cooling system using NX software.........................................38 Table 4.1: Dimensions of the mold parts ..................................................................53 Table 4.2: Manufacturing process of core plate in rough 1 ......................................58 Table 4.3: Manufacturing process of core plate in rough 2 ......................................61 Table 4.4: Manufacturing process of core plate in rough 3 ......................................63 Table 4.5: Manufacturing of cavity plate in rough 1 ................................................64 Table 4.6: Mold assembly .........................................................................................72 Table 4.7: Input parameter ........................................................................................77 Table 4.8: Manufacturing of cavity plate in rough 2 ................................................83 Table 4.9: Manufacturing of top clamp plate in rough 1 ..........................................86 Table 4.10: Manufacturing of top clamp plate in rough 2 ........................................90 Table 4.11: Manufacturing of spacer block in rough 1.............................................91 Table 4.12: Manufacturing of spacer block in rough 2.............................................93 Table 4.13: Manufacturing of retainer plate in rough 1............................................94 Table 4.14: Manufacturing of retainer plate in rough 2............................................98 Table 4.15: Manufacturing of ejector plate in rough 1 .............................................99
xi
Table 4.16:Manufacturing of ejector plate in rough 2 ............................................101 Table 4.17: Manufacturing of bottom plate in rough 1...........................................102 Table 4.18: Manufacturing of bottom plate in rough 2...........................................105
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LIST OF FIGURES
Figure 1.1: Applications of CTJMs.............................................................................2 Figure 2.1: Type I [1] ..................................................................................................7 Figure 2.2: Type II [1].................................................................................................7 Figure 2.3: Plastic injection molding machine [3]....................................................11 Figure 2.4: Spray system [3] .....................................................................................13 Figure 2.5: Basic two-plate mold [4]. .......................................................................15 Figure 2.6: Three-plate mold [5]...............................................................................17 Figure 2.7: Polypropylene plastic [5]........................................................................18 Figure 3.1: The mass and volume of the detail .........................................................22 Figure 3.2: Calculate the dimensions of the sprue ....................................................31 Figure 3.3: Table of common cross-sectional types of plastic runners.....................31 Figure 3.4: Fan gate [7].............................................................................................32 Figure 3.5: Caculate fan gate [7]...............................................................................33 Figure 3.6: Fan gate...................................................................................................33 Figure 3.7: Fan gate...................................................................................................34 Figure 3.8: Ejection system.........................................Error! Bookmark not defined. Figure 3.9: The importance of mold cooling time [7]...............................................35 Figure 3.10: Design cooling system..........................................................................36 Figure 3.11: Cooling system .....................................................................................37 Figure 3.12: Filling Melt Front Time........................................................................40 Figure 3.13: Air trap..................................................................................................41 Figure 3.14: Pressure.................................................................................................42
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Figure 3.15: Temperature..........................................................................................43 Figure 3.16: Temperature..........................................................................................44 Figure 3.17: Filling volumetric shrinkage.................................................................44 Figure 3.18: The temperature of the product after the cooling process ....................45 Figure 3.19: The efficiency of the cooling system....................................................46 Figure 3.20: The product's curvature due to temperature and shrinkage..................47 Figure 3.21: The parameters for evaluating the curvature of the product ................47 Figure 3.22: Sprue bushing according to Misumi standard [8]. ...............................48 Figure 3.23: Locating ring according to Misumi standard [8]..................................49 Figure 3.24: Return pin according to Misumi standard [8].......................................49 Figure 3.25: Guide pin according to Misumi standard [8]........................................50 Figure 3.26: Guide bushing according Misumi standard [8]. ...................................51 Figure 3.27: Ejector pin according to Misumi standard [8]......................................52 Figure 4.1: Installation of rough 1.............................................................................54 Figure 4.2: Grinding machine ...................................................................................66 Figure 4.3: Deburring