Thursday, 8 June 2017

Full Notes on Constant Mesh Gearbox

Constant mesh gearbox is used for the smooth working of an automobile. They are used to increase the rotating force (Torque); this is accompanied by a reduction in speed. It is a type of manual transmission. The invention of earliest manual gear system can be traced back to the nineteenth century. There are multiple gear ratios present which provides various torque and speed ratio. Along with this, the reverse mechanism is also present. This manual transmissions which are developed recently contain all the gears mesh at any given point of time. 

In technical terms, it can be defined as a gearbox in which all the gears are always in a state of mesh. The gears remain fixed at their original positions. The gears will remain engaged at all times. Learn more about its construction, working, advantages, disadvantages and applications in this article.


Constant Mesh Gearbox:


Construction:

It is made up of following components:


Full Notes on Constant Mesh Gearbox


1. Counter shaft or Lay Shaft: 
This shaft is in direct contact with the clutch and the main shaft. Keeping in mind according to the gear ratio, the speed of the counter shaft may be less that the speed of the engine. The gear ratio can be defined as the ratio of the teeth of driven gear to the teeth of the driver gear.

2. Main shaft:
This shaft operates the speed of the vehicle. The power is made available to the main shaft through the gears from the counter shaft. This is done in accordance with the gear ratio.

3. Dog clutch:
Dog clutch is special feature of constant mesh gearbox. It is used for the coupling of any two shafts. This is done by interference. Using a dog clutch, various gears can be locked to the output and input shafts.

4. Gears: 
The main work of the gears is the transmission of power between the shafts. If the gear ratio is more than one, the main shaft will work at a speed that is slower than the counter shaft, and vice versa. The arrangement of both reverse, as well as forward gears, is present.


Working:


Forward gear selection:
From the input shaft, the power starts flowing and is divided into four parts. Each part goes to one of the output gears, namely first, second, third and fourth. Gear ratios can be obtained for each of them. This can be done by the proper sliding of dog clutch over the teeth of the selected gearwheel. After this the path of the energy flow completes. This happens due to the locking movement of the output shaft.

Reverse gear selection:
The power will flow from the input shaft to the reverse gears. The power is then transmitted from the reverse gear to the reverse idler. The idler wheel will change the direction of the rotation. In the case of forwarding direction gear selection, the output gears will rotate in a direction opposite to the input gears. But in the case of reverse gear selection, the rotation is in the same direction as the input shaft.


The steps are taken to change any gear in the constant mesh gearbox system:

1. The first step when one wants to modify the gear would be the pressing of the clutch. After this comes the neutral state of the vehicle to be achieved. Proper optimization of the engine's speed is required.


2. After the neutral gear, one moves forward to the first gear. The first gear. This process is known as double clutching. Inefficiency in performing the above steps might lead to a harsh and gnashing sound.

Watch the following video for clear understanding of its working.




Advantages and Disadvantages of Constant Mesh Gearbox:


Advantages: 
  • The first and foremost benefit of the constant gear mesh is the utilization of helical gears. The double helical gears and the helical gears are extremely beneficial owing to their quieter operating capabilities
  • There are various conditions which might cause harm. In the case of constant mesh gearbox, any harm is suffered entirely by the dog clutch teeth. The teeth belonging to the gear wheels remain intact. This is not the case for sliding mesh gear box.
  • The other gear boxes are noisy and create an unwanted din.
Disadvantages:
  • It is less efficient than the others due to higher mesh teeth. Skill is required for it.
  • The double clutch mesh is required. This is required to have the spinning movements of the shaft.

Application:

Some of the vehicles which use this type of gearboxes are farm trucks, motorcycles, and heavy machinery.

It is very evident that the world today is full of vehicles and relies on this mode of transport. The availability of such mechanisms like constant mesh gearbox which create less noise and are cost effective is a boon for the people.

