Specific product 10 Trang 7 UNIVERSITY OF TECHNOLOGY ANDEDUCATIONFACULTY OF MECHANICAL ENGINEERING---VIETNAM SOCIALIST REPUBLICIndependent - Freedom - Happiness---EVALUATION SHEET OFDEF
INTRODUCTION
The urgency of the topic
Research into mechanizing meat cutting equipment is crucial for enhancing productivity, minimizing manual labor, and lowering costs This innovation plays a significant role in developing the meat-based food processing industry, ultimately boosting farmers' incomes and addressing the annual oversupply crisis in Vietnam.
Practical and scientific significance of the topic
As the market economy evolves and integrates with regional and international economies, heavy industry plays a crucial role in the social economy The automation of production processes is increasingly prevalent, enhanced by advanced computer applications that leverage modern machinery for improved productivity, quality, and precision Consequently, equipment and machinery are becoming more diverse and accessible, designed for quick operation, reduced labor requirements, and affordability This trend has led to the development of meat cutting machines tailored for household production facilities, effectively addressing the demand for meat processing solutions.
The topic also meets a number of needs of production facilities, markets and businesses to prepare for the stages of making food from meat.
Limit the number of workers, increase productivity, ensure safety and hygiene.
Contributing to the economic development of the country.
Compared with the manual cutting method, the meat slitting machine helps to reduce costs, increase profits, and also offers the following advantages:
Reduce the number of employees
1.2.2 Scientific significance of the topic
This research explores meat cutting technology, leading to the proposal and fabrication of structural principles for meat slicers The developed prototype will assess the machine's feasibility based on productivity, economic calculations, and its potential for mechanization and automation.
1.3 Research objectives of the topic
Proposing the principle of cutting meat, structure of meat cutting machine.
Manufacturing and testing a small capacity meat cutter.
Subjects and scope of research
Meat from livestock areas throughout the provinces of our country, domestic and foreign meat cutting equipment and the like.
Animal meats, design, manufacture and test the meat slitting machine,experimentally determine the machine's working parameters.
Research Methods
Based on the demand for domestic and foreign meats.
Based on the need to use meat cutting machine for manual method.
Based on technological capabilities, it is possible to manufacture meat cutting machines.
The research method consists of two main parts:
Research and analysis theory: collect documents from newspapers, magazines, books, internet related to the research content.
Experimental method: design, manufacture and test the meat slitting machine,test operation and complete the design.
Organization of the dissertation
This study is presented in the following orders
Chapter 1: Introduction This chapter introduces an overview of meat products, annual output in Vietnam as well as in the world In addition, a number of products made from pork are also introduced From there, the idea was given to make an automatic meat slitting machine to simplify the production process of the enterprise
Chapter 2: Background and Literature Review presents background and the discussion of patents, articles and essays related to fresh meat, meat cutting method and application of the automatic meat slitting machines.
Chapter 3: Methods and Solutions provide information (advantages and disadvantages) of each cluster to choose the appropriate method for the machine
Chapter 4: Calculation – Design select the motor and calculate the transmission suitable for the working condition of the machine Design assemblies using 2D and 3D design software
Chapter 5: Experiment Setup and Procedures focuses on equipment, machined parts, materials, and process for testing fresh meat on the machine.
Chapter 6: Results presenting product results after sawing, food safety and hygiene.
In addition, the performance results of the engine and detailed assemblies are presented.
Chapter 7: General Conclusions summarize the results achieved in the dissertation and provide future research directions.
BACKGROUND AND LITERATURE REVIEW
Background information on meat preparation
The meat processing industry encompasses the various stages involved in the packaging, slaughter handling, processing, and distribution of meat products from livestock, including buffaloes, cows, pigs, sheep, and poultry Primarily aimed at producing meat for human consumption, this sector also generates numerous by-products such as skin, feathers, blood, tallow, and protein and bone meal, contributing significantly to the overall meat industry.
In the United States and several other nations, meatpacking facilities are referred to as meatpacking plants, while in New Zealand, the term "freezing process" is used due to the focus on exports An abattoir is designated for the slaughtering of animals for food The growth of meat processing industries was significantly influenced by the development of railways and refrigeration techniques, which enhanced the transportation of raw meat to processing centers and facilitated the distribution of meat products for consumer consumption.
The evolution of cutting tools began with Homo habilis, affectionately named 'Uugh', who crafted the first meat-cutting tool known as the Hand Ax This primitive stone device was used to bite into meat and saw it off with its sharp edge, leading to potential lip injuries Fortunately, this tool was refined into a stone knife made from obsidian or flint, known for its exceptional sharpness, allowing for precise cuts Modern knives trace their origins to this early design, which has evolved through various materials such as bronze, iron, and steel, yet retains its fundamental structure.
During the Roman Age, professional food preparation relied on skilled hand-cutting of meat and vegetables, with expert cutters known as Slicers in high demand across Europe However, this manual slicing method was slow and inconsistent, making it challenging to meet the high volume needs of busy pubs and eateries This situation began to change in 1873, marking a significant shift in food preparation practices.
Bologna, Italy, is renowned for its exquisite local delicacy, Mortadella, which must be sliced thinly to fully appreciate its rich blend of spices The city's delis employed master cutters, celebrated as the rock stars of their time, to achieve the perfect slice In 1873, Bologna began exporting its exceptional cold cuts globally, but the manual slicing process couldn't keep up with the rising demand Luigi Giusti addressed this challenge by inventing a slicer that ensured consistent and efficient Mortadella slicing for export.
In 1898, WA van Berkel, a butcher from Rotterdam, established a factory that produced meat slicers, quickly gaining international distribution The innovation continued in the 1920s when Clarence Hobart integrated an electric motor into a meat slicer, creating the Electric Meat Cutter Today, Berkel and Hobart are recognized as the top brands in commercial meat slicers.
Methods and structures the automatic meat cutting machines
A/ The machine cuts in one or more parallel straight planes
The article discusses the use of disc, flat, and crescent-shaped knives, which are moved through rotary, reciprocating, or complex motions It highlights the role of gravity, whether through forced or self-pulling methods, in the process of inserting and removing products.