tool.........................................................................................66 Figure 4.4: Sandpaper ...............................................................................................66 Figure 4.5: Top plate .................................................................................................67 Figure 4.6: Cavity plate.............................................................................................67 Figure 4.7: Core ........................................................................................................68 Figure 4.8: Support plate...........................................................................................68 Figure 4.9: Ejector plate............................................................................................69 Figure 4.10: Ejector retainer plate.............................................................................69
xiv
Figure 4.11: Ejection system.....................................................................................70 Figure 4.12: Ejector pin.............................................................................................70 Figure 4.13: Bottom plate .........................................................................................71 Figure 4.14: Locating ring and sprue bushing ..........................................................71 Figure 4.15: Two mold plate and product.................................................................75 Figure 4.16: Haitian plastic molding machine ..........................................................76 Figure 4.17: Product defects during injection testing ...............................................76 Figure 4.18: Case 1 ...................................................................................................77 Figure 4.19: 4 other cases..........................................................................................78
xv
LIST OF ABBREVIATION
CTJM: Constant-torque joint mechanism CMs: Compliant mechanisms
CAE: Computer aided engineering CAD Computer aided design
CAM Computer aided manufacturing PP: Polypropylene
PE Polyethylene
ABS Acrylonitrin Butadien Styren PET Polyethylene Terephthalate PMMA Poly Methyl Methacrylate HDPE Hight Density Poli Etilen POM Polyoxymethylene
PA6 Nylon
PPO Polyphenylene Ether
PA66 PolyAmide – Nylon
LDPE low density Polyethylene
PC Polycarbonate
FEP Fluorinated Ethylene Propylene
xvi
PLA Polylactic Acid
TPU Thermoplastic Polyurethane
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CHAPTER 1: OVERVIEW
1.1 Overview of moment-resisting soft structure.
Compliant mechanisms are devices which can transform motion or force by the shape change of its self-structure. As compared with conventional mechanisms, the advantages of compliant mechanisms are prominent. They can avoid the harmful effects of backlash, friction and wear, which are the inherent defects of conventional mechanisms. Medical or healthcare devices assisting 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 sensorized control system.
On this day, among countless types of complex structures, the constant-torque joint mechanism (CTJM) provides nearly constant torque within a specific range of rotation as the rotational speed increases. Instead of using sensor control, CTJM passively maintains a constant torque Potential applications include dynamic and static balancing of machinery, joint function rehabilitation devices for humans, and assistive devices for human mobility. To meet practical needs, CTJM must have a large constant torque region with sufficient flatness [1].
1.2 Overview of the Constant-Torque J oint Mechanism (CTJ M)
CTJM stands for "Constant-Torque Joint Mechanism," which is a type of compliant mechanism capable of providing a constant torque output within a certain range of deformation. This can find applications in various fields, particularly in devices or systems that require maintaining a stable torque without the need for external sensors and controllers. In the specific context of the provided passage, CTJM is discussed in the context of compliant mechanisms that can maintain a constant torque level. It is compared to other mechanisms like CFM (Constant-Force Mechanism) and various applications in the fields of mechanics and engineering [1].
1
CTJM has two types:
• CTJM using lumped-compliance models.
• CTJM using distributed-compliance models.
CTJM using lumped-compliance models.
The Constant Torque Joint Mechanism (CTJMs) designed using lumped- compliance models focuses on achieving a constant-torque output by carefully manipulating compliant members. These models are classified into Groups A, B, and C based on their principles for obtaining constant torque. Group A, for instance, employs torsional springs for positive stiffness and linear springs for negative stiffness, combining them to create a constant-torque region. The CTJM can have multiple identical limbs connecting the inner shaft to the outer fixed rim, providing stability [1].
Figure 1.1: Applications of CTJMs: (A) gravity balancing, (B) mobility-assisting device, (C) rehabilitative device, (D) dynamic-torque balancing [1]
2
CTJM using distributed-compliance models [1].
The Constant Torque Joint Mechanism (CTJM) designed with distributed- compliance models aims to achieve a constant-torque output by introducing flexibility and adaptability into the connecting limbs. In contrast to lumped- compliance models, which rely on specific spring stiffnesses at distinct locations, distributed-compliance models offer additional degrees of freedom by making the entire limb compliant. The distributed-compliance models overcome the limitations of the lumped-compliance models, providing a new perspective on CTJM design. These models integrate linear and torsional springs along the entire limb, allowing for a more distributed and adjustable stiffness profile. This design flexibility enables the creation of a larger constant-torque region compared to the restricted region in lumped-compliance models.
