PROJECT TITLE A PROJECT REPORT Submitted to SUNRISE UNIVERSITY in partial fulfilment for the award of the diploma of POLYTECHNIC
In MECHANICAL ENGINEERING
DEPARTMENT DEPARTMENT OF MECHANICAL ENGINEERING
SUNRISE UNIVERSITY ALWAR
RAJASTHAN, INDIA
MAY 2014 “Annexure1”
PROJECT TITLE <1.5 line spacing>
1
A PROJECT REPORT
Submitted to SUNRISE UNIVERSITY
in partial fulfilment for the award of the diploma of <1.5 line spacing> POLYTECHNIC
IN MECHANICAL ENGINEERING
DEPARTMENT DEPARTMENT OF MECHANICAL ENGINEERING
SUNRISE UNIVERSITY
RAJASTHAN,
INDIA
MAY 2014
2
A PROJECT REPORT
Submitted to SUNRISE UNIVERSITY
in partial fulfilment for the award of the diploma of <1.5 line spacing> POLYTECHNIC
IN MECHANICAL ENGINEERING
DEPARTMENT DEPARTMENT OF MECHANICAL ENGINEERING
SUNRISE UNIVERSITY
RAJASTHAN,
INDIA
MAY 2014
2
CERTIFICATE
This is to certify that the project report entitled “ TITLE OF PROJECT WORK
”
submitted by NAME OF GROUP to the SunRise University Alwar,Rajasthan in partial fulfilment for the award of Diploma of Polytechnic in Mechanical Engineering is a confide record of the project work carried out by him under my supervision during the year 20152016.
Submitted to:
Submitted by:
Name of incharge
Name of student(Roll)
Designation
Name (Project Guide) Designation
SUNRISE UNIVERSITY Bagad Rajput, ALWAR-301030(Raj.) INDIA
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ACKNOWLEDGEMENT
I take this opportunity to express my profound gratitude and deep to my mentor Mr. Vinayak Hemadri for his exemplary guidance, monitoring and constant encouragement
throughout the course of this thesis. The blessing, help and guidance given by him time to time shall carry me a long way on the journey of life in which I am about to embark. I also take this opportunity to express a deep sense of gratitude to the mentor for his cordial support, valuable information and guidance, which helped me in completing this task through various stages. Lastly, I thank almighty, my parents, and friends for their constant encouragement without which this assignment would not be completed.
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ABSTRACT
In our Project work “FABRICATION OF PNEUMATIC CONTROLLED RIVETTING AND PUNCHING MACHINE” we used principles of Pneumatic control
system in developing this project work., In our project we are having two control switches, when first switch is pressed it works as a Riveting machine and when the second switch is pressed it works as Punching machine. The vibrating mechanism is a chieved by reciprocating the double acting cylinders, which controlled by solenoid operated 5/2 way DC valve which is actuated through the control system.
The operating pressure required for this system is 5 to 6 bar. The maintenance required for this system is less than the other systems.
For punching operation, a counter weight is added to the pneumatic cylinder force in order to make the punching operation effectively, and also for punching operation a separate Punching tool is fitted and the job is placed on the die, For riveting operation a riveting head is fitted.
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TABLE OF CONTENTS
CHAPTER NO
TITLE
PAGE NO
ABSTRACT
5
LIST OF FIGURES
6
LIST OF TABLES
8
1. CHAPTER
1.1 INTRODUCTION
9
1.2 GENERAL DESCRIPTION
9
1.2.1 PRODUCTION OF COMPRESSED AIR
9
1.3 ADVANTAGES
10
1.4 DISADVANTAGES
11
CHAPTER 2 2.1 BLOCK DIAGRAM
15
2.2 NEED FOR AUTOMATION
15
2.2.1 PRINCIPLE OF OPERATION OF A PRESS 2.3 MECHANICAL ADVANTAGE
16 16
PRINCIPLE OF LEVELLERS
16
2.4 THE ARMATURE
17
2.5 THE COMMUTATOR AND BRUSHES
17
CHAPTER 3
3.1 WORKING PRINCIPLE
18
3.2 SELECTION OF PNEUMATICS
19
3.2.1 SOLENOID VALVE
19
3.3 UNIT DESCRIPTION (CONSTRUCTION)
19
3.3.1 CYLINDER
19
3.3.2 DOUBLE ACTING CYLINDER
20
3.3.3 PUNCH AND DIE
20 6
3.3.4 FULCRUM LOAD AND EFFORT ARM
21
3.3.5 COMPRESSOR
21
3.3.6 DIRECTION CONTROL VALVES
22
CHAPTER 4
4.1 WORKING PRINCIPLE
31
4.2 WORKING
31
CHAPTER 5
5.1 PROPOSED DESIGN – MODEL OF PUNCHING AND RIVETING MACHINE
36
5.2 PROPOSED DESIGN – MODEL OF RIVETING CYLINDER
37
5.3 PROPOSED DESIGN – MODEL OF PUNCHING CYLINDER
38
5.4 PROPOSED DESIGN – HAND LEVER FOR PNEUMATIC CYLINDER FOR CRANKING THE OPTION LIKE INPUT AND OUTPUT
39
5.5 HARDWARE USED IN PROJECT
40
5.6 TOOLS USED IN PROJECT
41
5.7 ESTIMATION OF THE PROJECT WORK
42
CHAPTER 6
CONCLUSION
43
REFERENCES
BOOKS REFERRED
44
WEBSITE
44
7
LIST OF FIGURES
FIGURE.NO
NAME
PAGE.NO
1.1
Riveter and Puncher
10
2.1
Pneumatic Punching And Riveting Machine
17
3.1.1
Working Of Pneumatic Jack
20
3.3.3.1
Working Of Pneumatic Unit
22
5.1
Proposed Design – Model Of Punching And Riveting Machine
5.2
Proposed Design – Model Of Riveting Cylinder
5.3
39
Proposed Design – Model Of Punching Cylinder
5.4
38
40
Proposed Design – Hand Lever For Pneumatic Cylinder For Cranking The Option Like Input And Output
8
41
CHAPTER 1 INTRODUCTION
The press is the punching and riveting machine tool designed to punch letter or rivet metal by applying mechanical force or pressure. The metal is punched or riveted to the desired requirement. The presses are exclusively intended for mass production and they represent the fastest and more efficient way to form a metal into a finished punched or riveted product.
