OVERVIEW
Topic necessity
Natural resource depletion and escalating environmental pollution pose significant threats to our living conditions and public health This pressing challenge compels nations to reevaluate and transform their development strategies, emphasizing the necessity of economic growth that prioritizes environmental protection Adopting a green, clean, and circular economy is essential for achieving sustainable development and ensuring a healthier future for all.
The concept of a circular economy was first used formally by Pearce and Turner
(1990) [1] It is used to refer to a new economic model based on the basic principle of
The concept that "everything is an input to another" contrasts sharply with the traditional linear economy According to the Ellen MacArthur Foundation, this approach represents an industrial system designed to restore and regenerate resources intentionally.
Accordingly, not only reducing dependence on resources and limiting emissions, Circular Economy models still bring great benefits and promote
Every year, companies in the wood industry spend billions of VND to buy sandpaper n
Figure 1.2 A lot of money to buy sandpapers
In today's industrial, medical, and civil sectors, reliable cleaning equipment is essential for maintaining quality and efficiency Traditional cleaning methods, such as manual cleaning with hands and solutions, often fail to provide thorough cleanliness, particularly for complex parts with significant dirt and grime Moreover, manual cleaning increases the risk of introducing unsanitary elements, making it challenging to achieve the desired cleanliness standards.
Electrolysis cleaning is a widely utilized technique in the plating industry due to its simplicity and ease of use However, it is important to note that this method can be energy-intensive and, if used for extended periods, may lead to surface damage on parts due to corrosion.
High-pressure water spray cleaning is widely used across various industries due to its ease of use However, it may struggle to effectively clean rough surfaces and may not penetrate all the nooks and crannies, which can limit its overall cleaning efficacy.
Ultrasonic cleaning technology has emerged as an effective solution for modern industrial equipment, addressing the limitations of traditional cleaning methods This innovative approach provides rapid and highly efficient cleaning, often outperforming conventional techniques However, challenges such as cost and availability still exist, highlighting the need for ongoing advancements in this technology.
Statistics reveal the effectiveness of various cleaning methods, highlighting that manual cleaning leaves around 70% of dirt behind, while electrolysis cleaning removes approximately 50% of surface impurities High-pressure water spray cleaning eliminates about 20% of dirt, but ultrasonic cleaning stands out by removing less than 5% of dirt, making it the most desirable option for achieving optimal cleanliness.
Our team is committed to advancing ultrasonic cleaning technology specifically for the woodworking industry We focus on innovative methods to effectively remove wood chips from sandpaper, addressing the limitations of existing cleaning techniques Our objective is to deliver a dependable and efficient solution that meets the cleanliness standards of various industries.
Scientific purpose and practical significance of the topic
In today's environmentally-conscious landscape, ultrasonic cleaning equipment is increasingly favored for its health-friendly attributes Ultrasonic sandpaper cleaning machines are now surpassing traditional chemical-based cleaning methods, which pose risks to both the environment and human health By harnessing ultrasonic energy, these machines deliver exceptional cleaning results, especially for small and intricately shaped items.
Ultrasonic waves have diverse applications beyond cleaning, including quality control, crack detection, and ultrasonic welding This versatile technology offers significant potential for development across various sectors Investigating this field is essential for our research team to acquire valuable insights and experience, ultimately facilitating advancements and practical applications in everyday life.
Research objectives of the topic
In modern industrial production and medical fields, cleaning equipment is essential and a subject of ongoing research Our team aims to enhance our expertise in STM32 programming to develop innovative sandpaper cleaning machines that utilize ultrasonic technology By leveraging our design skills and experience with SOLIDWORKS, we intend to create cost-effective machines that meet technical requirements, offering an efficient solution for mass cleaning production suitable for everyday use.
We will leverage our foundational electronic knowledge to design safe and efficient circuits for the sandpaper cleaning machine, which comprises three key components: the fabrication of the sink, the development of a power amplifier circuit, and the creation of control software that monitors the machine's temperature and operational time.
This project utilizes rough sanding sandpaper, known for its durable surface and quality that remains effective even after recycling.
Subjects and scope of research
• Conducting a thorough examination of the ultrasonic cleaning machines available in the current market
• Investigating the suitable types of sandpaper that can effectively complement the cleaning capabilities of the machine
• Delving into the structure, operational principles, and synthesis of cleaning machine theories that utilize ultrasonic waves
• Creating a power circuit design that aligns with the machine's capabilities and theoretical knowledge acquired
• Choosing an appropriate frequency that matches with the design requirements and understanding the impact of frequency on cleaning effectiveness
• Gathering information from scientific research conducted both domestically and n
• The sandpaper cleaning machine has a capacity of 8-10 liters and utilizes an ultrasonic wave generator operating at a frequency of 40Khz with a power capacity of 60W
The control system utilizes an STM32 microcontroller, which facilitates essential features including timer display and countdown, temperature monitoring and regulation, and motor control along the X-axis.
Research Methods
• Collecting data from sources such as books, scientific articles, journals and documents from the Internet
• Researching methods from experiment and practice
• Surveys, interviews, observations, and secondary data analysis
Outline of the graduation thesis
• Chapter 4: Design Of Mechanical System
• Chapter 5: Design Of Electrical And Control System
• Chapter 6: Experiment Results/ Findings And Analysis
• Chapter 7: Conclusion And Future Development
The contents of the chapters are as follows:
This chapter provides an overview of the research topic, the objectives, the limitations, and the direction that the research must follow
This chapter explores the theoretical foundations of ultrasonic waves and transducers, provides an overview of sandpaper in the woodworking industry, and discusses current cleaning methods It also examines the factors that influence the ultrasonic cleaning process and reviews the various types of ultrasonic cleaning machines available on the market Additionally, the chapter introduces the STM32 microcontroller and pulse transformers.
This chapter covers the technical requirements of ultrasonic n cleaning machines, including the transmission mechanism and machine design, as well as material selection based on their advantages and disadvantages
• Chapter 4: Design Of Mechanical System
This chapter discusses the axes of the ultrasonic cleaning machine and the calculations related to material selection and travel distance when implementing the construction of these axes
Chapter 5 focuses on the design of the electrical and control system, detailing the construction steps for the electrical circuit and the creation of an algorithm flowchart It also offers comprehensive instructions for system usage Each stage concludes with the evaluation of various performance parameters to assess the operational effectiveness of each functional block.
• Chapter 6: Experiment Results/ Findings And Analysis
This chapter presents the achieved results, observations regarding the strengths, weaknesses, and evaluation compared to the objectives of the topic
• Chapter 7: Conclusion And Future Development
This chapter presents the research conclusions of the topic and proposes development solutions for the project n
THEORETICAL BASICS
The overview of wave
Waves transmit energy-carrying signals through elastic mediums like solids, liquids, or gases, and cannot travel in a vacuum Ultrasonic waves, a type of longitudinal wave, oscillate in the same direction as their propagation Sound waves, generated by vibrating objects, also travel through a medium, commonly referred to as sound waves.
Sound waves create pressure fluctuations that alter the medium's pressure During the initial phase of a wave cycle, pressure rises, followed by a decrease in the latter phase, leading to the mechanical effects of ultrasound Essentially, sound waves are mechanical waves characterized by various attributes, including frequency, wavelength, and density.
