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

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

INTRODUCTION

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.

Research objectives

The goal of the project is to research on the torsional strength of composite products manufactured from the plastic injection molding process.

Objects of research scope

− Overview of the Constant-Torque Joint Mechanism (CTJM)

− Researching the torsional strength of composite plastic products

− Compare simulation results and experimental data

− 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

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

Approaches, Research Methods

− 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

The study uses a combination of the following research methods:

− Researching method based on a theoretical foundation

− Learning documents about compliant mechanisms (CTJM) and understanding their definitions and applications

− Learning documents about injection molding technology, composite plastics

− Conducting the plastic injection molding process

− Performing torsional moment testing, analyzing, and collecting data from the experimental torsional strength testing of the product

− Comparing the prediction results of the ANN algorithm with the experimental results.

THEORETICAL BASIS

Overview of constant torque joint mechanism (CTJM)

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]

Figure 2.1: Real-world products applying the CTJM mechanism

The CTJM consists of mechanical joints connecting the inner shaft to the outer ring, with these joints being identical and symmetrically arranged, capable of maintaining a constant level of torque throughout a specific range of rotation

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: a Constant Torque:

CTJM is designed to provide constant torque throughout a specific range of rotation b Stability and Durability:

The design of CTJM typically focuses on maintaining stability and durability during continuous operation, especially when subjected to various motions and variable loads c Flexibility and diverse applications:

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

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

Tmax and Tmin to create a flat torsional curve and optimize the constant torque region[1] b A distributed-compliant limb parameterized by using three segments (Type II)

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

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

2.2.2 Comparison of constant-torque joint mechanisms

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

• 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.

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

Applications of constant torque joint mechanism

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

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

Figure A Robotics: CTJM is integrated into robot arms to balance loads and maintain equilibrium positions while performing specific tasks This helps improve the accuracy and efficiency of the robot

Figure B and C Medical: CTJM can be used to create constant torque angles in applications such as knee support devices or artificial limbs This helps reduce pressure and increase comfort for users

Figure D Automation and Industry: In automation and industrial systems, CTJM can be used to maintain stable torsional stiffness in joints and moving shafts

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

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

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

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

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

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

Plastic materials used in the injection molding process

2.7.1 Overview of PLA and TPU plastics

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]

Table 2.1: Physical properties of PLA

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

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

− In the garment industry, PLA is becoming popular as it is used in the production of environmentally friendly fabrics These fabrics are commonly used in clothing, bed sheets and other textile products

− PLA is a popular material for 3D printing filaments due to its ease of use, low toxicity, and biodegradability It is commonly used in 3D printers for prototyping and creating a variety of objects

− PLA films and coatings are used in many applications, including in the production of biodegradable bags, agricultural films and coatings for paper products

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

Thermoplastic Polyurethane (TPU) is a type of polymer belonging to the elastomer family of thermoplastic materials It is known for its combination of flexibility and resilience commonly found in rubber, with the processing and molding characteristics typical of thermoplastics It is soft to the touch but extremely durable and strong It offers high abrasion resistance and is capable of resisting oils, greases, and solvents well.[5]

Table 2.2: Physical properties of TPU

The chemical properties of TPU

− TPU typically has resistance to oils, greases, and some chemicals

− TPU can withstand the impact of ultraviolet (UV) radiation

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

The team will use PLA and TPU plastic materials with corresponding mixing ratiosto 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

Percentage ratio of plastic for each case Plastic mass of each case

Figure 2.12: Weighing and mixing PLA and TPU plastics

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]

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 thermoplastics or thermosets.[7]

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

2.8.2 Advantages and disadvantages of the injection molding technology a Advantages:

− Complex Shapes: Injection molded parts can retain very high precision for extremely small parts, which cannot be achieved through conventional machining processes economically

− Speed and Scale: The plastic injection process can rapidly produce large quantities of parts in batches, with a mold containing multiple cavities to produce identical products in a single injection cycle Therefore, it is highly suitable for mass production