Figure 2.1: Diagram of the working parts of the machine used for plane cutting [9]
The diagram in Figure 2.1-a illustrates a disc machine that utilizes a horizontally or tilted conveyor for product delivery, depending on whether meat or fish is being cut The blade rotation speed and feed speed are crucial, as they determine how the product is placed on the conveyor's working surface—either allowing free movement or forcing it against an ejector plate In scenarios where the blade speed (vt) is greater than or equal to the feed speed (vn), significant deformation of the product occurs Conversely, when lugs are employed to secure the product and the blade speed is much greater than the feed speed (vt >> vn), the deformation is considerably reduced.
Multi-saw cutters feature one or more discs attached to one or more shafts, making them versatile tools for cutting a variety of materials These devices are particularly effective for slicing through solid objects as well as flexible or small products.
The diagram 2.1-b illustrates the operational components of a multi-knife machine designed for cutting flexible products It features a shaft (1) equipped with a series of cutters (2) arranged at a specific pitch, alongside a rotating barrel (4) on shaft (3) that aligns with the cutting surface to facilitate product cutting The rotary barrel (4) serves as the feeding mechanism, with its lap speed matching the feed speed (v n), while the rotation speed of shaft (1) represents the sliding speed of the blade (v t) The scale indicates that the relationship between v t and v n is in the range of 3 to 5 [9].
The maximum thickness of the cut meat determines the width of the slot δ The capacity of the structure is calculated by:
In There:: The maximum capacity utilization factor achievable s: Slot width (m) l: Length of slot for product to pass freely m vn: sharpness (m/s)
Figure 2.1-c illustrates a mechanism featuring disc knives on a shaft, designed for self-feeding the product through the working area This self-feeding is facilitated by the friction between the product and the plates It's crucial that the cutting torque remains lower than the frictional torque at the tool's contact surface with the product.
The structural diagram in Figure 2.1-e illustrates the working mechanism of a disc cutter mounted on two parallel shafts, facilitating self-feeding of the product through the working area This self-feeding is achieved through the friction generated between the product and the mounting tool, symmetrically positioned around the product feed groove's axis The feed rate varies, being lowest at the mean feed time when the first half of the plate is submerged and reaching its maximum when the product occupies the entire cross-section of the slot containing the plate.
Figure 2.1-f illustrates the components of a flat saw cutting machine, highlighting the integration of the conveyor belt and product cutting speed at velocity vt The machine features an active pulley positioned at the bottom and a tension flywheel at the top, allowing for the simultaneous or sequential installation of one or multiple saw blades.
To effectively cut materials such as soap, bone glue, and hard-boiled eggs, which have low cutting resistance, tension cords are utilized These cords are securely attached to a frame that transmits oscillating motion, allowing for smooth sliding cuts.
Figure 2.2: Diagram of a machine for cutting soap and products such as eggs, bone glue [9].
B/ Machine for cutting products according to curved surface
Includes conical, spherical, spiral or combination knives, ensuring that when the product is inserted, the shape of the work-piece is divided according to the surface curve [9].
The conical knife mechanism, illustrated in Figure 2.3-a, effectively divides products along a cylindrical surface The disk's revolution speed is denoted as vt, while the feed rate to the disc or product is represented as vn For optimal cutting quality, the ratio of these speeds should be maintained within the range of 30-50.
The schematic diagram in Figure 2.3-b illustrates the cutting mechanism featuring a spherical knife that rotates around the horizontal axis XX at a speed of v_t = R Additionally, the tool can be rotated around the vertical axis at a medium speed of v_n = R_1 Due to the spherical design of the tool, the shear coefficient during the cutting process is influenced significantly.
Kc= : 1 , in there and 1 land the corresponding angular speeds [9].
Figure 2.3-c illustrates the design and operation of a helical knife, which is engineered to produce thin chips at lower feed speeds The optimal ratio of tool revolutions (vt) to product introduction speed (vn) is between 40 and 50, resulting in chip thicknesses ranging from 0.3 to 0.6 mm.
The multi-sided knife depicted in Figure 2.3-d is specifically designed for cutting sugar beets prior to their introduction into the diffuser Its trough-shaped structure ensures durability, preventing material blockage even when the diffuser is fully loaded.
Figure 2.3: Diagram of cutting devices according to curved surface [9].
C/ Machine for dividing products into pieces of different shapes and sizes
Used to cut the original product into small samples in the form of slices, plates, rings, small lumps, bars, fibers, cubes [9].
In Figure 2.4– a, b is a schematic diagram of the structure and working of the cutting machines into small pieces or into slices The working part consists of chamber
The feeding materials are designed in a wedge shape to ensure even pressing and direct the product to the cutter unit This unit features either a horizontal or vertical disc with a mounted tool; the horizontal machine includes a comb-shaped and flat knife, while the vertical machine uses a flat knife After cutting, the product is removed through a door by its own weight.
In machine (a), the knife is positioned perpendicular to the direction of motion, ensuring a secure fit, while in machine (b), the knife is angled relative to the radius, facilitating the cutting process.
Figure 2.4c illustrates the disc mechanism designed for cutting products into yarn The stamping plate features oval knife cutting details, while a round hole is incorporated to guarantee a thread-shaped cut.
Figure 2.4:Diagram of the working parts of machines for cutting into slices, rings, bars and into yarns [9].
D/ Working mechanisms for cutting the product into slices (plates):
Classification of materials for making food production equipment
2.3.1 Metals and alloys a Cast iron: The most common, making up 50% of the metal in food processing machines As an alloy of Fe-C: 2-4% [10].
Advantages: High castability, used to cast complex parts such as machine body, platform, slide, Compression capacity is 4 times higher than bending capacity [10]. Classify:
Neutral cast iron: Also gray cast iron, but add silicocalcium, silicoaluminum, felosilu additives Symbol CM4 [10].
Cast iron: It is also neutral cast iron but adds Mg alloy, very high durability, can cast the compressor crankshaft Symbol B4 [10].
Cast iron: low %C, easy to process [10].