Elastic mediums such as gases, liquids, and solids can be seen as continuous mediums composed of interconnected elements In their equilibrium state, each element maintains a stable position [1]
When a force is applied to an element in an elastic medium, it disrupts its stable position, leading to oscillatory motion around its equilibrium This motion causes one side of the element to be pulled back while the other side is influenced by the force, resulting in vibrations These vibrations propagate through neighboring elements, forming mechanical waves or sound waves Essentially, a wave is a physical phenomenon where energy is transmitted through the oscillation of material elements in the medium.
Figure 2.2 Classify sound waves by frequency
Sound waves are vibrations that occur in solids, liquids, and gases, which are classified as elastomers Essentially, a sound wave is an elastic wave that travels through an elastic medium, indicating that any elastic body has the capacity to transmit sound waves.
Depending on the frequency band, people divide elastic waves into the following regions:
- Infrasound region: Frequencies below 20Hz (typically not audible to humans)
- Audio frequency range: Frequencies from 20Hz to 20kHz (the range of frequencies audible to humans)
- Ultrasonic range: Frequencies above 20kHz (typically used for applications beyond human hearing, such as medical imaging, cleaning, and measuring)
- Radio frequency range: Frequencies above 100MHz
So ultrasonic waves are from 20kHz to 100MHz Although they have the same nature as an elastic wave, they have different applications due to their different frequencies
• Based on the oscillation of particles in relation to the direction of wave propagation in the medium, ultrasonic waves are classified into longitudinal waves and transverse waves
• Longitudinal waves: These are oscillations of particles parallel to the direction of wave propagation
• Transverse waves: These are oscillations of particles perpendicular to the direction of wave propagation
Ultrasonic waves possess significantly higher energy levels compared to sound waves; for instance, at identical oscillation amplitudes, a wave frequency of 1MHz carries a million times more energy than a frequency of 1kHz.
Ultrasonic waves, characterized by their shorter wavelengths, exhibit high directional properties that allow energy to propagate in a specific direction This unique trait enables the design of converging systems that concentrate a significant amount of energy in a narrow area, making ultrasonic technology valuable in various industrial applications and everyday life.
Figure 2.4 Rarefaction and Compression in Longitudinal Wave
The frequency of a mechanical wave refers to the oscillation rate of atoms in the medium it travels through, indicating the number of cycles per second Denoted by the symbol f, frequency is measured in Hertz (Hz).
The wavelength (λ) represents the distance a wave travels in one complete cycle (T) When atoms are spaced apart at a specific distance, they oscillate in unison, remaining in phase as the wave propagates through the medium.
The rate at which energy is transferred between two points in a medium due to wave motion is called the wave velocity (v)
D Absorption of ultrasonic waves by the transmitting medium: n
Wave propagation in a medium leads to a gradual decrease in wave intensity due to absorption and scattering Key factors influencing energy attenuation include thermal conductivity, friction coefficient, and the medium's inhomogeneity, along with the wave frequency The overall wave absorption can be expressed with the formula α = 4ρ²f².
E Acoustic Impedance of the Medium:
The acoustic impedance of a medium, also known as the sound reflection or sound density of the medium, is determined by the equation:
• V is the velocity of sound propagation in the medium (m/s)
• ρ is the mass density of the medium (Kg/m3)
• Z represents the acoustic impedance of the medium (Rayls)
Therefore, the total acoustic impedance is a parameter that depends on the transmitting medium
The speed of ultrasonic waves increases with the material's resistance to compression; harder materials allow for faster wave propagation In gases, the significant distance between molecules weakens intermolecular bonds, causing particles to travel longer distances before interacting with neighbors, which results in a slower wave velocity.
In solid and liquid mediums, molecules are closely packed, leading to stronger intermolecular bonds This proximity allows particles to interact more easily, resulting in higher wave propagation velocity.
High-density materials are generally made up of larger particles, which possess significant inertia, making them challenging to displace and halt Consequently, when focusing solely on density, materials with greater density exhibit lower wave velocities.
In a liquid medium, density and compression are usually inversely proportional, resulting in similar wave propagation velocities n
H Sound Pressure and Sound Intensity:
Sound pressure is a characteristic quantity that represents the cyclic variation in stress within a material caused by the propagation of ultrasonic waves Sound pressure is expressed by the formula:
• f represents the frequency of the sound wave,
• a represents the amplitude of the sound wave
Sound intensity measures the sound energy transmitted over time and area, directly linked to sound pressure It can be calculated using parameters like the speed of sound and the density of the medium.
Both sound pressure and sound intensity play crucial roles in the study and analysis of ultrasonic waves and their effects on materials and environments.
Overview about sandpaper
Sandpaper is an essential abrasive material utilized across industries and DIY projects for effectively smoothing, polishing, and shaping surfaces It features a backing material, often made of paper or cloth, that is coated with abrasive particles These particles, typically composed of minerals such as aluminum oxide, silicon carbide, or garnet, play a crucial role in defining the sandpaper's cutting and finishing capabilities.
The grit size of sandpaper indicates the number of abrasive particles per inch on its backing material Coarse grits, characterized by lower numbers, feature larger particles ideal for rough sanding and effective material removal In contrast, fine grits, with higher numbers, consist of smaller particles that are perfect for fine finishing and polishing tasks.
The grit of sandpaper, or its abrasive grade, indicates the size of the abrasive particles on its surface This grit value is crucial for manufacturers to evaluate and categorize their products within the market.
Higher grit values in sandpaper, including emery paper and sanding cloth rolls, indicate sharper abrasive particles and quicker sanding action However, it's important to recognize that not every project requires high-grit sandpaper for optimal results.
Selecting the appropriate grit for sanding is crucial and should be based on the surface material and the desired finish By considering these factors, users can effectively choose the best grit to meet their specific sanding requirements.
When purchasing sandpaper, you'll notice symbols such as the letters A or P on the packaging or product These letters indicate the grit value, which is essential for selecting the right sandpaper for your project.
• P: is the grit symbol according to the European standard (FEPA, the European Federation of Abrasives Producers)
• A: is the grit symbol according to the Japanese standard (JIS, the Japanese Industrial Standards)
Sandpaper grit is indicated by numerical values like P40, P120, and P240, where lower numbers signify coarser grit and higher numbers denote finer grit Selecting the correct sandpaper grit is essential for efficiently completing tasks and achieving optimal results on various materials.
Sandpaper is classified based on its function and grit
Sheet Sandpaper: Specifically designed for use by hand or with vibrating hand sanders, it comes in dimensions of 230 x 280 mm and is commonly used in PU painting technology
Roll Sandpaper: Specially used for handheld sanders (orbital sanders, belt sanders) with a width of less than 300 mm
Belt Sandpaper: Specifically used for wide belt sanders with widths of 600, 900, or 1300 mm, often applied in the woodworking industry n
The grit of sandpaper plays a crucial role in determining the smoothness of a material's surface after sanding Selecting the right grit is essential based on the specific task at hand.
Currently, sandpaper is classified according to grit as P40, P80 (for relatively coarse grit), P180 (for PU primer), P240 (for PU finishing), P320 (for high smoothness), and P400 (for very high smoothness)
Figure 2.6 Sandpaper selection chart based on grit
When using sandpaper, we need to pay attention to the following points:
* Choose the right type of sandpaper according to the purpose and usage needs
* Equip yourself with proper protective gear such as gloves, masks, goggles, ear protection,…to minimize accidents and risks
Proper installation of sanding machines is crucial for safety Ensure that all joints are securely fitted to prevent any parts from detaching, which could pose a risk to the operator and bystanders.