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

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

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

− Design Limitations: Due to the need for the mold to be opened and ejected, there are designs that cannot be injection molded or are very difficult to mold

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

2.8.3 Applications of injection molding in daily life

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

• Plastic packaging manufacturing industry: plastic bags, plastic shells, plastic bottles…

• Food packaging industry: shells, candy boxes, food trays

• Pharmaceutical industry: drug packaging, blister packs

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

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

Introduction to 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

Figure 2.14: Plastic Machine Haitian MA 1200III

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

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

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

2.9.2 The process of using the Haitian plastic injection molding machine

The first step of the injection molding process is clamping Injection molds are typically made in two, clamshell-style pieces In the clamping phase, the two metal plates of the mold are pushed up against each other in a machine press

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 control throughout this step of the process

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

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

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

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

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]

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

The Haitian plastic dryer is a type of drying machine used in the plastic manufacturing process to remove or reduce the moisture content of plastic materials before they are fed into injection molding machines or other production processes Before being put into use, the prepared types of plastic will be dried at 90 0 C for 2 hours

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

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

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

Mold Technology

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:

- According to the type of runner system:

- According to the runner layout:

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

Two-plate mold has a single cavity

Two-plate mold has multiple cavities

Two-plate mold has interchangeable cores

Two-plate mold has nested interchangeable cores

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

2.10.4.Technical requirements and quality control

Technical Requirements of the Plastic Mold:

• Ensure accuracy in product dimensions and shapes

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

• Ensure accurate alignment between the two mold halves

• Ensure easy product removal from the mold

• The mold material must have high wear resistance and be easy to process

• Check the hardness of the mold during operation

• The mold must have a cooling system around the perimeter of the mold cavity

• 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.

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]

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

− Test material: The torsion testing machine is capable of measuring torsional moment for plastic materials

2.11.2 The functions of the main components on the torque strength testing machine

The components of torque strength testing machine include:[11]

− Encoder: Encoder refers to a type of electronic device used to measure and record the number of rotations or rotation position of an axis or an object Each pulse corresponds to a specific rotation or position unit These pulses are sent to an electronic system to count and record information about position or number of rotations The encoder is connected to a circuit that displays the measured angle on a screen

− Gear Motor: The motor delivers consistent and precise torque for uniform and reliable testing of plastic material samples Its automatic operation and adjustable rotation speed ensure high performance and accuracy in the testing process

− Gear box: A gear box is a device with coaxial input and output used to reduce rotational speed Its structure includes a metal casing for protection, a motor input for power supply, and a planetary tooth actuator to create a high deceleration rate, allowing the output to rotate 1/n revolution per input rotation

− Sensor: A sensor is an electronic device that senses physical, chemical or biological states or processes of the environment to be investigated, and converts them into electrical signals to collect information about that state or process

− Transmitter: A transmitter in a sensor is a component that is responsible for sending the data or information collected by the sensor to a receiving device or system The transmitter in a sensor enables remote monitoring, recording, or analysis of sensor data by other devices or systems

− 3-jaw chuck: A 3-jaw chuck is a type of chuck used on lathes and other machine tools to hold cylindrical or round workpieces It consists of three jaws that are moved independently to grip the workpiece

− A PLC control panel, or Programmable Logic Controller control panel, is a device that provides an interface for the operation and monitoring of PLCs, which are industrial digital computers used for automation of typically industrial electromechanical processes

The main component of sensor and 4 parts as below to support the testing of torsional breaking moment

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

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

Part 1: Serves as fixing the product and connecting the product to part 2

Part 2: Serves as a protective shell for the product when clamped into the 3-jaw chuck Part 3: Serves as a connection to the sensor keeping the product fixed on its surface with bolts

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

Part 1: Serves as fixing the product and connecting the product to part 2

Part 2: Serves as a protective shell for the product when clamped into the 3-jaw chuck

Part 3: Serves as a connection to the sensor keeping the product fixed on its surface with bolts

M8 x 4 It has a function to fix and securely clamp the sensor into the 3-jaw chuck

The bridge between the sensor and part 3.