1.3 Reasons for choosing the topic 1.3.1 Why choose the CTJM structure
Because the type of functional joint mechanism and its related applications are still unexplored, and the potential applications of CTJM in medical and research fields are recognized. By using synthetic compliance models to design CTJM mechanisms, the team has delved into researching the manufacturing capability of moment-compliant soft structures using the plastic injection molding method. The selection of research on the possibility of manufacturing soft structures by plastic injection molding method topic is motivated by several important reasons stemming from practical needs in the field of torsional strength. Here are some specific reasons:
1. Real-world application: The chosen topic focuses on a specific problem, essential issue in a practical context in order to create valuable knowledge that can be applied in fields that use flexible and tolerant configurations.
2. Plastic injection molding technology: It is a versatile and widely applied and is 3
suitable for research and manufacturing of products in the learning and working environment.
3. The moment-soft structure: Nowadays, among various types of structures, the Constant-torque joint mechanism (CTJM) exhibits a constant torque when the rotational speed increases. The constant torque joint mechanism (CTJM) provides nearly constant torque within a specific range of rotation without relying on sensor feedback [1].
The above reasons show the importance and necessity of choosing a research topic on moment-compliant shape soft structures using the injection molding method.
1.3.2 Why choose moment-resisting soft structures using the plastic injection molding method?
There are numerous methods for processing and manufacturing soft structures:
- CNC machining
- Wire cutting method
- 3D printing
- Plastic injection molding method
CNC machining, Wire cutting method and 3D printing can manufacture the shape of product, but it creates two significant problems which are the outsourcing fees of product increasing and it can not be batched product.
Thus, recognizing that the plastic injection molding method ensures stability, can produce in bulk, can ensure that the dimensions of products are similar and minimized error product. There is fatigue testing machine available, has been instructed and using Haitain injection molding machine and many types of plastic provided for research purposes, ...
4
1.4 Topic objective
Research and summarize about plastic injection molding technology. Research and summarize about various types of flexible mechanisms. Designing two-plate molds for flexible moment-compliant. Manufacturing, assembling, and testing of molds.
1.5 Research methods
Refer to articles about CTJM structure to come up with product design ideas. Refer to the documentation on plastic injection molds to create a mold set. Use NX software to design molds.
Use moldex 3D software to analyze flow after design.
Processing injection molds.
Testing and synthesizing results.
1.6 Research scope
Design the compliant-moment soft structure based on research articles, from which choose the design for the product.
The project focuses solely on researching, designing, and calculating plastic injection molding based on the theoretical of plastic injection molding design. Specifically, it involves the research on the manufacturing capability of moment- compliant soft structures using the plastic injection molding method.
Research and progress on the two-plate, one-cavity mold set.
Reasons for choosing the two-plate mold:
- Lower production cost compared to other types of molds. - Shorter cycle time.
5
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Nghiên cứu khả năng chế tạo kết cấu mềm tuân theo mômen bằng phương pháp ép phun nhựa
Researching the manufacturing capability of moment-compliant soft structures using plastic injection molding method
ACKNOWLEDGEMENT
We could not have successfully completed our graduation project without the support of everyone around us. Thanks to the dedicated and passionate teaching of our instructors, who imparted knowledge and supported us throughout our learning journey. With deep appreciation, we sincerely thank:
✓Assoc. Prof. Ph.D. Pham Son Minh - our main project supervisor, who patiently guided and provided favorable conditions for us during the project implementation. He always took the time to make detailed corrections and give instructions to achieve the best results.
✓Ph.D. Nguyen Trong Hieu - project leader for his dedicated guidance in the process of researching, designing and manufacturing plastic injection molds to create soft moment structure models.
✓Ph.D. Tran Minh The Uyen - for providing equipment and tools that made our graduation project more efficient.
✓ We would also like to acknowledge the faculty members at Ho Chi Minh City University of Technology and Education for their dedication to teaching and their contributions to our academic development.
✓Lastly, we extend our gratitude to the Board of Directors of the university for creating a conducive environment that supports students and learners in their research and projects.
In conclusion, we wish to express our heartfelt appreciation to all the instructors for their dedication and tireless efforts. We wish them good health, happiness, and youthful spirits as they continue to educate future generations.
Author
v
SUMMARY
Topic: “Researching the manufacturing capability of moment-compliant soft structures using plastic injection molding method”.
Summary: Continuing the research process of previous students. In this topic, the team focuses on designing and manufacturing plastic molding dies for soft moment- resistant structures, laying the groundwork for subsequent groups to use the molds to create products for future research and storage purposes.