Figure 2.7 Using Sandpaper in Woodworking
2.2.4 Application of sandpaper in woodworking:
Sandpaper is a vital tool used extensively in woodworking for various applications
Sandpaper, made of abrasive particles attached to a paper or cloth backing, comes in various grit sizes, ranging from coarse to fine It is widely used in woodworking for tasks such as smoothing surfaces, shaping wood, and preparing surfaces for finishing.
Sandpaper is essential for achieving a smooth surface on wood It effectively eliminates rough spots, tool marks, and uneven areas after initial shaping and cutting, ensuring a refined and even finish.
Proper surface preparation is essential before applying finishes like paint, stain, or varnish to wood Using sandpaper helps achieve a smooth and uniform surface, ensuring that the finish adheres effectively and results in a professional-looking final product.
Sandpaper is an essential tool for eliminating minor imperfections in wood, including scratches, dents, and blemishes By using sandpaper, you can restore the wood's appearance and effectively prepare it for a flawless finish.
Contouring and shaping wood effectively requires the use of various sandpaper grits; coarse grits are ideal for initial shaping, while finer grits enable precise detailing for intricate woodwork.
Sanding the end grain of wood is essential for achieving a smooth and polished finish, as this area is often rough and porous Utilizing sandpaper effectively on the end grain ensures a consistent and visually appealing result in woodworking projects.
Cleaning Technology
Cleaning is a daily task that we all regularly face In a broader sense, it involves removing unwanted and complicated substances from the surfaces of devices and components [2] n
Cleaning can be achieved through various methods, with one traditional technique involving the immersion of equipment in a cleaning solution This method leverages both chemical and mechanical effects, primarily utilizing brushes or brooms for cleaning parts with simple structures While effective for flat and smooth surfaces, this approach is less suitable for tight or hard-to-reach areas.
• Quick and simple cleaning process that does not require advanced technology
• Ineffective for cleaning devices with complex structures or narrow gaps
• Surface scratching due to the use of brushes or brooms
• Surface deformation and structural damage to small and delicate components of the device
In modern industrial production, production lines are optimized to manufacture millions of uniform products annually, necessitating high-quality and consistent dimensions for efficient assembly and cost reduction To achieve this, ultrasonic cleaning devices are integrated at various stages to ensure the "absolute" cleanliness of product surfaces before further processing This technology is vital in producing high-density electronic circuit boards and complex metal components, where cleanliness, hardness, and precision are critical Ultrasonic cleaning effectively removes dirt from intricate surface details, paving the way for successful surface coating and polishing.
2.3.3 Principles of Cleaning using Ultrasonic Technology:
Ultrasonic waves are waves with frequencies higher than 18kHz, which cannot be heard by humans
Ultrasonic cleaning machines operate with wave frequencies ranging from 20kHz to 200kHz Frequencies between 10kHz and 50kHz are commonly utilized for cleaning in production lines and medical instruments, while frequencies exceeding 50kHz are ideal for cleaning optical instruments, biological filter membranes, and dental equipment in hospitals.
The ultrasonic waves in cleaning machines are mechanical waves and possess all the physical properties such as wave propagation, reflection, and wave interference in different transmitting media n
When a mechanical wave is produced in air or liquid due to pressure, it creates a compressed wave that travels towards lower-pressure areas, primarily in the direction of the driving force This wave comprises numerous higher frequency waves, often described as bubbles within bubbles, with their sizes varying based on the frequency of the ultrasonic wave; specifically, higher frequency ultrasonic waves lead to smaller bubble sizes.
Bubbles in a liquid medium travel continuously until they encounter a surface obstruction along their wave path When subjected to the compressive force of the wave, these bubbles rupture, leading to cavitation and propelling liquid particles onto the object's surface This impact effectively dislodges dirt, debris, and contaminants, which are then removed from the surface, particularly in the presence of negative pressure near the liquid surface.
2.3.4 Cleaning Process using Ultrasonic Technology:
Ultrasonic sensors, when powered, produce mechanical wave oscillations exceeding 20,000 Hz, which transmit high-frequency shockwaves through the stainless steel of ultrasonic cleaning tanks These shockwaves rapidly generate numerous small bubbles that propagate throughout the liquid, following the principles of mechanical wave propagation As these bubbles collide with the surfaces of objects, they create mechanical impacts that dislodge dirt particles, allowing them to dissolve in the cleaning solvent The smaller bubbles exhibit superior penetration capabilities, making them particularly effective for cleaning intricate surfaces, small crevices, and complex configurations that traditional cleaning methods struggle to address.
For effective cleaning, it is essential that the cleaning solution directly contacts the dirt particles, as this interaction allows the solution to dissolve the dirt The cleaning process is crucial in enhancing this contact between the chemicals and the dirt.
As cleaning chemicals dissolve dirt, a layer near the object's surface becomes saturated, slowing or halting their effectiveness To enhance the cleaning process, it is essential to regularly replenish fresh cleaning chemicals.
Ultrasonic waves enhance cleaning efficiency by creating bubble waves that disrupt the formation of a saturated layer of chemicals, ensuring that the active cleaning agents can directly contact the surface being cleaned.
Dirt particles that are not dissolved tend to loosely stick to surfaces due to ion bonding or cohesive forces These particles can be effortlessly removed by applying a force that exceeds their adhesion strength, allowing for easy separation from the surface.
To achieve high efficiency in ultrasonic cleaning, the cleaning solution needs to wet the dirt particles to be cleaned n
Ultrasonic cleaning technology's effectiveness hinges on selecting the right cleaning agent, delivering adequate ultrasonic energy, and considering temperature, as these factors significantly influence the dissolution of various types of dirt in the cleaning solution and enhance the surface cleaning process.
2.3.5 Advantages of Ultrasonic Cleaning Technology:
Unlike other cleaning methods, ultrasonic waves can effectively clean surfaces of objects in any shape by using bubbles that can reach different depths and angles
• There are several real benefits from the application of ultrasonic waves in precise cleaning
Ultrasonic cleaning technology offers significantly improved cleaning speed compared to traditional methods This advanced process eliminates the need for disassembly, resulting in reduced labor costs and making ultrasonic cleaning the most cost-effective option available.
Ultrasonic cleaning technology ensures a consistent and thorough cleaning process for objects of varying sizes and complexities, whether cleaning a single item or multiple parts simultaneously This method provides meticulous removal of dirt from the entire surface, independent of the operator's skill level.
• Safety and environmental compliance by reducing the concentration of hazardous chemicals or replacing corrosive cleaning agents with safer alternatives n
• Reduces direct contact between the operator and hazardous cleaning agents
• Energy-efficient, labor-saving, and cost-effective
• Ultrasonic cleaning machines provide real productivity value for precise cleaning applications.
Factors Influencing the Ultrasonic Cleaning Process
2.3.1 Relationship between Frequency and Bubble Size:
Higher frequencies lead to the formation of smaller bubbles, while lower frequencies produce larger bubbles Additionally, smaller bubbles can be generated over shorter distances compared to their larger counterparts The accompanying image illustrates the relationship between bubble size and frequency.