Alloyed cast iron incorporates chromium, manganese, nickel, and silicon, making it ideal for manufacturing pump impellers, acid-resistant pump casings, and pipes for various environments Steel, known for its mechanical properties and high machinability, exhibits varied characteristics based on the heat treatment method applied, leading to a range of mechanical properties There are four distinct groups of steel, each tailored for specific applications.
Alloy steel can be categorized into high and low varieties, while copper is known for its excellent electrical and thermal conductivity However, copper is unstable in the presence of chlorine, bromine, iodine, ammonia, and hydrogen sulfide Its properties make it easy to laminate and spin, leading to its widespread use in industries such as brewing and various types of tower constructions.
Aluminum alloys, such as those containing Al, Si, and Sn, exhibit resistance to concentrated nitric acid (HNO3) and acetic acid (CH3COOH) Stainless steel, known for its corrosion resistance, is categorized based on its chromium and nickel content, with various common grades available.
Stainless steel 201 offers good impact resistance, making it suitable for everyday kitchen items like pans, pots, and dishes Although its corrosion resistance and glossiness are lower than those of 304 stainless steel, its affordability makes it a popular choice for basic functional products in households and restaurants.
Stainless steel 304 is a widely used alloy that comprises 18% chromium and 8% nickel, known for its excellent corrosion resistance and ease of processing This versatile material is particularly favored in the kitchenware industry, where it is utilized to manufacture a variety of products such as pans, pots, dishes, knives, and cutting boards Its high gloss finish and durability make it ideal for applications in household appliances, medical equipment, and the food industry, especially for items that come into direct contact with food.
316 stainless steel is composed of 16% Chromium, 10% Nickel, and 2% Molybdenum, offering superior corrosion resistance compared to 304 stainless steel This enhanced durability makes it ideal for use in medical and chemical applications, particularly in environments exposed to salt water or highly acidic substances Common products made from 316 stainless steel include bathtubs, faucets, and drains.
Inox 430: This type of stainless steel has lower corrosion resistance than Inox
304 and 316, but it has good impact resistance and lower cost It is often used to manufacture hoods, refrigerators, etc [10-11].
Granite: granite + andezite + liquid glass called matite: acid resistant
Amian: Used as a heat-resistant mattress, as a fire-resistant bait, for insulation
Rubber: 2-4%S: Soft rubber, used for cushioning, shaft joints
Faolite: A mixture of phenol formaldehyde + asbestos High durability, making pipes, containers, pumps
There are also PVC, PP,
Calculation
2.4.1 General methods for calculating the engine
The capacity of cutters can be assessed through the kinematics of the process or by evaluating the product's ability to navigate the working and feeding equipment While the latter approach has been previously discussed, there are instances where relying solely on the kinematic analysis is more effective.
During the operation of any cutting machine, new surfaces of the material to be machined are formed Productivity:
In there: F_ cutting ability of the knife� 2 /s φ _ cutting capacity utilization factor of the tool
�1 _ separate surface or half of the new surface formed when 1 kg of product is cut,� 2 /kg
� _ ratio of auxiliary operations time to grinding time; For machines that operate continuously,�= 0
When designing the machine, the size and number of tools and their speed are determined in terms of F, which can be found from the formula.
For multi-knife or multi-conveyor machines:
In There: h _ average thickness of the cut product, m;
For machines with crescent knives:
In there: S _ sectional area of the product layer in the basin or trough of the machine,� 2 ;
� 0 , m _ corresponding to the number of tools and their revolutions per minute For machines with flat knives performing cross sectioning of moving products at a speed��
In There: a, b _cross-sectional dimensions of the product to be cut, m; c _distance between knives according to product length, m;
In There:φ � _ utilization factor of the area of the mesh under the hole (φ = 0,2 – 0,5);
D _ mesh diameter, m; n _ number of revolutions of the knife in 1 minute;
K�_ number of blades per knife;
The power of the motor for the circuit breaker can be determined by the formula:
In There:W� _frontal shear resistance, N/m; η � _mechanical performance of the machine η� _knife performance
The tool efficiency depends mainly on the energy consumption due to the friction between the product and the tool [9].
Transmissions play a crucial role in conveying mechanical energy to a machine's working components, often allowing for adjustments in speed, force, and torque, while also modifying the motion's form and characteristics.
The reason why it is necessary to use transmissions to make the connection between the engine and the working part of the machine is the following reasons [13- 14]:
The operational speed of working components typically differs from the optimal speed of standard motors, often being lower than the engine's RPM Engines designed for low-speed, high-torque applications tend to be larger in size and more costly.
Sometimes it is necessary to drive from one motor to many mechanisms working at different speeds.
The motor performs uniform rotation but has a working part that needs to move forward or move at a variable speed according to a certain Iuat rule.
Due to usage conditions and labor safety concerns related to the machine's size, direct connection to the engine and working components is often not feasible.
In machine manufacturing, various types of mechanical transmission, electric transmission, hydraulic transmission and pneumatic transmission are used In which mechanical transmission is used the most [13-14].
In the detailed machine textbooks, only mechanical transmissions are studied.According to the working principle, Mechanical transmission is divided into two types[13-14]:
Frictional transmission: directly between the friction wheels or indirectly by flexible belts (belts).
Geared drive: direct (gear, worm) or indirect (chain)
Classification of feeding device
Transport devices play an important role in the food preparation process, transporting raw materials from one place to another [9].
Classification: According to the working method, there are two types:
Continuous conveying type: Conveyor belt, screw conveyor, bucket conveyor, equipment for transporting materials by air, by hydraulic [9].
Type of intermittent transport: Cranes, hoists, cranes, elevators [9].
Continuous conveying machines operate non-stop, transporting materials in a designated direction without interruption during loading This capability allows them to achieve higher productivity compared to intermittent conveying systems.
Current continuous conveying machines and equipment can be divided into two main groups:
The machine has a pulling part: Conveyor, chain, rake, bucket, internal load, rack [9].
Machines without pulling parts: Screw conveyors, conveyors Mechanical conveying devices [9].
Among the continuous conveying machines, the conveyor is the most used type [9]:
Waterproof, resistant to chemical corrosion
The investment and manufacturing capital is not large
High productivity, low energy consumption
They have a low allowable slope, usually from 16-24° depending on the material
Unable to transport according to the curve
Unable to transport flexible and sticky materials.