Target: Apply and maximize the knowledge learned in the field molds in particular and mechanics in general. The group has researched, designed and manufactured a set of plastic injection molds for soft moment structures.
Content:
• Knowledge of injection molds.
• Knowledge of moment-compliant soft structures.
• Fabrication and assembly.
• Testing injection mold.
Conclusion: After completing the project. The resulting product is a complete set of injection molds and can be used in research and production with high automation. Besides, our team has gained more practical knowledge in the mold making process, thereby helping us to have more confidence when entering the actual work later. However, in the process of making, there are many mistakes due to lack of experience, leading to repeated corrections and time consuming.
vi
TABLE OF CONTENTS
MISSION OF THE GRADUATION THESIS ..........................................................i ASSESSMENT FORM OF INSTRUCT LECTURER.............................................ii ASSESSMENT FORM OF DECIPATION LECTURER...................................... iii GUARANTEE ...........................................................................................................iv ACKNOWLEDGEMENT ..........................................................................................v SUMMARY................................................................................................................vi TABLE OF CONTENTS .........................................................................................vii LIST OF TABLES ....................................................................................................xi LIST OF F IGURES ............................................................................................... xiii LIST OF ABBREVIATION....................................................................................xvi CHAPTER 1: OVERVIEW .......................................................................................1
1.1 Overview of moment-resisting soft structure. ...................................................1 1.2 Overview of the Constant-Torque Joint Mechanism (CTJM)...........................1 1.3 Reasons for choosing the topic ..........................................................................3
1.3.1 Why choose the CTJM structure .................................................................3 1.3.2 Why choose moment-resisting soft structures using the plastic injection
molding method?..................................................................................................4 1.4 Topic objective ..................................................................................................5 1.5 Research methods ..............................................................................................5 1.6 Research scope...................................................................................................5
CHAPTER 2: THEORETICAL BASIS ....................................................................7
2.5 Choose soft structures........................................................................................7 vii
2.1 Overview of mold ..............................................................................................9 2.2 Overview of plastic injection molding ..............................................................9 2.2.1 Plastic injection molding technology ..........................................................9 2.2.2 Overview of plastic injection machines ....................................................11 2.3 Classification of plastic injection molds..........................................................14 2.3.1 Two-plate mold. ........................................................................................14 2.3.2 Three-plate mold. ......................................................................................16 2.4 Overview of PP plastic (Polypropylene) .........................................................18 CHAPTER 3: DESIGN AND F ABRICATION OF MOLDS ................................21 3.1 Redesign product: ............................................................................................21 3.2 Shrinkage coefficient of the product................................................................23 3.3 Manufacturing the mold ..................................................................................23 3.3.1 Mold release angle.....................................................................................23 3.3.2 Calculate the number of mold cavities [6]. ...............................................23 3.3.3 Mold separation.........................................................................................26 3.4 Plastic runner design........................................................................................30 3.4.1 Sprue bushing design.................................................................................30 3.4.2 Calculate runner diameter .........................................................................31 3.4.3 The nozzle .................................................................................................32 3.5 Designing the ejection system .........................................................................34 3.6 Designing the cooling system..........................................................................35 3.7 Analysis of simulation results..........................................................................40 3.8 Selecting standard components........................................................................48
viii
3.8.1 Sprue bushing ............................................................................................48 3.8.2 Locating ring .............................................................................................49 3.8.3 Return pin ..................................................................................................49 3.8.4 Guide pin ...................................................................................................50 3.8.5 Ejector pin .................................................................................................52
CHAPTER 4: THE MANUFACTURING AND ASSEMBLY PROCESS...........53
4.1 Workpiece preparation.....................................................................................53
4.2 Manufacturing process of core plate................................................................54
4.2.1 Routing 1: Milling bottom surface, the side surface and machining holes ............................................................................................................................54
4.2.2 Rough 2: Milling top surface, 2 sides left, insert cavity ...........................61
