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Manufacturing of Crankshaft & Camshaft

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This is a project report. It is related to Manufacturing Engineering. …

This is a project report. It is related to Manufacturing Engineering.

The file will guide you about the manufacturing of Crankshaft and Camshaft. Crankshaft and Camshaft are used in IC Engines.

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  • 1. Manufacturing Process II Group Member Registration No Rasikh Tariq ME 113006 Muhammad Mubbasher Khan ME 113126 M.Taha ME113085 M. Ali ME 113115 Shoaib Rasheed ME 113061 Abdur Rehman ME 113072 Project Report Manufacturing of Crankshaft & Camshaft
  • 2. Page 1 of 13 Table of Contents Introduction to Crankshaft............................................................................................................................3 Forces Imposed on a Crankshaft...................................................................................................................3 Crankshaft Materials.....................................................................................................................................4 Forging and Casting..................................................................................................................................4 Machining .................................................................................................................................................4 Crankshaft Diagram Terminology ................................................................................................................5 Balancing Holes........................................................................................................................................5 Connecting Rod Journals (Pins)................................................................................................................5 Counter Weights .......................................................................................................................................5 Crankshaft Bolt Hole ................................................................................................................................5 Flywheel/Flexplate Bolt Holes .................................................................................................................6 Key and Keyways .....................................................................................................................................6 Main Journals Bearing & Connecting Rod Journals (Crankpin Journals)................................................6 Oil Passages ..............................................................................................................................................6 Pilot Bearing or Bushing Hole..................................................................................................................6 Radius or Rolled Fillet..............................................................................................................................6 Rear Flange...............................................................................................................................................6 Seal Surface ..............................................................................................................................................7 Snout.........................................................................................................................................................7 Thrust Bearing ..........................................................................................................................................7 Crankshaft Manufacturing using Conventional Machining Processes .........................................................7 Crankshaft Machining Step-by-Step.............................................................................................................7 General Cutting Machines Terminology...................................................................................................7 Requirements With Regard to the Ceratizit Inserts...................................................................................8 Basic Characteristics Of Ceratizit Inserts .................................................................................................8 Steps in The Machining Of A Crankshaft.................................................................................................8 Riffle/Gun Drilling....................................................................................................................................8 Surface Treatment Processes on Crankshaft.................................................................................................8 Crankshaft Balancing....................................................................................................................................9 Harmonic Balancer .......................................................................................................................................9 Other Processes of Crankshaft Manufacturing .............................................................................................9 Casting ......................................................................................................................................................9 Forging....................................................................................................................................................10