Roll shaft used to feed and pull products in/out of the machine [25].
Can perform both functions of fixing and feeding the workpiece to the cutter shaft
The distance from the top of the blade to the meat must be within the allowed distance.
Pneumatic cylinder used to put meat in and push out meat automatically [25].
Can work continuously for many hours
Need to use more compressed air
Roller table has the effect of letting the object move by itself according to the inclination of the table [25].
The price is not high
Working continuously for many hours
Friction with large meat makes it difficult to work
Still need to have the help of the worker in the process of working
Classification of Transmission
The friction wheel drive system effectively transmits power between shafts by utilizing the frictional force generated at the contact points of the wheels on the driven shaft This mechanism is essential for creating the necessary frictional force to securely connect the shafts.
Friction wheel drive has the following advantages:
The friction wheel has a simple structure
Capable of stepless speed adjustment
The force acting on the shaft and bearing is quite large
The gear ratio is not stable, due to the slip between the wheels when working
Relatively low load capacity (compared to gears)
In conclusion, due to its inherent limitations, the friction wheel drive system is primarily suitable for transmitting small to medium power levels, typically under 20kW When faced with larger transmission requirements or significant size constraints, maintaining effective force transmission becomes challenging.
Belt drives utilize traction to transmit torque and speed between two shafts, accommodating larger gaps compared to gear transmissions Made from plastic or textile materials, belt drives exhibit distinct properties that set them apart from traditional gear or chain drives.
The force transmission is elastic
Smooth running and less stable, shock resistant
Shaft distance can be large
Slipped through the expansion of the belt
Thereby there is no exact transmission ratio
Extra load on the bearing due to the required tension of the belt
Conclusion: Belt transmission is often used to find power not exceeding 40 ÷
The 50 kW flat belt drive operates at a normal speed range of 5 to 30 m/s, with a typical gear ratio not exceeding 5 In contrast, trapezoidal belt drives can have a gear ratio of up to 10 These belt drives are typically designed for high-speed applications, with the guide wheel positioned on the motor shaft, resulting in a relatively compact transmitter size.
Chain transmission, commonly referred to as chain drive, is a complete power transmission system made up of interconnected chains and sprockets The sprocket plays a crucial role in maintaining the tension of the chain, ensuring efficient operation.
Technical experts note that various drivetrain and sprocket configurations exist, often incorporating multiple interconnected sprockets to enhance machine functionality For optimal performance, the power transmission system relies on precise point-to-point engagement of the sprockets when they are installed on the designated components.
The chain drive can work when the equipment is suddenly overloaded At the same time, the chain transmission is also more efficient and never slips.
Compared to the belt, the chain transmission does not require chain tension and the force acting on the shaft and drive is smaller.
When transmitting the same power and number of revolutions, the chain transmission size is smaller than the belt transmission.
A chain drive efficiently transmits power through the interaction between the sprocket and the chain, enabling it to deliver power and motion to multiple sprockets simultaneously, a capability that belts lack.
When working, the chain drive makes a loud noise.
For the chain transmission to operate smoothly and efficiently, regular cleaning and lubrication is required.
The chain transmission has an instantaneous speed and transmission ratio that is not as stable as a belt.
The transmission's service life is generally shorter than that of a belt due to the rapid wear of the chain hinge and the numerous joints present in chain transmissions.
In conclusion, transmission systems are ideal for applications involving medium-distance shafts, particularly when gear transmission is employed, necessitating the use of intermediate gears These systems are designed to maintain compact dimensions and ensure non-slip operation, making them suitable for scenarios where belt drives are not applicable.
Definition: Realization of motion and load transmission through the engagement of the teeth on the gear (or rack) [25].
Gear drives are classified by geometry and by function [25].
Compared with other mechanical transmissions, gear drives have many outstanding advantages:
Small size large load capacity
There is a lot of noise when the speed is high.
Gear drives play a crucial role in various machines, ranging from intricate watches and tools to heavy machinery They are capable of transmitting power across a wide spectrum, from small applications to large-scale operations of up to 300MW Additionally, gear drives can efficiently handle speeds from low to high, reaching up to 200m/s.
A worm gear drive is a mechanical system that transmits motion and load between two crossed axes, typically at a 90-degree angle It consists of a worm with multiple threads and a large gear, enabling efficient power transfer and torque reduction in various applications.
Working quietly and without noise
Low efficiency, high heat generation, so cooling methods are often required
It is necessary to use relatively expensive (copper) friction-reducing materials to make worm gears
Conclusion: Because of their low efficiency, screw drives usually use only small or medium power.
Electrical circuit
In this project we will not use PLC because PLC has a high cost, requires understanding of PLC programming software, high maintenance and repair costs.
Instead, we use relay control circuit to save costs, easy installation and maintenance.
2.7.1 The circuit controlled by relay
The working principle involves supplying power to the control panel and inverter, where a 24V source converts 220V alternating current (AC) into direct current (DC) to energize the controller via a relay When the start button is pressed, the relay transitions from a normally open (NO) to a normally closed (NC) state, maintaining the signal current to the inverter and powering the motor, which subsequently transmits force to the machine's axes.
Figure 2.17: Structure of the circuit controlled by relay
Definition: Inverter is a device that converts direct current or alternating current into alternating current with adjustable frequency and voltage [26].
The inverter operates by first converting a single-phase or three-phase AC power source into a flat DC power source through a diode bridge rectifier and a capacitor This process ensures that the inverter system maintains a power factor (cosphi) of at least 0.96, which remains unaffected by the load.
The 3-phase AC voltage system at the output can change the amplitude and frequency values steplessly depending on the controller Theoretically, there is a certain rule between frequency and voltage depending on the control mode For loads with constant torque, the voltage-frequency ratio is constant However, for pump and fan loads, this rule is a quaternary function Voltage is a quaternary function of frequency [26].
A relay functions as an electrically operated switch, utilizing a magnetic field generated by current flowing through its coil This magnetic field attracts a young iron core, which alters the switch's position The relay offers two switching states, as the current through the coil can be toggled on or off.
