Advantages and disadvantages of EDM

Electric discharge machining also is known as spark erosion. It is the process of material removal based on the principle of metals by an interrupted electric spark discharge between the electrode tool and workpiece. Let us have a deep insight into the pros and cons that this process provided. 

Advantages of EDM : 

• It can be applied to all electrically conducting metals.
• Any complicated shape that can be machined.
• Machining time is less than conventional machining processes.
• It can also be employed for the extremely hardened workpiece.
• No mechanical stress is present in this process because of no contact between the tool and the workpiece.
• No burrs.
• Tolerances range +/- 0.005 can be achieved.
• Good surface finish can be attained.
• Creating small holes is not easily achieved by any other process other than EDM.
• Fragile and slender workplaces can be machined without distortion.
• The heat treatment process can be eliminated.
• Hard and corrosion-resistant surfaces, essentially needed for die making, can be developed by this process.
• Little or no polishing is required after the completion of the process.

Disadvantages of EDM : 

• Machining time is too long.
• Excessive tool wear.
• High specific power consumption.
• Profile machining of complex contours is not possible.
• Only able to machine conductive materials.
• The metal removal rate is slow.
• Reproduction of sharp corners is the limitation of the process.
• Surface cracking may take place in some materials owing to their affinity to become brittle at room temperature.
• Especially when higher energy per pulse is used.

Difference between kinematics and dynamics

Kinematics and dynamics are two branches of mechanics that deal with the motion of a particle that plays an important role in robotics and mechanical engineering field. 

What is kinematics?

A study that describes the motion of bodies and the system of bodies without taking into consideration of the cause of motion. 

What is the dynamics?

A study of the motion of a particle along with their cause like force and torque.

Now let us have a deep insight into the comparison between them and check some difference between kinematics and dynamics. 

Key difference : 

Kinematics will give you the values of change whereas dynamics provide the reasoning behind it. 

Kinematics :

• Kinematics originates from the Greek word kinesis, meaning motion.
• Galileo worked on with his numerous experiments measuring displacement, velocity and acceleration of balls rolling down inclined planes.
• More concern with the movement in general.
• A description of how objects move.
• kinematics describes movement, acceleration, speed, of objects.
• Kinematics is based on the nature of force, nature of the body.
• Kinematics is the geometry of motion.
• Motion is teated geometrically without reference to things like cause and effects. 

Dynamics :

• Dynamics from the Greek word dunamis which means power.
• Newton worked on when he formulated his three laws.
• Concern about measuring the causes and quantity of it and how it contributes and relates to the movement.
• It deals with force and why objects move as they do.
• Dynamics describes forces applied to the objects.
• Dynamics is based on the concept of force.
• Dynamics is geometry + physics of motion.
• Motion is treated in terms of trajectories and time so force and motion come in. 

What is Kinematics and Dynamics

What is Kinematics?

It deals with the relative motion of different parts of a mechanism without taking into consideration the forces producing the motions.

Kinematics is the geometry of motion.

What is Dynamics?

It involves the calculations of forces impressed upon different parts of the mechanism.

Dynamics is geometry + physics of motion.

The forces can be either static or dynamics.

Dynamics is further subdivided into two groups :

• Kinetics
• Statics

Kinetics is the study of forces when the body is in motion. 

Statics is the study of forces when the body is stationary.

Absolute entropy definition

Definition of Absolute Entropy :

Answer :

• The increase in entropy of a substance as it goes from a perfectly ordered crystalline form at 0 K temperature where its entropy considers as zero.

Full form of ESC

What is the full form of ESC?

Answer :

• Electronic Stability Control

What does ESC mean?

ESC helps drivers to avoid crashes from skidding or losing control as a result of over-steering.

It is a fully computerized technology used to improve the safety of cars.


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Capstan and turret lathe

Introduction :
A capstan and turret lathe is a production lathe. It is used to manufacture any number of identical pieces in the minimum time.
These lathes were first developed in the United States of America by Pratt and Whitney in 1960.

Types of the machine :
There are two main types of horizontal lathe of this family are :

• The capstan or Ram type lathe
• The turret or Saddle type lathe

The capstan or Ram type lathe :

The ram-type lathe carries the hexagonal turret on a ram or a short slide.