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Thursday, 25 May 2017

Powder Metallurgy Process with its Advantages and Disadvantages

Powder Metallurgy Process

Powder Metallurgy or P/M is a manufacturing process of producing finished or semi-finished objects by compressing the metal powder into suitable dies. It is one of the cheapest process which gives high quality, high strength, complex shapes with high degree of accuracy. These factors make this process most suitable for mass production. It mainly involves four basic steps.

1. Powder Preparation:
2. Mixing and Blending:
3. Compacting:
4. Sintering:

Sometimes, this process accomplished with some secondary operation like sizing, coining, infiltration, hot forging etc.

Powder metallurgy is continuously growing technology. Almost all metals can cast by P/M technology but mostly iron powder is used with some alloying elements like copper, graphite which gives greater strength.

Learn more about this process with its pros and cons in this article.


Powder Metallurgy Process:


As we discussed earlier, P/M involves basic four processes. These are:

Powder Metallurgy Process

1. Powder Preparation:

This is first and basic step for producing any object by powder metallurgy process. Any material can convert into powder. There are various processes of producing powder such as atomization, grinding, chemical reaction, electrolysis process etc.

2. Mixing and Blending:

As the name implies, this step involves mixing of two or more material powder to produce a high strength alloy material according to the product requirement. This process ensure even distribution of powder with additives, binders etc.  Sometime lubricants also added in the blending process to improve flow characteristics of powder.

3. Compacting:

Compacting means compressed the prepared powder mixture into pre-defined dies. This step ensures to reduce voids and increase density of the product. The powder is compacted into mould by the application of pressure to form a product which is called green compact (the product get by compacting). It involves pressure range from 80 to 1600 MPa.  This pressure depends on the properties of metal powder and binders. 

For soft powder compacting pressure is about 100 – 350 MPa.

For steel , iron etc. the pressure is in between  400 – 700 MPa.

4. Sintering:

The green compact, produced by compressing, is not very strong and can’t be used as final product. This step involves heating of green compact at an elevated temperature which ensure permanent strong bond between adjacent particles. This process provides strength to green compact and converts it into final product. The sintering temperature is generally about 70 to 90 percent of melting temperature of metal powder.

5. Secondary Operation

The sintered object is more porous compare to fully dense material. The density of product depends upon press capacity, sintering temperature, compressing pressure etc. Sometimes, the product does not require high density and the sintered product is directly used as final product. But sometimes, a highly dense product is required (for example manufacturing bearing etc.) where sintered product cannot be used as finished product. That's why a secondary operation required to obtain high density and high dimensional accuracy. The most common secondary operation used are sizing, hot forging, coining, infiltration, impregnation etc.


Advantages and Disadvantages:

Advantages:

  • P/M is Cost effective for mass production due to absence of labour cost, further machining cost etc.
  • This process does not require high skilled operator. 
  • Some alloys can only produce by P/M technology.
  • High production rate. It can produced 500 to 1000 pieces in one hour.
  • Complex Shape can produce.
  • Bimetallic and laminated product can be easily produced by P/M method.

Disadvantages:

  • High equipment cost.
  • It is economical only for mass production.
  • Intricate designs is difficult to produce due to less flow ability of metal powder.
  • It cannot produce a complete uniform dense product.
  • Size of the product is restricted due to capacity of press.
  • Some metals powder, which can produce explosion in powder form, cannot be used.
  • Low impact and fatigue property of final product.
  • It is difficult to cast low melting point metals by P/M technology.

Application:

  • Cutting tools like cemented carbide tool, ceramic tool etc. are Powder metallurgy product.
  • Electric bushes made by mixing Cu and Ag with graphite is P/M product.
  • Nozzles for rocket and missiles.
  • Small parts in automotive and appliance applications where the ability to produce a nearly final shape requiring a minimum machining, provides a strong economic advantage.
  • Bearing, Bushes etc.
  • Magnetic soft metals like Fe, Fe-3Si etc. can easily formed into final shape by P/M.


This is all about powder metallurgy process with its advantages and disadvantages. 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. Subscribe our website for more informative articles.
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Tuesday, 23 May 2017

18 Mechanical Properties Which Every Mechanical Engineer Should Know

Material selection for any product is main part of a manufacturing industries. The quality of product is highly depends upon its material properties. These properties are used to distinguish materials from each other. 