Figure 2.16 The relationship between frequency and bubble size n
The intensity of cavitation in water is influenced by bubble size, with larger bubbles typically resulting from high-intensity cavitation This size is inversely related to ultrasonic frequency; lower frequencies produce larger bubbles due to longer intervals between formations Consequently, while the number of bubbles increases with higher frequencies, bubbles formed at lower frequencies are more likely to experience intense implosion if the ultrasonic power remains constant.
Temperature plays a crucial role in maximizing bubble intensity, as fluctuations in temperature affect viscosity, gas solubility, gas diffusion rates, and vapor pressure In pure water, the optimal temperature for bubble generation is approximately 160°F (around 71°C).
The viscosity of a liquid plays a crucial role in bubble generation, as higher viscosity reduces bubble formation intensity Typically, most liquids experience a decrease in viscosity with rising temperatures, which is essential for efficient bubble generation For optimal results, the liquid must contain a specific amount of dissolved gas, which is released during bubble formation to prevent the implosion of forcefully shaped bubbles However, as temperature increases, the concentration of dissolved gas in the liquid decreases, while the diffusion of this gas becomes more pronounced.
As the liquid temperature approaches boiling, the likelihood of bubble formation through vapor increases, leading to the generation of vapor-filled bubbles that exhibit reduced intensity, causing certain areas within the tank to begin evaporating.
• The best ultrasonic performance is achieved at around 65% of the liquid's boiling point
• Temperatures above 65% of the boiling point will reduce the system's effectiveness
• Most ultrasonic cleaning agents use temperatures between 54 and 82°C
• When using materials with acidic properties, use the lowest temperature possible to minimize damage to the ultrasonic tank surface
Appropriate temperatures for cleaning objects:
• Most industrial parts are best cleaned at temperatures between 50-70°C, especially when cleaning microscope parts
• Electrical and electronic components are best cleaned at 45-55°C n
• Objects made of soft and delicate materials with chemical bonding typically only need to be cleaned at room temperature
• Laboratory equipment and specialized medical instruments should be cleaned ultrasonically at temperatures between 55-65°C
Choosing the appropriate chemical compounds is crucial for the success of ultrasonic cleaning These chemicals must be compatible with the metal's composition and demonstrate effective cleaning properties.
Effective ultrasonic cleaning requires agents that can produce robust bubble agitation Many chemical cleaning solutions are specially designed for use with ultrasonic technology, ensuring optimal performance The following table outlines several commonly used chemicals in ultrasonic cleaning.
Table 2.1 Some common cleaning solutions for metal
Temperature ºC Metal to Clean Application
40-50ºC Steel Cleaning dirty parts
40-60ºC Steel Cleaning dirty parts
50ºC Steel Cleaning dirty parts
50ºC Rusty Steel Removing scales and rust
The effectiveness of the cleaning process is influenced by factors like temperature, soil type, concentration of cleaning chemicals, and pulse frequency Typically, cleaning in a tank requires 10 to 15 minutes, whereas using a high-pressure spray vessel with a quality cleaning agent can significantly reduce the time to just a few seconds.
Ultrasonic power, expressed in watts per gallon or liter, varies among equipment manufacturers It is determined by the energy delivered to the transducer and typically ranges from 50 to 100 watts per gallon (3.78 liters) for most cleaning agents.
Increasing ultrasonic power enhances both the quantity of bubbles and the effectiveness of cleaning, but this improvement is only effective up to a specific threshold Exceeding this limit can lead to energy wastage and potential damage to the components being cleaned.
Total power encompasses the energy needed to run the entire ultrasonic tank system, including both the ultrasonic generator and any heating components, if applicable It is essential to distinguish total power from ultrasonic power, as they represent different aspects of the system's energy requirements.
Peak power is defined as the ultrasonic power generated at the peak of the sound wave and can be 2, 4, or 8 times higher than the average power
Ultrasound waves have an important role in various areas of life and are applied in different fields such as medicine, industrial machinery, scientific research, and geographical exploration
Ultrasound technology is integral to modern medicine, significantly enhancing diagnosis, treatment, and patient care It facilitates the early detection of tumors by analyzing changes in sound wave velocity as they pass through altered tissue By utilizing focused ultrasound beams and capturing reflected signals, healthcare professionals can pinpoint tumor locations and assess their development stages Various ultrasound machines, including therapeutic devices and Doppler ultrasound systems, are essential for imaging tissues and identifying abnormalities swiftly and accurately, making ultrasound a vital tool in disease diagnosis.
Industrial applications of ultrasound waves: Ultrasound is applied for product defect detection, weld quality assessment, and thickness measurement, among other industrial processes n
Geographical exploration applications of ultrasound waves: Ultrasound waves are used to survey and map challenging terrains such as deep ocean floors and mountainous regions
Figure 2.19 Survey and map challenging terrains
Ultrasonic welding is a process that utilizes ultrasonic vibrations, usually around 20 kHz, produced by high-power oscillators to soften the workpieces This is followed by the application of mechanical or pneumatic pressure to effectively join the components, resulting in atomic-level bonding.
Ultrasonic cleaning tanks are essential tools in both industrial and household settings for safely cleaning items that could be hazardous or easily damaged These cleaners excel at removing dirt and contaminants from complex components and delicate instruments, making them invaluable in laboratories, hospitals, mineral extraction, and electronic assembly.
Ultrasonic cleaners are versatile tools for cleaning and maintaining various items, including watches, eyeglasses, jewelry, and electronic devices They provide a non-toxic alternative for cleaning fruits and vegetables, making them an effective choice over traditional methods.
In summary, ultrasound waves have diverse applications in medical diagnostics, industrial processes, geological exploration, welding, scientific research, and cleaning n
These applications contribute to advancements in various fields, leading to improved healthcare, manufacturing efficiency, and scientific understanding
Factors to consider when using ultrasonic cleaning with a cleaning solution:
Roles and Classification of Transducers
An ultrasonic transducer is a device that converts electrical energy into mechanical oscillations at ultrasonic frequencies and vice versa This dual functionality allows for the classification of transducers into two categories: receiving transducers, which convert mechanical oscillations into electrical signals, and transmitting transducers, which perform the opposite function.
Ultrasonic frequencies are processed and amplified before being transmitted to a transducer, which converts electrical oscillations into mechanical oscillations that travel through a medium to fulfill a specific purpose Transducers can be categorized as electrostrictive or magnetostrictive, depending on the materials used in their construction.
Electrostrictive transducers typically have low power and operate at high frequency ranges Conversely, magnetostrictive transducers are commonly used in high-power devices and operate at low frequencies [4] n
The receiving transducer captures mechanical oscillations from the surrounding environment and converts them into electrical oscillations This electrical signal is then processed and amplified to the required level, serving as input for various indicating, measuring, or alerting devices.
Receiving transducers are typically electrostrictive transducers with high sensitivity
Piezoelectric transducers utilize the piezoelectric effect, first identified by Curie in 1880, where materials like quartz crystals and barium titanate generate mechanical vibrations under an electric field, leading to alternating electric charges Despite their effectiveness, these materials typically face challenges such as unstable vibrations and limited mechanical load-bearing capacity Since the 1940s, American scientists have advanced the development of piezoelectric sensors, enhancing their power, durability, and frequency stability even in challenging mechanical and environmental conditions.
Piezoelectric materials exhibit a deformation effect that is generally smaller than that of magnetostrictive transducers, with oscillation amplitudes typically ranging from 0.1 åm to 7 åm However, these piezoelectric transducers can operate at frequencies as high as 5 MHz.
