Wednesday, 13 December 2017

Engine Air Filter : Requirement and Types

Clean air is the need when it comes to breathing, yes its true. But have you ever noticed that an automobile engine also breaths? Feeling curious?, of course you are, we the human beings need fresh and clean air for our survival, if the air is contaminated than it will directly effects our health. Same is with engine as the engine breaths i.e. needs air, through the intake manifold for the combustion of fuel, As the engine takes air from the atmosphere so the questions arise, Do engine needs clean air?, What effects does the polluted air causes to the engine? , How the cleaning of air takes place in an engine? Let’s just till the cat.

An engine air filter system of an automobile is the system that consists of filters made up of various materials that helps the engine for removing or filtering the foreign materials like solid particles, dust, bacteria and odour from the intake air which in turn prevents the engine from various defects like corrosion, wear and tear e.tc. caused by the pollutants in the air, and also increases the quality of the combustion.

Engine air filter system also prevents the passengers from harmful air from the outer atmosphere.

Why do we require Engine air filter system?

As we have already discussed the engine requires fresh or clean air to breath because polluted    air can effects the proper working of the engine so due to the following reasons an automobile vehicle should be equipped with the air filter system-
Engine Air Filter : Requirement and Types
  • A vehicle needs air filter in its air intake system as the main source of combustion, which requires fresh air for the preparation of proper air-fuel mixture than can improve the quality of the combustion.
  • A vehicle must be equipped with an air filter system as the contaminants in the air can cause various defects in the engine like corrosion of the piston, cylinder wall , and also the solid contaminants can cause wear and tear of the various components of the engine.
  • An air filter system is required in a vehicle because the clean air gives less emission through the exhaust of a vehicle as clean air provides complete combustion of the air-fuel which in turn leaves less residual for the exhaust.
  • A vehicle with proper engine air filter system requires less maintenance.
  • When it comes to air ventilation in passenger’s compartment the need of the air filter system increases as the passenger’s health is the priority.
  • The better air filter system in an automobile decreases the need of changing engine oil as the life of the engine oil depends on the wear and tear of the engines components as greater wear and tear decreases the lubricating and cleansing property of the engine oil.
So by the above mentioned points it is clear that engine air filter system as compared to other systems is also important for the well being of the engine.

Air filters used in an automobile Engine:

Passenger’s cabin air filter:

As we have discussed due to the increase in air pollution in the cities like Delhi in India various majors have been made to prevent people with these hazardous pollutants which can cause breathing problem to the people. One of the measure is to introduce an air filter in the ventilator of passenger’s compartment whose idea was introduced in 1940 by Nash Motors which becomes the need of today’s automobile.

Passenger’s cabin air filter are the air filters that is used to filter the atmospheric air entering the passenger’s compartment so that while travelling through the vehicle passengers breath the filtered non polluted air which in turn keep the passengers healthy.

Passenger’s cabin filters are usually fit in the duct that connects the cabin ventilator to the atmosphere and can be change whenever required by just pulling the lower dashboard cabin.

They are usually rectangular in shape and are usually in a shape of steel tea strainer with a paper filter embedded with it.

Internal combustion engine air filter or intake air filter:

As we have already discussed the combustion of fuel in internal combustion engine requires a proper pre-defined mixture of air and fuel, and the air used is taken from the outer atmosphere which is contaminated with lots of foreign materials like dust ,solid particles etc. that can harm the engine by causing wear and tear and by contaminating the engine oil which in turn decreases the overall life of an engine, so an intake system of a car is fitted with an air filter known as intake air filter.

An intake air filter is a rectangular filter consisting of a filtering material like paper placed inside a housing and is fitted inside the air box of an intake system of an automobile vehicle that can filter the air entering the engine’s cylinder during suction stroke of an engine cycle, which in turn prevent the engine from wear and tear and also helps in maintaining the quality of engine in order to increase the engine life and performance.

This filter also provides a high quality air-fuel mixture which is essential for proper and complete combustion of the fuel. Intake air filter also decreases the engine exhaust emissions by filtering the intake air which in turn causes complete combustion of fuel.

Various types of intake engine air filter used in an automobile are-

1. Paper – Unlike normal paper used for writing, a special filter with small pores that looks like paper is used as an air filter which provide filtering of air by restricted the flow of solid contaminants and dust particles.