4.2.3 Manufacturing process of cavity plate ......................................................64 4.3 Deburring and polishing ..................................................................................66 4.4 Mold assembly .................................................................................................72 4.5 Procedure .........................................................................................................75 4.6 Parameters of the molding machine used ........................................................76 4.7 Test molding ....................................................................................................76
CONCLUSION.........................................................................................................79
Conclusion .............................................................................................................79 Limitations of the project: .....................................................................................79 Development and orientation.................................................................................80
REFERENCES ............................................................Error! Bookmark not defined. APPENDIX...............................................................................................................81
ix
Milling mold cavity and machining holes .............................................................83 Manufacturing process of top clamp plate.............................................................86 Rough 1: Milling bottom surface, 2 sides surface and machining holes ...........86 Rough 2: Milling top surface and another sides surface ....................................90 Manufacturing process of spacer block .................................................................91 Rough 1: Milling bottom surface, 2 sides surface and machining holes ...........91 Rough 2: Milling top surface and another sides surface ....................................93 Manufacturing process of retainer plate ................................................................94 Rough 1: Milling bottom surface, 2 sides surface and machining holes ...........94 Rough 2: Milling top surface and another sides surface ....................................98 Manufacturing process of ejector plate..................................................................99 Rough 1: Milling bottom surface, 2 sides surface and machining holes ...........99 Rough 2: Milling top surface and another side surfaces ..................................101 Manufacturing process of bottom plate ...............................................................102 Rough 1: Milling bottom surface, 2 sides surface and machining holes .........102 Rough 2: Milling top surface and another sides...............................................105
x
LIST OF TABLES
Table 2.1: The physical characteristics of PP plastic................................................20 Table 2.2: The mechanical properties of PP plastic..................................................19 Table 2.3: Compare 2 type of soft structure................................................................8 Table 3.1: Redesign product .....................................................................................21 Table 3.2: Table caculate number mold cavities.......................................................26 Table 3.3: Create workpiece and separate mold .......................................................26 Table 3.4: Designing cooling system using NX software.........................................38 Table 4.1: Dimensions of the mold parts ..................................................................53 Table 4.2: Manufacturing process of core plate in rough 1 ......................................58 Table 4.3: Manufacturing process of core plate in rough 2 ......................................61 Table 4.4: Manufacturing process of core plate in rough 3 ......................................63 Table 4.5: Manufacturing of cavity plate in rough 1 ................................................64 Table 4.6: Mold assembly .........................................................................................72 Table 4.7: Input parameter ........................................................................................77 Table 4.8: Manufacturing of cavity plate in rough 2 ................................................83 Table 4.9: Manufacturing of top clamp plate in rough 1 ..........................................86 Table 4.10: Manufacturing of top clamp plate in rough 2 ........................................90 Table 4.11: Manufacturing of spacer block in rough 1.............................................91 Table 4.12: Manufacturing of spacer block in rough 2.............................................93 Table 4.13: Manufacturing of retainer plate in rough 1............................................94 Table 4.14: Manufacturing of retainer plate in rough 2............................................98 Table 4.15: Manufacturing of ejector plate in rough 1 .............................................99
xi
Table 4.16:Manufacturing of ejector plate in rough 2 ............................................101 Table 4.17: Manufacturing of bottom plate in rough 1...........................................102 Table 4.18: Manufacturing of bottom plate in rough 2...........................................105
xii
LIST OF FIGURES
Figure 1.1: Applications of CTJMs.............................................................................2 Figure 2.1: Type I [1] ..................................................................................................7 Figure 2.2: Type II [1].................................................................................................7 Figure 2.3: Plastic injection molding machine [3]....................................................11 Figure 2.4: Spray system [3] .....................................................................................13 Figure 2.5: Basic two-plate mold [4]. .......................................................................15 Figure 2.6: Three-plate mold [5]...............................................................................17 Figure 2.7: Polypropylene plastic [5]........................................................................18 Figure 3.1: The mass and volume of the detail .........................................................22 Figure 3.2: Calculate the dimensions of the sprue ....................................................31 Figure 3.3: Table of common cross-sectional types of plastic runners.....................31 Figure 3.4: Fan gate [7].............................................................................................32 Figure 3.5: Caculate fan gate [7]...............................................................................33 Figure 3.6: Fan gate...................................................................................................33 Figure 3.7: Fan gate...................................................................................................34 Figure 3.8: Ejection system.........................................Error! Bookmark not defined. Figure 3.9: The importance of mold cooling time [7]...............................................35 Figure 3.10: Design cooling system..........................................................................36 Figure 3.11: Cooling system .....................................................................................37 Figure 3.12: Filling Melt Front Time........................................................................40 Figure 3.13: Air trap..................................................................................................41 Figure 3.14: Pressure.................................................................................................42