  • 3. Page 2 of 13 Comparison of Forged Crankshaft versus Cast Crankshaft....................................................................10 Different Organization Manufacturing Crankshafts ...................................................................................10 Introduction to CAM...................................................................................................................................11 Cam Shaft ...................................................................................................................................................11 Material Selection for Cam Design.............................................................................................................11  Chilled Iron Castings: .....................................................................................................................11  Billet Steel:......................................................................................................................................11 Importance of Cam .....................................................................................................................................11 Types of Cam Failure..................................................................................................................................12 Dry Wear.................................................................................................................................................12 Contact Fatigue.......................................................................................................................................12 Diesel Engine Cam Galling ....................................................................................................................12 Reasons and Causes for Cam Failure..........................................................................................................12 Incorrect Break-In Lubricant ..................................................................................................................12 Correct Break-In Procedure ....................................................................................................................12 Spring Pressure .......................................................................................................................................12 Manufacturing of Camshaft ........................................................................................................................13 Forging Process to Manufacture Camshaft.................................................................................................13 Machining Process Sequence to Manufacture Camshaft............................................................................13 Surface Finishing Process on Camshaft......................................................................................................13
  • 4. Page 3 of 13 Introduction to Crankshaft The crankshaft, sometimes abbreviated to crank, is responsible for conversion between reciprocating motion and rotational motion. In a reciprocating engine, it translates reciprocating linear piston motion into rotational motion, whereas in a reciprocating compressor, it converts the rotational motion into reciprocating motion. Crankshaft (red), pistons (gray) in their cylinders (blue), and flywheel (black) It is typically connected to a flywheel to reduce the pulsation characteristic of the four-stroke cycle, and sometimes a torsional or vibrational damper at the opposite end, to reduce the torsional vibrations often caused along the length of the crankshaft by the cylinders farthest from the output end acting on the torsional elasticity of the metal. Crankshaft used in high production automotive engines may be either forged or cast. Forged crankshafts are stronger than the cast crankshaft, but they are more expensive. Casting materials and techniques have improved cast crankshaft quality so that they are used in most production automotive engines. Forces Imposed on a Crankshaft The obvious source of forces applied to a crankshaft is the product of combustion chamber pressure acting on the top of the piston. High-performance, normally-aspirated Spark-ignition (SI) engines can have combustion pressures in the 100-bar neighborhood (1450 psi) That level of force exerted onto a crankshaft rod journal produces substantial bending and torsional moments and the resulting tensile, compressive and shear stresses. However, there is another major source of forces imposed on a crankshaft, namely Piston Acceleration. The combined weight of the piston, ring package, wristpin, retainers, the conrod small end and a small amount of oil are being continuously accelerated from rest to very high velocity and back to rest twice each crankshaft revolution. FIGURE 1: A CRANKSHAFT, FLYWHEEL WITH A PISTON USING A CONNECTING ROD
  • 5. Page 4 of 13 A piston engine is a vibration machine. It generates horizontal and vertical shaking vibrations, fore and aft rocking moments, and torsional excitations galore. The torsional component of the output is the subject of this discussion. There is a rotating mass associated with each crankpin, which must be counteracted. Crankshaft Materials The steel alloys typically used in high strength crankshafts have been selected for what each designer perceives as the most desirable combination of properties. The alloying elements typically used in these carbon steels are manganese, chromium, molybdenum, nickel, silicon, cobalt, vanadium, and sometimes aluminum and titanium. Each of those elements adds specific properties in a given material. The carbon content is the main determinant of the ultimate strength and hardness to which such an alloy can be heat treated. Different Procedures to Manufactures Crankshaft Forging and Casting Crankshafts can be forged from a steel bar usually through roll forging or cast in ductile steel. Today more and more manufacturers tend to favor the use of forged crankshafts due to their lighter weight, more compact dimensions. Machining Crankshafts can also be machined out of a billet, often a bar of high quality vacuum remelted steel. Though the fiber flow (local in homogeneities of the material's chemical composition generated during casting) doesn’t follow the shape of the crankshaft (which is undesirable), this is usually not a problem since higher quality steels, which normally are difficult to forge, can be used.