Magnetostrictive sensors offer significantly higher power than piezoelectric sensors However, piezoelectric sensors excel in energy conversion, effectively transforming various forms of energy, including electrical, mechanical, and acoustic Their compact design makes piezoelectric transducers ideal for use in ultrasonic cleaning machines.
The piezoelectric effect is the phenomenon where applying force to a piezoelectric material leads to its deformation and the generation of an electrical signal Specifically, in the direct piezoelectric effect, the application of force creates opposite charges on the material's surfaces This effect can be demonstrated by attaching electrodes to a quartz plate coated with silver and measuring the resulting deflection of an electrometer needle.
When a tensile force is applied to a thin plate, it expands, causing the electrometer needle to deflect left, which indicates opposite charges on the plate's surfaces In contrast, when a compressive force contracts the plate, the needle deflects right, signifying a reversal in the charge direction on the two surfaces.
Figure 2.22 Direct piezoelectric effect (a) Tension Force (b) Compressive Force
The direct piezoelectric effect occurs when mechanical deformation generates opposite charges on the surfaces of piezoelectric materials This principle underlies the application of piezoelectric materials in a variety of technologies, including sensors, ultrasound devices, and actuators.
The relationship between the charge Q and the force F is determined by the equation:
✓ Q is the charge in Coulombs
✓ F is the magnitude of the applied force in kilograms
When a mechanical force is applied to the surface of a thin plate, it induces mechanical oscillations that generate an alternating electrical signal on the plate's electrodes, matching the frequency of the oscillations.
Materials that exhibit properties as described above are known as piezoelectric materials
This principle is the basis for constructing piezoelectric sensors for ultrasound wave detection
When two electrodes of a piezoelectric plate are connected to a DC power source, the plate's thickness expands, while reversing the polarity causes it to contract This phenomenon, induced by the applied electric field, showcases the capacity of piezoelectric materials to convert electrical energy into mechanical strain.
The relationship between 𝑙 and the applied voltage V is determined by the equation:
- L is the variation in the geometric dimension of the piezoelectric plate
- K is the piezoelectric constant, which has a value of 6.9 × 10^(-8)
- V is the magnitude of the applied polarizing voltage from the power source
Applying an alternating electrical signal with frequency f to a piezoelectric plate results in continuous thickness changes in the plate at the same frequency, generating mechanical oscillations in the surrounding environment.
This principle is the basis for constructing ultrasonic transducers
Experiments indicate that the oscillation amplitude reaches its peak when the voltage source frequency aligns with the piezoelectric plate's natural oscillation frequency This natural frequency is influenced by the plate's material and thickness, which can be quantified using a specific equation.
- 𝑓𝑜 is the natural oscillation frequency of the piezoelectric plate
- k is the natural oscillation coefficient (kHzãmm)
- l is the thickness of the piezoelectric plate (mm)
C The structure and shape of an ultrasonic transducer: n
Figure 2.24 The structure of an ultrasonic transducer
Magnetostriction is a phenomenon in which magnetic materials change their dimensions and shape when exposed to a magnetic field This occurs as the interaction between the material's magnetic structure and the magnetic field modifies the spacing between its atoms or molecules, causing the material to either expand or contract.
Connecting the two ends of a coil to a DC power source causes the magnetic core's length to expand, while reversing the power supply's direction leads to a contraction of the core.
Microprocessor STM32
The STM32F103C8T6 microcontroller features a robust ARM Cortex-M3 32-bit RISC core running at 72 MHz, complemented by high-speed embedded memory with up to 128Kbytes of Flash and 20 Kbytes of SRAM It offers extensive I/O options and peripherals linked to two APB buses, including two 12-bit ADCs, three 16-bit general-purpose timers, and a PWM timer Additionally, it supports a variety of communication interfaces such as I2C, SPI, USART, USB, and CAN, making it a versatile choice for various applications.
Figure 2.85 Pin descriptions of STM32
Power 3.3V, 5V, GND 3.3V – Regulated output voltage from the onboard regulator (drawing current is not recommended), can also be used to supply the chip
5V from USB or onboard regulator can be used to supply the onboard 3.3V regulator GND – Ground pins
Pins act as ADCs with 12-bit resolution
Input/output pins PA0 – PA15
UART with RTS and CTS pins
All digital pins have interrupt capability
PA6 – PA10 PB0 - PB1 PB6 – PB9
Inbuilt LED PC13 LED to act as a general- purpose GPIO indicator
Inter-Integrated Circuit communication ports
CAN CAN0TX, CAN0RX CAN bus ports n
Figure 2.26 Pin function of STM32
The following applications can benefit from the features offered by the STM32F103C6T8 performance line microcontroller:
- Motor drive and application control
- PC peripherals, gaming platforms, and GPS devices
- Industrial applications such as PLCs, inverters, printers, and scanners
- Alarm systems, video intercoms, and HVAC (heating, ventilation, and air conditioning) systems
Similar products on the market
The CO-Z Ultrasonic Cleaner features a durable construction with reinforced inner tank walls, ensuring long-lasting ultrasonic cavitation that effectively cleans hard-to-reach areas Designed for industrial use, it boasts a minimum service life of 2 years, outperforming competitors Its digital control panel allows for customizable temperature and working time settings, delivering spotless results for various household and professional items For those seeking thorough cleanliness and reliable safety, the CO-Z Ultrasonic Cleaner is the premier choice for professional-grade cleaning.
The ultrasonic cleaner is equipped with a 2-liter stainless steel tank, ideal for accommodating larger items or multiple smaller items simultaneously It features user-friendly digital controls and adjustable timer settings, operating at a frequency of 40 kHz Specifically designed for commercial use, this machine delivers efficient cleaning for a wide range of objects.
• Tank Capacity: 1.8-2L (Since the bottom of the ultrasonic cleaner is a curved surface, the actual volume will be smaller.)
• Time Setting: 0-30 min (LED Digital Display)
DESIGN OPTIONS
Choose machine structure
Based on the technical requirements of the machine, each operating method has its own advantages and disadvantages, depending on the manufacturing needs to choose the appropriate model type
Table 3.1 Advantages and Disadvantages of one cleaning tank and multiple cleaning tanks
There is only one cleaning tank There are multiple cleaning tanks
• Reduced load-bearing capacity of the machine frame
• Applicable on a small scale, for households
•Can clean at different temperatures simultaneously
• Can clean with multiple solvents simultaneously
• Can be dried after cleaning
•Cannot clean with multiple solvents simultaneously
•Cannot clean at different temperatures simultaneously
• Residue of solvents may remain after cleaning
Figure 3.1 Ultrasonic cleaning tank with one basin
Figure 3.2 Ultrasonic cleaning tank with multiple basins
Conclusion: Thus, after evaluating the above two structural options, our group chose ultrasonic washing tank with many tanks.
