INTRODUCTION
Introduction
In today's market, plastic stamps are widely utilized across various industries, including garments and footwear, to enhance brand promotion and improve product aesthetics These versatile stamps can be applied to numerous products, effectively showcasing brand identity and elevating visual appeal Among these, flexible rubber labels stand out as a popular choice for their adaptability and effectiveness in branding.
- Stamps of flexible rubber rubbers used to make brand identity logos
- Stamps of plastic rubber labels used as key chains
- Stamps of plastic rubber labels used in fashion and apparel industry
- Stamps of plastic rubber labels for making household appliances labels
- Stamps of plastic rubber labels make the team of interior labels
- Stamps of plastic rubber labels for making briefcases, suitcases and bags
- Stamps of plastic rubber labels for making footwear labels
The plastic labeling machine market is primarily led by China, where prices tend to be high However, Vietnam presents a significant opportunity with its quality products offered at more competitive prices As major global brands increasingly establish their presence in Vietnam, the demand for labeling solutions is surging, creating a robust market for plastic stamps.
The development of machines under a Vietnamese brand is essential for facilitating investment in plastic label production Researching and manufacturing various types of machinery for this process is both necessary and practical for manufacturers.
Manufacturing process of Plastic tag products
Taking out of mold, classifying
Greatly affecting the production efficiency
Figure 1: Manufactory process of plastic tag
The process of dripping raw material into the mold will determine if the product will achieve the level of clarity and correct shape of the mold or not
The Heating and Cooling process of the mold post-Dripping significantly influences the physical properties and overall quality of the finished products, impacting all items within the mold at once Consequently, an effective manufacturing process requires a Heater and Cooler system that ensures precise temperature control and stability Incorporating built-in thermostats to regulate temperature and time enhances product quality while minimizing waste and improving energy efficiency This understanding has inspired the design and creation of an advanced heating furnace to meet these essential requirements.
Built-in thermostats in heating ovens enhance product quality by effectively controlling temperature and time, leading to reduced waste and improved energy efficiency This insight has inspired the design and creation of a heating furnace that optimally utilizes energy resources, ensuring both effectiveness and efficiency.
Electric ovens offer high efficiency and significant advantages for users and the environment They are extensively utilized in various industries to fulfill diverse practical requirements In both industrial applications and daily life, thermal energy is crucial, serving essential functions such as heating and drying.
Therefore, the rational and effective use of energy resources is very necessary Electric resistance furnace is widely used in industry because of the response many practical requirements are posed
The objective of the project is to apply the product design and development process to:
- Market survey of product needs: find out about existing products, evaluate the potential of products, survey prices, functions and models of products from the market
- Heating furnace design: analyzing customer needs, applying product design process to perform product shaping steps, drawing detailed drawings, prototyping and processing samples
- Product development: experiment with equipment, conduct product innovations and upgrades, and test market reality.
Subject and scope
- Research, design, and improvement techniques for controlling cooling systems
- Modify the operation of the machine
- Research and design a SCADA system for the heating machine
The machine currently lacks a foundational basis for industrial operation, and many of its functions require enhancements to meet the specific needs of THACH GIA CO Notably, the implementation of a SCADA system is essential for optimizing the machine's performance.
- 1 PLC LOGO! 12-24rce Siemens 6ed1052-1md00-0ba8.
- Verify the PI Algorithm for temperature control
- Find the time and temperature that suitable for the product and mold
- Improve the cooler control method with the threshold voltage.
- Design a SCADA system for the machine.
Improvement methodology
In order to improvement, research the topic, the improvement team uses the following methods:
- Scientific observation method: in order to obtain practical information about products and equipment already on the market Observing science also helps the team realize market demand for products
Analyzing and summarizing experiences is essential for assessing a product's demand and capabilities This process helps identify the device's limitations and shortcomings, enabling improvements and advancements in its development.
The experimental method involves conducting product experiments to evaluate how well the product meets actual market demands This approach allows for the analysis of results and the identification of improvement strategies for the equipment.