  • 6. Page 5 of 13 Crankshaft Diagram Terminology Following diagram shows the terminology of a crankshaft generally identified by manufacturing industry. Balancing Holes When the crankshaft rotates, at high RPMs, vibration can occur. Balancing the crankshaft, which requires that weight is either removed or added to the crankshaft, is often accomplished. Connecting Rod Journals (Pins) Connecting rod journals, often referred as pins are the part of the crankshaft where the connecting rods attach to. There is one rod journal for each piston/connecting rod in the engine. These journals have a machined surface so the connecting rod bearings can move smoothly as the crankshaft rotates. To maintain adequate timing, the connecting rod journals maintain a specific degree apart from each other, which does vary for specific engines and ignition firing orders. Counter Weights Counterweights adds weight to the crankshaft so that it reduces vibration at any RPM or position. Crankshaft Bolt Hole The crankshaft bolt, or as is commonly referred to as a balancer bolt, is used to secure the harmonic balancer (damper) to the crankshaft. FIGURE 3: FLEXPLATE BOLT HOLE, PILOT BLUSING HOLE AND CRANKSHAFT BOLT HOLE FIGURE 2: CRANKSHAFT DIAGRAM TERMINOLOGY
  • 7. Page 6 of 13 Flywheel/Flexplate Bolt Holes A flywheel or flexplate contains a ring gear which a vehicle’s starter turns when the ignition is turned into the starting position. Regardless of what type of transmission the vehicle has, these bolt holes are used to secure either the flexplate or flywheel to the crankshaft. Key and Keyways The crankshaft key, which fits into the keyway as a press fit, is a significant part of the crankshaft as it aids to align the crankshaft in the proper position. Main Journals Bearing & Connecting Rod Journals (Crankpin Journals) The main journal bearings hold the crankshaft in place and prevent the forces created by the piston and transmitted to the crankshaft by the connecting rods from dislodging the crankshaft. The connecting rod bearings help resolve the reciprocating linear motion of pistons to the rotating motion of the crankshaft by means of crankpin on the crankshaft. Oil Passages Oil passages on the crankpin and main journals help to feed oil directly to the bearings. The thin film of oil that forms between the bearings and the journals is what protects the crankshaft from damage. Pilot Bearing or Bushing Hole Manual transmissions utilize an input shaft that aids in the alignment of the clutch assembly to the flywheel. The input shaft alignment is made possible with the use of a pilot bearing or bushing, which is normally a pressed fit into the hole on the. Because manual transmissions use a torque converter to connect the flexplate to the transmission. Radius or Rolled Fillet On each journal, where the bearing surface meets the counterweight, there is a radius or rolled fillet. Although small and typically measured with a radius gauge, this area adds a great deal of strength to the crankshaft. By minimizing 90 degree angles on each journal, the force of the combustion process is evenly distributed throughout the crankshaft. Rear Flange The rear flange of the crankshaft provides a strong surface area to accept the flexplate or flywheel bolts. The rear flange is often machined to help in balancing crankshafts as well. FIGURE 4: SEAL SURFACE, SEAL SURFACE OIL GROOVES, CRANK BOLT, KEY AND WASHER
  • 8. Page 7 of 13 Seal Surface The seal surface on a crankshaft is responsible for helping to keep oil within the engine. Snout The crankshaft snout, or nose as many people refer to it as, provides a location for the crankshaft timing gear sprocket and harmonic balancer to attach to. The crankshaft snout contains a keyway and key so that the sprocket and balancer may be accurately positioned to ensure proper timing and balance. Thrust Bearing A crankshaft must also have a limited amount of backward and forward motion, which is commonly referred to as endplay. Most crankshafts are installed with .005-.010” of endplay, and the thrust surface of the crankshaft is what prohibits excessive endplay. Crankshaft Manufacturing using Conventional Machining Processes Billet crankshafts are fully machined from a round bar of the selected material. This method of manufacture provides extreme flexibility of design and allows rapid alterations to a design in search of optimal performance characteristics. In addition to the fully-machined surfaces, the billet process makes it much easier to locate the counterweights and journal webs exactly where the designer wants them to be. This process involves demanding machining operations, especially with regard to counterweight shaping and undercutting, rifle-drilling main and rod journals, and drilling lubrication passages. The availability of multi-axis, high-speed, high precision CNC machining equipment has made the carved-from-billet method quite cost-effective, and, together with exacting 3D-CAD and Finite Element Analysis design methodologies, has enabled the manufacture of extremely precise crankshafts which often require very little in the way of subsequent massaging for balance purposes. Some years ago, there was an effort at Cosworth to build a Formula One crankshaft by welding together various sections, which comprised the journals, webs and counterweights. The purported intent was to be better able to create exactly the shape and section of the various components, thereby reducing moment of inertia while achieving the same or better stiffness. While no one was willing to reveal details about the effort, it is rumored to have been run once or twice then abandoned due to the high cost and complexity compared to the measurable benefits. Crankshaft Machining Step-by-Step General Cutting Machines Terminology  Cutting speeds (up to 260 m/min.)  