10-04-2017, 07:58 PM
scope of pneumatic grinding machine
INTRODUCTION
The pneumatic grinding is a metal grinding machine tool designed to cut/grind metal by applying pneumatic pressure. It is widely used in carding machine to grind wire.
Automatic Pneumatic Grinding Machine
Automatic Pneumatic Grinding Machine
The machine is exclusively intended for mass production and they represent the fastent and more efficient way to cut a metal. The slow speed operation is occurs in a grinding operation. This machine is a multipurpose machine.
Hacksaws are used to cut thin and soft metals. The grinding shaft is used to grinding operation by replacing the hacksaw frame. The operation of the unit is simplified to a few simple operations involving a cylinder block and piston arrangement.
There are numerous types of grinding machines in Engineering field, which are used to fulfil the requirements. We are interested to introduce pneumatic system in especially in grinding machine and also grinding operation.
The main function of Pneumatic grinding is to cut thin and soft metals by pneumatic power.
LITERATURE SURVEY
PNEUMATICS
The word pneuma comes from Greek and means breather wind. The word pneumatics is the study of air movement and its phenomena is derived from the word pneuma. Today pneumatics is mainly understood to means the application of air as a working medium in industry especially the driving and controlling of machines and equipment.
Pneumatics has for some considerable time between used for carrying out the simplest mechanical tasks in more recent times has played a more important role in the development of pneumatic technology for automation.
Pneumatic systems operate on a supply of compressed air which must be made available in sufficient quantity and at a pressure to suit the capacity of the system. When the pneumatic system is being adopted for the first 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 by means using reciprocating compressor. A compressor is a machine that takes in air, gas at a certain pressure and delivered 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.
The compressibility of the air was first investigated by Robert Boyle in 1962 and that found that the product of pressure and volume of a particular quantity of gas.
The usual written as:
PV = C (or) P V = P2V2
In this equation the pressure is the absolute pressured which for free is about 14.7 Psi and is of courage capable of maintaining a column of mercury, nearly 30 inches high in an ordinary barometer. Any gas can be used in pneumatic system but air is the mostly used system now a days.
SELECTION OF PNEUMATICS
Mechanization is broadly defined as the replacement of manual effort by mechanical power. Pneumatic 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 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 advantage of an all pneumatic system are usually economic and simplicity the latter reducing maintenance to a low level. It can also have out standing advantages in terms of safety.
PRODUCTION OF COMPRESSED AIR
Pneumatic systems operate on a supply of compressed air, which must be made available. In sufficient quantity and at a pressure to suit the capacity of the system. When pneumatic system is being adopted for the first 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 by means using reciprocating compressor. A compressor is a machine that takes in air, gas at a certain pressure and delivered 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 a compressor. Warm and moist suction air will result in increased precipitation of condense from the compressed air. Compressor may be classified in two general types.
Positive displacement compressor.
Turbo compressor
Positive displacement compressors are most frequently employed for compressed air plant and have proved highly successful and supply air for pneumatic control application.
The types of positive compressor
Reciprocating type compressor
Rotary type compressor
Turbo compressors are employed where large capacity of air required at low discharge pressures. They cannot attain pressure necessary for pneumatic control application unless built in multistage designs and are seldom encountered in pneumatic service.
RECIPROCATING COMPRESSORS
Built for either stationary (or) portable service the reciprocating compressor is by far the most common type. Reciprocating compressors lap be had is sizes from the smallest capacities to deliver more than 500 m /min. In single stage compressor, the air pressure may be of 6 bar machines discharge of pressure is up to 15 bars. Discharge pressure in the range of 250 bars can be obtained with high pressure reciprocating compressors that of three & four stages.
Single stage and 1200 stage models are particularly suitable for pneumatic applications , with preference going to the two stage design as soon as the discharge pressure exceeds 6 bar , because it in capable of matching the performance of single stage machine at lower costs per driving powers in the range .
COMPONENTS AND DESCRIPTION
PNEUMATIC CONTROL COMPONENT
Pneumatic cylinder
An air cylinder is an operative device in which the state input energy of compressed air i.e. pneumatic power is converted in to mechanical output power, by reducing the pressure of the air to that of the atmosphere.