Figure 2.27: Complete clamping device along with the standard sensor

Introduction to MATLAB

Matlab or Matrix Laboratory is a high-level programming language consisting of an interactive environment mainly used for numeric computation, programming, and visualization It has been developed by MathWorks The basic functions of Matlab are plotting of functions and data, the creation of user interfaces, matrix manipulations.[12]

Matlab is widely used in the industry as a tool for mathematical computation and different streams of studies like physics chemistry, engineering, mathematics, Etc The various applications involving Matlab are below:

Introduction to artificial neural network (ANN) in MATLAB

A neural network is a supervised machine learning algorithm We can train neural networks to solve classification or regression problems Yet, building a neural network model requires answering lots of architecture-oriented questions Depending on the complexity of the problem and available data, we can train neural networks with different sizes and depths.[13]

The objective of using ANN in MATLAB is to predict torque moments compared to experimental results The team utilizes neural networks to predict outcomes with 8 input parameters: the percentage ratio of mixing PLA and TPU plastics, injection pressure, Holding pressure, plastic temperature, mold temperature, Holding time, rotation angle and the target data is the torque moment.

Introduction to Origin software

Origin is the data analysis and graphing software of choice for over a million scientists and engineers in commercial industries, academia, and government laboratories worldwide Origin offers an easy-to-use interface for beginners, combined with the ability to perform advanced customization as you become more familiar with the application.[14]

EXPERIMENT

The implementation process

The team will conduct experiments to inject mold composite plastic products and measure their torsional strength according to the following steps:

Clamping the mold onto the Haitian plastic injection molding machine

Opening the mold and removing the product from the mold

Conducting torsion moment testing of the product

Injection molding parameters

After drying the plastic at 90 0 C for 3 hours, the team proceeds to clamp the mold onto the Haitian plastic injection molding machine and start the injection molding process However, to achieve a finished product, it is necessary to set up suitable machine parameters to produce standard products according to the following 5 injection molding parameters: Press injection, Holding pressure, Holding time, Plastic temperature, Mold temperature

Figure 3.1: Image of 5 injection molding parameters a Injection case 1 (100% PLA Plastic)

Table 3.1: Injection molding parameters for Case 1

Figure 3.2: Image of injection molding parameters in case 1 b Injection case 2 (90% PLA and 10% TPU)

Ho ldi ng pre ssure

Ho ldi ng ti me

Figure 3.3: Image of injection molding parameters in case 2 c Injection case 3 (80% PLA and 20% TPU)

Ho ldi ng press ure

Ho ldi ng ti me

Figure 3.4: Image of injection molding parameters in case 3 d Injection case 4 (70% PLA and 30% TPU)

Ho ldi ng press ure

Ho ldi ng ti me

Figure 3.5: Image of injection molding parameters in case 4 e Injection case 5 (60% PLA and 40% TPU)

Ho ldi ng press ure

Ho ldi ng ti me

Figure 3.6: Image of injection molding parameters in case 5

Figure 3.7: Actual products of the 5 cases

Perform torque measurement

After injection molding the finished product, the team will carry out measurement of the torsion torque following these steps:

Step 1: Attach the product to the fixture and secure it with screws

Figure 3.8: Actual images of the product and the fixture

Step 2: Assemble the product with the fixture onto the torsion testing machine and tighten the 3-jaw chuck using an Allen wrench, double-check the setup, and proceed with the measurement

3-jaw chuck Product and fixture

Figure 3.9: Installation and fixation of the product onto the completed torque testing machine

Step 3: Use the TIA Portal software to control the torsion testing machine and record the measurement results

Twist the part counterclockwise Twist the part clockwise

Figure 3.10: The interface of the TIA Portal software and torque strength testing machine

After completing the torsion torque measurement process, the team obtained the following results:

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

Case Sample Record Torsional angle ( 0 ) Torsional moment (N.m)

EXPERIMENTAL RESULTS

The steps of data processing

The team will proceed with data processing according to the following steps:

To ensure the consistency of the average value, we calculated the standard deviation of the average value according to the formula as follows:

𝑛 𝑖 : is the number of measurements in sample i

𝑥 𝑖𝑗 : is the jth measurement value of sample i

𝑥 𝑖 : is the average value of measurements in sample i.