xiii
Figure 3.15: Temperature..........................................................................................43 Figure 3.16: Temperature..........................................................................................44 Figure 3.17: Filling volumetric shrinkage.................................................................44 Figure 3.18: The temperature of the product after the cooling process ....................45 Figure 3.19: The efficiency of the cooling system....................................................46 Figure 3.20: The product's curvature due to temperature and shrinkage..................47 Figure 3.21: The parameters for evaluating the curvature of the product ................47 Figure 3.22: Sprue bushing according to Misumi standard [8]. ...............................48 Figure 3.23: Locating ring according to Misumi standard [8]..................................49 Figure 3.24: Return pin according to Misumi standard [8].......................................49 Figure 3.25: Guide pin according to Misumi standard [8]........................................50 Figure 3.26: Guide bushing according Misumi standard [8]. ...................................51 Figure 3.27: Ejector pin according to Misumi standard [8]......................................52 Figure 4.1: Installation of rough 1.............................................................................54 Figure 4.2: Grinding machine ...................................................................................66 Figure 4.3: Deburring tool.........................................................................................66 Figure 4.4: Sandpaper ...............................................................................................66 Figure 4.5: Top plate .................................................................................................67 Figure 4.6: Cavity plate.............................................................................................67 Figure 4.7: Core ........................................................................................................68 Figure 4.8: Support plate...........................................................................................68 Figure 4.9: Ejector plate............................................................................................69 Figure 4.10: Ejector retainer plate.............................................................................69
xiv
Figure 4.11: Ejection system.....................................................................................70 Figure 4.12: Ejector pin.............................................................................................70 Figure 4.13: Bottom plate .........................................................................................71 Figure 4.14: Locating ring and sprue bushing ..........................................................71 Figure 4.15: Two mold plate and product.................................................................75 Figure 4.16: Haitian plastic molding machine ..........................................................76 Figure 4.17: Product defects during injection testing ...............................................76 Figure 4.18: Case 1 ...................................................................................................77 Figure 4.19: 4 other cases..........................................................................................78
xv
LIST OF ABBREVIATION
CTJM: Constant-torque joint mechanism CMs: Compliant mechanisms
CAE: Computer aided engineering CAD Computer aided design
CAM Computer aided manufacturing PP: Polypropylene
PE Polyethylene
ABS Acrylonitrin Butadien Styren PET Polyethylene Terephthalate PMMA Poly Methyl Methacrylate HDPE Hight Density Poli Etilen POM Polyoxymethylene
PA6 Nylon
PPO Polyphenylene Ether
PA66 PolyAmide – Nylon
LDPE low density Polyethylene
PC Polycarbonate
FEP Fluorinated Ethylene Propylene
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PLA Polylactic Acid
TPU Thermoplastic Polyurethane
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CHAPTER 1: OVERVIEW
1.1 Overview of moment-resisting soft structure.
Compliant mechanisms are devices which can transform motion or force by the shape change of its self-structure. As compared with conventional mechanisms, the advantages of compliant mechanisms are prominent. They can avoid the harmful effects of backlash, friction and wear, which are the inherent defects of conventional mechanisms. Medical or healthcare devices assisting 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 sensorized control system.
On this day, among countless types of complex structures, the constant-torque joint mechanism (CTJM) provides nearly constant torque within a specific range of rotation as the rotational speed increases. Instead of using sensor control, CTJM passively maintains a constant torque Potential applications include dynamic and static balancing of machinery, joint function rehabilitation devices for humans, and assistive devices for human mobility. To meet practical needs, CTJM must have a large constant torque region with sufficient flatness [1].
1.2 Overview of the Constant-Torque J oint Mechanism (CTJ M)
CTJM stands for "Constant-Torque Joint Mechanism," which is a type of compliant mechanism capable of providing a constant torque output within a certain range of deformation. This can find applications in various fields, particularly in devices or systems that require maintaining a stable torque without the need for external sensors and controllers. In the specific context of the provided passage, CTJM is discussed in the context of compliant mechanisms that can maintain a constant torque level. It is compared to other mechanisms like CFM (Constant-Force Mechanism) and various applications in the fields of mechanics and engineering [1].