For Example: 

A harder material is used to make tools.

A ductile material is used to draw wires

So the knowledge of mechanical properties of material is desirable for any mechanical student or for any person belongs to mechanical industries. This article brings top 18 mechanical properties. I hope you will like it.

18 Mechanical Properties Which Every Mechanical Engineer Should Know


Mechanical properties of material:



There are mainly two types of materials. First one is metal and other one is non metals. Metals are classified into two types : Ferrous metals and Non-ferrous metals.

Ferrous metals mainly consist iron with comparatively small addition of other materials. It includes iron and its alloy such as cast iron, steel, HSS etc. Ferrous metals are widely used in mechanical industries for its various advantages.

Nonferrous metals contain little or no iron. It includes aluminum, magnesium, copper, zinc etc.

Most Mechanical properties are associated with metals. These are


#1. Strength:

The ability of material to withstand load without failure is known as strength. If a material can bear more load, it means it has more strength. Strength of any material mainly depends on type of loading and deformation before fracture. According to loading types, strength can be classified into three types.

a. Tensile strength:
b. Compressive strength:
3. Shear strength:

According to the deformation before fracture, strength can be classified into three types.

a. Elastic strength:
b. Yield strength:
c. Ultimate strength:

#2. Homogeneity:

If a material has same properties throughout its geometry, known as homogeneous material and the property is known as homogeneity. It is an ideal situation but practically no material is homogeneous.

#3. Isotropy:

A material which has same elastic properties along its all loading direction known as isotropic material.

#4. Anisotropy:

A material which exhibits different elastic properties in different loading direction known as an-isotropic material.

#5. Elasticity:

If a material regain its original dimension after removal of load, it is known as elastic material and the property by virtue of which it regains its original shape is known as elasticity.

Every material possess some elasticity. It is measure as the ratio of stress to strain under elastic limit.

#6. Plasticity:

The ability of material to undergo some degree of permanent deformation without failure after removal of load is known as plasticity. This property is used for shaping material by metal working. It is mainly depends on temperature and elastic strength of material.

#7. Ductility:

Ductility is a property by virtue of which metal can be drawn into wires. It can also define as a property which permits permanent deformation before fracture under tensile loading. The amount of permanent deformation (measure in percentage elongation) decides either the material is ductile or not.

Percentage elongation = (Final Gauge Length – Original Gauge Length )*100/ Original Gauge Length

If the percentage elongation is greater than 5% in a gauge length 50 mm, the material is ductile and if it less than 5% it is not.

#8. Brittleness:

Brittleness is a property by virtue of which, a material will fail under loading without significant change in dimension. Glass and cast iron are well known brittle materials.

#9. Stiffness:

The ability of material to resist elastic deformation or deflection during loading, known as stiffness.  A material which offers small change in dimension during loading is more stiffer. For example steel is stiffer than aluminum.

#10. Hardness:

The property of a material to resist penetration is known as hardness. It is an ability to resist scratching, abrasion or cutting.

It is also define as an ability to resist fracture under point loading.

#11. Toughness:

Toughness is defined as an ability to withstand with plastic or elastic deformation without failure. It is defined as the amount of energy absorbed before actual fracture.

#12. Malleability:

A property by virtue of which a metal can flatten into thin sheets, known  as malleability. It is also define as a property which permits plastic deformation under compression loading.

#13. Machinability:

A property by virtue of which a material can be cut easily.

#14. Damping:

The ability of metal to dissipate the energy of vibration or cyclic stress is called damping. Cast iron has good damping property, that’s why most of machines body made by cast iron.

#15. Creep:

The slow and progressive change in dimension of a material under influence of its safe working stress for long time is known as creep. Creep is mainly depend on time and temperature. The maximum amount of stress under which a material withstand during infinite time is known as creep strength.