Press tools are used to form and cut thin metals. Press tools operation can be simplified to a few simple operations involving a punch a die. There are Nemours types of presses in engineering field, which are used to fulfil the requirements. We are interested to introduce pneumatic system in presses. The main function of pneumatic press is to form or cut thin sheet metals or non metals using pneumatic power. In this project we have used to punching process and riveting process for simple application.
Fig 1.1: Riveter and Puncher 1.2 General Description: 1.2.1 Production of Compressed Air
Pneumatic systems operate on a supply of compressed air, which must be made available in sufficient quantity end at a pressure to suit the capacity of the system. When a
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pneumatic system is being adopted for the time, however it wills indeed the necessary to deal with the question of compressed air supply. The key part of any facility for supply of compressed air is the compressor. A compressor is a machine that takes in air, gas or vapours at any certain pressure and delivers the air at a high pressure. Compressor capacity is the actual quantity of air compressed and delivered and the volume expressed is that of the air at intake conditions, namely at atmosphere pressure and normal ambient temperature. Clean condition of the suction air is one of the factors, which decides the life of the compressors. Warm and moist air will result in Compressors may be classified into two types, namely 1. Positive displacement compressors 2. Turbo compressors. Positive displacement compressors are most frequently employed for compressed air plants and have proved. Highly successful to supply air for pneumatic control application. The types of positive Compressors are, a. Reciprocating type compressors b. Rotary type compressors. Turbo compressors are employed where large capacity of air is required at low discharge pressures. They cannot attain pressure necessary for pneumatic control applications unless built in multi stage designs are seldom en counted in pneumatic service. Basically all activities or anything in our lives, there must be the advantages and disadvantages to be caused. And so is in the Pneumatic system.
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1.3 Advantages: • Infinite availability of the source
Air is the most important thing in the pneumatic system, and as we all know, air is available in the world around us in unlimited quantities at all times and places. • Easy channelled
Air is a substance that is easily passed or move from one place to another through a small pipe, the long and winding. • Temperature is flexible
Air can be used flexibly at various temperatures are required, through equipment designed for specific circumstances, even in quite extreme conditions; the air was still able to work. • Safe The air can be loaded more safely than it is not flammable and does not short circuit occurs (konsleting) or explode, so protection against both of these things pretty easily, unlike the electrical system that could lead to fires konsleting. • Clean The air around us are tend to clean without chemicals that are harmful, and also, it can be minimized or cleaned with some processes, so it is safe to use pneumatic systems to the pharmaceutical industry, food and beverages and textiles. • The transfer of power and the speed is very easy to set up
Air could move at speeds that can be adjusted from low to high or vice versa. When using a pneumatic cylinder actuator, the piston speed can reach 3 m / s. For pneumatic motors can spins at 30,000 rpm, while the turbine engine systems can reach 450,000 rpm.
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• Can be stored
The air can be stored through the seat tube fed excess air pressure. Moreover, it can be installed so that the pressure boundary or the safety of the system to be safe. • Easy utilized
Easy air either directly utilized to clean surfaces such as metal and machinery, or indirectly, ie through pneumatic equipment to produce certain movements.
1.4 Disadvantages:
• Requires installation of air-producing equipment.
Compressed air should be well prepared to meet the requirements. Meet certain criteria, such as dry, clean, and contain the necessary lubricant for pneumatic equipment. Therefore require installation of pneumatic systems is relatively expensive equipment, such as compressors, air filter, lube tube, dryer, regulators, etc. • Easy to leak
One of the properties of pressurized air is like to always occupy the empty space and the air pressure is maintained in hard work. Therefore we need a seal so that air does not leak. Seal leakage can cause energy loss. Pneumatic equipment should be equipped with airtight equipment that compressed air leaks in the system can be minimized. • Potential noise
Pneumatic using open system, meaning that the air that has been used will be thrown out of the system, the air comes out pretty loud and noisy so will cause noise, especially on the exhaust tract. The fix is to put a silencer on each dump line.