2. Foam – A normal sponge like filter is used in an automobile that absorbs the contaminants inside the air flowing through this filter.

3. Cotton filter- Oiled cotton gauze is used as a filter in an automobile vehicle that is the modified version of paper and foam filters as it provide adsorption and absorption of solid particles and other harmful contaminants respectively.

Note – latest of all in all the modified cars trapezoidal shaped filters are used as they provide better filtering of air along with desired velocity flow of the air the K&N filters are the example of these type of filters.

Author Bio:
Pankaj Mishra is a mechanical engineer by profession and blogger by hobby. He is owner of www.mechanicalbooster.com website where you can learn about mechanical topics.
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Saturday, 9 December 2017

What is Governor? What are main Types of Governor?

Governor is a type of mechanical device which is generally used to determine and regulate the speed of the engine to the desired level. It is a particular feedback system used where is the need to control variation of load present in the system. The main purpose of the governor is to control the flow of fuel into the engine to maintain a constant speed hence sometimes it is known as speed limiter. When the load of an engine increases the speed of engine decreases and vice versa when the load on engine decreases speed of engine increases. This is where governors play an important role to increase or reduce the fuel flow to engine according to the requirements.

Types of Governor:


The Governors are mainly divided into two types i.e Centrifugal Governor and Inertia Governor. These are further divided into following types according to their design. 

What is Governor? What are main Types of Governor?

1. Centrifugal Governor

In Centrifugal Governor only centrifugal force and change in speed are responsible for controlling the actions. It widely used due to the variety of applications and mostly preferred when balance on the masses is needed in the operation.

Principle
It works on the principle of balancing centrifugal force of the rotating balls.

Construction
A Centrifugal Governor has a simple design. This type of governor has multiple masses known as governor balls which rotate at the distance from the axis of a shaft and driven through suitable gearing from the engine crankshaft. It has two balls of equal masses attached to the arm. These balls are provided by the combination of dead weight or spring. Spindle axis is connected to the sleeve and driven by bevel gear mechanism connected with crankshaft. Throttle valve is connected to the sleeves and operate by the actual change of speed of engine. As load increases speed got decreases and the speed of governor ball as well as governor also decreases which is geared with the crankshaft.

Working
It works as the mechanical link between the throttle which is responsible for fuel supply and the speed. The governor balls revolve with spindles and create a centrifugal force in the inward direction which is generally known as the controlling force. A governing action is depends upon the change of speed and centrifugal force provided by the balls. As soon as the throttle valve opens it increase the supply of fluid increasing speed of the engine. The inward and upward movement of the ball is transmitted by the governor sleeve to the throttle valve which controls the amount of fuel supplied to the engine. As soon as the shaft rotates, the object start rotating around the shaft and goes away from it due to action of centrifugal force which operate the throttle valve.

Advantages
1. Easy to balance revolving parts.

Limitations
1. Slow response and less sensitive.

Applications
1. It limits the rotation speed in the internal combustion engine of automobile and keep it controlled according desired speed.
2. It is used to control speed of turbine shaft in Hydro-electric power plant.
3. Centrifugal governors are also used to control speed of mechanical music box.

The Centrifugal Governors are further classified into two types. Pendulum and spring control governor.

A.) Pendulum type Governor:

Watt Governor is a pendulum governor according to their design. 

a.) Watt Governor:

It is oldest and simplest type of Centrifugal governor. Previously it was used by James watt in his steam engine.

Construction
In Watt governor two balls are arranged on the sleeves consisting arms. Upper side of the arm is connected to the spindle to move the ball in the upward and downward direction when they revolve with Spindle. The lower arm is connected to the sleeve which is joined to the spindle to operate the throttle valve. The spindle gets drives through a bevel gear and two stoppers are provide to the bottom and top of the spindle to restrict the movements of the sleeves.

What is Governor? What are main Types of Governor?

Working
When the load at the engine increases the angular velocity as well as speed of the engine automatically decreases. At the uniform speed controlling force is equal to the centrifugal force which balances each other but when centrifugal force on balls decreases, the balls and spindle start to move inward and downward direction, respectively. These movements are responsible for the mechanism of the throttle valve and cause it opening widely which increases the fuel supply to maintain the speed. 
Limitations
1. suitable for only vertical position application.

