INJECTION MOULDING

Injection Moulding Process

It is very similar to pressure die casting. In this process plastic material in a very highly softened state, is forced to flow at high pressure through a nozzle(according to the required shape) into the mould cavity.
The plastic slowly solidifies in the die and then ejected by opening the die. After this the shape of the component is almost in its final form and by this process products can be produced in an extremely fast rate. The cycle times may be in the range of 10 to 30 seconds. Unlike molten metal in die casting process, plastics melts have a very high viscosity and have to be injected with a large force into the hollow mould cavity. More melted plastic most be packed onto the mould during solidification because of avoiding shrinkages in the mould. Injection moulding pressures generally range from 70 MPa to 200 MPa.

Injection moulding is the most widely used plastic-processing method all over the world. Also it can be used to produce wide variety of products. Very complex parts can be produced also whose sizes may vary from very small (50g) to very large (25Kg) with excellent control of tolerances.

So most of the polymers may be type of injection moulded, including thermoplastics, fiber reinforced thermoplastics, thermosetting plastics and elastomers. Structural injection moulding process is also possible in which a core and skin may be made of different polymers. So reaction injection moulding and liquid injection moulding, which are different in manner of mixing ingredients, involve the injection of liquid polyurethane systems that polymerize within the mould. Moulds with moving and unscrewing mandrels are not much unusual, and allow the moulding of parts with multiple cavities and internal and external threads. Additional advantage is that metallic inserts such as screws, pins and strips can also be placed in the mould cavity to become an integral part of the injection moulded product.

Injection Moulding Machine

An injection moulding machine produces components by injection moulding process. So most commonly used machines are hydraulically powered in-line screw machines but electric machines are also appearing and will be more dominant in the market in near future.

The main units of a typical injection moulding machine are the clamping unit, the plasticizing unit, and the drive unit; they are shown in Figure given below. The clamping unit holds the mould. It is capable of closing, clamping, and opening the mould. Its main components are the fixed and moving plates like the tie bars and the mechanism for opening, closing and clamping.

The work of the injection unit or plasticizing unit is to melt the plastic and inject it into the mould. Now the drive unit provides power to the plasticizing unit and clamping unit. Injection moulding machines are often classified on the basis of the maximum clamp force that the machine can generate. This is the force that pushes the two mold halves together to avoid opening of the mould due to internal pressure of the plastic melt in the mould. The clamping force of typical injection moulding machines is in the range of 200 to 100,000 kN.

Injection Moulding Defects

• Ring shaped miniature bands appear on the molded product surface around gates or narrow sections.
• Many times streaks of a silvery white color appear in the material flow direction.
• The material splits off and flows in two or more directions. When the divergent flow fronts converge again, hair-like lines appear where they meet. This results in reduced strength, as well as burn-mark and bubble defects.
• The presence of holes inside moulded products.
• The surface of the moulded product collapses somewhat-something that is particularly common in thicker products.
• Ordinarily a moulded product is removed from the mold by having the product stick to the moving side of the mold when the mold opens, after which the product is ejected using ejector pins. Sticking occurs when the part fails to separate from the stationary mold or from the moving mold. In the case of the latter, the problem could result in broken ejector pins.

Advantages of Injection Moulding

• Almost every polymer can be processed or made.
• High production rate.
• Low labour cost.
• Injection moulded parts have an almost limitless amount of flexibility, you just need to be able to design around certain restrictions outlined below.

Disadvantages of Injection Moulding

• Cost of the machine is very high.
• Tools are costlier.
• Designing of mould is bit difficult and time consuming.

STEERING SYSTEM

FUNCTION AND PRINCIPLE 

The purpose of the steering system is to allow the driver to control the direction of the vehicle by turning the front wheels.
This is done by means of steering wheel, a steering column which transmits the rotation of the steering wheel to the steering gears, the steering gears which increase the rotational force of the steering wheel in order to transmit greater torque to the steering linkage, and the steering linkage which transmits the steering gear movement to the front wheels. The steering system configuration depends on vehicle design (the drive train and suspension system used, whether it is a passenger car or a commercial vehicle, etc.). At present, the rack-and-pinion type and the recirculation-ball types are in use.

Requirements of steering system

The steering system plays, together with the suspension system, an important role in ensuring easy, comfortable driving all the way from the low speed range to the high speed ranges. The drive train transmits the power from the engine to the driving wheels to move the car forward; the steering system steers the car in the desired direction; and the brake system ensures positive, stable slowing and stopping.