The relay has 2 states ON and OFF The relay is in the ON or OFF state depending on whether current flows through the relay or not [26].
The relay features three symbols: NO (Normally Open), NC (Normally Closed), and COM (Common) The COM pin serves as the connection point for the standby power line and is consistently linked to either the NO or NC pin, depending on the relay's operational state.
+ NC and NO are two conversion pins:
NC (Normally Closed): Means it is normally closed That is, when the relay is in the OFF state, the COM pin will be connected to this pin [26].
NO (Normally Open): When the relay is in the ON state (with current flowing through the coil), the COM pin will be connected to this pin Connect COM and
In an NC (Normally Closed) configuration, the current remains controllable while the relay is in the OFF state When the relay is activated to the ON position, this current is interrupted To maintain proper functionality, ensure that the COM and other necessary connections are established correctly.
A fuse is an essential electrical device designed to safeguard equipment and the power grid from short circuits, thereby preventing fire and explosion hazards Specifically, it protects conductors, electrical equipment, and circuits during overloaded conditions or excessive current flow.
Under normal operating conditions, the fuse allows a rated current to pass through without melting, as the heat produced is effectively managed This thermal balance ensures that none of the fuse components experience aging or damage, maintaining optimal performance.
A short circuit occurs when the short circuit current exceeds the rated current, disrupting the balance within the fuse This results in excessive heat energy that melts the fuse's short circuit element, ultimately opening the circuit at both ends of the fuse.
Definition: MCCB (Molded Case Circuit Breaker) is a Molded Case Circuit Breaker, also known as Block CB or Molded Aptomat This is a very important electrical protection device after the MCB [26].
Figure 2.21: Molded Case Circuit Breaker [26].
MCCBs are mostly used in industrial applications It is used for electrical protection purposes along with switching power supply Any type of switchgear has an MCCB in it [26].
MCCB is used for switching, overload protection, short circuit protection from low voltage current circuit to high voltage - high voltage current circuit [26].
MCCB is used in the power supply distribution board as a main circuit breaker [26].
MCCB is used to protect high-voltage capacitor cabinets, electrical machinery, Motor Center Control Panel (MCC) [26].
MCCB is used in high-current equipment, machinery as the main switch [26].
The 24V power supply, available in 10A and 20A variants, is a commonly utilized power source found in various applications today Its versatility makes it essential in automatic systems, powering buildings, companies, and factories, as well as providing control power for a diverse range of sensors.
With 24V power supply can apply to power a wide range 24V power includes both AC and DC voltages.
The operating principle of 24V power supplies is similar to that of 12V and 5V systems, as they convert 220V or 240V input current This process involves two primary and secondary windings that effectively lower the voltage to 24V.
An electric cabinet push button is a crucial tool for controlling electrical equipment and machinery, allowing users to easily turn processes on or off Typically found on control panels and electrical cabinets, these push buttons require a decisive action to effectively open or close electrical circuits Made from durable plastic or metal, they are designed to comfortably fit the operator's fingers and hands With a focus on quality construction and sleek design, electric cabinet push buttons are manufactured to high standards, ensuring they are sturdy, easy to install, and replace.
Classification of ball-bearings
Thrust ball bearings are specifically designed with inner and outer ring roller grooves, allowing for axial movement between them This unique design makes them ideal for rolling bearings that experience mixed loads, meaning they can handle both radial and axial loads simultaneously For more information, explore the various types of angular contact ball bearings available today.
Figure 2.24: contact angle of ball bearings[34].
The axial load capacity of a thrust ball bearing is directly related to the contact angle, which is defined as the angle formed between the line connecting the two contact points of the roller and the track in the radial plane This internal force is transmitted from one ring to another along this path, with the line being perpendicular to the horizontal axis of the bearing.
SKF thrust ball bearings are available in a diverse range of designs and sizes, offering compatibility with various applications While SKF is a leading brand, other manufacturers produce similar thrust ball bearings, ensuring a broad selection for consumers Common types of thrust ball bearings include those designed for high axial loads and specific operational requirements.
1 Single row thrust ball bearing
Single row thrust ball bearings are designed to handle axial loads in one direction, often necessitating the use of a second ball bearing for enhanced support The SKF series includes standard options from the 72B and 73B series, offering two configurations to accommodate diverse applications.
Bearings have a basic design that cannot be coupled It is used for single bearing arrangement.
The most common rolling bearings are those that can be fitted in any set.
Figure 2.25: Single row thrust ball bearing [33].
2 Double row thrust ball bearing
Two-row thrust ball bearings are designed to be equivalent to two smaller single-row thrust ball bearings[33].
This bearing is ideal for applications that experience axial and radial loads in both directions, making it highly effective for structures that demand high rigidity and can withstand bending moments.
Figure 2.26: Double row thrust ball bearing[33].
+ Standard SKF double row thrust ball bearings:
Conventional double row ball bearings (a)
Double-row ball bearings with additional shielding cover (b)
Double row thrust ball bearing with inner ring in two halves (c)
3 Four-point contact ball bearing
Single row angular contact ball bearings are designed to accommodate axial loads in both directions, making them ideal for applications requiring robust support These four-point contact ball bearings primarily handle axial loads while also providing limited radial load support.
Figure 2.27: Four-point contact ball bearing[33].
SKF four-point angular contact ball bearings, such as the QJ2 and QJ3 models, are designed to occupy less axial space compared to double row ball bearings, making them a more compact option for various applications.
Four-point contact ball bearing with basic design.
Four-point contact ball bearing with locating groove.
In addition, this type of ball bearing also has many different sizes and designs.
4 Double row cam roller ball bearing
SKF 2-row cam rollers are designed based on 2-row angular contact ball bearings with a contact angle of 25 degrees They are pre-lubricated, easy to install. This type of roller is used mostly in cam drive systems, conveyor systems, [34].
The double row cam roller features a stamped steel stopper that creates a long slit along the shoulder of the inner ring, effectively retaining lubricant and preventing external contamination.
Figure 2.28: Double row cam roller[34].
+ SKF double row cam rollers come in two main designs:
For optimal performance, cam rollers featuring spherical rollers are recommended when there is an angular deviation from the designated taxiway Additionally, it is essential to reduce stress at the edges of the roller boundary to ensure longevity and efficiency.