Applications
1. It is used in ship and train to maintain the speed of engine.
2. It can be used in AC generators to maintain electric supply.

B.) Gravity Loaded Governor:

There are two different design of gravity controlled centrifugal governor.

1. Porter Governor
2. Proell Governor

a.) Porter Governor

It is a dead weight loaded type governor works on the action of gravity. Porter Governor is a modification of Watt governor.

Construction
In Porter Governor two balls are located at the top and load is attached to the sleeves.  The lower link is connected to central sleeve and two stoppers are provided to control the movements of sleeves.  A mechanism is attached to the sleeves to operate the throttle valve.

What is Governor? What are main Types of Governor?

Working
The balls tend to moves up and down on the spindle due to the speed of revolution of the spindle. As load at the engine decreases speed of the engine as well as spindle also tends to increases. Centrifugal force is responsible for movement of balls in the upward direction while lower arm pushes the sleeves upward to move the ball outward. These movements actuate the throttle valve and fuel supply gets decreases through the mechanism connected to the sleeves.

b.) Proell Governor

It is another type of governor works on the gravity control. The function of porter and proell governor are same with little difference in working.

Construction and working
The construction and working of the Proell Governor is nearly similar to the porter governor. Here revolving balls are attached to the extension link situated at lower part and it reduces the change in the speed responsible for movement of the sleeves. The movements of sleeve and balls operates the throttle valve and decreases fuel supply to the engine.

What is Governor? What are main Types of Governor?

C.) Spring Controlled Governor"

There are four different design of spring control governor. 

1. Hartnell Governor
2. Wilson Hartnell Governor
3. Hartung Governor
4. Pickering Governor

a.) Hartnell Governor

Construction
Hartnell Governors consists two bell cranks situated the different points of the frame. A frame is attached to the spindle, each lever carries a ball to the horizontal roller at the end of vertical arm. The helical ring is provided to maintain the equal level force on the rollers and arrangement of the screw is there to adjust a force of the spring.

What is Governor? What are main Types of Governor?


Working
The working of Hartnell governor is depends on control of spring force. Here spring rotates around the spindle axis and controls the movement of the ball and sleeves.  The spring applies the downward force while sleeves move upward and downward depending on the speed. Two bell cranks situated at the frames carries a ball at one end and roller carry it at the other end. As speed of the engine increases ball moves outward and bell crank lever moves at the pivot lifting sleeves upward against the spring force. These movements then passed to the throttle valve with the help of mechanism and it results in lowering fuel supply as well as speed.

Advantages
1.  Suitable for very high speed
2. Pre-compression can be adjusted to achieve desired equilibrium speed.

b.) Wilson- Hartnell

Construction and working
The balls are associated with the vertical arm and attached to the spring arranged on either side of the sleeves. The spring consists two parts which belongs to the each ball. At the horizontal arm roller comes into contact with sleeves and press it and make the bell-cranks to rotate along the spindle. Speed tends to improve the ball movement and spring gets exerted at the inward pressing roller against the sleeves due to centrifugal force. One end of the spring is attached to the spring and other is connected to the lever and it tends to remain the sleeves down.


c.) Hartung Governor:

Construction and working
This is another type of governor work on the principle of controlled by the movement of spring. In Hartung type governor bell crank levers are connected with the rotating spring balls. These balls are compressed against the frame of the governor while rollers are pressed against the sleeves at the horizontal arms.

What is Governor? What are main Types of Governor?

d.) Pickering Governors

Construction and working
In Pickering Governor there are three springs arranged around the spindle. The arrangement ids angular and each spring hold similar weight at the centers. The revolving balls act against these flat spring and weights move outwards. Spring tends to bend as the ball rotate about the axis of the spindle with greater speed.

What is Governor? What are main Types of Governor?


Advantages
1. Quick response to the change in load
2. Great durability and reliability

Application
1. It is used in Gramophone for adjusting the speed of turntable

2. Inertia Governor

Inertia governor is completely different from the centrifugal governor. The combination of angular and centrifugal force is used to control the position of the balls as well as operation of the Governor. Since it is not very popular, it is preferred when a rapid response is the main concern.