Proceeding with data processing

Case 1: Sample Product with 100% PLA

Draw line and column charts using Originlab software

Create a statistical table to compare the samples and the average value

Select the sample that is closest to the average value

Repeat the process for the remaining cases

Synthesis, Comparison, Analysis, and Conclusion

Figure 4.1: Graph illustrating the deformation of the product in Case 1

Constant-Torque region ranging from 35 degrees to 100 degrees

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

According to 2 graphs, we have the following statistical table:

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

Constant torque ranging from 35 to 100 (N.m) Torsional Fracture Angle ()

We calculate the standard deviation of the average value of constant torque and the average value of torsional fracture angle according to the following formula:

The average value of constant torque: 𝑥 𝑖 = 𝑥 𝑖1 + 𝑥 𝑖2 + 𝑥 𝑖3

The average value of torsional fracture angle: 𝑥 𝑖 = 𝑥 𝑖1 + 𝑥 𝑖2 + 𝑥 𝑖3

3 = 193 ( 0 C) Standard deviation of the average value of constant torque

3(|1.02 − 0.93| + |0.92 − 0.93| + |0.855 − 0.93| ) = 0.058 Standard deviation of the average value of torsional fracture angle

3(|208 − 193| + |186 − 193| + |186 − 193| ) = 9.7 From the statistical table, we observe that sample 2 has the most similar data to the average value, so we choose it as the primary data for case 1 (100% PLA, 0% TPU)

Case 2: Sample Product with 90% PLA and 10% TPU

3(|202 − 195| + |191 − 195| + |194 − 195| ) = 4 From the statistical table, we observe that sample 2 has the most similar data to the average value, so we choose it as the primary data for case 2 (90% PLA, 10% TPU)

During the plastic molding process, the samples in this case experienced defects in filling, resulting in only 2 samples meeting the standards for experimentation

The average value of constant torque: 𝑥 𝑖 = 𝑥 𝑖1 + 𝑥 𝑖2

The average value of torsional fracture angle: 𝑥 𝑖 = 𝑥 𝑖1 + 𝑥 𝑖2

2(|0.66 − 0.63| + |0.6 − 0.63|) = 0.03 Standard deviation of the average value of torsional fracture angle

2(|159 − 161| + |176 − 161|) = 8.5 From the statistical table, we observe that sample 1 has the most similar data to the average value, so we choose it as the primary data for case 3 (80% PLA, 20% TPU)

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

3(|235 − 231| + |203 − 231| + |244 − 231| ) = 15 From the statistical table, we observe that sample 3 has the most similar data to the average value, so we choose it as the primary data for case 4 (70% PLA, 30% TPU)

Case 5: Sample product 60% PLA and 40% TPU

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

3(|247 − 248| + |234 − 248| + |262 − 248| ) = 9.7 From the statistical table, we observe that sample 1 has the most similar data to the average value, so we choose it as the primary data for case 5 (60% PLA, 40% TPU)

After choosing primary data for 5 cases, we combine the result into the following chart:

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

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

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

When mixing a higher percentage of TPU into the component, the part may have weaker load-bearing capacity, although it is not critically significant because the resistance to deformation during rotation of the object is still maintained (from about 35° to 100°) However, when comparing the resistance to destruction, the part with a higher percentage of TPU plastic actually has better resistance to destruction In the case of Sample 3 during the injection molding process, an error occurred (the plastic was not dried properly, or it may have been mixed with another type of plastic because the molding machine did not completely eject the old plastic ), so the test parameters for Sample 3 are weaker than the other cases