Single acting cylinder
Single acting cylinder is only capable of performing an operating medium in only one direction. Single acting cylinders equipped with one inlet for the operating air pressure, can be production in several fundamentally different designs.
Single cylinders develop power in one direction only. Therefore no heavy control equipment should be attached to them, which requires to be moved on the piston return stoke single action cylinder requires only about half the air volume consumed by a double acting for one operating cycle.
Double acting cylinders:
A double acting cylinder is employed in control systems with the full pneumatic cushioning and it is essential when the cylinder itself is required to retard heavy messes. This can only be done at the end positions of the piston stock. In all intermediate position a separate externally mounted cushioning derive most be provided with the damping feature.
The normal escape of air is out off by a cushioning piston before the end of the stock is required. As a result the sit in the cushioning chamber is again compressed since it cannot escape but slowly according to the setting made on reverses. The air freely enters the cylinder and the piston stokes in the other direction at full force and velocity.
CONTROL VALVE:
Various types of control valves are used to regulate, control and monitor the air energy for control of direction pressure, flow, etc.
Pneumatic energy is regulated and controlled by pneumatic valves. Functionally valves are divided into four major groups.
Direction Control
Flow Control
In our project electrically actuated solenoid operated 5/2 DC valves are used.
Solenoid is another name for an electromagnet. Direction control valves are very often actuated by electromagnets. An electromagnet is a temporary magnet. A magnetic force is developed in an electromagnet when electrical current passes through it and force drops down as soon as it is de energized.
This electromagnet is commonly termed as solenoid. The proper working of a solenoid operated valve depends on the reliability of the electromagnets.
It ensures
Quick and sure action
Long life.
Easy maintenance.
Less wastage of energy.
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.
HOUSE AND FITTINGS:
It is provided for the passage of compressed air from the compressor outlet to the operating valve.
Two separate pipes also connect the operating valve with the working cylinder pressure drop through and air line depends on the flow rate, pipe diameter, pipe length and pipe geometry. It can be determined directly for straight pipes of any given length. A small chaining bore size can have marked effect on pressure drop, where as even doubling the pipe length, will only result in doubling the pressure drop.
Pressure drop through bends and fittings can only be determined by empirical tests, since it is specific to the internal geometry involved. Rigid pipes however are less manipulated through remain form of bends with arrangements increase and variable air have to flow and the flow itself may be of fluctuating or pulsating nature. In this case it is thus normally based on practical recommendation.
SEALS:
Seal is an important component of a pneumatic system and is used to prevent the air leakage through the joint.
This project passes the static seal which are used to prevent the leakage through the stationary surface.
Material of the seal is Teflon tape. Teflon has the following properties
Withstand the system pressure and temperature without any damage.
Resist the wear and abrasion.
Recover from deformation.
Resists the adverse effects such as deterioration and shrinking caused by the system air.
Seals are devices for closing gaps to prevent leakage or make pressure joints and also to prevent the entry of air and dirt from outside into the system. The material of seal must be compatible with the fluid medium. It is a circular ring made of synthetic rubber. It is used for providing tight sealing between the piston and the cylinder wall. It prevents air leakage from the top and bottom of the cylinder.
Seals for air cylinder and valves are not normally called upon to seal pressure higher than about 2 bars. Since the fluid to be seated is a gas, (in our case air) rubbing speeds tends to be high and the seal the seal may have to be operated under dry conditions with minimal lubrication.
CONTROL TIMER CIRCUIT:
Need for a Timer Circuit:
Main purpose to timer circuit is to actuate the solenoid valve at regular interval of time to achieve proper lubrication at the desired interval.
ELECTRONIC CONTROL TIMING UNIT:-
Here the 555 IC has been used as a multi vibrator. The output of IC 555 is fed to the input pin (pin no 14) of CD 4017 continues counting.
The output of the IC becomes available at pin Nos. 3, 2 and 4. The output pulse of any one of output pin triggers (Puts ON) the Triac and current starts flowing across the load connected. This process continues on other pins at different time intervals and the cycle continues. The frequency interval (Time) of the cycle can be adjusted by the pre-set look connected to pin 6 of 555 Timer IC.