Principle
It works on the principle of movement of inertia due to both centrifugal and inertia force.

Construction
This type of governor is connected to the crankshaft and flywheels of an engine. The governor balls are arranged in such a way that the position of it is affected by the force due to angular acceleration of the shaft.  A suitable spring is loaded inside the governor to control the amount of displacement of governor balls and the mechanism of governor alters the supply of energy to the engine.

Working
In inertia governor more rapid response is obtained to the change of load as the position of the balls are affected by the rate of change of speed of the governor shaft. This type of governors action is depends upon acceleration and not due to the finite change in speed. A movement of the ball is controlled by spring and mechanism of governor and through this the supply of air fuel mixture can be controlled.

Advantages
1. Highly sensitive to varying load
2. Quick response due to fast reaction

Limitations
1. Hard to balance revolving parts

Applications
1. It is used in the steam turbine to control and maintain desired speed of the turbine when load increase or decrease during working
2. It is used in a diesel engine to control speed of the engine at a  particular set point.

This is all about what is governor and types of governor. If you have any query regarding this article, ask by commenting. If you like this article, don't forget to share it with your friends on social networks. Subscribe our website for more informative articles. Thanks for reading it. 
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Monday, 4 December 2017

What is Stress? What are main Types of Stress?

In my last lecture we have learnt about strain and types of strain. Today we will learn about types of stress. We know that when a body is under loading some kind of stress developed in it. Mathematically this stress is the ratio of the applied force to cross section area of the body. If this stress reaches its ultimate limit or failure limit for particular object, it breaks it into two half. If this stress is under a certain limit (Elastic Limit), the body gets its actual dimension after removal loading. So the stress play very important role for designing any object.

What is Stress? What are main Types of Stress?

There are various kinds of stress induced in the body due to loading. 

Let’s learn them one by one.

Types of Stress:

Tensile Stress:

When a body is under tensile load or pull loading, the stress induce in it is known as tensile stress. The ultimate limit under tensile loading is called ultimate tensile stress.

What is Stress? What are main Types of Stress?

Compressive Stress:

When a body is under compressive load or push loading, the stress induce in it is known as compressive stress. The ultimate limit under compressive loading is known as ultimate compressive stress.

What is Stress? What are main Types of Stress?

Shear Stress:

When two equal and opposite forces acted on parallel faces of a body, the stress induce in it is called shear stress. This stress tends to deform the shape of a body without changing its volume.

What is Stress? What are main Types of Stress?

Thermal Stress:

When a body is resisted to expand and there is change in its thermal condition, some stress developed in it, is known as thermal stress. Thermal stress set up only when the body is not allowed to expand.


This is all about types of stress. If you have any query regarding this article, ask by commenting. If you like this article, don’t forget to share it on social network. Subscribe our website for more informative articles. Thanks for reading it. 
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Friday, 1 December 2017

What is Cooling Tower? What are main Types of Cooling Tower?

Cooling tower is a special type of heat exchanger which rejects waste heat to the atmosphere by making direct contact between air and water to lower down the temperature of water. It works on basic principle of heat transfer due to evaporation. It is mostly use to cool down large amount of water so it recirculate again for cyclic operation. cooling towers are used in many industries like thermal power station, chemical industries, refineries etc. According to the requirement and weather conditions, there are various types of cooling towers available. Today we will discuss about all of them.

Let’s start leaning its types.

Types of Cooling Tower:


It is generally categorized according to its working and applications. Various types of it given below.

1.) Categorized by Air to water flow:


a.) Crossflow cooling tower:

As the name implies in cross flow cooling tower air flow perpendicular to the water flow. Air enters the tower from vertical faces to meet the fill located inside the tower and hot water enters the basin located at the top of the tower. Gravity distributes the water uniformly through the nozzle across the fill upright the air flow. Turbulent air passing through the fill causes water to pass into an open area which improves the contact between air and water resulting effective cooling. The air is taken out from the system by an induce for force draft system.

What is Cooling Tower? What are main Types of Cooling Tower?

Advantages:
1. Lower operation cost due to low pumping head
2. Minimum maintenance
3. Low energy consumption

Limitations:
1. Maximum water overturn
2. Easily build up the dirt into the fill of tower.