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• Easy condenses
Pressurized air is easily condensed, so before entering the system must be processed first in order to meet certain requirements, such as dry, have enough pressure, and contains a small amount of lubricant to reduce friction in the valves and actuators. Expected after knowing the advantages and disadvantages of the use of compressed air we can make the anticipation that these losses can be avoided. Despite the immense capabilities of hydraulics presented in terms of moving higher loads and in other industrial utilization, pneumatics are still in wide use today. The article discusses some applications and advantages of pneumatics in industry. Pneumatics is study of mechanical motion caused by pressurized gases and how this motion can be used to perform engineering tasks. Pneumatics is used mainly in mining and general construction works. Pneumatic devices are used frequently in the dentistry industry across the world. On the other hand, hydraulics means use of pressurized fluids to execute a mechanical task. Hydraulics is frequently used in the concepts of turbines, dams, and rivers. Air brakes in buses, air compressors, compressed air engines, jackhammers, and vacuum pumps are some of the most commonly used types of mechanical equipment that are based on pneumatics technology. Commonly seen hydraulics based equipment types are hydraulic presses, hydraulic hoppers, hydraulic cylinders, and hydraulic rams. In the subsequent sections of this article, you will learn how a pneumatic system works, what its best features are, and its major advantages over hydraulic systems. In order to affect mechanical motion, pneumatics employs compression of gases, based on the working principles of fluid dynamics in the concept of pressure. Any equipment employing pneumatics uses an interconnecting set of components: a pneumatic circuit consisting of active components such as gas compressor, transition lines, air tanks, hoses, open atmosphere, and passive components. Compressed air is supplied by the compressor and 13
is transmitted through a series of hoses. Air flows are regulated by valves and the pneumatic cylinder transfers the energy provided by the compressed gas to mechanical energy. Aside from compressed air, inert gases are also applied particularly for self-contained systems. Pneumatics is applied in a wide range in industries, even in mining and dentistry. The majority of industries use gas pressures of about 80 to 100 pounds per square inch. Over pneumatics, hydraulics is capable of moving heavier loads and having greater force, and since its working fluids are incompressible, it minimum spring actions. But at the same time pneumatics are cleaner; the system uses no return lines and gases are exhausted to the atmosphere. Thus leaks will be of less concern since the working fluid of pneumatics is air, unlike oil in hydraulics. Its working fluid is also widely available and most factories are pre-plumbed for compressed air distribution, hence pneumatic equipment is easier to set-up. To control the system, only ON and OFF are used and the system consists only of standard cylinders
and
other
components,
making
it
simpler
than hydraulics.
Pneumatic
systems require low maintenance and have long operating lives. Lastly the working fluid of the pneumatic system absorbs excessive force, leading to less frequent damage to equipment. Compressible gases are also easy to store and safer; no fire hazard is presented and machines could be made to be overload safe.
•
Advantages of Pneumatics over Hydraulics
Like hydraulics, pneumatics is a type of fluid power application where instead of an incompressible
liquid,
pneumatics
employ
gas
in
their
system. Hydraulics present
certain advantages over pneumatics, but in a given application, pneumatic powered equipment is more suitable, particularly in industries where the factory units are plumbed for compressed air.
14
The air used in pneumatic devices is dried and free from moisture so that it does not create any problem to the internal parts of the system. Moreover, to avoid corrosive actions, oil or lubricants are added so that friction effects can be reduced. Compressed air is used in most of the machines and in some cases compressed carbon dioxide is used. As most of the pneumatic devices are air based, they have a less complicated design and can be made of inexpensive material. Mass production techniques can be adopted to produce pneumatic systems, which not only save money but save time too. Other major advantages are listed below. 1. Initial cost is less; hydraulics equipment cost as much as twice the price of pneumatic equipment. 2. A pneumatic water treatment automation system reduces the costs of installation and operation compared with conventional electrical installations. For opening and closing of underwater valves, pneumatic systems work well because they can sustain overload pressure conditions. 3. Pneumatic actuators also have long life and perform well with negligible maintenance requirement throughout their life cycle. 4. Very suitable for power transmission when distance of transmission is more. The major disadvantage of pneumatic systems is that they cannot be employed for tasks that require working under high pressures. However, modern technology is working on finding better solutions to this address this problem so that heavy engineering tasks can be executed using pneumatic devices. In a nutshell, in order to execute low scale engineering and mechanical tasks, pneumatic devices would be the best suited and a viable alternative over hydraulic systems.
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CHAPTER 2 2.1 BLOCK DIAGRAM
Fig 2.1 Pneumatic Punching and Riveting machine
2.2 Need for Automation Automation can be achieved through computers, hydraulics, pneumatics, robotics, etc. Automation plays an important role in mass production. For mass production of the product, the machining operations decide the sequence of machining. The machines designed for producing a particular product are called transfer machines. The components must be moved automatically from the bins to various machines sequentially and the final component can be placed separately for packaging. Materials can also be repeatedly transferred from the moving conveyors to the work place and vice versa. Nowadays, almost all the manufacturing processes are being atomized in order to deliver the products at a faster rate. The manufacturing
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•
Operation is being atomized for the following reasons:
•
To achieve mass production
•
To reduce man power
•
To increase the efficiency of the plant
•
To reduce the work load
•
To reduce the production cost
•
To reduce the production time
•
To reduce the material handling
•
To reduce the fatigue of workers
•
To achieve good product quality
•
Less Maintenance
2.2.1 Principle of Operation of a Press:
Every press has got certain basic units. They are bed frame, sliding ram, drive for the ram and power source. Base or bed is the lower part of the press frame. A thick plate called bolster plate is placed on the top of the bed. A die is fitted on the top of the bolster plate. The driving mechanism is mounted on the frame. The frame has got guide ways for the sliding movement of the ram. The driving mechanism is connected to the ram. The punch is fitted at the bottom of the ram. The die and punch are correctly aligned. The work piece is in the form of sheet metal. It is fed over the die. When the ram comes down, the punch presses the sheet metal. The required operation is carried out. As said earlier the force from the press is used to do a particular operation. This is done by two main parts die and punch.