Choose transmission mechanism
Our team has found the right transmission mechanism option for ultrasonic cleaner: screw drive, pneumatic, hydraulic Here we analyze the advantages, disadvantages of the above 3 options: n
Table 3.2 Advantages and disadvantages of transmission mechanism
• Easy and non-invasive operation noise
• Easy to control precise position
• A considerable amount of heat is generated in the actuator, so need lubrication
• The lubrication must be strictly maintained to ensure the life of the shaft
Hydraulics • Strong and fast transmission with high power
• Easy to use and repair
• Use at high speed without fear of strong impact like in case of electric shock
• Suitable for systems requiring large loads (kN)
• When starting up, the temperature of the system is not stable, the working speed will change
• Loss in oil pipelines and leaks inside elements reduce performance and application range
• It is difficult to keep the speed constant when the load changes
• Difficult to achieve 1mm position accuracy (achievable but costly very high)
Pneumatic • Do not pollute the environment
• Capable of transmitting energy far
• Limited pressure prevention system is guaranteed
• Inability to generate great force
• As the load in the system changes, the velocity also changes
• The control is often not very accurate
• Compressed air exits at the inlet
In conclusion, after analyzing the advantages and disadvantages alongside the maximum load requirement of 300N, it is evident that a screw actuator is the optimal choice for applications that necessitate constant speed, high positional accuracy, and cost-effectiveness.
Choose material of frame
The machine frame can be constructed from various materials, including steel, aluminum sheet, corrugated iron, aluminum profiles, and wood Each material offers distinct levels of durability and accuracy, making it essential to choose the right one based on the specific technical requirements of the project.
• The machine frame must ensure rigidity
• No vibration, shaking during machining
• The machine frame is easy to clean, ensuring aesthetics
• Easy to disassemble and maintain
When selecting the ideal material for chassis construction, options such as corrugated iron, steel plate, and aluminum plate are worth considering This analysis aims to identify the most optimal material that meets the necessary requirements for durability and performance.
Table 3.3 Advantages and disadvantages of material for frame
• Anti-corrosion caused by the environment
• Heat resistant, extremely heat resistant efficiently, durable
• High economic efficiency thanks to affordable price
• Low rust resistance in harsh weather conditions containing corrosive substances
• The surface is easily scratched, affecting aesthetics
Steel plate • Steel plate with high hardness and high strength
• The steel is well-processed, meticulously, with no roughness or ripples
• Unaffected by environmental factors and weather
• Large in size, bulky and difficult to transport transfer
• There should be a separate preservation method for each different type of steel plate
• Aluminum plate has good heat resistance
• Has high chemical resistance, good wear resistance
• Poor durability and bearing capacity
• Specific gravity is lighter than steel
• The surface is smooth, beautiful, easy to process, drill holes, plan grooves
In conclusion, while all three materials—steel, aluminum, and Ton—satisfy the technical requirements for chassis construction, aluminum stands out due to its superior corrosion resistance, heat resistance, and aesthetic appeal The decision to use aluminum for the chassis design is driven by its smooth surface, ease of processing, and capability for precise machining, making it the optimal choice for this application.
Choose material of tank
So with the technical requirements of the topic, the material selected for the tank ensures the following factors:
• Capable of withstanding high cavitation
• The machine frame is easy to clean, ensuring aesthetics
• Easy to disassemble and maintain
Therefore, Inox will be choice by team
Table 3.4 Advantages and disadvantages of material for tank
Inox 304 • Corrosion resistance: Stainless steel 304 has high corrosion resistance to water, air, organic compounds and many common chemicals
• High strength, making it resistant to strong impacts
• Easily cut, weld, shape and machine complex shapes This reduces production time and costs
• Especially very safe when in contact with food
Small amounts of substances like magnesium (Mg) and sulfide (S) can be absorbed, leading to the appearance of black dots on the surface, which detracts from the material's aesthetic appeal.
Inox 201 • This type of stainless steel is also non-magnetic, durable with time
• The price of the product is not too high
• Not suitable for salt environments: Type 304 is not recommended for use in environments with high salt concentrations, such as by the sea, as it is susceptible to salt corrosion
• There should be a separate preservation method for each different type of steel plate
Inox403 • Low cost • This stainless steel is susceptible to magnetic contamination
• Easily affected by the surrounding environment, making the product tarnished, no longer shiny
Conclusion: Based on the characteristics of each type of stainless steel, the team decided to choose 304 stainless steel as the most suitable type.
Sketch machine structure
DESIGN OF MECHANICAL SYSTEM
Introduction
The chosen mechanism and transmission plan from Chapter 3 establish a foundation for calculating, comparing, and selecting appropriate machine components and details, while ensuring the technical requirements of the group are met.
This chapter outlines the comprehensive methods for calculating and designing a complete mechanical machine configuration It includes essential formulas and references to calculation websites, alongside guidance on selecting necessary equipment for the system The team has successfully developed the mechanical components based on input criteria, ensuring that all parts meet initial requirements The mechanical design guarantees smooth, continuous operation with minimal vibrations, thereby enhancing measurement accuracy and reducing delays.
Machine structure requirements
• The machine operates reciprocally along the X axis according to the selected mechanism “Screw Drive” Movement range from 50 mm to 1000 mm
• The machine operates reciprocally along the X axis according to the selected mechanism “Pneumatic” Movement range from 0 mm to 200 mm
• Always ensure safety when operating the machine
Calculation and selection of components
A Choose type of ball screw:
There are two types of lead screws: normal lead screws and ball screws n
Normal lead screws Ball screws
• High transmission precision, large gear ratio
• Smooth transmission, capable of self- braking, large transmission force
• Fast drive is possible with lead screw with large pitch or number of revolutions
• The transmission efficiency is low, so it is rarely used to perform the main movements
• Low friction loss should have high efficiency, can reach 90-95%
• Friction force is almost independent of motion speed, so it ensures movement at small speeds
• There is almost no gap in the joint and can generate initial tension, ensuring high axial rigidity
• Because of these advantages, ball nut ball screws are often used for machines that require precise linear transmission such as drilling machines, coordinate boring machines, numerical program control machines n
Figure 4.3 The relationship between friction and speed of two types of roller screws n
In conclusion, the team opted for a ball screw due to its low and stable friction, which remains nearly constant regardless of speed As illustrated in the diagram, the ball screw requires significantly less time to initiate movement compared to a standard lead screw Consequently, the ball screw emerges as the most efficient and suitable choice for optimal working performance.
Table 4.2 Advantages and disadvantages of Motion
C The drive mechanism integrates the roller screw and the rail:
Linear Motion • Because the linear guide is influenced by the rolling friction of the bearing, it is easier to slip
• High hardness, good load bearing
• Long life, rarely abraded, good anti-vibration
• Easy to maintain and repair
Steel Ball Rail • High-precision circular sliders and sliders
• Easy to maintain and repair
• Low hardness, not good load bearing n
Figure 4.4 Structure of LM Guide Actuator Model KR
• Available on the market in a variety of sizes (Reducing design and installation time)
• Can be used in any installation direction
• Reduced load fluctuations allow high-precision operation
Conclusion of selection of drive and guide:
To optimize space and time in machine design while maintaining rigidity and smooth operation, the team selected a transmission mechanism that combines a vitme with a sliding rail They utilized THK's slide rail lead screw, Model Kr, across all three axes: X, Y, and Z Given that the Y axis must support a significant load, the addition of two square rail sliders was essential to enhance rigidity.
The design process emphasizes simplicity, focusing on the simplest machine concept, which requires that the components be easy to repair and handle This approach ensures the stability and rigidity of systems aligned along the X-axis.
The design of the pedestal is crucial for supporting the rail's sliding mechanism and the lead screw It must be sturdy, with a top surface precisely machined to ensure smoothness and flatness, allowing for the proper installation of two sieves and lead screws.