The ram slides longitudinally on a saddle and clamp-on lathe bed ways.

This type of machine is lighter in construction and it is suitable for machining bar of smaller diameter. The tools are mounted on the square turret and six faces of the hexagonal turret.

Ram moves from left to right the feeding movement is obtained.

The turret or Saddle type lathe :

The hexagonal turret-mounted directly on a saddle and the whole unit moves back and forth on the bed ways to apply feed.
This type of turret lathe is heavier in construction and is particularly used for larger diameter bar work and chucking.work.

Principle parts of Capstan and Turret lathe :

Bed :
The bed is long box-like casting provided with accurate guide ways upon which are mounted the carriage and turret saddle.
The bed is designed to ensure strength, rigidity and permanency under heavy duty services.

Head stock :
The head stock is a large casting located at the left hand of the bed.
Different types of head stock maybe use that are listed below :

• Step cone pulley driven head stock
• The direct electric motor is driven head stock
• All geared head stock
• Perspective head stock

Cross-slide & Saddle :

In small capstan and turret lathe hand-operated cross-slide and saddle are used which are clamped on the lathe bed at the required position.

The larger capstan lathes are usually used two designs of the carriage like :

• Conventional type carriage
• Side hung type carriage 

The turret saddle and auxiliary slide :

The turret saddle bridges the gap between two-bed ways and the top face is accurately machined to provide a bearing surface for the auxiliary slide.

The hexagonal turret is mounted on the auxiliary slide.

Capstan and turret lathe mechanism :

The carriage, cross-slide and turret slide may be fed into the work by hand or power. 

The various mechanism for machining. 

• Turret indexing mechanism
• Bar-feeding mechanism

Capstan and turret lathe operation :

In this lathe operations are similar to that of the centre lathe machine.

The usual operations performed in this lathe are :

• Straight turning
• Shoulder turning
• Taper turning
• Chamfering
• Thread cutting
• Facing
• Knurling
• Forming
• Drilling
• Reaming
• Boring
• Counter boring
• Tapping
• Undercutting
• Parting off 

Cutting speed, feed and depth of cut are similar to the simple lathe machine.

Full form of PDI in automobile

What is the full form of PDI?

Answer :

• Pre Delivery Inspection

What does PDI mean?

It is the inspection only to make sure that the vehicle is 100% perfect condition and make a finishing touch before the customer takes delivery. 

In the inspection finishing touch such as following.

• Feeling the car up with gas 
• Washer fluid 
• Engine oil
• Installing the radio and license plate brackets
• Bolt checking
• Check for damage 

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Difference between capstan turret and engine lathe

A capstan and turret lathes are the development of an engine lathe. The capstan lathe was first developed in the United States of America by Pratt and Whitney in 1860. These types of lathe are the development of an engine lathe so they possess certain basic difference as their construction, operation and use. Let us have a deep insight into the comparison and difference between them. 

Difference :

• The headstock of a turret lathe is similar to that of an engine lathe in construction but it has a wider range of speeds.
• Engine lathe required motor of 3 h.p. to drive its spindle and other parts whereas capstan and turret lathe requires high power as 15 h.p. for a high rate of production.
• The tailstock of and engine lathe is replaced by a turret in turret lathe thus it resembles a big six-sided nut with can carry six tools for rotating jobs on the other side engine lathe holds one tool of limited size.
• Turret lathe it acts like production machines while engine lathe is used for various types of odd jobs within limits.
• In a turret lathe, combination cuts can be taken while in centre lathe this type of arrangement is quite uncommon.
• The labour cost required to operate a capstan and turret lathe is less than that required in centre lathe.
• Capstan and turret lathe are not usually fitted with lead screws for cutting threads similar to an engine lathe.
• In capstan and turret lathe one time setting of job then you must not change the tools while in engine lathe you can change tools as per your requirement.
• Turret movement can be controlled automatically. engine lathe tool movement can control manually. 
• In capstan and turret lathe number of speeds is more in engine lathe number of speeds is less.
• Capstan and turret lathe is suitable for mass production while engine lathe is not suitable for that.
• Capstan and turret lathe tool is centred automatically while an engine lathe tool is centred manually after changing the tool.

Summary : 

An engine lathe is a versatile machine capable of machining any types of jobs with different sizes and shapes. The machine is not suitable for production unit because time is taken to set different tools on the tool post of lathe after each and every operation.