2.3 Mechanical Advantage Mechanical advantage can be defined as the ratio or the load lifted to the power or the effort applied in the system to overcome the load successfully. 17
Principle of Levellers
The points A and B through which the load and effort is applied are known as load and effort point respectively. F is the fulcrum about which the lever is capable of turning. The perpendicular distance between the load point and the fulcrum is known as the load arm. The perpendicular distance between the effort point and the fulcrum is called as effort arm.
2.4 The Armature The armature takes the place of the nail in an electric motor. The armature is an electromagnet made by coiling thin wire around two or more poles of a metal core. The armature has an axle, and the commutator is attached to the axle. In the diagram above you can see three different views of the same armature: front, side and end-on. In the end-on view the winding is eliminated to make the commutator more obvious. The commutator is simply a pair of plates attached to the axle. These plates provide the two connections for the coil of the Electromagnet.
2.5 The Commutator and brushes The "flipping the electric field" part of an electric motor is accomplished by two parts: the commutator and the brushes. The diagram at the right shows how the commutator and brushes work together to let current flow to the electromagnet, and also to flip the direction that the electrons are flowing at just the right moment. The contacts of the commutator are attached to the axle of the electromagnet, so they spin with the magnet. The brushes are just two pieces of springy metal or carbon that make contact with the contacts of the commutator.
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CHAPTER 3 3.1 Working Principle Selection of Pneumatics
Mechanization is broadly defined as the replacement of manual effort by mechanical power. Pneumatics is an attractive medium for low cost mechanization particularly for sequential or repetitive operations. Many factories and plants already have a compressed air system, which is capable of providing both the power or energy requirements and the control system (although equally pneumatic control systems may be economic and can be advantageously applied to other forms of power). The main advantages of an all-pneumatic system are usually economy and simplicity, the latter reducing maintenance to a low level. It can also have outstanding advantages in terms of safety.
Fig.3.1.1 Working Of Pneumatic Jack 19
The pneumatic punching and riveting machine consists of the following components to fulfil the requirements of complete operation of the machine. i. Pneumatic cylinder ii. Solenoid valve iii. Flow control value iv. Connectors and v. Hoses
3.2 Solenoid valve: The directional valve is one of the important parts of a pneumatic system. Commonly known as DCV, this valve is used to control the direction of air flow in the pneumatic system. The directional valve does this by changing the position of its internal movable parts. This valve was selected for speedy operation and to reduce the manual effort and also for the modification of the machine into automatic machine by means of using a solenoid valve. A solenoid is an electrical device that converts electrical energy into straight line motion and force. These are also used to operate a mechanical operation which in turn operates the valve mechanism. Solenoids may be push type or pull type. The push type solenoid is one in which the plunger is pushed when the solenoid is energized electrically. The pull type solenoid is one is which the plunger is pulled when the solenoid is energized. The name of the parts of the solenoid should be learned so that they can be recognized when called upon to make repairs, to do service work or to install them . 3.3 UNIT DESCRIPTION ( CONSTRUCTION): 3.3.1 CYLINDER
An (pneumatic) air cylinder is an operative device in which the state input energy of compressed air; (i.e.) pneumatic power is converted into mechanical output power, by reducing the pressure of the air to that of the atmosphere. The bore of the cylinder has very 20
smooth finishing reduces friction and losses. There are to angle plates welded to the cylinder as fitting means. 3.3.2 DOUBLE ACTING CYLINDER
A double acting cylinder is employed in a control system with a full pneumatic cushioning and it is essential when the cylinders itself is required heavy masses. The normal escape of air is out by ‘cushioning piston’.
3.3.3 PUNCH AND DIE
Die and punch are known as ‘press tools’. Die is the lower part of press tool. It is clamped on the bolster plate of the press. It remains stationary during the operation. The die has a cavity to receive the punch. The cavity may be with clearance or without clearance. Punch is the upper part of the press tool. It is attached to the lower end of the ram of the press. It sheds with the ram during the operation and is forced into the die cavity. Die and punch must be in prefect alignment for proper operation.
Fig.3.3.3.1 Working Of Pneumatic unit
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Die and punches are always used together. Dies are classified according to either the type of construction or operation to be performed. High speed steel, satellite or cemented carbide is the materials used for making dies and punches. The die materials selected depend on the type of production, operation, sheet metal thickness and accuracy.
3.3.4 FULCRUM LOAD AND EFFORT ARM
A lever is a mechanical devices used to lift heavy loads by application of a small effort. It is a rigid rod or bar, which turns about a fixed point called fulcrum. A lever may be straight or curved. Lever works on the same principle as that of principle of moments. The load W is applied to the point A and hence the point A is known as load point and point B is effort point. The point F is fulcrum. The perpendicular distance (L1) between the load point A is load arm and L2 between is known as effort arm. The ratio of effort arm and load arm is called as leverage. The ratio of load lifted and the effort applied is mechanical advantage. Taking moments about fulcrum P*L2 =W*L1
3.3.5 COMPRESSOR
The compressor forms the main part of the pneumatic system by producing the compressed air. Compressor capacity is the actual quantity of air compressed and delivered and the volume expressed is that of the air intake conduction, namely at atmospheric pressure and normal ambient temperature. The clear conduction of the suction air one of the factors which decide the life of a compressor. Compressor is generally classified into two types, namely 1. Positive displacement compressor 2. Turbo compressor
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3.3.6 DIRECTION CONTROL VALVES
Direction control valves control the way the air passes and used for controlling the commencements, termination and direction of air flow. Depending on the number of paths the air is allowed to pass, directional valves termed two way, three way, and four way or multi way valves. The different number of rays by means the number of controlled connection of the valve. Inlet connection to the compressed air supplies outlet connections to the air consumer and exhaust connection to the atmosphere. The solenoid valve is used to control the air flow direction. This is the direction control valve in our project .