LM Guide + Ball Screw = Integral-structure Actuator
LM Guide Actuator Model KR n
Load m=3 kg (minus factor of safety k = 1.5)
Maximum acceleration of the system a = g/2 = 5 m/𝑠 2
No-load position accuracy ± 0,03/1000mm
- Maximum axial force when turning to the right:
- Maximum axial force when going left:
F 1max ; F 2max : Maximum axial force when machined and unmachined
The maximum rotation speed during both machining and idle modes remains constant due to the machine's consistent weight This is represented by N 1max for idle and N 2max for loaded conditions Additionally, the operational times are denoted as t 1 for idle mode and t 2 for load mode.
Axial force of X Velocity (rpm) Time (%)
• Calculation of static load: a max o o s a max s
- f s : Static safety factor (for industrial production machines: 1.2 ÷ 2; for machine tools: 1.5 ÷ 3), inferred to choose fs = 2
- F amax : Maximum axial force (Famax = 58 (N)
- Load factor: f w are checked based on the following table:
- Choose a motor rotation speed of about 80% of the critical motor speed, so: n = 0.8.75 = 60 (rpm)
- The radius of the screw shaft is calculated by the formula:
With lead screw diameter = 10 mm choose bearing T1 Kp000
Based on the available input parameters to calculate the necessary parameters of the motor to satisfy the initial requirements
Choose roller screw with step h = 10mm
Coefficient of sliding friction between steel and cast iron
The mass of the displacement head part m = 3 kg
Maximum rotational speed of the motor 2000 vg/ph
To choose the right engine, first of all, it is necessary to compare the advantages and disadvantages of different types of engines
Table 4.8 Type of Servo Motor
Stepper Motor DC Servo Motor AC Servo Motor
Control method Used in open loop controller
Used in closed loop controller
Used in closed loop controller
No feedback signal, error prone
There is feedback about, less error
There is feedback about, less error
No need Encoder Need Encoder and
Need Encoder and Gearbox to control accuracy
Moment At low speed there is large torque At high speed there is small torque
There is a huge moment Beneficial when driving at high torque
Size Motor Small Size Big size Bigger than stepper motor but smaller than
DC Servo in the same power
Causes more noise and vibration
Noise Very Noise Fewer noise Limit noise n
Price Less expensive than servo motor
• Conclusion: After making a table to compare motor types with each other, we decide to choose Step motor Because There are compact motor, low travel speed, medium torque, low cost
Calculate the moment of friction:
2.𝜋.1.0,9 = 1,1(𝑁𝑚) (22) Since the structure is horizontal, α=0 or Mwz=0
Conclusion: From the static torque and screw radius, we choose the size 57 stepper motor n
Figure 4.6 Step Motor Size 57 Table 4.9 Techincal specifications of stepper motor
To be able to completely immerse the object in the washing tank, with the weight of the basket about 300g, we can choose the type of cylinder AIRTAC TN16 n
Figure 4.8 Specification of Cylinder AIRTAC TN16-125
Manufacture Parts
Table 4.10 List of manufacture Parts
1 Pressing, cut laser, manufact ure hole
1 Cut laser, manufa cture hole
1 Pressin g,cut laser, manufa cture hole
1 Pressin g,cut laser, manufa cture hole
After selection and calculation We proceed to process the parts and assemble Finally we have the complete model:
DESIGN OF ELECTRICAL AND CONTROL SYSTEM
System block diagram
Functions of each main block:
Figure 5.1 Block diagram of the entire system
The 1-phase 220V AC source is converted into 24VDC and 12VDC power through an AC/DC converter This setup powers various devices, with 24VDC used for cooling fans, step drivers, and solid-state relays (SSRs), while 12VDC is utilized for relays, water level sensors, pumps, and temperature sensors.
The STM32F103C8T6 microcontroller efficiently processes input signals, including sensor feedback and temperature data, while also receiving control signals from a C# interface It effectively manages information processing and displays the required values on the interface, making it an ideal choice for various applications.
The Display and Control Block features a user-friendly C# Winform interface, designed to effectively manage system functions Our team's goal is to create a clear and straightforward experience, allowing users to control parameters such as set temperature, PID controller settings, and ultrasonic cleaning duration Results are visually displayed on the screen for easy monitoring.
The Execution Mechanism Block comprises the X-axis drive transmission system and the material supply system, playing a crucial role in operating the machine based on directives from the central processing block.
• Signal Acquisition Block: Specifically, temperature sensors and water level sensors Its main task is to measure data and send the parameters to the central processing unit as required.
Calculation and Selection of Components
5.2.1 Pump Motor and Water Level Sensor Selection:
To optimize the washing tank design, measuring 25x25x15 mm with a 10-liter capacity, a compact pump motor is essential The selected mini submersible pump motor, powered by 5V, should achieve a flow rate between 1.2 to 1.6 liters per minute, ensuring efficient water circulation relative to the tank's volume.
Table 5.1 Specifications of the 5V mini pump
Figure 5.3 Picture of 5V mini pump
A water level sensor is essential for monitoring the water level in a tank It alerts users with a red light on the interface when the water level falls below the necessary threshold before pumping Conversely, when the tank reaches the required water level, the sensor indicates this by displaying a green light.
Table 5.2 Specifications of the water level sensor
Figure 5.4 Picture of the water level sensor
A Overview of the Temperature Control Unit: n
Temperature control units are essential in numerous industrial applications, including drying ovens, egg incubators, baking ovens, steam boilers, humidity control systems, and compressed air systems These units utilize various control modes, such as on-off control, linear control, PID control, and ON-OFF control, to effectively manage temperature.
In addition, with PID control mode, the temperature control unit adjusts the system temperature to match the set temperature as quickly and accurately as possible
The control unit efficiently manages humidity, pressure, and flow rate using input signals of 4-20mA or 0-10 VDC, 0-5 VDC It offers advanced features including temperature alarms, a display screen for direct value setting, self-adjustment mode, and adaptive mode for enhanced performance.
Figure 5.6 Closed-loop PID control diagram
In temperature control applications, the system relies on two key input signals: the set temperature and the actual temperature feedback The control output signal corresponds to the angle value for the triac Given the challenges in modeling the system, an identification method is employed to ascertain the transfer function, which is identified as a first-order lag element This forms the basis for designing the PID parameters effectively.
PID, or Proportional Integral Derivative, is a widely utilized feedback control mechanism in various fields such as industrial control systems, electrical systems, automation, and electronics This controller comprises three essential components: proportional, integral, and derivative, making it the most common type of control system in use today.
PID control is a complex process used to achieve a desired setpoint value, such as temperature, pressure, or flow rate
There are four types of control:
• Proportional and Integral (PI) Controller
• Proportional and Derivative (PD) Controller
• Proportional, Integral, and Derivative (PID) Controller
PID controllers are widely regarded as the optimal choice for contemporary control systems, playing a crucial role in automated process control across diverse industries They effectively minimize steady-state errors, reduce oscillations, and enhance settling time and overshoot.
Figure 5.7 Response Graph when using the components of a PID controller
This circuit utilizes a PID controller to regulate the temperature of a 220V/500W heating resistor It effectively manages the on/off operation of a TRIAC by adjusting the voltage delivered to the heating element.
The circuit detects the zero-crossing point of AC voltage, implements a PID controller, and adjusts the TRIAC gate's firing angle to regulate the temperature of the heating resistor.