On the other hand capstan and turret lathe is a mass-production machine. They are unsuitable where only one or a few jobs are to be machined. The high initial setting time compared to an engine lathe.

Factors affecting charge efficiency

There is a various factor affecting charge efficiency. let we check it out below :

• The compression ratio.
• The amount of heat picked up during passage of the charge through the intake manifold.
• The valve timing of the engine.
• The resistance offered to air-fuel charge during its passage through induction manifold.

Internal combustion engine efficiency

We expressing engine performance in terms of power, it is also essential to express in terms of efficiency. 
Various efficiency are listed below : 

• Air-standard efficiency
• Brake thermal efficiency
• Indicated thermal efficiency
• Mechanical efficiency
• Relative efficiency
• Volumetric efficiency
• Scavenging efficiency
• Charge efficiency
• Combustion efficiency

we can discuss various engine efficiency one by one.

• Air-standard Efficiency :

The air-standard efficiency is also known as thermodynamic efficiency. It is mainly a function of compression ratio and other parameters.

• Brake thermal Efficiency :

The brake thermal efficiency is based on brake power of the engine. These efficiency give an idea of the output generated by the engine with respect to heat supplied in form of fuel.

• Indicated thermal Efficiency :

The indicated thermal efficiency is based on indicated power of the engine.
In modern engine an it is almost 28% obtained with gas and gasoline spark-ignition engines having a moderate compression ratio. 

• Mechanical Efficiency :

Mechanical efficiency takes into account the mechanical losses in an engine.
There is various mechanical losses in the engine :
Friction losses as in case of pistons, bearing, gears, valve mechanisms etc.
Power is absorbed by engine such as fuel pump, lubricating oil pump, water circulating pump, radiator and distributor etc.
Ventilating action of the flywheel. 
Charging in cylinder with fresh charge and discharging the exhaust gases during the exhaust stroke.
In general, mechanical efficiency of engines varies from 65 to 85%.

• Relative Efficiency :

The relative efficiency is the ratio of actual efficiency obtained from an engine to the theoretical efficiency of the engine cycle.

Relative efficiency = Actual brake thermal efficiency / Air-standard efficiency

• Volumetric Efficiency :

Volumetric efficiency is defined as the ratio of the actual mass of air drawn into the engine during a given period of time to the theoretical mass which should have been drawn in during that same period of time.

n_v = ṁ_act / ṁ_th 

• Scavenging Efficiency :

In case of two-stroke engines scavenging efficiency is defined as the ratio of the amount of air or gas-air mixture, which remains in the cylinder, at the actual beginning of the compression to the product of the total volume and air density of the inlet.

• Charge Efficiency :

The charge efficiency shows how well the piston displacement of a four-stroke engine is utilized. Various factor affecting the charge efficiency.

• Combustion Efficiency :

Combustion efficiency is the ratio of heat liberated to the theoretical heat in the fuel.
For a well adjusted engine it is varies form 92% to 97%. 

Advantages and disadvantages of two stroke engine

A two-stroke cycle engine is a type of internal combustion engine that completes a single crankshaft revolution power cycle with two-piston strokes. This engine provided some advantages and disadvantages comparing with a four-stroke engine. Let us have a deep insight into the pros and cons of the two-stroke engine in this article.   

Advantages of two-stroke engine : 

• Simpler in design because don't have valve only port.
• Power developed is twice as compared to same dimensions four-stroke engine with the same operating speed.
• The work required to overcome the friction of the exhaust and suction strokes is saved.
• Burnt gases do not remain in the clearance space because of scavenging.
• Two-stroke engines can work in any position since oil flow is not a concern with any valves to worry about.
• It occupies lesser space.
• Lighter in weight because the lighter flywheel is used.
• Easy to maintain.
• Less cost.
• It produces Uniform torque.
• Power to weight ratio is high.

Disadvantages of two-stroke engine : 

• A high-speed two-stroke engine is less efficient.
• When the inlet valve of the engine is opened for the intake of the air-fuel mixture, the exhaust valve is also open so the part of the fuel is wasted this increase fuel consumption and reduce overall efficiency.
• Effective compression is less in case of a two-stroke engine.
• These engines are liable to cause heavier combustion of lubricating oil.
• With heavy loads, it gets heated due to excessive heat produced.
• Thermal efficiency is also less.
• It causes pollution and smoky.