Pneumatic systems require air to operate successfully. As a result of air being extremely abundant, and free, it is easy to restock the system. Safety: As a result of pneumatic systems running on air, safety hazards are significantly reduced. There are limited occurrences of fires because air is non-flammable, and leakages in the system do not negatively effect the outside environment
Cost effectiveness: The initial cost of manufacturing a pneumatic device is minimal as a result of the low cost design materials. Plastics, zinc, and aluminium are all relatively affordable materials that are commonly found in pneumatic designs.
Cleanliness- As a result of the system being powered solely by air, the pneumatic device typically requires limited cleaning. Pressurized air constantly pushes out dirt or debris that get stuck in the system. If there is a blockage, the simplicity of the design also helps. Due to the limited amounts of tubes, the system can be easily disassembled and cleaned.
Maintenance- In order for the system to properly operate it must be lubricated with oil consistently but they have less plumbing than hydraulic systems. Control and Speed- Air is a
23
compressible gas, which makes control and speed in a pneumatic system more difficult, in comparison to electric or hydraulic systems. When specific speeds are needed, additional devices have to be attached to the pneumatic system in order to procure the desired result.
Maintenance- Pneumatic systems are less durable that hydraulic counterparts. Due to moisture accumulation the system can freeze up. Safety: Pipes that feed the system air have the ability to move on uncontrollably on their own, which could cause serious injuries to those nearby
The word pneumatics is a derivative of the Greek word pneuma, which means air, wind, or breath. Pneumatics can be defined as that branch of engineering science that pertains to gaseous pressure and flow. As used in this manual, pneumatics is the portion of fluid power in which compressed air, or other gas, is used to transmit and control power to actuating mechanisms. This section discusses the basic principles of pneumatics, characteristics of gases, heavy-duty air compressors, and air compressor maintenance. It also discusses the hazards of pneumatics, methods of controlling contamination, and safety precautions associated with compressed gases. Basic Principles of Pneumatics Gases differ from liquids in that they have no definite volume, that is, regardless of the size or shape of a vessel, a gas will completely fill it. Gases are highly compressible, while liquids are only slightly so. Also, gases are lighter than equal volumes of liquids, making gases less dense than liquids. Boyle’s Law When the automobile tire is initially inflated, air that normally occupies a specific volume is compressed into a smaller volume inside the tire. This increases the pressure on the inside of the tire. Charles Boyle, an English scientist, was among the first to experiment with the pressure-volume relationship of gas. During an experiment when he compressed a volume of air, he found that the volume decreased as pressure increased, and 24
by doubling the force exerted on the air, he could decrease the volume of the air by half Temperature is a dominant factor affecting the physical properties of gases. It is of particular concern in calculating changes in the state of gases. Therefore, the experiment must be performed at a constant temperature. The relationship between pressure and volume is known as Boyle's law. Boyle's law states when the temperature of a gas is constant, the volume of an enclosed gas varies inversely with pressure. Boyle's law assumes conditions of constant temperature. In actual situations this is rarely the case. Temperature changes continually and affects the volume of a given mass of gas. Charles’ Law Jacques Charles, a French physicist, provided much of the foundation for modem kinetic theory of gases. Through experiments, he found that all gases expand and contract proportionally to the change in absolute temperature, providing the pressure remains constant. The relationship between volume and temperature is known as Charles's law. Charles's law states that the volume of a gas is proportional to its absolute temperature if constant pressure is maintained. Kinetic Theory of Gases In an attempt to explain the compressibility of gases, consider the container shown in as containing a gas. At any given time, some molecules are moving in one direction, some are travelling. Gas compressed to half its original size by a doubled force. Figure 9-36 — Molecular bombardment that creates pressure. NAVEDTRA 14264A 9-32 directions, and some may be in a state of rest. The average effect of the molecules bombarding each container wall corresponds to the pressure of the gas. As more gas is pumped into the container, more molecules are available to bombard the walls, thus the pressure in the container increases. Increasing the speed with which the molecules hit the walls can also increase the gas pressure in a container. If the temperature of the gas is raised, the molecules move faster, causing an increase in pressure. This can be shown by considering the automobile tire. When you take a long drive on a hot day, the pressure in the tires 25
increases, and a tire that appeared to be soft in cool morning temperature may appear normal at a higher midday temperature. Compressibility and Expansion of Gases Gases can be readily compressed and are assumed to be perfectly elastic. This combination of properties gives gas the ability to yield to a force and return promptly to its original condition when the force is removed. These are the properties of air that are used in pneumatic tires, tennis balls, and other deformable objects whose shapes are maintained by compressed air. Pneumatic Gases serve the same purpose in pneumatic systems as liquids serve in hydraulic systems. Therefore, many of the same qualities that are considered when selecting a liquid for a hydraulic system must be considered when selecting a gas for a pneumatic system. Qualities The ideal fluid medium for a pneumatic system must be a readily available gas that is non-poisonous, chemically stable, non-flammable, and free from any acids that can cause corrosion of system components. It should be a gas that will not support combustion of other elements. Gases that have these desired qualities may not have the required lubricating power. Therefore, lubrication of the components must be arranged by other means. For example, some air compressors are provided with a lubricating system, some components are lubricated upon installation, or in some cases lubrication is introduced into the air supply line (inline oilers). Two gases that meet these qualities and are most commonly used in pneumatic systems are compressed air and nitrogen. Since nitrogen is used very little except in gascharged accumulators, we will discuss only compressed air. Compressed Air Compressed air is a mixture of all gases contained in the atmosphere. However, in this manual it is referred to as one of the gases used as a fluid medium for pneumatic systems. The unlimited supply of air and the ease of compression make 26