Double row cam rollers are available in various designs beyond the standard options, including supporting rollers and cam roller assemblies.
Figure 2.29:Self- Aligning ball bearings [34].
Ideal for addressing shaft deflection, this maintenance-free solution features pre-lubricated seals and a tapered sleeve for efficient installation The design incorporates a bearing, resulting in a cost-effective mounting structure Available types include drum, seal, tapered sleeve, and extended inner ring options.
The innovative EC design for single row roller bearings is engineered to handle substantial radial loads at high speeds, featuring optimized geometry that enhances both radial and axial load capacity This design also improves axial resistance and simplifies lubrication Additionally, the special variant includes more rollers without a cage, providing exceptional load capacity while operating efficiently at medium speeds.
Including: Single-row NU type, single-row NUP type, single-sequence special type, two-row special type[33].
Figure 2.31:Cylindrical roller thrust bearings[34].
Cylindrical roller thrust bearings are designed to handle heavy axial loads on one side, providing exceptional rigidity and resistance to impulse loads Their compact structure allows for efficient use of the bearing surface as a rolling track.
In conclusion, we selected a four-point contact ball bearing for this machine due to its ability to handle axial loads in both directions This type of bearing primarily supports axial loads while also accommodating a small amount of radial load, making it an ideal choice for our application.
Taper roller bearings are designed to handle mixed loads Having a large ratio of “load-bearing capacity/section size”, giving a structure with high economic value.
Block diagram
A machine dynamic diagram is a standard representation, either in a plane or perspective view, illustrating the various mechanisms and interconnected components of a machine This diagram effectively conveys how motion is transmitted from the drive to the machine's other parts, providing insight into its operational structure.
Dynamic diagrams must align with the design task and production conditions, emphasizing simplicity through the use of standardized components These assemblies should be organized in a logical manner to minimize both the quantity and size of parts.
Dynamic diagrams are essential for understanding the revolutions, speeds, and displacements of all machine components throughout various stages They provide a comprehensive and logical framework for automating machine operations, ensuring optimal performance for both the machine and its individual components.
Efficiency serves as a key indicator of a machine's technical excellence Many contemporary automatic machines exhibit minimal effective resistance, resulting in a low ratio of useful work to energy loss Despite this, red machines stand out as highly advanced in design and functionality.
In that case, the technical level of the machine can be assessed by the individual work darts per unit of product.
When designing dynamic diagrams it is best to follow the following guidelines:
1 The dynamic circuit must include a minimum number of apertures to transmit the drive from the electric motor to the working part Therefore, for the case of a fast rotating camera, it is advisable to choose a motor whose number of revolutions is close to the number of revolutions of the driven aperture (working part) For slow running machine, it is most reasonable to use high speed motor and reducer.
2 In the old structures, people have used many long arteries; In modern machines the length of these circuits is shortened by:
Divide them into parts that have their own electric motors.
Using multi-speed motors in stepless and stepless combined drives.
3 Total gear ratio of the dynamic circuit in the reducers.
i。 = i_1*i_2*i_3*…i_q (IV-3) are properly classified into specific gear ratios so that they are in descending order of magnitude, i.e.:
i_1 > i_2> i_3 > > i_g (IV-4) where the greatest reduction should be in the last transmission near the engine.
4 In special machines used for mass production and large-scale production, it is possible to use a change gear in parallel with the transmission.
5 When designing parallel drives (eg trapezoidal belts), attention should be paid to the possibility of closed circuit generation of circulating power.
6 Dynamic diagram of the designed mechanism, normally according to the nominal size of the links, not taking into account manufacturing tolerances and clearances in the drive pair; The computational dynamic diagram of the mechanism found in this way is different from the real thing Therefore, the speed displacement and acceleration of the driven links of the actual mechanism will be different from those parameters of the calculated mechanism.
7 In order to avoid damage to technological requirements when machining, to avoid fast wear and possible problems, in necessary cases, it should be checked by accurately calculating the dynamic diagram
METHODS AND SOLUTIONS
Requirements of the topic – Design parameters
Meat slitting machine must be faster and more efficient
The machine can be improved to be able to cut a variety of meat
Safe for the surrounding environment.
Productivity used for households, production and business establishments.
Meat after cutting must be beautiful and safe for food hygiene.
Type of meat: Fresh pork belly, boneless
Size of meat block: 400x400x70 mm
Methods and solutions for implementation
Meat cutting and cutting machines usually have the main structure including:
Execution structures have working parts
Modern machines often have a wide range of extra parts to:
Adjust and adjust the working of the machine
Adjust the machine, start and stop the testing machine
From the feeder theories in chapter 2 we have the following table:
Transportation equipment Reason Accept Reject
Coveyor High cost, large area x
Rolling shaft Simple design, low cost, easy to process and install
Pneumatic cylinder High cost, large area x
Roller table Simple design, low cost, easy to process and install
The combination of rolling shaft and roller table is the optimum between production cost and manufacturing design.
The combination of the roller table and rolling shaft also makes the repair and replacement of spare parts easier
Roller table is more durable and economical than motor driven conveyor
=> Combination of rolling shaft and roller table is the feeder device for this machine
Choose the angle of inclination of the roller table:
Inefficiency in the use of inclined conveyors:
Tilt up to 10 degrees - Loss of effective conveying is minimal when tilted up to
A screw conveyor with a full U-trough and screw is adequate for most applications at a 10-degree incline To enhance efficiency, consider increasing the screw conveyor's speed, enlarging its diameter, or reducing the screw's pitch.
Tilt from 10 to 20 degrees - Loss in effective communication is typically 10 to
A screw conveyor with a U-trough and a 2/3 screw is typically effective for various applications, especially when tilted up to 20 degrees, where efficiency can be maintained at 40 percent To enhance performance, increasing the speed or diameter of the screw conveyor can mitigate efficiency loss Additionally, extra horsepower is required to counteract gravity and prevent the backflow of block material.