1.         Excellent maneuverability. When the car is cornering on narrow, twisting road, the steering system must be able to turn the front wheels sharply yet easily and smoothly.

2.         Proper steering effort. If nothing is done to prevent it, steering effort will be greater when the car is stopped and will decrease as the speed of the car increases.  Therefore, in order to obtain easier steering and better feel of the road, the steering should be made lighter at low speeds and heavier at high speeds.

3.         Smooth recovery. While the car is turning, the driver must hold the steering wheel firmly. After the turn is completed, however, recovery that is the return of the wheels to the straight-ahead position should occur smoothly as the driver relaxes the force with which he is turning the steering wheel.

4.         Minimum transmission of shock from road surface. Loss of steering wheel control and transmission of kickback due to road surface roughen must not occur.

Principle

The relative motion between the wheels of a vehicle at the road surface should be of a pure rolling type so that wear of the tires is minimum and uniform. When the vehicle is moving on a curved path, the steering gear must be so designed that the paths of the points of contact of each wheel with the ground are concentric circular ares. For proper steering the axis of rotation of all the wheels should meet at the instantaneous centre of rotation of the vehicle.. To satisfy this inner wells should be turned through a greater angle.

There are two types of steering gear mechanisms:

1. Davis steering gear.

2. Ackermann steering gear.

The main difference between the two steering gear mechanisms is that the Davis steering gear has sliding pairs, whereas the Ackermann steering gear has only turning pairs. The sliding pair has more friction than the turning pair, therefore, the Davis steering gear will wear out earlier and become inaccurate after certain time. Although, the Ackermann steering gear is not mathematically accurate except in the positions, contrary to the Davis steering gear which is mathematically correct in all positions. However, the Ackermann steering gear is preferred to the Davis steering gear.

PATTERN ALLOWANCES IN FOUNDRY

Pattern:

A pattern may be defined as a model of desired casting which when moulded in sand forms an impression called mould. The mould when filled with the molten metal forms casting after solidification of the poured metal. The quality and accuracy of casting depends upon the pattern making. The pattern may be made of wood, metal(cast iron, brass, aluminium and alloy steel.), plaster, plastics and wax.

Pattern Allowances:

A pattern is always made larger than the required size of the casting considering the various allowances. These are the allowances which are usually provided in a pattern.

1: shrinkage or contraction allowance:

The various metals used for casting contract after solidification in the mould. Since the contraction is different for different materials, therefore it will also differ with the form or type of metal.

2: Draft allowance

It is a taper which is given to all the vertical walls of the pattern for easy and clean withdraw of the pattern from the sand without damaging the mould cavity. It may be expressed in millimeters on a side or in degrees. The amount of taper varies with the type of patterns. The wooden patterns require more taper than metal patterns because of the greater frictional resistance of the wooden surfaces.

3: Finish or machining allowance

The allowance is provided on the pattern if the casting is to be machined. This allowance is given in addition to shrinkage allowance. The amount of this allowance varies from 1.6 to 12.5 mm which depends upon the type of the casting metal, size and the shape of the casting. The ferrous metals require more machining allowance than non ferrous metals.

4: Distortion or camber allowance

This allowance is provided on patterns used for casting of such design in which the contraction is not uniform throughout.

5: Rapping or shaking allowance

This allowance is provided in the pattern to compensate for the rapping of mould because the pattern is to be rapped before removing it from the mould.

Types of Patterns:

The common types of patterns are as follows:

1.Solid or single piece patterns

2. Split or two/multiple piece patterns

3.Match plate pattern

4.Cope and drag pattern

5.Loose piece pattern

6.Gated patterns

7.Sweep pattern

8.Skeleton pattern

9.Shell pattern

10. Segmental pattern

11. Follow board pattern

12. Lagged up pattern

13. Left and right hand pattern

ENGINE AND ITS TYPE

Any device which can convert heat energy of fuel into mechanical energy is known as engine or heat engine. Engine is widely used in automobile industries or we can say that engine is the heart of an automobile. Basically engine may be classified into two types.

Types of Engine:

1. External combustion (E.C.) Engine

It is an engine in which combustion of fuel take place outside of the engine. In this type of engine heat, which is generated by burning of fuel is use to convert the water or other low boiling temperature fluid into steam. This high pressure steam used to rotate a turbine. In this engine we can use all solid, liquid and gases fuel. These engines are generally used in driving locomotive, ships, generation of electric power etc.

Advantages of E.C. engine-

• In these engines starting torque is generally high.
• Because of external combustion we can use cheaper fuels as well as solid fuel.
• They are more flexible compare to internal combustion engines.