#16. Resilience:

The amount of energy absorb under elastic limit during loading is called resilience. The maximum amount of the energy absorb under elastic limit is called proof resilience.  

#17. Fatigue Strength:

The failure of a work piece under cyclic load or repeated load below its ultimate limit is known as fatigue. The maximum amount of cyclic load which a work piece can bear for infinite number of cycle is called fatigue strength. Fatigue strength is also depend on work piece shape, geometry, surface finish etc.

#18. Embrittlement:

The loss of ductility of a metal caused by physical or chemical changes, which make it brittle, is called embrittlement.


This is all about mechanical properties of material. 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. Subscribe our website for more interesting articles.
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Monday, 22 May 2017

Top 5 Fastest Car in the World

Every car lover wants to drive a fastest car. Cars is always an interesting topic on which we want to discuss. Often we like cars because of its speed and cool looks. Today I am going to tell you about top five coolest and fastest cars with their cool pics. I hope after reading this article, you want to ride one of them.  


Top 5 Fastest Cars in the World:


5. Porsche 9ff GT9-R:

Overview:
Engine type      : Flat 6 cylinder turbocharged engine
Acceleration      : 100km/h in just 2.9 seconds
Power              : 1105 bhp at 8150rpm
Torque             : 1050 Nm at 6170rpm
Displacement    : 4000cc

Top speed : 413 km/h (256.68 mph)

Top 5 Fastest Car in The World 2014

4. SSC Ultimate Aero:

Overview:
Engine type      : SSC Designed Billet Aluminum V8 engine
Acceleration      : 96.56km/h in just 2.78 seconds
Power              : 1287 bhp at 6075 rpm
Torque             :1508 Nm at 6150 rpm
Displacement    : 6350cc

Top speed : 414.26 km/h (257.41 mph)

Top 5 Fastest Car in The World 2014

3. Koenigsegg Agera R:

Overview:
Engine type      : Koenigsegg aluminum 5.0L V8, 4 valves per cylinder, DOHC
Acceleration      : 100 km/h in just 2.8 seconds
Power              : 1140 bhp at 7100 rpm
Torque             : 1000 Nm at 2700 to 7300 rpm 
Displacement    :5000cc

Top speed : 418.43 km/h (260 mph)

Top 5 Fastest Car in The World 2014

2. Bugatti Veyron Super Sport:

Overview:
Acceleration      : 80km/h in just 2.2 seconds
Power              : 1183 bhp at 6400 rpm
Torque             : 1500 Nm at 3000 rpm
Displacement    : 8000cc

Top speed : 434 km/h (269.08 mph)

Top 5 Fastest Car in The World 2014

1. Hennessey Venom GT:

Overview:
Engine type      : 90-degree V8 engine
Acceleration      : 100km/h in just 2.7 sec.
Power              : 1244 bhp at 6600 rpm
Torque             : 1566 lNm at 4400 rpm
Displacement    : 7000 cc

Top speed          : 435.31 km/h (270.49 mph)
Projected speed : 447.4 km/h (278 mph)

Top 5 Fastest Car in The World 2014


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Sunday, 21 May 2017

Different Cutting Tool Materials

Today we will discuss about most common cutting tool materials used in mechanical industries. Tool play very important role in machining. The shape of work piece, its surface finish and some other properties are directly dependable on the tool material and its design. A proper designed tool with appropriate material gives better surface finish and high accuracy. Most important characteristic of tool are:

  • It should have high hot hardness.
  • High Wear Resistance.
  • Tool should have high Toughness and hardness.
  • It should have high thermal conductivity.
  • Tool works at high temperature during cutting so it should have low coefficient of thermal expansion.
  • Tool should have high strength.
  • It should have Low coefficient of friction and should be chemically stable.

Different Cutting Tool Materials

Cutting Tool Materials:


Most common engineering materials used in tool making are:

Carbon Steel Tool:

Carbon Steel is widely used for machining soft materials like, Magnesium, Aluminum, Wood etc. It contains carbon, silicon and magnesium as its constitute.  This material used for making hand drills narrow blade, taps, dies, chisels etc. Its cutting speed is about 10 m\mm and highest temperature up to which it can work is 200 – 250 degree centigrade.