- Method of experts: consulting instructors, teachers, friends, contacts, using a regular drill to consult, solutions to contribute to the complete equipment
LITERATURE REVIEW
Concept and definition about heating ovens
An oven is a thermally insulated chamber primarily used for cooking, baking, and drying various substances In addition to culinary applications, specialized ovens like kilns and furnaces serve specific purposes in pottery and metalworking Beyond the kitchen, ovens have diverse uses across different industries.
A furnace serves dual purposes: it heats buildings and melts materials like glass or metal for processing Among the various types, a blast furnace is specifically designed for metal smelting, particularly in steel production, utilizing refined coke as fuel and pressurized air to enhance the fire's temperature Additionally, blacksmiths employ a temporarily blown furnace, known as the smith's heart, to heat iron to a bright red or yellow hue.
A kiln is a high-temperature oven essential for manufacturing wood, ceramics, and cement, transforming mineral feedstock like clay and calcium or aluminum rocks into a more solid and glass-like form Ceramic kilns yield shaped clay objects, while cement kilns produce clinker, which is subsequently crushed to create cement Additionally, certain drying ovens in food production, particularly those used in malting, are also known as kilns.
An autoclave is a specialized device resembling an oven or pressure cooker, designed to heat aqueous solutions to temperatures exceeding the boiling point of water, effectively sterilizing its contents.
Industrial ovens are similar to their culinary equivalents and are used for a number of different applications that do not require the high temperature of a kiln or furnace
An electric oven is a device that converts electricity into heat used in appliances Various technological processes such as: calcining or smelting materials, needles types and other alloys
Electric ovens are widely used in many different fields such as:
In the field of metallurgical engineering and machine manufacturing:
- Specialized training and heat treatment
- Burn items before rolling, forging, stamping and spinning
- Producing castings and metal powders
- In light industry and food: Electric ovens are used for drying and plating products and item preparation
- In chemical technology: Electric furnaces are used to produce objects
Electric ovens have become increasingly prevalent in both industrial settings and everyday life, offering a diverse range of appliances such as electric cookers, rice cookers, water heaters, solid fuel burning equipment, and dryers.
Industrial oven
There are two main configurations of industrial ovens, batch and continuous
A batch oven, often referred to as a 'walk-in' oven, is designed for processing multiple batches of materials that require the same heat treatment at varying times This type of oven is ideal for situations where materials need to be heat-treated in different batches The industrial oven accommodates these batches on carts, trays, or racks, allowing for either manual or automatic loading, which facilitates seamless transitions between different batches.
In mass-production settings, continuous ovens are preferred over batch ovens due to their ability to maintain a consistent heating environment These ovens typically feature separate heating and cooling chambers, which significantly enhance processing speed and efficiency.
- The most common heat sources for an industrial oven are hot water, gas, and electricity, and these heat sources are often introduced into the oven via forced convection
Electric heated industrial ovens are the most popular choice among heat sources due to their rapid heat-up times and long lifespan These ovens are cost-effective and environmentally friendly, producing no pollution during operation.
2.2.2 Commercially available industrial ovens a.Promotional two layers PVC Baking Oven
The upper layer is to bake the logo color, the under layer is to bake the base color
Figure 2: Promotional two layers PVC baking oven [9]
- Stainless steel material: easy to clean
- Intelligent two layers construction: The speed of two layers can be adjusted separately
- Equipped with automatic pushing equipment, can avoid manual mistake and burn
- Due to the open design, it causes heat loss to the environment, wastes electricity, makes the working environment always at a relatively high temperature, uncomfortable for production workers
- Make noise during operation due to the conveyor belt being made of chain
- Large size, takes up a lot of space
The PVC label machine is versatile, capable of producing a wide range of PVC and silicone products including photo frames, keychains, luggage tags, key covers, lighter covers, mouse mats, hair clips, brooches, mugs, refrigerator magnets, coasters, bar mats, table mats, bottle openers, anti-slip mats, door cards, USB flash disk covers, card reader covers, mobile phone straps, mobile phone holders, mobile cleaners, mobile phone covers, file clamps, and pen containers Additionally, it features an energy-saving PVC baking oven for enhanced efficiency.