compressed air the most widely used fluid for pneumatic systems. Although moisture and solid particles must be removed from the air, a pneumatic system does not require the extensive distillation or separation process required in the production of other gases. Compressed air has most of the desired characteristics of a gas for pneumatic systems. It is non-poisonous and non-flammable but does contain oxygen, which supports c ombustion. The most undesirable quality of compressed air as a fluid medium for a pneumatic system is moisture content. The atmosphere contains varying amounts of moisture in vapour form. Changes in the temperature of compressed air will cause condensation of moisture in the system. This condensed moisture can be very harmful to the system and may freeze the line and components during cold weather. Moisture separators and hair dryers are installed in the lines to minimize or eliminate moisture in systems where moisture would deteriorate system performance. An air compressor provides the supply of compressed air at the required volume and pressure. In most systems the compressor is part of the system with distribution lines leading from the compressor to the devices to be operated. Compressed air systems are categorized by their operating pressure as follows: • High-pressure (HP)—3,000 to 5,000 psi • Medium-pressure (MP )—151 to 1,000 psi • Low-pressure (LP)—150 psi and below Heavy-Duty Air Compressors are used in pneumatic systems to provide requirements similar to those required by pumps in hydraulic systems. They furnish compressed air as required to operate the units of the pneumatic systems. Even though manufactured by different companies, most compressors are quite similar. They are governed by a pressure control system that can be adjusted to compress air to the maximum pressure. Rotary the rotary compressor has a number of vanes held captive in slots in the rotor. These vanes slide 27
in and out of the slots, as the rotor rotates an end view of the vanes in the slots. The rotor revolves about the centre of the shaft that is offset from the centre of the pumping casing. Centrifugal force acting on the rotating vanes maintains contact Rotary compressor operation. This feature causes the vanes to slide in and out of the slots as the rotor turns. Notice in the variation in the clearance between the vanes and the bottom of the slots, as the rotor revolves. The vanes divide the crescent-shaped space between the offset rotor and the pump casing into compartments that increase in size and then decrease in size as the rotor rotates. Free air enters each compartment as successive vanes pass across the air intake. This air is carried around in each compartment and is discharged at a higher pressure due to the decreasing compartment size (volume) of the moving compartments as they progress from one end t o the other of the crescent-shaped space. The compressor is lubricated by oil circulating throughout the unit. All oil is removed from the air by an oil separator before the compressed air leaves the service valves Screw The screw compressors used in the NCF are direct drive, two-stage machines with two precisely matched spiral-grooved rotors The rotors provide positive displacement internal compression smoothly and without surging. Oil is injected into the compressor unit and mixes directly with the air as the rotors turn, compressing the air. The oil has three primary functions: • As a coolant, it controls the rise in air temperature normally associated with the heat of compression. • It seals the leakage paths between the rotors and the stator and also between the rotors themselves. • It acts as lubricating film between the rotors, allowing one rotor to directly drive the other, which is an idler. After the air/oil mixture is discharged from the compressor unit, the 28
oil is separated from the air. The oil that mixes with the air during compression passes into the receiver-separator where it is removed and returned to the oil cooler in preparation for reinjection. All large volume compressors have protection devices that shut them down automatically when any of the following conditions develop : • The engine oil pressure drops below a certain point. • The engine coolant rises above a predetermined temperature. • The compressor discharge rises above a certain temperature. • Any of the protective safety circuits develop a malfunction. Other features that may be observed in the operation of the air compressors is a governor system whereby the engine speed is reduced when less than full air delivery is used. An engine- and compression-control system prevents excessive build-up in the receiver Screw compressor. When air is compressed, heat is generated. This heat causes the air to expand, thus requiring an increase in power for further compression. If this heat is successfully removed between stages of compression, the total power required for additional compression may be reduced by as much as 15 percent. In multistage reciprocating compressors, this heat is removed by means of intercoolers that are heat exchangers placed between each compression stage. Rotary air compressors are cooled by oil and do not use intercoolers After coolers It is obvious that the presence of water or moisture in an air line is not desirable. The water is carried along through the line into the tool where the water washes away the lubricating oil, causing the tool to run sluggishly and increases maintenance. The effect is particularly pronounced in the case of high-speed tools where the wearing surfaces are limited in size, and excessive wear reduces efficiency by creating internal air leakage. Further problems may result from the decrease in temperature caused by
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the sudden expansion of air at the tool. This low temperature creates condensation that freezes around the valves, ports, and outlets. This condition obviously impairs the operational efficiency of the tool and cannot be allowed. The most satisfactory means of minimizing these conditions is the removal of the moisture from the air immediately after compression and before the air enters the distribution system. This may be accomplished in reciprocating compressors through the use of an after cooler that is an air radiator that transfers heat from the compressed air to the atmosphere. The after cooler reduces the temperature of the compressed air to the condensation point where most of the moisture is removed. Cooling the air not only eliminates the difficulties which moisture causes at points where air is used but also ensures better distribution Receiver Tank The receiver tank is of welded steel construction and is installed on the discharge side of the compressor. It acts as a surge tank as well as a condensation chamber for the removal of oil and water vapours. It stores enough air during operation to actuate the pressure control system and is fitted with at least one service valve, a drain or blow-by valve, and a safety valve. Pressure-Control System All portable air compressors are governed by a pressure-control system. The control system is designed to balance the compressor's air delivery and engine speed with varied demands for compressed air. The rotary compressor output is governed by varying the engine speed. The engine will operate at the speed required to compress enough air to supply the demand at a fairly constant pressure. When the engine has slowed to idling speed as a result of low demand, a valve controls the amount of free air that may enter the compressor. A screw compressor output is governed by automatic control that provides smooth, steeples capacity regulation from full load to no load in response to the demand for air. From a full load down to no load is accomplished by a floating-speed engine control in combination with the variable-inlet compressor.