Types of two-stroke engine

A two-stroke engine is which it completes its cycle of operation in one complete revolution of the crankshaft in other word in two stroke of the piston.

Two-stroke engine are basically two types and its depend on the scavenging method.

Types of two-stroke engine are listed below :

• Crankcase Scavenged Engine
• Separately Scavenged Engine

The details of above two types of engine are describe below :

Crankcase scavenged engine :

It is one of the simplest types of two-stroke engine. In this engine the charge is compressed in the crankcase during the expansion stroke. 

There are three ports in this engine :

• Intake port at the crankcase 
• Transfer port 
• Exhaust port 

Through the transfer port compressed charge passes into the engine cylinder and flushing the products of combustion is called scavenging.

Separately scavenged engine :

It is same engine as crankcase engine but in this engine uses external device like a blower to scavenge the products of combustion is called externally or separately scavenged engine.

  

Components of CRDI

CRDI is a modern fuel system and advanced technology used in an automobile. Let us know about the composition of that are listed below :

Pressure supply pump : 

The electric fuel pump comprises: 

• Electric Moter 
• Roller-Cell Pump 
• Non-Return Valve
• Rail-pressure sensor  (RDS)
• Injector

High-pressure pump : 

• The pump plunger moves downward
• The inlet valve open
• The fuel is drawn into the  pumping element chamber(suction stroke)
• At BDC, the inlet valve closes
• The fuel in the chamber can be compressed by the upward moving plunger.
• High- pressure accumulator (Rail).

Pressure-control valve (DRV) :

• Responsible for maintaining the pressure in the rail at a constant level.

ECU with Sensors :  

• Common Rail is an EDC controlled injection system
• The ECU controls & monitors the complete injection process
• The sensors deliver all the measured values which are required in the process

Rail-pressure sensor(RDS) :

• Measures the pressure in the rail
• Inputs the information to the ECU.

LPG properties

The various properties of LPG are listed below. we can check it one by one. 

Properties of LPG: 

• It is a mixture of gases, mainly constituting Propane and Butane.
• It has a simple structure in chemical terms.
• It is one of the cleanest of all alternative fuels.
• It is a liquid under normal pressure in ambient conditions, usually, it is found to be gaseous form.
• Vaporous form in LPG is two times heavier than air and it is half of the same volume of water.
• Density of liquid LPG is 0.55 gm/ cm.cube.
• LPG boiling point is -42°C or-44°F.
• LPG freeing point is -188°C or -306.4°F.
• LPG heating value is 11920 to 11997 kcal/kg.
• LPG Flashpoint is -76 degrees Fahrenheit.
• Ignition temperature of LPG is 410 to 580 degree Celsius.
• LPG maximum flame temperature in oxygen is 2830 degree cent. 
• LPG maximum flame temperature in the air is 2000 degree cent.
• The gross calorific value of LPG is 11400 Kcal/kg.
• It is almost colourless and odourless.
• Ethyl Mercaptan is normally used as a stenching agent for an odorant purpose helps to know about LPG leaks.
• LPG vapours are tasteless and non-toxic.
• LPG is also caused suffocation in some closed condition.
• LPG is mildly anaesthetic and can be harmful so LPG has never been used or considered safe enough for medicinal purposes.

LPG heating value

Gross heating and Net heating value for LPG :

Gross heating value in kcal/kg - 11920

Net heating value in kcal/kg - 11997

Gross heating value in kcal/nm³ -  28000

Net heating value in kcal/nm³ -  25775

What is melting point

Melting Point :

The temperature at which a given solid will melt is called the melting point.

The melting point is also called Liquefaction point. 

The melting point of a solid is the temperature at which it changes state from solid to liquid at atmospheric pressure. 

In theory, the melting point of a solid should be the same as the freezing point of the liquid.

At the melting point, the solid and liquid phase exist in equilibrium.

What is freezing point

Freezing point :

The temperature at which a liquid turns into a solid when it is cooled is called freeing point.

In other word, Liquids have a characteristic temperature at which they turn into solids, known as their freezing point.

Freezing point is also called the crystallization point.