Figure 3: Energy-saving PVC baking oven [10]
- High fever power, rapid warming
The heating system features three 220V/2KW heating elements and six 220V/600W heating tubes, delivering a total heating power of 9.6KW It can efficiently raise the temperature from 20 degrees Celsius to 300 degrees Celsius in under 10 minutes.
- Insulation effect is good, reduce energy consumption
The oven features advanced thermal insulation, with the upper section insulated using cotton insulation and the lower section equipped with a thermal insulation board This design enhances the overall thermal efficiency, minimizes heat loss, and ultimately reduces energy consumption.
- Optimize the cooling water circulation process to improve the cooling rate while avoiding splashing water
Baking the fabric reduces the water level in the sink, ensuring that when the final product is released, the mold does not disturb the water surface, preventing any splashes As the mold descends onto the stainless steel bar, the water level quickly rises to cool the mold effectively Once the water reaches a specific level, it stabilizes to avoid submerging the mold.
Thermal concepts and principles
Heat is the energy that moves spontaneously from a hotter body to a colder one, representing energy in transit rather than a characteristic of a specific system In contrast, internal energy refers to the intrinsic energy contained within a system itself.
The heat that an object adds or loses during heat transfer is called heat
Calorific is denoted: Q unit of calorimeter J b Thermal energy
In an ideal gas, internal energy consists of the total kinetic energy of gas particles, which plays a crucial role in heat transfer across a system's boundary Consequently, "thermal energy" is often used interchangeably with internal energy.
- Heat transfer from high temperature objects to low temperature objects
- The process of heat transfer until the temperature of the objects is equal, then reused
- Total heat output is equal to the total heat energy collected:
2.3.2 The rocess of heat gain and exothermic
Heat gained to heat up objects:
The formula for calculating the heat gain of an object:
𝑄 𝑡𝑣 : Heat collected for heating objects (J)
M: Weight of object (kg) c: Specific heat of substance (J / kg.K)
Specific heat is the amount of heat needed to transfer 1 kg of material to increase by 1 o C
Matter Capacity heat (J/Kg.K) Matter Capacity heat (J/Kg.K)
Table 2: Specific capacities of some substances a Cooling process i Concept
Freezing is the process by which a substance changes from a liquid to a solid state The process of freezing is the process of exothermic ii Equation
Formula to calculate the amount of heat emitted to the solid substance (for the solidification of PVC)
Freezing heat refers to the heat energy released when 1 kg of a substance transitions from a liquid to a solid state This phenomenon is equally significant as molten heat, indicating that the heat absorbed during the freezing process is precisely the same amount of heat released when the substance solidifies Understanding freezing heat is essential for various applications in thermodynamics and material science.
- A substance only solidifies when it is at the freezing temperature
- During Cooling, the temperature of the object does not change (at the freezing temperature)
- Cooling point is also the melting point
The process of Cooling and baking can be described as follows:
Figure 4: The process of cooling and baking b Basic structure of heating oven
General structure of electric ovens:
Conventional electric Ovens consist of three main parts: the furnace shell, the lining, the thermostat c Oven shell
The electric Oven shell is a rigid frame, mainly to bear the process load
Do furnace work On the other hand, the furnace shell is also used to keep the insulation loose and secure full or absolute tightness of the furnace
Furnaces operating with protective gas require a fully enclosed housing to function effectively In contrast, normal resistance furnaces benefit from a tight furnace shell, which minimizes heat loss and prevents cold air from entering the oven, particularly in taller models.
In particular cases, the resistance furnace can make the shell uncoated private
The furnace shell must possess a robust frame to support the weight of the furnace lining, calcined materials, and mechanical components Round furnace shells are commonly utilized in gongs and certain ovens, while rectangular casings are typically found in chamber ovens, continuous ovens, and vibrating bottom ovens Additionally, round bearing shells demonstrate greater efficiency in handling internal elements compared to rectangular designs, especially when a significant amount of metal is processed within the furnace shell.