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Air Compressor Maintenance A number of built-in features make portable compressors easy to maintain: • An automatic blow down valve for releasing air pressure when the engine is stopped. • A valve for draining moisture that accumulates in the receiver tank. • A drain cock at the bottom of the piping at the bottom of the oil storage tank. • An air filter service indicator to show when the filter needs servicing. • A demister, or special filter, that separates lubricating oil from compressed air. Remember: a good maintenance program is the key to a long machine life. So it is up to both the operator and the mechanic to ensure that the maintenance is performed on time, every time. Air Cleaner Servicing The air cleaner contains a primary and secondary dry filter element An air filter restriction indicator is located at the rear of the air filter housing to alert the operator of the need to service the filters. When a red band appears in the air filter restriction indicator, secure the compressor and service the filters. Use compressed air to clean the primary element; however, never let the air pressure exceed 30 psi. The secondary filter is not cleanable and should be replaced when necessary. Reverse flush the primary element by directing compressed air up from the inside out. Continue reverse flushing until all dust is removed. Should any oil or greasy dirt remain on the filter surface, replace the element.
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CHAPTER 4 4.1 WORKING PRINCIPLE: Compressed air from a compressor is used to press the work by means of the piston and piston rod, cylinder through a lever. The high pressurized air striking against the piston tends to push it upwards. This force is transmitted to a punch by means of a lever by its mechanical advantage. The punch forced downward pierces the work material. This is the main principle of the unit. 4.2 WORKING
The compressed air from the compressor at the pressure of 5 to 7bar is passed through a pipe connected to the Solenoid valve with one input. The Solenoid Valve is actuated with Control Timing Unit. The Solenoid valve has two outputs and one input. The air entering into the input goes out through the two outputs when the timing control unit is actuated. Due to the high air pressure at the bottom of the piston, the air pressure below the piston is more than the pressure above the piston. So these moves the piston rod upwards which move up the effort are, which is pivoted by control unit. This force acting is passed on to punch which also moves downwards.
The punch is guided by a punch guide who is fixed such that the punch is clearly guided to the die. The materials are in between the punch and die. So as the punch comes down the materials are sheared to the required profile of the punch and the blank is moved downwards through the die clearance. Pneumatic systems require air to operate successfully. As a result of air being extremely abundant, and free, it is easy to restock the system. Safety: As a result of pneumatic systems running on air, safety hazards are significantly reduced. There are limited occurrences of fires because air is non-flammable, and leakages in the system do not negatively effect the outside environment
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Cost effectiveness: The initial cost of manufacturing a pneumatic device is minimal as a result of the low cost design materials. Plastics, zinc, and aluminum are all relatively affordable materials that are commonly found in pneumatic designs.
Cleanliness- As a result of the system being powered solely by air, the pneumatic device typically requires limited cleaning. Pressurized air constantly pushes out dirt or debris that get stuck in the system. If there is a blockage, the simplicity of the design also helps. Due to the limited amounts of tubes, the system can be easily disassembled and cleaned.
Maintenance- In order for the system to properly operate it must be lubricated with oil consistently but they have less plumbing than hydraulic systems. Control and Speed- Air is a compressible gas, which makes control and speed in a pneumatic system more difficult, in comparison to electric or hydraulic systems. When specific speeds are needed, additional devices have to be attached to the pneumatic system in order to procure the desired result.
Maintenance- Pneumatic systems are less durable that hydraulic counterparts. Due to moisture accumulation the system can freeze up. Safety: Pipes that feed the system air have the ability to move on uncontrollably on their own, which could cause serious injuries to those nearby
Environment suitability: Devices are known to fail over long periods of time due to the dampening of inside edges in the tubes. Additionally, systems cannot operate underwater and are sensitive to changing temperatures and vibrations
When the piston is at the extreme point of the stock length, the exhaust valve is opened and the air is exhausted through it and the pressurized air come in at the top of the piston and it pushes the piston downwards. So the one side of the air is pulled downwards and the other side is lifted upwards. So the punch is therefore pulled upwards from the die. Now 33
the piston reaches the bottom point of the required stroke length. Now the material is fed and the next stroke of the piston is made ready.
When the material is correctly positioned then this machine is again actuated automatically. The time duration of the succeeding punching is adjusted with the help of control timing unit. Pneumatic systems require air to operate successfully. As a result of air being extremely abundant, and free, it is easy to restock the system. Safety: As a result of pneumatic systems running on air, safety hazards are significantly reduced. There are limited occurrences of fires because air is non-flammable, and leakages in the system do not negatively effect the outside environment
Cost effectiveness: The initial cost of manufacturing a pneumatic device is minimal as a result of the low cost design materials. Plastics, zinc, and aluminium are all relatively affordable materials that are commonly found in pneumatic designs.