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CTJM has two types:
• CTJM using lumped-compliance models.
• CTJM using distributed-compliance models.
CTJM using lumped-compliance models.
The Constant Torque Joint Mechanism (CTJMs) designed using lumped- compliance models focuses on achieving a constant-torque output by carefully manipulating compliant members. These models are classified into Groups A, B, and C based on their principles for obtaining constant torque. Group A, for instance, employs torsional springs for positive stiffness and linear springs for negative stiffness, combining them to create a constant-torque region. The CTJM can have multiple identical limbs connecting the inner shaft to the outer fixed rim, providing stability [1].
Figure 1.1: Applications of CTJMs: (A) gravity balancing, (B) mobility-assisting device, (C) rehabilitative device, (D) dynamic-torque balancing [1]
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CTJM using distributed-compliance models [1].
The Constant Torque Joint Mechanism (CTJM) designed with distributed- compliance models aims to achieve a constant-torque output by introducing flexibility and adaptability into the connecting limbs. In contrast to lumped- compliance models, which rely on specific spring stiffnesses at distinct locations, distributed-compliance models offer additional degrees of freedom by making the entire limb compliant. The distributed-compliance models overcome the limitations of the lumped-compliance models, providing a new perspective on CTJM design. These models integrate linear and torsional springs along the entire limb, allowing for a more distributed and adjustable stiffness profile. This design flexibility enables the creation of a larger constant-torque region compared to the restricted region in lumped-compliance models.
1.3 Reasons for choosing the topic 1.3.1 Why choose the CTJM structure
Because the type of functional joint mechanism and its related applications are still unexplored, and the potential applications of CTJM in medical and research fields are recognized. By using synthetic compliance models to design CTJM mechanisms, the team has delved into researching the manufacturing capability of moment-compliant soft structures using the plastic injection molding method. The selection of research on the possibility of manufacturing soft structures by plastic injection molding method topic is motivated by several important reasons stemming from practical needs in the field of torsional strength. Here are some specific reasons:
1. Real-world application: The chosen topic focuses on a specific problem, essential issue in a practical context in order to create valuable knowledge that can be applied in fields that use flexible and tolerant configurations.
2. Plastic injection molding technology: It is a versatile and widely applied and is 3
suitable for research and manufacturing of products in the learning and working environment.
3. The moment-soft structure: Nowadays, among various types of structures, the Constant-torque joint mechanism (CTJM) exhibits a constant torque when the rotational speed increases. The constant torque joint mechanism (CTJM) provides nearly constant torque within a specific range of rotation without relying on sensor feedback [1].
The above reasons show the importance and necessity of choosing a research topic on moment-compliant shape soft structures using the injection molding method.
1.3.2 Why choose moment-resisting soft structures using the plastic injection molding method?
There are numerous methods for processing and manufacturing soft structures:
- CNC machining
- Wire cutting method
- 3D printing
- Plastic injection molding method
CNC machining, Wire cutting method and 3D printing can manufacture the shape of product, but it creates two significant problems which are the outsourcing fees of product increasing and it can not be batched product.
Thus, recognizing that the plastic injection molding method ensures stability, can produce in bulk, can ensure that the dimensions of products are similar and minimized error product. There is fatigue testing machine available, has been instructed and using Haitain injection molding machine and many types of plastic provided for research purposes, ...
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1.4 Topic objective
Research and summarize about plastic injection molding technology. Research and summarize about various types of flexible mechanisms. Designing two-plate molds for flexible moment-compliant. Manufacturing, assembling, and testing of molds.
1.5 Research methods
Refer to articles about CTJM structure to come up with product design ideas. Refer to the documentation on plastic injection molds to create a mold set. Use NX software to design molds.
Use moldex 3D software to analyze flow after design.
Processing injection molds.
Testing and synthesizing results.
1.6 Research scope
Design the compliant-moment soft structure based on research articles, from which choose the design for the product.
The project focuses solely on researching, designing, and calculating plastic injection molding based on the theoretical of plastic injection molding design. Specifically, it involves the research on the manufacturing capability of moment- compliant soft structures using the plastic injection molding method.
Research and progress on the two-plate, one-cavity mold set.
Reasons for choosing the two-plate mold:
- Lower production cost compared to other types of molds. - Shorter cycle time.
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