When constructing the round furnace shell, people often use thick steel plates:
- About 3 to 6 mm when the diameter of the furnace shell is from 1000 to 2000 mm
- About 8 to 12 mm when the diameter of the furnace shell is from 2500 to 4000 mm
- About 14 to 20 mm when the diameter of the furnace shell is from 4500 to 6500 mm
To enhance the hardness of round furnace shells, a ring gasket made of shaped steel is utilized Rectangular furnace shells are constructed from U, L, and steel plates, tailored to the required shape The sealing of the shell depends on the specific closure requirements of the furnace The primary techniques for processing these furnace shells include welding and canopies.
The lining of an electric furnace consists of two parts: a refractory part and a part insulation
Refractory components can be made from standard bricks, shaped bricks, or specialized bricks, tailored to the specific dimensions of the kiln In some cases, refractory powders and binders are used to create blocks known as beams These beams can be applied directly to the oven shell or produced externally using molds.
The refractories section must meet the following requirements:
- Withstand the maximum working temperature of the furnace
- Has enough heat endurance when working
- There is enough mechanical strength when lining materials and placing transport equipment in working condition
- Ensuring the ability to attach a durable and strong wire
- Sufficient chemical stability when working, withstand the effects of the atmosphere oven and the effect of the burning material
- Ensuring minimum thermal capacity, this is especially important for cycle working oven
The insulation, located between the furnace shell and the refractory section, plays a crucial role in minimizing heat loss during operation The bottom of the insulating section demands the highest mechanical strength, while other areas typically do not have the same requirements.
Basic requirements of the insulation:
- Stable in terms of physical and thermal properties under specified working conditions The insulation may be constructed of insulating bricks or may be filled in insulation powder e Heat tray:
Basic requirements of heating plate materials
The heating tray is a heating element of the furnace, working under conditions harsh so requires the following requirements:
- Good heat resistance, not oxidized in an air environment with high temperature
- Must have high mechanical strength, not deformed at working temperature
PI control temperature
a What is a PI Temperature Controller?
PID temperature control is a crucial feature in process controllers that enhances accuracy by calculating the difference between the desired temperature setpoint and the current process temperature Utilizing a formula, PI temperature controllers predict the necessary power for future cycles to maintain the process temperature close to the setpoint, effectively mitigating the effects of environmental changes on the process.
PI temperature controllers operate differently from On/Off temperature controllers by providing a more precise control mechanism Instead of applying 100% power until the setpoint is reached and then cutting power to 0%, PI controllers modulate power output, reducing overshoots and lag This enhanced control helps maintain a stable process temperature, ultimately improving the overall quality of the product.
PI temperature controllers are highly effective in managing process disturbances, such as the impact of opening an oven door, which can alter the temperature and affect product quality When properly tuned, a PI temperature controller compensates for these disturbances, restoring the process temperature to the desired setpoint while gradually reducing power to prevent overshooting and potential damage to the product.
The proportional term generates an output that corresponds directly to the current error value This response can be fine-tuned by multiplying the error by a constant known as the proportional gain constant, denoted as Kp.
The proportional term is given by
Pout: output value in proportional term,
Kp: the proportional gain constant, e(t) = SP – PV(t): the error (SP is the setpoint, and PV(t) is the process variable)
Figure 5: Response of PV to step change of SP vs time for Kp
High proportional gain leads to significant output changes for minimal error adjustments, but excessive gain can destabilize the system Conversely, low gain results in minimal output response to substantial errors, resulting in a less sensitive controller If the gain is too low, the system may inadequately respond to disturbances Tuning theory and industrial practices suggest that the proportional term should primarily drive output changes.
The integral term in a PI controller plays a crucial role by being proportional to both the magnitude and duration of the error It represents the cumulative sum of instantaneous errors over time, reflecting the accumulated offset that needs correction This accumulated error is then multiplied by the integral gain (K i) and incorporated into the controller's output, enhancing the system's accuracy and stability.
The integral term is given by
𝐼out : output value in integral term,
𝐾𝐼 : the integral gain constant, e(t) = SP – PV(t): the error
Figure 6: Response of PV to step change of SP vs time for Ki
The integral term enhances the speed of reaching the setpoint and removes the steady-state error present in a pure proportional controller However, because it reacts to accumulated past errors, it may lead to overshooting the current setpoint.