Cleanliness- As a result of the system being powered solely by air, the pneumatic device typically requires limited cleaning. Pressurized air constantly pushes out dirt or debris that get stuck in the system. If there is a blockage, the simplicity of the design also helps. Due to the limited amounts of tubes, the system can be easily disassembled and cleaned.
Maintenance- In order for the system to properly operate it must be lubricated with oil consistently but they have less plumbing than hydraulic systems. Control and Speed- Air is a compressible gas, which makes control and speed in a pneumatic system more difficult, in comparison to electric or hydraulic systems. When specific speeds are needed, additional devices have to be attached to the pneumatic system in order to procure the desired result.
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Loudness: Pneumatic systems are the loudest type of designs that power machines. Actuators that run the system are the source of the noise and are sometimes placed in a separate room to limit sound pollution.
Toxins and chemicals: Sometimes, pneumatic systems use hazardous chemicals in their design. This can result in accidental launches of chemicals into the air, which can be harmful to the surrounding environment.
Maintenance- Pneumatic systems are less durable that hydraulic counterparts. Due to moisture accumulation the system can freeze up. Safety: Pipes that feed the system air have the ability to move on uncontrollably on their own, which could cause serious injuries to those nearby Pneumatic systems require air to operate successfully. As a result of air being extremely abundant, and free, it is easy to restock the system. Safety: As a result of pneumatic systems running on air, safety hazards are significantly reduced. There are limited occurrences of fires because air is non-flammable, and leakages in the system do not negatively effect the outside environment
Cost effectiveness: The initial cost of manufacturing a pneumatic device is minimal as a result of the low cost design materials. Plastics, zinc, and aluminium are all relatively affordable materials that are commonly found in pneumatic designs.
Cleanliness- As a result of the system being powered solely by air, the pneumatic device typically requires limited cleaning. Pressurized air constantly pushes out dirt or debris that get stuck in the system. If there is a blockage, the simplicity of the design also helps. Due to the limited amounts of tubes, the system can be easily disassembled and cleaned.
Maintenance- In order for the system to properly operate it must be lubricated with oil consistently but they have less plumbing than hydraulic systems. Control and Speed- Air is a 35
compressible gas, which makes control and speed in a pneumatic system more difficult, in comparison to electric or hydraulic systems. When specific speeds are needed, additional devices have to be attached to the pneumatic system in order to procure the desired result.
Maintenance- Pneumatic systems are less durable that hydraulic counterparts. Due to moisture accumulation the system can freeze up. Safety: Pipes that feed the system air have the ability to move on uncontrollably on their own, which could cause serious injuries to those nearby
Environment suitability: Devices are known to fail over long periods of time due to the dampening of inside edges in the tubes. Additionally, systems cannot operate underwater and are sensitive to changing temperatures and vibrations
Environment suitability: Devices are known to fail over long periods of time due to the dampening of inside edges in the tubes. Additionally, systems cannot operate underwater and are sensitive to changing temperatures and vibrations
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CHAPTER 5 FABRICATION OF PNEUMATIC PUNCHING AND RIVETING MACHINE 5.1 PROPOSED DESIGN – MODEL OF PUNCHING AND RIVETING MACHINE
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5.2 PROPOSED DESIGN – MODEL OF RIVETING CYLINDER
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5.3 PROPOSED DESIGN – MODEL OF PUNCHING CYLINDER
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5.4 PROPOSED DESIGN – HAND LEVER FOR PNEUMATIC CYLINDER FOR CRANKING THE OPTION LIKE INPUT AND OUTPUT
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5.5 HARDWARE USED IN PROJECT:
Fabricated Pneumatic Jack •
Mounting Plate
•
Threaded Screw
•
Base Plate
•
Bearing
•
Coupling
•
Movable Joints
•
Steel Plates For Supporting
•
Welding Electrodes
•
Cylinder worming
•
Cylinder stroke
Motor
Hardware’s To Fit
Power Supply
Switch
PU fitting
Teflon tape
Polyurethane hose
Riveting mount
Punching mount
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5.6 TOOLS USED IN PROJECT:
Welding Machine
Screw driver
Spanner
Soldering Rod
Soldering flux
Cutter
Lathe
Knurling Tool
Tapper Tool
Machine Vice
Axe Frame
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5.7 ESTIMATION OF THE PROJECT WORK:
HARDWARE WORKS
ESTIMATION OF COST
CYLINDER 32*50 FITTING
1050
CYLINDER 20*50 FITTING
950
RIVETER AND PUNCHER
350
SILENCER
200
HAND LEVER
900
PU FITTING
200
POLYURETHANE HOSE
250
H.S TEFLON TAPE
50
MOULED PLASTIC HANDLE
50
PU ‘Y’ FITTING
150
STEEL SHEET COATING
450
CYLINDER RINGS
625
INNER WINDINS
200
LATHE WORK (LABOUR)
175
WELDING
175
OTHER EXPENSES
225
TOTAL
6000
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CHAPTER 6 CONCLUSION:
The pneumatic punching and riveting has been successfully completed with fullest satisfaction. We are optimistic based on the revolution, the machine is going to make in the pressing field. This project may be further developed into a unit with an automatic material handling system.
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