Applications:

1. Widely used in heating process in chemical industry
2. Used in Aluminium die casting and air compressor

b.) Counterflow cooling tower: 

In this type of cooling tower air flows in opposite direction to the water flow.  Air is drawn from the bottom of the cooling tower near the fill and pulls into open space of tower. Water passes downward into the fill media parallel but opposite to the air direction which increases the contact area as well as contact time. Cooling air drawn out heat from the water and increases heat transfer.

What is Cooling Tower? What are main Types of Cooling Tower?

Advantages:
1. More efficient air to water contact due to droplet distribution.
2. Maximum tower performance.

Limitations:
1. More noise production due to spraying and falling water.
2. Uneasy maintenance and difficult to clean up.

Application:
1. Refineries and natural gas processing plants.
  

2.) Categorized by drawing air through the tower:


a.) Natural draft cooling tower:

Natural draft cooling tower basically removes waste heat from the system and release it into the atmosphere. In this process hot water enters through the series of pumps to the top area of tower near hot water inlet. Series of nozzles connected to the hot water inlet used to sprays water over the fill and distributed throughout the tower. Simultaneously air is introduced from the bottom of the tower flowing in upward direction. It then circulated inside the cooling tower by natural convection. While flowing down water emits heat due to evaporation which mixes with the air flowing upward causing water to cool down. Cooled water is collected into the basin and then used for cooling various hot process fluid.

What is Cooling Tower? What are main Types of Cooling Tower?

Advantages:
1. Less operating and maintenance cost.
2. Safe to operate.
3. Energy efficient.

Limitations:
1. Not adoptable with every climate conditions.
2. Large space is required to install.
3. High initial Cost.

Application:

1. Used in power stations and for process cooling applications.


b.) Mechanical draft cooling tower

Mechanical draft cooling tower utilizes mechanical devices such as fan or blower to move air through the tower. It is classified into two types.

I.) Forced Draft cooling tower:

In forces draft cooling tower air is blown through tower with the help of a fan located at the bottom of tower. Hot water enters from top of the tower. Counter flow of air and water in the fill results in a heat transfer. It uses atmospheric cooling with wet technology. This type of cooling tower removes low potential heat generated during production process and having limited application due to recirculation difficulties.

Advantages:
1. Easy maintenance as it has better access to the fan, drives and motor.
2. Suitable for high air resistance.

Limitations:
1. Higher fan power requirement.
2. It may be susceptible to recirculation.

Applications:
1. Petrochemical industry and energy industry.


II.) Induced Draft:

It works similar to the forces draft cooling tower except little difference. In this type of tower, air is introduced from the bottom and water enters from the top. Water gets spread throughout the tower with the help of spray distribution header. Fan is situated at air outlet which draws air across the fill at high level and drawn through the baffled area by fan which causes cooling of the water. Time of contact is greater in induced draft which also improves heat transfer area.

Advantage:
1. Less recirculation as compare to Forced draft.
2. Does not require large space to install.

Limitations:
1. Fan, motor and drives located in moist air stream so electrical protection is required.
2. More maintenance required and corrosion is likely.

Application:
1. Best suitable for A/C plants, chemical industries and sugar industries.

  

3.) Categorized by Heat transfer method:


a.) Dry cooling tower:

It utilizes air instead of water so named as Dry cooling tower. It transfer heat to the atmosphere without evaporation and consumption of water is relatively less. This type of cooling tower operates by convective heat transfer through a surface which separates fluid from the air. It is most suitable for cooling of processing liquid.

Advantages:
1. Only frequent maintenance is needed.
2. A large amount of water gets conserved.

Limitations:
1. It tends to produce large mechanical noise.

Application:
1. It is used in power generation units.
2. Suitable in heat treatment furnace in forging unit.

b.) Wet cooling tower:

Wet cooling tower is otherwise known as Open circuit cooling tower. It operates on evaporative cooling. Water to be cooled is pumped from the plant and distributed over the fill. Water vapor are added into the air which lowers the temperature pf water as well as air. Fills plays important role in providing better heat transfer by increasing contact surface as well as contact time.

Advantage:
1. Thermal efficiency and net power output is high.

Limitation:
1. Operating cost is little high.