Planetary milling cutters with diameters ranging from 350 to 750 mm  Dry machining leading to high temperature stress on the cutting material  High number of teeth of the planetary milling cutters (40 up to 200 teeth)
  • 9. Page 8 of 13  Main bearing and webs are machined at the same time with two planetary milling cutters  Due to the length and the relatively small diameter of the crankshaft, machining stability is low. Requirements With Regard to the Ceratizit Inserts  High resistance to thermal shock.  Consistent quality of the cutting material providing process security at the customer  Long tool life, therefore low tool changing costs.  Smooth surface thanks to lower frictional heat and wear Basic Characteristics Of Ceratizit Inserts  Geometry of the insert is mainly defined by the profile of the crankshaft.  Ceratizit chooses the insert to be applied as well as the geometry of the cutting edge Steps in The Machining Of A Crankshaft  Cutting and centering.  Internal and external profile milling of the pin of the bearing and connection rod bearing pin.  Turning of the main bearing pins and the end parts.  Deburring.  Solid carbide deep hole drilling Riffle/Gun Drilling Gun drilling is a process that produces deep, straight holes in a variety of materials. A gundrill tool differs from a conventional twist drill by its unique head geometry; a standard gundrill has a single effective cutting edge. Guide pads burnish the hole while drilling, allowing the hole to maintain straightness. The result of this burnishing activity is a very round hole with a precision diameter. Surface Treatment Processes on Crankshaft Surface treatments are used to improve wear characteristics of crankshaft journals. Surface treatments only affect a shallow area and if the crank is ground it must be re-treated to retain the same surface hardness. Generally following surface treatment processes are used:  Nitriding  Induction Hardening  Deep-Case Nitriding An older heat-treating process that hardens the material to a greater depth. Deep case- hardened cranks often can’t be repaired.  Hard Chroming
  • 10. Page 9 of 13 An electrolytic process that deposits chromium on metal. Hard chroming creates a 0.010- to 0.030-inch-thick surface that improves wear, corrosion, and heat resistance.  Crankshaft Polishing This is a necessary step to prepare the crankshaft for the assembly of an engine. Crankshaft Balancing As the cylinders in engine fire, they move up and down, generating torque that's transferred into the crankshaft. Each time a cylinder fires, a force acts upon the crankshaft, causing it to twist. But this force also causes vibrations in the crankshaft, and at certain frequencies, the shaft can resonate, which makes the vibrations even worse. These vibrations from the engine can become too much for the crankshaft to bear, causing it to fail. So, it is very important that a crankshaft must be balanced properly, this is the reason that the counterweights are added or crankshaft is grinded very precisely to make it perfectly balanced. Harmonic Balancer Harmonic balancer is a circular device, made of rubber and metal, is bolted at the front end of the crankshaft to help absorb vibrations. It's usually connected to the crank pulley, which drives accessories like the air conditioner. The rubber inside the pulley is what actually absorbs the vibrations and keeps them at a safe level. In essence, the device is designed to help prevent crankshaft failure. It's also sometimes called a "dampener." However, the rubber material can deteriorate over time. So if your harmonic balancer is going bad, you could get rough engine vibrations, a cracked crankshaft, or even a serpentine belt (multi-vee, or multi-rib belt) that gets thrown off its track. Replacing one is excellent preventative maintenances. Other Processes of Crankshaft Manufacturing A crankshaft can be manufactured by casting, forging or machining. Manufacturing by either of methods results in different properties which are discussed below. Casting A cast part is made from material being forced or poured into a mold. The part will have thicker and thinner areas, and takes shape from this molten state. Therefore the material must have good castability. One of the main properties of a material that has good castability is that it does not form internal voids on cooling. As a material cools, it shrinks. If there are thick and thin areas, the thick areas will cool slower than the thin ones, and the thick areas can form voids, and the part can warp out of shape or crack, or worse, form internal stresses that come out when the part is used, then crack later. A cast crankshaft is “weaker” because it is made from cast or nodular