- Advantages: Integrator eliminates residual deviations of the system, less affected effects of high frequency interference
- Disadvantages: The controller has low effect, so the stability of the system is poor
In analyzing the advantages and disadvantages of various controller types, it is crucial to note that controller I is slow-acting, leading to poor system stability; thus, it should be paired with a proportional (P) component to form a PI controller Additionally, when employing a controller that includes the differential (D) term, the system becomes vulnerable to high-frequency interference, a common issue in industrial settings Consequently, we have opted to implement a PI controller for the heating system to enhance performance and stability.
Methods for determining the parameters of a PI controller
Increase KP until the system oscillates circulating
Set the integral time by the oscillation cycle
Adjust the KP value accordingly
If there is a fluctuation, adjust the value of KD
Advantages: no need to know math, use online methods
2.5.2 Determining parameters for PI controller by experimental method (the second method of Ziegler - Nichols)
Increase KP until the system oscillates circulating
Put this KP with Kcrit
Measure the oscillation period set to Tcrit
/8 Table 3: Determining parameters for PID controller Ziegler-Nichols method
Figure 7: Response of the system to Ziegler-Nichols method [4]
2.5.3 Method Chien - Hrones - Reswick (CHR)
Transfer function of the object to be controlled:
The CHR method is widely utilized in industrial settings for adjusting controller parameters, leveraging system time parameters and hiccup responses The Chien-Hrones-Reswick approach provides various options for system controllers based on the R parameter, as detailed in the accompanying table.
Table 4: Select controller according to CHR method
This method is often used when:
- Functional characteristic lines conveying an air-conditioned closed system
- Functional trajectories conveying closed systems oscillate with a leap of about 20%
Table 5: The PID set parameter according to CHR method
A design method based on a number of typical system responses, providing estimation capabilities to calculate system parameters Different control systems can be designed by using the following Table 6 directly:
Table 6: Control parameter of Cohen-Coon method
Here, it can be seen that the special feature of the Cohen - Coon method is allowed Select the calibration parameters for the PD stitch
Figure 8: Response of the system when adjusting Cohen-Coon [4]
2.5.5 Method Wang - Juang - Chan (WJC)
The control algorithm developed by Wang, Juang, and Chan offers a straightforward and efficient approach to selecting coefficients for a PID controller, based on the optimal ITAE (Integral of Time multiplied by Absolute Error) standard When the values of K, T1, and T2 are known, the coefficients of the controller can be accurately determined.
Figure 9: System response to the Wang-Juang-Chan method [4]
This correction method effectively eliminates overshoot in system responses, making it an ideal choice for applications where precise control is essential By selecting this approach, users can ensure that their systems respond accurately without exceeding desired limits.
The Tyreus - Luyben method was developed from the Ziegler – Nichols 2 method, reducing the amplification factor, increasing the differential time and integration time with the control parameters shown in Table 2.5
Table 7: Control parameter of Tyreus-Luyben method
- TU: oscillation cycle is critical
Select controller design method
There are many methods to choose parameters for PID controller, in which Ziegler - Nichols method is commonly used for P, PI and PID controllers, this method is simple and
The method described is user-friendly and leverages the transient characteristics observed in experiments involving step changes It is particularly effective for processes with inertial characteristics and minimal time delays Due to these advantages, this method is frequently employed to mitigate system disturbances.
DESIGN AND IMPROVEMENT
Mechanical design
3.1.1 Calculation and selecting components: a Calculation and selecting components for heating system:
The mechanical design of the machine qualified, so the mechanical part does not need to improve
Requirements on the working ability of the furnace set by the enterprise are:
● Left oven: temperature 250-300, yield 8 minutes / product
● Right oven: temperature 200-250, yield 2 minutes / product
● The volume of each mold is 530 grams, each mold contains 16 products, volume of each product is 2,5 grams
Table 8: Specific heat of aluminum mold
Figure 10: Properties of plastic material
The plastic used is Unplasticized Polivinylchloride, so it has a specific heat of cpvc 1.3 kJ
The capacity of each furnace in operation
- The radiant heat of each mold of the right oven:
- The radiant heat of each mold of the left oven:
- The baking time of the left oven is 10 minutes, the baking time of the right oven is
4 minutes, we have the cooling system heat for 1 hour:
2 106,48= 4138.2(KJ) Calculation of equipment for electricity systems:
- The capacity of the two furnaces in operation is:
- Heat of PVC consumed in 1 hour:
- The capacity of each furnace in operation is:
The initial heating process requires a larger capacity wire to accelerate heating, while the stable working capacity is 3600 = 0.58 kW = 580 W Once the desired temperature is reached, the kiln capacity can be maintained at a stable level.