2. Internal Combustion (I.C.) Engine

It is an engine in which combustion of fuel take place inside the engine. When the fuel burns inside the engine cylinder, it generates a high temperature and pressure. This high pressure force is exerted on the piston (A device which free to moves inside the cylinder and transmit the pressure force to crank by use of connecting rod), which used to rotate the wheels of vehicle. In these engines we can use only gases and high volatile fuel like petrol, diesel. These engines are generally used in automobile industries, generation of electric power etc.

Advantages of I.C. engine-

• It has overall high efficiency over E.C. engine.
• These engines are compact and required less space.
• Initial cost of I.C. engine is lower than E.C. engine.
• This engine easily starts in cold because of it uses high volatile fuel.

Types of I.C. Engine

I.C. engine is widely used in automobile industries so it is also known as automobile engine. An automobile engine may be classified in many manners. Today I am going to tell you some important classification of an automobile engine.

According to number of stroke:

1. Two stroke engine

In a two stroke engine a piston moves one time up and down inside the cylinder and complete one crankshaft revolution during single time of fuel burn. This type of engine has high torque compare to four stroke engine. These are generally used in scooters, pumping sets etc.

2. Four stroke engine

In a four stroke engine piston moves two times up and down inside the cylinder and complete two crankshaft revolutions during single time of fuel burn. This type of engines has high average compare to two stroke engine. These are generally used in bikes, cars, truck etc.

According to design of engine:

1. Reciprocating engine (piston engine)

In reciprocating engine the pressure force generate by combustion of fuel exerted on the piston (A device which free to move in reciprocation inside the cylinder). So the piston starts reciprocating motion (too and fro motion).  This reciprocating motion converts into rotary motion by use of crank shaft. So the crank shaft starts to rotate and rotate the wheels of vehicle. These are generally used in all automobile.

2. Rotary engine (Wankel engine)

In rotary engine there is a rotor which frees to rotate. The pressure force generate by burning of fuel is exerted on this rotor so the rotor rotate and starts to rotate the wheels of vehicle. This engine is developed by Wankel in 1957. This engine is not used in automobile in present days.

According to fuel used:

1. Diesel engine

These engines use diesel as the fuel. These are used in trucks, buses, cars etc.

2. Petrol engine

These engines use petrol as the fuel. These are used in bikes, sport cars, luxury cars etc.

3. Gas engine

These engines use CNG and LPG as the fuel. These are used in some light motor vehicles.

4. Electric engine

It is eco-friendly engine. It doesn’t use any fuel to burn. It uses electric energy to rotate wheel.

According to method of ignition:

1. Compression ignition engine

In these types of engines, there is no extra equipment to burn the fuel. In these engines burning of fuel starts due to temperature rise during compression of air. So it is known as compression ignition engine.

2. Spark ignition engine

In these types of engines, ignition of fuel start by the spark, generate inside the cylinder by some extra equipment. So it is known as spark ignition engine.

According to number of cylinder:

1. Single cylinder engine

In this type of engines have only one cylinder and one piston connected to the crank shaft.

2. Multi-cylinder engine

In this type of engines have more than one cylinder and piston connected to the crank shaft.

According to arrangement of cylinder:

1. In-line engine

In this type of engines, cylinders are positioned in a straight line one behind the other along the length of the crankshaft.

2. V-type engine

An engine with two cylinder banks inclined at an angle to each other and with one crankshaft known as V-type engine.

3. Opposed cylinder engine

An engine with two cylinders banks opposite to each other on a single crankshaft (V-type engine with 180^o angle between banks).

4. W-type engine

An engine same as V-type engine except with three banks of cylinders on the same crankshaft known as W-type engine.

5. Opposite piston engine

In this type of engine there are two pistons in each cylinder with the combustion chamber in the center between the pistons. In this engine a single combustion process causes two power strokes, at the same time.

6. Radial engine

It is an engine with pistons positioned in circular plane around the central crankshaft. The connecting rods of pistons are connected to a master rod which, in turn, connected to the crankshaft.

According to air intake process:

1. Naturally aspirated

In this types of engine intake of air into cylinder occur by the atmospheric pressure.

2. Supercharged engine

In this type of engine air intake pressure is increased by the compressor driven by the engine crankshaft.

3. Turbocharged engine

In this type of engine intake air pressure is increase by use of turbine compressor driven by the exhaust gases of burning fuel.

MILLING MACHINE OPERATIONS

Milling can perform various operations to convert the work piece into desire shape. It is a very useful machine and mostly used in die making industries. The most popular operation done on milling machine is described below.

Plain milling:

As the name implies, this operation used to get place surface. In this milling, the cutting tool axis is parallel to the machining surface or the face of the machining surface. This operation is very common and done on almost all jobs. This can be carried out on every milling machine.

End milling:

This operation is also used to get plain surface. In this operation, the cutting tool axis is perpendicular to the machining surface or the face of the machining surface. It is also used to slot cutting on the milling axis. 

Gang milling:

As the name is gang, in this milling operation more than one milling cutters are used to machining. It is a horizontal milling operation, more than one cutter with different shape and sizes are fixed at the arbor, which cut the desire shape in one pass. This milling operation can save most of time of milling.

Straddle milling:

In this operation, two or more parallel vertical surface machined in a single pass. In this milling the work piece is situated between the two cutters which can machined the surface vertically. The cutter are fixed on the same arbor and cut the metal in one pass.

Slotting:

In this operation slots are cut by a cutter on the work piece. The slots are in various shapes like circular, rectangular etc. and sizes according to the requirement. 

Angular milling:

In this operation, surfaces which are at an angle to the axis of the cutter, is machined by the rotary cutter.

Milling machine can perform all other common operations like turning, facing, fillet making, chamfering, drilling, gear cutting, planning, slot cutting etc. These are all main milling machine operation.

5 MINDBLOWING FACTS ABOUT LAMBORGHINI AVENTADOR

1. The Aventador’s wing features 3 positions that change with driving conditions and speed. The wing will remain flat against the body (and what a body!) under 50 mph, then lifts 4 degrees until the speed drops back down to 37 mph.
At 81 mph and over, the wing angles 11 degrees, where it looks even cooler. Don’t worry about cops noticing the angle of your wing, if you are going 56 mph in an Aventador—you are going to get pulled over so the officer can examine the awesomeness and ask you 100 questions. You have to expect that.

2. The Aventador is both the most powerful Lambo ever, and the most fuel-efficient! The 6.5-liter V12 packs 691 environmentally conscious horses that get 11/17 mpg city/highway. Not too shabby!

3. The waiting line for an Aventador is approximately 18 months. You could technically almost produce 2  human children while you wait…but good luck transporting them in this car!

4. Yes, it will hit 217 miles per hour, and yes…that bragging right will cost you $393,695 USD

5. Some of the interior controls come from VW/Audi products. The Audi MMI-based infotainment system and steering wheel controls are obvious, while many are disguised so as not to detract from the exotic and special vibe.

WORKING OF HYDRAULIC JACK

Hydraulic jacks and many other technological advancements such as automobile brakes and dental chairs work on the basis of Pascal's Principle, named for Blaise Pascal, who lived in the seventeenth century. Basically, the principle
states that the pressure in a closed container is the same at all points. Pressure is described mathematically by a Force divided by Area. Therefore if you have two cylinders connected together, a small one and a large one, and apply a small Force to the small cylinder, this would result in a given pressure. By Pascal's Principle, this pressure would be the same in the larger cylinder, but since the larger cylinder has more area, the force emitted by the second cylinder would be greater. This is represented by rearranging the pressure formula P = F/A, to F = PA. The pressure stayed the same in the second cylinder, but Area was increased, resulting in a larger Force. The greater the differences in the areas of the cylinders, the greater the potential force output of the big cylinder. 

An enclosed fluid under pressure exerts that pressure throughout its volume and against any surface containing it. That's called 'Pascal's Principle', and allows a hydraulic lift to generate large amounts of FORCE from the application of a small FORCE. 

Assume a small piston (one square inch area) applies a weight of 1 lbs. to a confined hydraulic fluid. That provides a pressure of 1 lbs. per square inch throughout the fluid. If another larger piston with an area of 10 square inches is in contact with the fluid, that piston will feel a force of 1 lbs/square inch x 10 square inches = 10 lbs. 

So we can apply 1 lbs. to the small piston and get 10 lbs. of force to lift a heavy object with the large piston. Is this 'getting something for nothing'? Unfortunately, no. Just as a lever provides more force near the fulcrum in exchange for more distance further away, the hydraulic lift merely converts work (force x distance) at the smaller piston for the SAME work at the larger one. In the example, when the smaller piston moves a distance of 10 inches it displaces 10 cubic inch of fluid. That 10 cubic inch displaced at the 10 square inch piston moves it only 1 inch, so a small force and larger distance has been exchanged for a large force through a smaller distance.