  • 11. Page 10 of 13 cast iron, not really because it is cast. It is cast because the material is very castable, but is impossible to forge. Forging Forged part is made from a chunk of metal. It is then usually heated, and it is pounded into shape in a forging die. The extra metal oozes out from between the forging dies and must be ground off. This is why there is a wide parting line on crankshaft when forged. A forged crank is stronger because of the steel it is made from. It could be an alloyed 4340 steel with .40% carbon, or a weaker 1020 steel that is not alloyed and has less (.20%) carbon. The steel used to make a forged part must have good forgability. It is forged because the material is not very castable. The forging process does add grain flow and add strength to the part as above, but it is primarily the higher material Ultimate Tensile Strength (UTS) and Yield Strength (YS) that make it strong. Now a forged part generally is more ductile than a cast part. 4340 steel is probably the most common material for connecting rod and crank forgings. One of the reasons is its balance of high tensile strength, ductility, and cost. It also responds positively to heat treating, so the surface hardness and the overall material tensile strength can be increased after machining. It is cheaper to machine the part when soft, then heat treat it hard. Comparison of Forged Crankshaft versus Cast Crankshaft  A forged crankshaft is recommended for high power transmission and high rpm applications whereas a cast crankshaft can tolerate less power  Cast cranks are more economical, but are more brittle and susceptible to breakage  Cast cranks are generally lighter than a comparable forged one  A cast crank will have a narrow parting line whereas a forged one will have a wide parting line  Forged crankshaft has higher cost than casted one  In fatigue loading the crack growth rate of the forged steel crankshaft is slower than the ductile cast iron crankshaft  At 106 cycles the fatigue strength of forged steel crankshaft is 36% higher than the fatigue strength of the ductile cast iron crankshaft Different Organization Manufacturing Crankshafts  International Crankshaft Inc in Georgetown KY - Companies.  Crankshaft Rebuilders Inc in Sanford FL – Companies.  Hind Autocranks Pvt. Ltd.  Crankshaft Manufacture - Lahoma Engineers Ltd.  NSI Crankshaft.
  • 12. Page 11 of 13 Introduction to CAM A cam is a mechanical device used to transmit motion to a follower by direct contact. The driver is called the cam and the driven member is called the follower. In a cam follower pair, the cam normally rotates while the follower may translate or oscillate. A familiar example is the camshaft of an automobile engine, where the cams drive the push rods (the followers) to open and close the valves in synchronization with the motion of the pistons. Cam Shaft A shaft having one or more cams attached to it, and used to operate the valves of an internal- combustion engine. Combustion engines, rotating shaft with attached disks of irregular shape (the cams), which actuate the intake and exhaust valves of the cylinders. The cams and the camshaft are usually formed as a unit, with the cams set at angles so as to open and close the valves in a prescribed sequence as the cams rotate. A separate camshaft for each row of cylinders is driven by gears or chains from the crankshaft. Material Selection for Cam Design Camshafts can be made out of several different types of material. These include:  Chilled Iron Castings: this is a good choice for high volume production. A chilled iron camshaft has a resistance against wear because the camshaft lobes have been chilled, generally making them harder. When making chilled iron castings, other elements are added to the iron before casting to make the material more suitable for its application.  Billet Steel: When a high quality camshaft is required, engine builders and camshaft manufacturers choose to make the camshaft from steel billet. This method is also used for low volume production. This is a much more time consuming process, and is generally more expensive than other methods. However the finished product is far superior. When making the camshaft, CNC lathes, CNC milling machines and CNC camshaft grinders will be used. Different types of steel bar can be used. These types of camshafts can be used in high- performance engines. Importance of Cam Since the inception of the automobile industry, high speed has always been an important requirement of the vehicles. Due to this fact, where on one side manufacturers focus on fuel efficiency and environmental impact, they are also bound to meet the demands of extremely high power for certain applications. The problem that we are concerned about here is the induction of oscillations in the camshaft when engine is running at steady high speed of 5000 rpm and above, like in racing cars, for a significant vehicle mileage. These oscillations are caused by cyclic variations in the resisting torque acting on the camshaft due to valve spring load. If the frequency of these oscillations is close to surge frequency there may be premature failure of the spring.