When selecting a heater wire, it's essential to consider factors such as convenience, size, insulation quality, and available installation support After evaluating various options, we chose the Mayso heater wire, which boasts a maximum capacity of 1.8KW, making it a reliable choice for efficient heating.
❖ Wire burning resistance: Mayso heat coil
❖ Maximum electric current on the wire:
- Power consumption device includes 2 mayso coils, power 1800W and some low power control devices We have amperage on wire
- And with the condition of long-term heat test
- Type of wire with core cross section is calculated as follows:
S: is the conductor cross-section, in mm2
I: current flowing through the square section, in Ampere (A)
- Permissible current density of copper wire J ~ 6A / mm2
- Allowable current density of aluminum wire J ~ 4.5 A / mm2
- Conductor cross section is S = 20/6 = 3.33 (mm2)
For optimal performance, select conductors with a cross-sectional area of 4 mm² for the total source wire, use 2.5 mm² conductors for each oven, and choose smaller wires for other components.
❖ Controller: PLC provided by the enterprise is
Figure 12: LOGO! 12-24 RCE siemens 6ed1052-1md00-0ba8 [13]
LOGO! 12/24RCE, logic module, display PS/I/O: 12/24VDC/relay, 8 DI (4AI)/4DO, memory 400 blocks, modular expandable, Ethernet integr (LOGO! 12-24rce siemens 6ed1052-1md00-0ba8)
To meet the enterprise's accuracy demands in the baking process, we have selected the PT100 temperature sensor, which operates effectively within a range of 50-300 degrees Celsius, ensuring precise measurements.
Figure 13: PT100 M6 screw thermocouple temperature sensor [14]
We need to convert the signal from the PT100 temperature sensor into a 0-10V signal before transmitting into the analog input pin of the PLC
Through the transmitter, resistance signal of the thermal resistance can convert into 0-10V signal
- Accuracy: plus or minus 0.2 percent FS
We utilize an HMI panel to make it easier to operate and monitor the system
We chose the HMI Weintek because it effectively interacts with the PLC via Ethernet, meeting our requirements for both functionality and budget After evaluating various heating machines, we determined that the Weintek offers the best value, providing essential features for a SCADA system at an affordable price.
-Touch Panel : 4-wire resistive type
-Processor : 32 bits RISC Cortex-A8 600Mhz
-COM port: COM 1 RS-232, COM2 RS-485 2W/4W
To operate the pump directly from the PLC, as well as monitor and control the system using Factory IO software, we need to add an extension module
Figure 16: Expansion module for LOGO!
❖ AM2 AQ Analog output module
LOGO! AM2 AQ expansion module for LOGO! 8
❖ Calculation about the cylinder for taking baked product out the mold
-Due to the heating furnace of the machine is about 210 mm long, compared with Vietnam's cylinder standard (TCVN), we choose the Piston S = 200 mm journey
- The weight of the input mold ranges from 500g-1000g, for a general calculation, we choose the largest weight for this calculation m = 1000g
- Pressure of commonly used commonly used air compressor is p = 6kg / cm2
-The diameter of a cylinder is calculated by the formula:
After conducting calculations and referencing the standard cylinder sizes available in the market, we have determined that, in conjunction with the original piston stroke of 200mm, the appropriate cylinder diameter is D.
Materials used: galvanized Iron box
Galvanized Box Steel offers significant advantages, including high-temperature galvanization that effectively shields the inner steel from external air exposure With superior abrasion resistance compared to Black Box Steel, it prevents rusting and boasts an impressive service life of 50 to 60 years.