High Speed Steel (HSS):

High speed steel is very common tool material which is an alloy of steel tungsten, Chromium and Vanadium. It contains 18% Tungsten, 4% Chromium and 1% Vanadium. This material is deep hardening and can be quenched in oil, air or salt. It has highest toughness. Its cutting speed is about 30 – 50 m\mm. It can work up to 650 degree centigrade.  

According to the composition of material, it can be divided into two major types.

1. Tungsten type steels in which tungsten is used as the major alloying element.
2. Molybdenum type steel in which tungsten is partially or completely replaced by molybdenum. It is cheaper than tungsten type steel and has greater toughness at the same level of hardness.

Stellite:

Stellite is a non ferrous alloy with cobalt, chromium, Tungsten, with molybdenum and boron. Cobalt is used about 38 – 53 percent, chromium is 30 – 33 percent, tungsten is about 10 – 20 percent and carbon contain is about 1 – 3 percent. This material has intermediate properties between HSS and cemented carbide.  Its cutting speed is about 50 – 80 m\mm. Its highest working temperature is about 900 degree centigrade.

This tool material is mostly used for rough machining at relatively high speed and feed rate and it can machine more difficult materials such as high tensile steel, stainless steels and heat treated resistant steels.

Cemented Carbide Tool:

It is made by powder metallurgy technique.  In this material, cobalt acts as binding material. These material can be divided into three types.

1. Straight tungsten carbide with cobalt as a binder.
2. Tungsten carbide with cobalt as a binder and having large percentages of carbides of titanium, tantalum, niobium and columbium etc.
3. Titanium carbide with nickel or molybdenum as the binding material.

Its highest speed up to which it can work is about 60-200 m\mm and its working temperature limit is up to 1000-1200 degree centigrade.

All carbides when finished are extremely brittle and weak in their resistance to impact and shock loading. That’s why vibrations are very harmful for carbide tools.

Ceramics:

This tool is combination of silicon carbide and aluminum oxide. It is also made by powder metallurgy.  It cannot work at low speed. This tool material has very high abrasion resistance and hard compare to cemented carbide tool. It is particularly used for machining cast iron and high tensile steel with higher cutting speed compare to cemented carbide tool.  Its highest working temperature is about 1400 degree centigrade. Its cutting speed is about 300 – 600 m\mm.

Cermets:

Combination of ceramic with metal is known as cermets. This material has high refractoriness of ceramics and high toughness and thermal shock resistance of metal. The usual combination is aluminium oxide with metal (W, Mo, Boron, Ti etc.) in an amount of 10 percent.

Diamond

Diamond is a highest known hard tool material on the earth. It has good thermal conductivity, low thermal expansion and low friction coefficient. It's cutting speed is about 1500 - 2000 m\mm. It is used for machining hard material like hard carbide, nitrides etc. It is mostly used to machining nonferrous material. 

Cubic Boron Nitride

It is the second hardest material after diamond. It is not a natural material. It consists of atoms of nitrogen and boron. This has high hardness and high thermal conductivity. CBN is chemically inert and is used as a substitute of diamond for machining steel. It is mostly used as abrasive in grinding wheel.  Its highest cutting speed is about 600 – 800 m\mm.  

UCON:

It is a new cutting material. It constitute are columbium 50 percent, titanium 30% and tungsten 20%. This has high hardness, high toughness and excellent shock resistance. It is mainly used for steel cutting material and not suitable for cutting cast iron, stainless steel and super alloys containing Ni, Co and Ti as base material. UCON gives 60 percent increases in cutting speed when compared with tungsten carbide.

Coronite:

It is a new cutting material whose properties lies in between those of HSS and cemented carbide. This material consists of fine grain of TiCN evenly dispersed in a material of heat treatable steel. It is used for producing small and medium size drill and milling cutters. It is also used for compounding and coating technology. It is mainly used as core material for HSS or spring steel.