The K-type thermocouple is the most commonly utilized thermal sensing device across multiple industries It consists of two different metal wires connected at both ends, forming a closed circuit When a temperature difference occurs between the junctions, it generates an electric current, enabling accurate temperature measurement.
There are various types of thermocouples, each represented by a letter (K, J, E, T,
K Type Thermocouple has main ingredient is Nickel, which is commonly used in industry with temperature measurement applications due to the following advantages:
Table 5.3 Advantages and disadvantages of K Type Thermalcouple
The ability to measure extremely high temperatures for a long time
The error is about 1% over the full range
Can measure high temperature continuously
Able to with stand temperature rise/fall suddenly
Its output is in the form of mV (millivolts) This signal is very small, so it is easy to noise when transmitting over long distances
Reasonable price When used, there will be a certain delay n
Table 5.4 Specifications of the temperature sensor
Temperature Sensor Type: Thermocouple K Type
Wire: Metal coated sensor wire
The MAX6675 is designed to amplify measurements from K-type thermocouples, ensuring high accuracy and stable operation Utilizing the SPI communication standard, it effectively transmits sensor values to microcontrollers This heat sensor is ideal for temperature measurement systems in industrial environments, providing both accuracy and durability.
Table 5.5 Specifications of the MAX6675 Converter
Resolution: ADC 12bit, 0.25 degree K/unit
• How to use MAX6675 and K-type Thermalcouple:
The K-type thermocouple produces a minimal output voltage, making signal processing challenging To address this issue, I utilize the MAX6675 ADC converter circuit, which communicates with the microprocessor through an SPI interface.
Figure 5.11 Connect between MAX6675 and Microcontroller
When the CS pin is low, the SCK clock pin activates, allowing the SO pin to transmit data from bit 15 to bit 0 Once the CS pin goes high, it triggers a line transmit interrupt, ending the data read cycle Each data transfer comprises 16 bits, with bit 15 and bits 0, 1, and 2 designated for device information, while the remaining 12 bits, from bits 3 to 14, represent the temperature value being read.
The manufacturer's datasheet indicates that a string value of all bits equal to 0 represents 0 degrees Celsius, while all bits equal to 1 signify 1024 degrees Celsius With 12 bits of data, which equals 2^12 or 4096, the temperature value is determined by dividing the reading by 4.
- Configure PIN STM32 on MXCube n
Figure 5.13 Configure Pin STM32 on MXCube
- Coding base on datasheet of MAX6675 and simulation on Proteus
Figure 5.15 Read value from Oscilliscope
The 220V sinusoidal voltage operates at a frequency of 50Hz, with a period of 0.02 seconds Each half cycle lasts 10 milliseconds (or 1000 microseconds), during which the voltage alternates between negative and positive values, reaching zero at specific intervals.
Construction of electrical cabinets
5.4.1 Design printed circuit on Altium:
Figure 5.50 Layout of board circuit
Monitoring and Control Interface
We have created a C# application designed for easy monitoring and management of the system, featuring an intuitive user interface for enhanced user experience.
The application consists of three main parts:
• Parameter setup and basic control section
Connection section: This part of the application establishes a connection between the user’s computer and the sandpaper washing machine through UART communication
To establish the connection, the user needs to enter the correct COM port and Baudrate, and then press the “Connect” button n
5.5.2 Parameter setup and basic control section:
This section includes settings for temperature, Kp, Ki, Kd, set timer, Jog +, Jog-, and water pump
Temperature setting and PID parameters: used to control the water temperature in the washing tank so that it responds as quickly and stably as possible
Set timer: sets the desired time for the sandpaper washing system
Jog +, Jog - : used to control the working arm to the desired position When in normal running mode, the machine will control it automatically
The water pump activates when the button is pressed, delivering water to the washing tank Once the water level is adequate for sandpaper washing, the system automatically shuts off the pump.
Run: when the temperature and water level are sufficient for sandpaper washing, the user n
Water level monitoring is crucial for efficient washing operations Initially, the interface indicates a low water level in red when the washing tank is empty Once the tank is filled to the required level for the washing process, the interface changes to green, signaling that it is ready for use.
Temperature monitoring: It shows the temperature in numerical form and also through a chart to allow users to easily track the temperature n
EXPERIMENT RESULTS/ FINDINGS AND ANALYSIS
Establish Target Specifications
1 It needs to be high durability
2 The surface of the sandpaper must still be clean
3 The surface of the sandpaper must still be usable
4 It needs to be high power
5 It is easy to product
No Need No Metric Imp
Table 6.2 Metrics and needs correlation
1 It needs to be high durability
2 The surface of the sandpaper must still be clean X
3 The surface of the sandpaper must still be usable X X
4 It needs to be high power X
5 It is easy to product X X X
Experiments
To evaluate the machine's operational range and reliability, we conduct two actual tests, including a Static Test that measures static parameters such as dimensions, total mass, stiffness, and other non-electric characteristics.
I use a straight steel ruler to measure the dimensions Using my eyes to read all measured value As for total mass, I measure each of part and esimate machine’s total mass n
Table 6.3 Dimension and measured value
METRICS DESIGN VALUE ACTUAL VALUE
- Check the working ability of the machine
- Check the safety of the device
- After putting the machine in the test position and making the electrical connection, check the safety, close the power supply and safely put the machine in 10 liters of water
- Consider the structure of the washing machine when operating
- Machine works stably without vibration during running time
A Cleaning solution test by temperature:
The group establishes its own evaluation criteria for the machine's effectiveness, aiming for an 80% cleaning capacity while ensuring the surface remains usable Key factors influencing the washing process are analyzed to optimize performance.
Table 6.4 Result depend on Temperature
In conclusion, the findings indicate that unheated water temperatures yield poor results; however, increasing the water temperature significantly improves the outcomes.
B Cleaning solution test by solven:
Table 6.5 Result depend on Solvent
In conclusion, the results indicate that the performance of the two solvents tested in different environments is quite similar, yet overall effectiveness remains low, suggesting that these solvents are not suitable for the intended application.
C Cleaning solution test by power: n
We will in turn change the power of the machine by changing the number of transducers
Table 6.6 Result depend on Power
Check the working surface of sandpaper test
To test the surface of the sandpaper, the team decided to use the hand and eye method to assess the quality of the surface
When touch it, I can see that the roughness of the surface does not change much Sanding ability is still relatively effective compared to the original.
Comments
During the experiment, the parameters affecting the washing process can be changed easily and accurately We also found that the influence of temperature, solvent and power on washing
Assessing cleanliness parameters can be time-consuming, primarily due to the reliance on sensory evaluation, which offers only relative results Additionally, the limitations of available equipment hinder precise evaluations based on calculated standards.
CONCLUSION AND FUTURE DEVELOPMENT
Conclusion
After extensive research and implementation of our graduation project titled "Design and Manufacture of a Sandpaper Washing Machine in Woodworking Using Ultrasonic Wave Technology," our team has successfully developed a machine model, the results of which are detailed below.
The achieved results are as follows:
- The model is designed, constructed, and completed with meticulous craftsmanship, where each detail is carefully processed and connected to form a solid unit, ensuring both sturdiness and aesthetic appeal
- Meets the demand for automatic and precise operation
- The sandpaper washing results are also relatively clean.
Future Development
- Use large capacity thermistor for better temperature response time n
- Do more research to speed up the sandpaper washing speed
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