Applications:
1. Petrochemical, oil refinery and thermal power plant.

c.) Fluid cooler:

It is also known as Closed circuit cooling tower. It operates on similar principle as open circuit cooling tower only difference is that process fluid does not contact cooling air. Two separate external fluid circuits and coil are present inside the fluid cooler. Coil isolates the process fluid from outside air to keep it contamination free. Internal circuit circulates process fluid inside the coil and External circuits circulate water over the coil mixing with outside air. Heat is transferred from the internal circuit to water and then to the atmosphere by evaporating water.

Advantage:
1. Reduced pumping requirement and cost.
2. It conserves more space due to compact design.

Limitations:
1. Slightly expensive.
2. It can be heavier and larger than open circuit cooling tower.

Applications:
1. It is used for heating, ventilation and air conditioning in refrigeration industry.


This is all about what is cooling tower and types of cooling tower. If you have any query regarding this article, ask by commenting. If you like this article, don’t forget to share it on social networks with your friends. Subscribe our website for more informative articles. Thanks for reading it.
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Wednesday, 22 November 2017

What is Strain? What are Types of Strain?

Hello friends,

Hope you are doing well. In our last lecture we have studied about stress and strain. We have learnt about basic concept behind it. Strain is a measurement quantity which is ratio of change in length to original length under loading condition. But when we stretch a body, its dimensions changes in all directions. According to it strain can be divided into two types. There are many other factors on which we can categorized strain. So today we will learn about types of strain. Hope you like it.

Let’s starts with its types.

Types of strain:


Strain can be categorized into following aspects.

According to the direction of loading:

Let’s try to learn with example. Take a rubber piece of L length, and B width. Apply a pull load on its two parallel faces along its length and observe it. The length of the rubber piece slightly increases, suppose it is ∆L. We also observed some little change in the width and height as they both decrease slightly. Suppose change in width is ∆B and change in height is ∆W.

So we have observed three value of change in length in all three direction. According to it strain can be divided into two types.

What is Strain? What are Types of Strain?

Lateral Strain:

The ratio of change in length to its original length in the perpendicular direction of the loading is called lateral strain. In the above example it can be represented by

What is Strain? What are Types of Strain?

Longitudinal Strain:

The ratio of change in length to its original length in the direction of loading is known as longitudinal strain. In the above example longitudinal strain can be represent by.

What is Strain? What are Types of Strain?

According to the loading:

According to the types of loading strain can be divided into three types.

Normal strain:

It can further divided into two types.

Compressive strain:
Strain measure under compressive loading is known as compressive strain. It tends to increase the cross section area and decrease the length of the body.

What is Strain? What are Types of Strain?

Tensile Strain:
Strain measure under tensile loading is known as tensile strain. It tends to decrease the cross section and increase the length of the body.

What is Strain? What are Types of Strain?

Shear Strain:

When the shear stress is applied on a body, it tends to deform the shape of the body as shown in the figure. The change in tangential angle in the direction of the loading is called shear strain.

What is Strain? What are Types of Strain?

What is Strain? What are Types of Strain?

Volumetric strain:

The ratio of change in volume to original volume under normal loading condition is known as volumetric strain.


This is all about types of strain. If you have any query regarding this article, ask by commenting. If you find something missing or wrong, inform us through commenting. If you like this article, don't forget to share it on social networks. Subscribe our website for more informative articles. Thanks for reading it. 
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Sunday, 19 November 2017

Difference between NC and CNC Machine

Today we will discuss about difference between NC and CNC machine. NC stands for numerical control whereas CNC stands for computer numerical control. Both of these are automatic machines which are used for machining any metal with accurate dimensions. These both machines work on feeding mechanism in which we command the machine in some defined code language and the machine compile and convert it into machine language and perform the predefine operation. Today we will learn about both of these machines and also differentiate them in later portion of this article. Now let's start the discussion. 


Numerical Control (NC) Machine:

Numerical Control (NC) refers, the method of controlling the manufacturing operation by directly inserted numerical codes into the machine tool. It is important to realize that it is not a machining method, rather, it is a concept of machine control.

In a Numerical Control machine, the program is fed to the machine through punched card, magnetic tapes and other such media. The program consists of precise instructions about the manufacturing method as well as the movements. It has no memory storage and it run off of the "tape" each time the machine cycles.