In conclusion, we can draw the following conclusions:

− PLA plastic has better load-bearing capacity and can be applied to structures requiring high load-bearing

− TPU plastic has better resistance to destruction and is suitable for structures requiring more flexibility

Finally, depending on the characteristics and requirements of the product, we can mix these two types of plastic to achieve the most suitable plastic structure for the product

 Compare with the other research:

Figure 4.13: Product and experiment in Taiwan research

In the research paper on CTJM by the team from Taiwan, they developed a design with a 4-legged structure having a thickness of 0.4 mm, using PEEK plastic material This product can generate stable torsional moments ranging from 20 to over 70 degrees, and has the capability to withstand a moment load of up to 150 N.mm Meanwhile, our research team designed a different component with a 4-legged structure thickness of 0.9 mm, using a composite plastic material (PLA + TPU) Our product can produce stable torsional moments ranging from 35 to 100 degrees, and has a higher moment load capacity compared to the Taiwan paper, ranging from 410 N.mm to 930 N.mm Therefore, we conclude that the applicability of our product is entirely feasible.

Using artificial neural network (ANN) in MATLAB

Because the function of ANN is the prediction and calculation of results based on input parameters Therefore, we need to provide the necessary input parameters to perform ANN calculation and compare with experimental output results The input data consists of 8 parameters consisting of mixing ratios of PLA and TPU plastics, Pinjection, Pholding, Tmelt, Tmold, tholding and torsional angle In which the team will select samples closest to the average for each case, including sample 2 of case 1 with 2424 values, sample 2 of case 2 with 2584 values, sample 1 of case 3 with 2636 values, sample 3 of case 4 with 4982 values, and sample 1 of case 5 with 4845 values Therefore, each parameter includes 17,471 variables

Table 4.7: Table of 8 input variables

The output data consists of 1 parameter with 17,471 variables of torsional moment

Table 4.8: Table of input variables

After providing the necessary input and output parameters on MATLAB, the team obtained the result:

Figure 4.17: Results after running with input and output parameters

After training, we can see the R value seems acceptable because it is approximately to 1, reflecting how well the prediction values align with the experiment ones.

Comparing results between ANN and the experiment

To demonstrate how uniform with the actual result, we have the data as following:

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

Figure 4.19: Graph illustrating the constant-torque and TFA of the ANN and experiment in

Based on the chart, we notice that the ANN predictions closely match the experimental results There is a small gap between ANN and experiment at 35 0 and 100 0 , ANN predicts 0.94 N.m while experiment is 0.93 N.m However, there are slight differences in the torsional fracture angles: the ANN predicts 188 0 , while the experiment is 186 0

Overall, the ANN prediction closely matches the actual data, with a similarity of 98% from the start to the fracture point This suggests that ANN is suitable for engineering design purposes

Based on the chart, we notice that the ANN predictions closely match the experimental results Both the ANN and experimental data show the same constant torque value between

35 0 and 100 0 At the same time, they also share the torsional moment fracture at a value of

Based on the chart, we notice that the ANN predictions closely match the experimental results There is a small gap between ANN and the experiment at 35 0 and 100 0 , ANN predicts 0.65 N.m while the experiment is 0.66 N.m There are only 1 0 differences in the torsional fracture angles: the ANN predicts 160 0 , while the experiment is 159 0

Based on the chart, we notice that the ANN predictions closely match the experimental results Both the ANN and experimental data show the same constant torque value between

35 0 and 100 0 There are only 1 0 differences in the torsional fracture angles: the ANN predicts

Based on the chart, we notice that the ANN predictions closely match the experimental results There is a small gap between ANN and experiment at 35 0 and 100 0 , ANN predicts 0.45 N.m while experiment is 0.46 N.m There is only 1 0 difference in the torsional fracture angles: the ANN predicts 248 0 , while the experiment is 247 0

In conclusion, it can be affirmed that the ANN tool stands as a reliable and precise method, boasting high levels of accuracy Its application in experimental settings serves as a proactive measure, enabling us to anticipate precise outcomes in case of experimental error and from there we can research further without actual experimenting.