Tilting a screw conveyor by 20 to 30 degrees can lead to a significant loss in effective communication, ranging from 10 to 70 percent For optimal performance in most applications, it is advisable to use a screw conveyor with tubular housing and a reduced screw size of either 1/2 or 2/3 To mitigate efficiency loss, increasing the speed or diameter of the screw conveyor is beneficial, though additional horsepower may be required to counteract gravity and prevent material from falling back into the block.
Effective communication loss can reach 30 to 90 percent when tilted at angles between 30 to 45 degrees For optimal performance, it is advisable to use a screw conveyor featuring tubular housing, reduced pitch screws (1/2 or 2/3), and a larger diameter Additionally, increasing the speed of the screw conveyor is essential, as more horsepower is necessary to counteract gravity and prevent material from falling back.
The maximum slope of the conveyor belt depends on the material to be loaded.
Table 3.2 Material statistics table and conveyor slope
We have selected a roller table tilt angle of 20 degrees, determined by the conveyor's inclination angle and loss coefficient This angle is essential as it facilitates the rolling motion, allowing materials to slide down while countering the upward force exerted by the conveyor belt.
From the transmission theories in chapter 2 we have the following table:
Wheel drive Low load, unstable working x
Belt drive Large transmission size chain drive when operating at the same capacity x
Chain drive Compact size, non- slip working, good overload resistance
Gear drive Manufacturing is too complicated, high cost x
Worm gear drive Low efficiency, high heat generation, so cooling methods are often required x
We choose the chain drive but not the belt drive because:
Roller table is more durable and economical than motor driven conveyor
Chain transmission consumes less force than belt transmission
Chain transmission is more compact than belt transmission if it has the same engine power
The belt transmission has an unstable transmission ratio because there is elastic slip of the belt on the wheel
The effective working speed of the belt drive exceeds the required parameter
=> Select chain drive for this machine.
From the ball-bearing theories in chapter 2 we have the following table:
Table 3.4 Ball-bearing selection table
Ball-bearing Reasons Accept Reject
Single row thrust ball bearing Designed for use in mixed load situations and where a rigid structure is required x
Double row thrust ball bearing cannot self-select when the working shaft has taper x
Four-point contact ball bearing cannot self-select when the working shaft has taper x
Double row cam roller ball bearing cannot self-select when the working shaft has taper x
Self- Aligning ball bearings Suitable in case of shaft deflection.
Can be sealed and pre-lubricated, maintenance-free
Cylindrical roller bearings cannot self-select when the working shaft has taper x
Cylindrical roller thrust bearings heavy load and axial load on one side x
Tapper roller bearings designed to withstand mixed loads x
Spherical roller bearings designed to withstand mixed loads x
We choose tha Self-Aligning ball bearings because:
Self-aligning bearings are designed to effectively accommodate angular misalignment between the shaft and housing, ensuring optimal performance They exhibit lower friction compared to other bearing types, resulting in reduced heat generation even during high-speed operations.
The design of self-aligning bearings has undergone multiple enhancements, featuring two rows of balls and a spherical roller groove on the outer ring These improvements enable the bearings to self-adjust for axial deviation, resulting in minimal friction, reduced vibration, and significantly lower lubrication requirements.
Figure 3.2: Block diagram of automatic meat slitting machine with transmission
CALCULATION - DESIGN
Calculation – Engine
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4.1.1 Main shaft, main motor shaft
The process of calculating friction force:
Force between meat and knife N = 1 (N)
=> Drag� �� =μ N =1,36* 1 = 1,36 (N) (1,36 is the assumption of the coefficient of friction NBR - steel) [25].
Cutter shaft torque => Gearbox shaft torque
Required cutting velocity: 400mm long piece of meat in 2(s) => V= 200 (mm/s)
=> Shear velocity : n = � 60 � � = 3,14 180 200∗60 = 21,22 (rpm) (D: Knife diameter) [25].
The actual engine has n = 1450 (rpm)
=>Gear ratio between chain and engine: i= 1450/21,22 = 68,33
We have: The gear ratio of the chain in the range of 2 - 3 = > the gear ratio of the motor in the range 20 – 30 [25].
Case 1 test, we choose ixích= 2 và iđộng cơ= 20
Table 4.1: Output torque of motor 1 [25].
Table 4.1: Output torque of motor 1 [25].
Torque moment: 9 (N.m) >� 1 = 4,738 (meet the conditions) [14-18].
The process of calculating friction force:
Assume the force between the meat and the knife N = 1N (1 knife)
=> Drag � �� = μ N = 1,36 * 1 = 1,36 N (1,36 is the assumption of coefficient of friction NBR - steel) [25].
From coil torque => gearbox shaft torque
To ensure a smooth operation and prevent any sudden meat catches that could lead to irritation, our team has optimized the roller speed to half of the main shaft's cutting speed, specifically set at 100mm/s for winding.
Table 4.3: Output torque of motor 2 [25].
The required power is calculated as:
Table 4.3: Output torque of motor 2 [25].
Calculation – Chain drive
4.2.1 Choosing a chain for the main engine
Because of the low impact and low speed of the chain, the roller chain should be selected [14-18].
A Determination of chain and transmission parameters
According to the table 5.4 of the document [14], we choose the number of teeth of the small sprocket
Z1 = 21 Number of teeth of large sprocket: [14].
We choose a 1:1 gear ratio for the crawler transmission because the machine capacity is already 3-4 times the required capacity, so we choose the same sprocket to save installation space.
According to the formula 5.3 document [14], we have the calculation formula:
According to formula 5.4 and table 5.6 document According to formula 5.4 and table of document [14].
K0 = 1,25 (sprocket center to horizontal >60˚) Ka = 1 (choose a from 30p-50p)
K đc = 1 (adjusted by one of the sprockets) Kbt = 1 (dust-free working environment)
Substituting into formula 5.3 of document [14] we get:
We have P ≥ �� �� = 1,58 (kw) , kd=1 ( due to a single-row chain transmission).