  • 13. Page 12 of 13 Types of Cam Failure Dry Wear The wear was determined as weight losses of the samples as a function of wear test duration and loads. The variation of camshaft profile was captured by level sensor during the wear. The profile variation was continuously monitored on the computer screen throughout the tests. It was found that the wear mechanisms of the cam surface change along the contact surface. The maximum wear value was obtained just to cam tip. Contact Fatigue Generally, one surface moves over the other in a rolling motion as in a ball rolling over a race in a ball bearing. The contact geometry and the motion of the rolling elements produce an alternating subsurface shear stress. Subsurface plastic strain builds up with increasing cycles until a crack is generated. Diesel Engine Cam Galling Heavy duty diesel engines typically use roller followers in contact with the cam to reduce friction and accommodate high Hertzian stresses. When the rolling contact slips into sliding, cam galling can occur that may lead to major cam failures. Oil traction has been identified as a possible source to cause slipping. Reasons and Causes for Cam Failure Incorrect Break-In Lubricant Use only the Moly Paste, Part Number 99002-1 that is included with the cam. This Moly Paste must be applied to every cam lobe surface, and to the bottom of every lifter face of all flat tappet cams. Roller tappet cams only require engine oil to be applied to the lifters and cam. Correct Break-In Procedure After the correct break-in lubricant is applied to the cam and lifters fill the crankcase with fresh non-synthetic oil. Prime the oil system with a priming tool and an electric drill so that all oil passages and the oil filter are full of oil. Pre-set the ignition timing and prime the fuel system. During this break-in time, verify that the pushrods are rotating, as this will show that the lifters are also rotating. If the lifters don't rotate, the cam lobe and lifter will fail. Spring Pressure Normal recommended spring seat pressure for most mild street-type flat tappet cams is between 85 to 105 lbs. More radical street and race applications may use valve spring seat pressure between 105 to 130 lbs. This high spring pressure causes the heat created at the cam to be transferred to the roller wheel, resulting in its early failure.
  • 14. Page 13 of 13 Manufacturing of Camshaft It can be produced by different methods  Forging  Machining Forging Process to Manufacture Camshaft In this process the metal rod is produced to exact size of the camshaft, and is then forged under high pressure presses having shape of camshaft (in this very high pressure hammers (punches) are required), this is very difficult method because 1 wrong step can lead to big disaster (can cause damage to machine (cost of machine is very high), can take life of worker). Machining Process Sequence to Manufacture Camshaft  It starts with a forged metal rod of specified length.  Then lathe machine cut and machine it to some of its shape.  Then the special grinding machine took place.  The grinding machine contains a head for the master pattern of the cam shaft.  The pattern is place in the head and the machine is turned on the wheel rotates and follow the master cam design converting it on the pre finished form of the camshaft.  Camshaft slowly takes shape in this machine.  Then specialize tool check the finished part for flaws and also check its dimensions and the rise and fall of the each and every cam (usually 16 cams are on 4 cylinder engine). Surface Finishing Process on Camshaft Then the finished product further goes for surface treatment.  First step for surface treatment is to protect the bearing from the chemical reacting that is going to take place after this step, so for this the bearing are covered with protective layer of some dye.  Then the cam is 1st rinsed in warm water, and is then placed in weak phosphorous acid for surface treatment, in this the acid etches the metal at microscopic level which help metal to resist the wearing and rusting.  After which the cam is finally examined for flaws and final adjustment are made, the dye which is used to coat the bearing are removed with help of buffing wheel and then the acid residue was removed by worker bye thorough cleaning.  Then the camshaft is flooded with lubricating oil, excess oil drain out and some of it left on it helps in prevention of rusting while on the way to shop/car factory.