The essential features of numerically controlled machines have been established for many years. They comprise a controller, known as the machine control unit MCU, capable of reading and interpreting a stored program and using the instructions in this to control a machine via actuation devices. 

The detailed step-by-step commands that direct the actions of the processing equipment called program of instructions. In machine tool applications, the program of instructions is called a part program, and the person who prepares the program is called a part programmer. In these applications, the individual commands refer to positions of a cutting tool relative to the worktable on which the workpart is fixtured. Additional instructions are usually included, such as spindle speed, feed rate, cutting tool selection, and other functions. The program is coded on a suitable medium for submission to the machine control unit.

NC Coordinate System:



In machine tools the cutter may typically move in multiple directions with respect to the workpiece, or vice versa, and therefore the controller normally drives more than one machine axis. Examples of machine applications and numbers of axes are as follows:

1.) 2-axis motion, generally in two orthogonal directions in a plane, which applies to most lathes as well as punch presses, flame and plasma-arc and cloth cutting machines, electronic component insertion and some drilling machines.

2.) 3-axis motion, which is generally along the three principal directions (x, y and z) of the Cartesian coordinate system, and applies to milling, boring, drilling and coordinate measuring machines.

3.) 4-axis motion typically involves three linear and one rotary axis, or perhaps two x-y motions, as for example for some lathes fitted with supplementary milling heads.

4.) 5-axis machines normally involve three linear (x, y and z) axes, with rotation about two of these, normally x and y.

Computer Numerical Control (CNC) Machine:

It is the next method of NC machine. In a Computer Numerical Controlled machine, the machines are interfaced with computers. This makes them more versatile in the sense that, suppose a change in dimension of a part is required. In a NC machine, you would have to change the program in the tape and then feed it to the machine again. But in a CNC machine, you just change a variable in the computer and you can modify the program. It has the memory storage and the programs can be stored in its control. In modern CNC systems, the design of a mechanical part and its manufacturing program is highly automated. The part's mechanical dimensions are defined using computer-aided design (CAD) software, and then translated into manufacturing directives by computer-aided manufacturing (CAM) software. The resulting directives are transformed (by "post processor" software) into the specific commands necessary for a particular machine to produce the component, and then loaded into the CNC machine. Consists of main memory and secondary memory. Main memory (Primary storage) consists of ROM (read-only memory) and RAM (Random access memory) devices. 

Operating system software and machine interface programs are generally stored in ROM. Numerical control part programs are stored in RAM devices. Current programs in RAM can be erased and replaced by new programs as jobs are changed. High-capacity secondary memory (also called auxiliary storage or secondary storage) devices are used to store large programs and data files, which are transferred to main memory as needed. In NC machine if an error occurs in the program than its debugging and modification is not easy. In CNC machine the debugging and modification is very easy. High skilled operator is required to operate the NC machine whereas to operate a CNC machine, a semiskilled operator may work. The cost of the NC machine is less as compared with the computer control machines.

Difference Between NC and CNC Machine:



S.No.

NUMERICAL CONTROL (NC) MACHINE:


COMPUTER NUMERICAL CONTROL (NC) MACHINE:


1.

Input method: Punched tape, punched card and other such media.


Input method: programs are fed directly into the computer by small key board similar to our traditional key board.



2.

Programs should be changed in punched card and then fed to machine.


We can modify the program in computer.

3.

Operation parameters could not be changed.



Operation parameters can be changed.


4.

It has no memory storage.


We can store programs using the memory storage in computer.


5.

Run off the "Tape" each time of machine cycle.



It have the facility of running the program without actually running it ON the machine tool.



6.

NC machine cost is less.


CNC machine cost is high.

7.

Maintenance is less.



Maintenance is high.


8.

Accuracy is less.



It has more accuracy.

9.

High skill operator required.



High skilled not required.

10.

It is less flexible.



It is highly flexible.

11.

It required more time to perform a operation.



It requires less time.


This is all about difference between NC and CNC machine. If you have any query regarding this article, ask by commenting. If you like this article, don't forgot to share it with your friends on social networks. Subscribe our website for more informative articles. Thanks for reading it. 
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