Material Name Unit mass, kg/𝑚 3 Thermal conductivity,
In conclusion, galvanized steel boxes are an excellent choice for heating applications due to their low thermal conductivity, which enhances heat storage capacity Additionally, they are cost-effective, user-friendly, and highly durable, making them a practical option for various uses.
Reason to choose materials: Easy to process, cheap price, easy to find, less deformation due to heat
Reason to choose materials: Good heat resistance, good heat transfer
Reason to choose materials: Light, good heat transfer
Materials used: Thin emulsion sheet
Reason to choose materials: Easy to process, popular in water storage b Calculation and selecting components for heating system:
⮚ Survey cooling options for molds after baking:
Cool the mold naturally by transferring heat to the surrounding air Combine with fan to increase cooling speed
Figure 23: Cooling system by air [17] Advantages: simple, low cost
Disadvantages: too long time to cool the product, does not meet the requirements of general operation
Cool the mold by transferring heat from the mold to the source of contact water
Figure 24: Cooling system by water (using radiator) [17] Advantages: rapid cooling due to aluminum material, high heat transfer, high cooling efficiency, average cost
Disadvantages: in the process of working, it is necessary to supplement the amount of water lost due to evaporation
Water cooling is used as an intermediate solvent to transfer heat away from components
❖ Cooling with chillers from cold air in combination with water tanks:
To enhance the cooling process of the mold, we efficiently transfer heat from the mold to the metal tray surface Given the limited heat transfer capability of plastic labels, we opt for submerging the entire mold in cool water after baking, achieving the maximum cooling rate essential for optimal manufacturing.
Figure 25: Cooling system combine cooling table and water [18] Advantages: optimal cooling speed
Disadvantages: high implementation cost, complex system
⮚ Choose a cooling option for the system:
A cooling system is essential for machinery due to the unique properties of the product being processed Excessively hot water can adversely affect the product's quality, making a water cooler an ideal solution to maintain optimal temperatures.
In the cooing system, a radiator and cooling fan was combined to build cooling system
To upgrade the warmth sink for the shape after the warming time frame
❖ Water-cooled methods for cooling systems:
In water-cooled systems, 3 categories was use very popular: evaporation, natural convection, forced circulation
The previous water cooler systems:
- Open circulatory system: Used on engines of ships and ships Take the river water to cool and then discharge directly to the outside
The cooling system operates based on a user-defined PID controller, leading to frequent on-and-off cycling that can strain the temperature controller.
Solution: Base on the threshold voltage and upper limit The temperature will be set
The cooling system operates based on two critical limits: the setpoint and the alarm setpoint When the water temperature exceeds the setpoint, the system remains inactive until it reaches the alarm setpoint Once the alarm setpoint is triggered, the cooling process begins, lowering the water temperature back to the setpoint, at which point the cooling system ceases operation.