This is all about most common cutting tool materials used in mechanical industries. If you have any query regarding this article, ask by commenting. If you like this article, don’t forget to share it on your social networks. Subscribe our website for more informative articles. 
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Saturday, 20 May 2017

Broaching Operation : Principle, Tools, Types, Advantages and Disadvantages

Broaching is a machining process with a special designed multi point cutting tool called broach. This process is widely used in automobile industries for machining various holes, key ways, gears etc. Broaching operation involves linear motion of tool about the work piece. This movement of tool removes material from work piece and provides a desired shape.

Broaching tools involve a large number of progressive teeth which make this operation different from other process. Each tooth takes off a successive layer of the material which removes large material in a single pass. 

One of the major advantages of using this operation in various industries is its ability to give better surface finish and good accuracy with mass production rate. In this article we will discuss about broaching operation Principle, tools, types, advantages and disadvantages.


Let's start the discussion.


Broaching Process:


Principle and Operation:

As we discussed the metal removal process in broaching operation is similar to shaping process except it uses a series of progressive teeth which can cut more material in a single pass. Shaping process requires number of strokes to cut required width of work piece in which each stroke removes a thin layer of metal. This process needs more time which is not beneficial. This limitation is taken off by broaching process by providing a successive series of cutting edges on a rod or bar type cutter. 

Broaching Operation : Principle, Tools, Types, Advantages and Disadvantages

Machine Tool:

Broaching uses a multi point cutting tool having a series of progressive cutting teeth. This tool should have high strength, hardness, cutting speed and wear resistance properties. It is made by high strength tooling material like high speed steel, cemented carbide etc.  This tool is mounted on broaching machine.


Broaching Operation : Principle, Tools, Types, Advantages and Disadvantages
Broaching Tool

Broaching machine is simple in construction. It is used to provide linear motion of the tool and hold the work piece at stationary position. The tool movement can be either vertically or horizontally. According to it, these machines can be classified into two type vertical machine and horizontal machine. Horizontal machine is mostly used for internal machining and vertical machines are used for external and surface machining.

Broaching Operation : Principle, Tools, Types, Advantages and Disadvantages

Types:

Broaching can be classified into following types:

Internal Broaching: 
Internal broaching is mainly used to enlarge holes. This process generally uses pull type broach but for lighter work piece, it sometime uses push type broach.

External Broaching:
External broaching is mainly used to flattening of a surface, machining key ways, slots, grooves on outer part of an object such as shaft etc. This process is also used for gear manufacturing process.

Pull Types Broaching:
A broach which is subjected to tensile force during machining, called pull broach and the type of broaching operation by pull broach is known as pull broaching. This operation prevents misalignment and buckling. The pull broach is usually made in single piece and used for internal broaching.

Push Type Broaching:
Push type broach is usually subjected to compression force during machining. These are made shorter compare to pull type broach and mostly used for external broaching.  

Ordinary Cut Broaching:
Ordinary cut broaching uses ordinary broach in which teeth increases in height gradually from tooth to tooth along length of broach.

Progressive Cut Broaching:
In progressive cut broaching teeth increase in width instead of height along length of the broach.

Solid, Section and Modular Broaching:
Solid broaches are made in single piece which are mostly used for internal broaching. Sectional broaches are made in section by assembling various section of broach. Module broaches are made by various modules assembled in a single unit. It is used for external broaching.

Advantages and Disadvantages:

Advantages:                                                                              
  • High production rate because whole amount of metal is removed in single stroke.
  • High surface finish and better accuracy.
  • Broaching can be used for both internal and external machining.
  • Broaching machines are simple in design and construction.
  • It can be used for mass production.
Disadvantages:
  • High tool cost.
  • This process needs a special design tool for each process.
  • This is not suitable for small batch production.
  • It is only suitable for machining holes and flat surfaces.

This is all about broaching operation, tools, types, advantages and disadvantages. If you have any query regarding this article, ask by commenting. If you like this article, don’t forget to share it. Subscribe our website for more informative articles.
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