CONCLUSION AND DEVELOPMENT DIRECTION

Achievements

After finishing the research process and completing the graduation project, the group completed the requirements and summarized them in this report with full content and form The main objective of the project is to study the torsional strength of composite products made from the plastic injection molding process In fact, the graduation project has been completed and met the set requirements, including:

− Apply the knowledge learned to apply to research and implementation of this topic

− Overview of CTJM soft structure

− Ability to operate a plastic injection machine and press product samples by mixing the ratio of two types of composite plastic materials (PLA and TPU)

− Ability to operate breaking torque measuring machine

− Performing analysis, synthesis and evaluation is demonstrated in the analysis of experimental results measuring torsional strength of CTJM soft structure models.

Conclusion

After completing the experimental process and analyzing the results, the team found that mixing the composite plastic material ratio significantly affects the moment-bearing capacity and stability of the CTJM model using the distributed model compliance In cases with a higher percentage of PLA plastic, the moment-bearing capacity is greater, conversely, in cases with a higher percentage of TPU plastic, the force-bearing capacity is reduced and the ability torsion resistance, increased flexibility The results achieved can be widely applied in the fields of robotics, industrial automation, medicine and many other fields.

Development

Some development directions to help the project become more complete:

− Further research on the impact on torsional strength when changing or mixing different types of materials

− Further research on the influence of changing injection molding parameters

[1] Functional joint mechanisms with constant-torque outputs Chia-Wen Hou, Chao- Chieh Lan ⁎ Department of Mechanical Engineering, National Cheng Kung

University, No 1, University Road, Tainan City 701, Taiwan

[2] Design and Analysis of a Compliant Constant-Torque Mechanism for

[3] Design and Optimization of a New Compliant Rotary Positioning Stage with

Constant Output Torque by Piyu Wang , Sijie Yang , and Qingsong Xu

[4] Farah, Shady, et al “Physical and Mechanical Properties of PLA, and Their

Functions in Widespread Applications — A Comprehensive Review.” Advanced Drug Delivery Reviews, vol 107, Dec 2016, pp 367–92

[5] Li, N.; Dong, C.; Wu, Y Reinforcement of Frictional Vibration Noise Reduction Properties of a Polymer Material by PTFE Particles Materials 2022, 15, 1365

[6] COMPOSITES MANUFACTURING Materials, Product, and Process Engineering [7] https://www.plasticmoulds.net/injection-molding-process

[8] https://www.linkedin.com/pulse/mold-design-ten-elements-injection-molding-lily- l-

[9] https://sybridge.com/injection-molding-guide

[10] Phạm Sơn Minh, Trần Minh Thế Uyên, Giáo trình Thiết kế và Chế tạo khuôn phun ép nhựa, NXB ĐGQG, Thành phố Hồ Chí Minh, 2014

[11] Đề tài: “CHẾ TẠO MÔ HÌNH MÁY THỬ ĐỘ BỀN CHO CHI TIẾT NHỰA”

[12] https://www.educba.com/introduction-to-matlab/

[13] https://www.baeldung.com/cs/epoch-neural-networks

[14] https://www.originlab.com/origin

Tiêu đề	Research On The Torsional Strength Of Composite Products Manufactured From The Plastic Injection Molding Process
Tác giả	Tran Minh Dat, Cao Nguyen Hoang Tien, Nguyen Minh Duc
Người hướng dẫn	Mr. Nguyen Van Thuc
Trường học	Ho Chi Minh City University of Technology and Education
Chuyên ngành	Mechanical Engineering Technology
Thể loại	Graduation Project
Năm xuất bản	2024
Thành phố	Ho Chi Minh City

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Số trang	83
Dung lượng	6,72 MB