Table 5.5 with �01= 200 (rpm) We choose a single-row chain drive with pitch 12,7 (mm)
According to the formula 5.12 document [14] we have the number of links: x= 2� � + � 1 +� 2 2 + (� − �) 4� 2 � 2 � x= 2.381 12,7 + (21+21) 2 = 81
Get even number of links: x = 82
Recalculate the shaft distance according to the document 5.13 formula [14-18]. ac = a + 0,5 (xc – x)p = 381+ 0,5(82 – 81).12.7 = 386,35 (mm)
In order for the chain not to bear too much tension, we reduce a quantity Δa Δa = 0,003a =1,143 (mm) [14-18].
The number of impacts of the chain according to the formula 5.14 document [14-18]. i = � 1 15.� +� 1 = 21+70 15.82 = 0.074 ≤ [i] = 30
According to the formula 5.15 documents [14]. s = � �
According to the table 5.2 of document [14], we have the breaking load Q = 18,2 (kN). Mass of 1m chain q1 = 0,75 kg
Fv - tension due to centrifugal force: Fv = q.� 2 = 0,75.0,311 2 = 0,0725 (N)
F0 - tension produced by the passive chain branch: F0= 9,81.��.q.a
Take � � = 1 (because of the angle of inclination of the line joining the center >40 ° )
According to table 5.10 of document [14] with n = 200 vg/ph, [s] = 7,8 so s > [s]: Chain transmission ensures enough durability.
According to formula 5.17 and table 13.4 of document [14]. d1= ���( � �
���( 180 21 )= 85,21 mm da1= p.[0,5 + cotg( π /z1)] = 24,4 (mm) da2= p.[0,5 + cotg( π /z2)] = 24,4 (mm) df1= d1– 2r = 85,21 – 2.4,326 = 76,556 (mm) df2= df1= 76,588
Testing the contact durability of the sprocket: according to the formula 5.18 document
Kr: Factor considering the influence of the number of sprocket teeth.
Kd= 1 due to a single-row chain transmission.
Fvd: impact force on a chain (N).
A = 106 projection area of hinge (see table 5.12 document [14])
[σ H ] allowable contact stress according to table 5.11 document [14].
Thus, according to table 5.11 of document [14], to ensure the contact durability of the sprockets, we use mechanical carbon steel S45C with good wear resistance and strong impact resistance.
Figure 4.3: Allowable contact stress [σ H ] of steel S45C [32]
4.2.2 Choose the type of chain for small machines
Because of the low impact and low speed of the chain, the roller chain should be selected.
A Determination of chain and transmission parameters
According to the table to look up the number of teeth according to the machine capacity of MISUMI, we choose the number of teeth of the small sprocket z1= 13 [25]
We choose a 1:1 gear ratio for the crawler transmission because the machine capacity is already 3-4 times the required capacity, so we choose the same sprocket to save installation space.
According to the formula 5.3 document [14], we have the calculation formula:
According to formula 5.4 and table 5.6 document According to formula 5.4 and table 5.6 document [14] we have:
K = k0.ka.kđc.kbt.kđ.kc
K0= 1,25 (sprocket center relative to horizontal >60˚)Ka = 0,8 (chọn a> 60-80p)
Kđc = 1 (điều chỉnh bằng một trong các đĩa xích)Kbt = 1 (dust-free working environment)
Substituting into formula 5.3 of document [14],we get:
We have P ≥ �� �� = 1,14 (kW) , kd= 1 because chain 1 row
According to table 5.5 with � 01 = 200 (rpm) We choose a single-row chain transmission with a pitch of 12.7 (mm)
=> Satisfy the condition of durability
According to the formula 5.12 document [14], we have the number of links: x= 2� � + � 1 +� 2 2 + (� − �) 4� 2 � 2 � x= 2.762 12,7 + (13+13+13) 2 = 139,5
Get an even number of links: xc= 140
Recalculate the axis distance according to the document 5.13 formula [14] ac = a + 0,5(xc – x)p = 762+ 0,5(140 – 139,5).12,7 = 765,175 (mm)
In order for the chain not to bear too much tension, we reduce a quantity Δa Δa = 0,003.a =2,286 (mm)
The number of impacts of the chain according to the formula 5.14 document [14] i = � 1 15.� +� 1 = 13+50 15.140 = 0.03 ≤ [i] = 30
According to the document 5.15 formula [14] s = � �
According to the table 5.2 of document [14], we have the breaking load Q = 18,2 (kN). Mass of 1m chain q1 = 0,75 kg
Fv - tension due to centrifugal force: Fv = q.� 2 = 0,75.0,137 2 = 0,014 (N)
F0 - tension produced by the passive chain branch: F0= 9,81.��.q.a
Take � � = 1 (because of the angle of inclination of the line joining the center >40 ° )
According to table 5.10 with n = 200 vg/min, [s] = 7.8 so s > [s]: the chain drive is durable enough.
According to formula 5.17 and table 13 4 of document [14]. d1= ���( � �
���( 180 13 )= 59 mm da1= p[0,5 + cotg( π /z1)] = 23,2 (mm) da2= p[0,5 + cotg( π /z2)] = 23,2 (mm) da3= p[0,5 + cotg( π /z3)] = 23,2 (mm) df1= d1– 2r = 53 – 2.4,32 = 44,36 (mm) df2= df1=df3= 44,36
Testing the contact durability of the sprocket: according to the formula 5.18 document
Kr: Factor considering the influence of the number of sprocket teeth.
Kd= 1 due to single-row chain transmission.
Kd= 1.2 load factor in dynamic
Fvd: impact force on a chain (N).
A = 39,6 projection area of hinge (see table 5.12 document [14])
[σ H ] allowable contact stress according to table 5.11 document [14].
Thus, according to table 5.11 of document [14-18-25], to ensure the contact durability of the sprockets, we use mechanical carbon steel S45C with good wear resistance and strong impact resistance.
Figure 4.3: Allowable contact stress [σ H ] of steel S45C [32]
Caculation-Rolling bearing
Because the load is small and has only radial force, one-row bearings are chosen for the B and D shaft supports
We choose a medium weight ball bearing, denoted 6205 [28]
Table 4.4: Load capacity test 1[28] sign d D B r C � �
Calculated according to rolling bearing D because it is subject to more load
With X=1 only bearing radial force
10 6 c million revs According to Equation 11.19
�� = ��∗ �� + ��∗ ��=0.6*0,352+0=0.21 KN