❖ Calculation of temperature exchange between baking mold and water:
Calculate the calorie that the system needs to respond:
The radiant heat of each mold of the left oven:
The radiant heat of each mold of the right oven:
The heat of the water tank can be obtained under non-cooling conditions:
Choose the baking time of the left oven is 8 minutes, the baking time of the right oven is 2 minutes, we have the cooling system heat for 4 hours:
❖ Calculation of the radiator of the cooling system:
- Working length of pipe: l = 438 mm;
- Width of the radiator: a = 328 mm;
- Thickness of the compartment: b = 18 mm;
- The number of tubes in a compartment: n = 40;
- Number of pipe ranges: 1 row;
- How to arrange pipes: line;
- Outer dimensions of pipes 16x2mm;
- Number of heat dissipation blades: k = 400 mm
- The thickness of the fins: 0.12 mm
Calculate and re-test the cooling capacity of the radiator is selected Cross-section of liquid circulation through the tank: b= 2 – 2.0,2 = 1,6 mm a= 16 – 2.0,2 = 15.6 mm
Area in contact with liquid 𝐹 1 :
N: Number of pipes on a radiator;
𝑝 1 : Inner circumference of the tube;
Figure 27: Diaper calculation of water tank
𝐹 3 : Area of water pipes in contact with air
𝐹 4 : The area of the radiator wings that come into contact with the air
Figure 28: Detail calculation diagram of the radiator
𝑃 2 : Outer circumference of the tube:
H: The working length of the tube in contact with the air:
H= h-k.s= 438- 0,2.40058[mm] h: the lenght of tube, h= 438 [mm] s: The length of the radiator wings k: numbers of radiator wings n: numbers of tube
=0,5 [𝑚 2 ] The area of the radiator wings that come into contact with the air F4:
Figure 29: Diaper calculation of the radiator
𝐹 41 : Area of all radiator wings;
𝐹 42 :Area of water holes on the radiator wings
𝐹 42 = 𝑛 𝑆 2 𝑘 with: n = 56: numbers of tube k: numbers of radiator wings
Area of the radiator of the cooling systems:
𝑘(𝑡 𝑛 −𝑡 𝑘𝑘 ) [𝑚 2 ] Inside that: k: General coefficient of heat transfer between water and cooling medium
The coefficient α1 can be determined by empirical formula experimental value of the coefficient 1 change in a range α1#26÷4070 [W/m2.degree], choose α1#26 [W/m2.degree]
Coefficient of copper foil λ= 83,9 ÷126 [W/m 𝑑𝑒𝑔𝑟𝑒𝑒], of aluminum alloy λ= 104,8 ÷198 [W/m 𝑑𝑒𝑔𝑟𝑒𝑒], also of stainless steel λ= 9,3 ÷18,6 [W/m 𝑑𝑒𝑔𝑟𝑒𝑒] Choosing materials for heat pipe is aluminum alloy, = 150 [W/m 𝑑𝑒𝑔𝑟𝑒𝑒]
The coefficient α2 depends primarily on air speed 𝜔 𝑘𝑘
When changing 𝜔 𝑘𝑘 from 5 to 60 m/s then α2 changes covariates 40,6 ÷ 303 [W/m 𝑑𝑒𝑔𝑟𝑒𝑒]
The factor k for tubular radiators can be determined graphically k = f (𝜔 𝑘𝑘 ) According to experimental data, determine the cooling surface of the set heat sink, can take k ≈ α2 and can be approximate α2 = 11,38 𝜔 𝑘𝑘 0,8 ( W/𝑚 2 𝑑𝑒𝑔𝑟𝑒𝑒)
𝜔 𝑘𝑘 : air speed across the radiator (m/s)
We have the cooling heat of a radiator is:
𝑡 𝑛 : Average temperature of cooling water [ ℃]
𝑡 𝑘𝑘 : Average temperature of cooling air [ ℃]
Cooling heat of the radiator:
So, the radiator is selected to ensure the requirements of the water cooling system
❖ Calculation of blower of cooling system:
The required air flow that the blower should provide:
𝐶 𝑝 : Specific heat capacity of water = 1005 [J/kg.độ]
∆𝑡 𝑘𝑘 : The difference in temperature of the air through the radiator, ∆𝑡 𝑘𝑘 in the range 15÷ 30℃
1,1.1005.15 = 0,11 [𝑘𝑔/𝑠 ] Therefore, it is necessary to select a fan that satisfies the supply flow necessary level
With the above model, we choose a cooling fan that is compatible with the cooler to fit the needs and be more convenient for assembly c Parts list:
General controls for the system 1
Output analog signal for power controller
Converts signal from thermal sensor to 0-10V
Measure the temperature in the oven
Receive 4- 20mA signal to adjust the power supply to the coils
Open/close the compressed air source
Open/close oven door,Push molds out of the oven
Pump water to create forced circulation for cooling system
Filter the source before entering the radiator
Prevent reverse water flow when shutdown, protect radiator
Radiate for water source to cool the product
Support the process of cooling water
Control and display system 1 d Drawing and Improvement:
Figure 32: Left oven cover drawing
Figure 33: Right oven cover drawing
Figure 38: Overall view of the machine
- Weight of mold input: