Submitted By
Shivek dhar

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ABSTRACT
Gone through a rigorous four weeks training under the guidance of capable engineers and workers of bajaj motors limited, headed by the executive director of the company Mr. J.C Jha in the machining plant situated in Narsinghpur, Gurgaon, Haryana.
The training was specified under the CAMSHAFT department of the machining unit. Working under the cam machining department the basic grinding, scaling and machining was shown on heavy to medium duty lathes planted in the same line where the specified work was undertaken.
Various types of cams were manufactured under the camshaft department in the lathe line including hydraulic cam, solid lifter cam, overhead camshaft, hydraulic roller camshaft etc according to the specifications and requirements of the vehicle for which a particular cam is intended.
The work staff constituted of chief engineers, sub engineers, lathe workers. The training ran smoothly under an efficient and friendly staff with every possible machine and tool shown and overviewed during the training sessions which lasted from the reporting time of 9 am to training closure at 3pm.
INTRODUCTION
MANUFACTURING
CAMSHAFT PARTS:
Main Journals
The Main Journals hold the cam in place as it spins around. Cam bearings are placed around the main journals to prevent the cam from damaging the block in case of malfunction in the engine.
Lobes
The lobes create the cam's lift and duratation. Lift is the distance the valve is open and duratation is how long the valve will stay open. An example would be a cam have a .429 intake lift and a .438 exhaust lift and a duration of 203 degrees on the intake and 212 degrees on the exhaust. (CompCam) The intake valve would be lifted .429" and stay open for 203 degrees of the cams rotation and the exhaust would be lifted .438" and stay open for 212 degrees of the cams rotation.
Ends
The rear end of the cam has a gear that turns the distributor of the engine keeping the ignition timing in tune with the rest of the engine, while the front of the cam bolts up the the timing chain keeping the cam timed with the crankshaft.
TRAINING DEPARTMENT( CAMSHAFT MANUFACTURING AND MACHINING LINE):
As told at BML 'camshaft' is "a shaft bearing integral cam." Webster's defines a 'cam' as a disk or cylinder having an irregular form such that its rotary motion gives to a part or parts in contact with it a specific rocking or reciprocating motion.
In an internal combustion engine, the cam shaft actuates the intake and exhaust valves which feed and evacuate the air/fuel mix in/from the combustion chamber. In the case of an overhead valve engine (OHV), like the V-8 shown at right, the red camshaft causes the yellow lifter to reciprocate up and down. The lifter activates the blue rocker arm which causes the green valve and stem to open and close in a reciprocating fashion.
When an engine is described as OHV (for OverHead Valve) it means that the valves are located at the top of the combustion chamber which is part of the cylinder head. Earlier engine designs had the valves located in the cylinder block alongside the cylinders. These were called side-valve or valve-in-head engines (aka - flatheads) and are not very common anymore. Sometimes the term cam-in-block is added to the description to further specify the location of the cam in an OHV engine. This is used to differentiate the other camshaft configuration - OHC - that also has its valves in the cylinder head.
When an engine has the designation OHC (OverHead Camshaft) it means that the camshaft is located in the cylinder head. If an engine has two overhead camshafts, one to operate the intake valves and the other for the exhaust, it is called a DOHC (Double OverHead Camshaft) engine. It is accepted that the OHC designation also means that the engine has a single camshaft, but the more formal term for it is SOHC (Single OverHead Camshaft). For overhead cam engines (OHC), the camshaft is mounted above the valve and stem and the lobe of the cam directly actuates the stem, causing the valve to open and close at a time and rate determined by the 'profile' of the cam. Cams in OHC engines are driven by a toothed timing belt which loops between the camshaft and crankshaft.
The flow of air in and out of the combustion chamber is timed by the operation of its valve train which consists of one or more camshafts that push follower mechanisms to open spring loaded valves, which would remain normally shut without actuation from the camshaft. Each cylinder of a 4-stroke engine will have at least one intake and one exhaust valve.
A camshaft rotates once for every two revolutions of the engine, or once for every four-stroke cycle (remember, one cycle takes two revolutions to complete). On this shaft are cams or lobes - the egg-shaped bulges which, because their rotation is concentric to the shaft, can perform the function of moving a mechanism called the cam follower up or down on its surface when it rotates. The follower is subsequently moves the engine valves, spring loaded to remain normally shut, up and down as well.
Generally, although there is an overlap during their operation, the valves will follow the following cycle:
Intake Stroke - exhaust valve is closed, intake valve is open to let air into the cylinder.
Compression Stroke - both valves are closed so that no air leaks out of the cylinder, lowering pressurization.
Power Stroke - both valves are still closed so that expanding air can transmit its force completely to the piston.
Exhaust Stroke - intake valve is closed, exhaust valve opens to let the exhaust out of the cylinder.
The operation of intake and exhaust valves overlaps nearing the end of the exhaust stroke because the intake valve actually starts to open before the piston has completed its travel to the top of the cylinder. The overlap is supposed to take advantage of the scavenging effect whereby the sudden rush of air-fuel mixture suddenly entering the combustion chamber forces more of the exhaust gases out of it. Overlapping the intake and exhaust strokes also makes engine run more smoothly.
Valve timing - The sequence of the opening and closing of the valves, overlap, and lift (how much they open the valve) have a great effect on engine performance at a given speed. These parameters are controlled by the cam design (i.e. - the height of the lobes, the angle at which they are positioned on the cam shaft) but until recently, they were fixed for a given engine running at all speeds. The result is varying engine efficiency and output at different speeds. Late model cars, most notably the Hondas, are now featuring variable cam timing that tries to maintain optimum engine performance and efficiency by compensating for the different valve timing required at various engine speeds and loads. Another recent development in valve train design is to use more than one intake and/or exhaust valve per cylinder because the total opening available for the same valve lift is greater leading to better 'respiration' on the part of the engine. Some multi-valve engines have 3 valves per cylinder - one exhaust and two intake (making 12 valves on a 4 cylinder engine). Others have 4 valves per cylinder - two of each (making 16 valves on a 4 cylinder engine). Toyota has even released a 20 valve four cylinder engine that has 3 intake and 2 exhaust valves per cylinder. Increasing the number of valves per cylinder is limited by the complexity of manufacturing the camshafts and followers for those designs, the increased unreliability brought about by introducing so many moving parts in the engine, and the difficulty that will be encountered in making the valves strong enough to withstand engine stresses when they become smaller as their number increases.
In automotive applications, the camshaft is an internal engine part driven by the crank shaft. In a typical internal combustion engine, the same piston used in compressing the air absorbs the energy of expansion and turns it into linear motion. As it travels down its cylinder, it pushes, via a connecting rod linked by pins, against its corresponding crank on the crankshaft which, like a bicycle's converts the linear motion into rotational. From here on in, it is easy to tap the mechanical energy at the flywheel and the crankshaft pulley (located at the rear and front of the engine, respectively) for transfer to the various car components needing it - most importantly, the transmission and drive train which ultimately convert the motion back into linear at the wheels and propel the car forward