Manufacturing Engineering: The Forging of Combustion Engine - Essay Example

Introduction The connecting rod translates the rotary motion into reciprocating motion. The extreme ends of the connecting rod are bearing support area. The connecting rod is heavy industrial application, and it widely used in reciprocating compressors and internal combustion engines. The design of the connecting rod is critical to ensure the integrity of the machine, and damage or failure of the connecting rod will result in fatal damage to the machine component. The performance and health of internal combustion engine is driven by the connecting rod. During the design and fabrication, the dimensional vulnerability for the connecting rod is severe, and any misalignment of the connecting rod will affect the health of the engine. The damage to the connecting rod shall not only damage the combustion cylinder, but will also severely damage the bearings and valves. The end gaps for the engine are critical, and this end gap influences the combustion process within the cylinder, any misalignment or fabrication failure of the connecting rod will disturb the proportion of the end gap and will affect the combustion process. The processes undertaken for the fabrication of the connecting rods include C-70 forging process, powder forging process and cracking process. Description of Forging Process The details of the manufacturing procedure is as explained, The material is machined for dimensional adjustment, followed by hot forging. However in some cases prior to hot forging the object is billet heated. The significance of this step is that the desired geometry is achieved. The object is then pierced and trimmed. The object then undergoes shot blasting or shot peening. Once the process is completed, the object is then machined for dimensional accuracy. During machining process the outer contours of the object are machined, followed by the grinding of the surfaces, and drilling of the piston ends. The object then undergoes the process where broaching of crank and piston rods take place. The holes are then drilled into the objects to accommodate bolts, followed by tapping. The fabrication process for the connecting rod also includes the machining fracture splitting groove, fracture splitting and assembly of the connecting rod. The object is machined after every series of steps to ensure and verify the dimensional accuracy. The process is followed by the grinding of the side surfaces, and drilling of crank and piston pin ends is initiated. The process is followed by honing of the crank and piston pin bushes for appropriate surface finish. Manufacturing Procedure Description The material for the fabrication is generally pre-blended. The material then undergoes the process of compacting. The object undergoes pre-form heating; this process is also known as sintering. The object is then forged, and shot peening is conducted on the object. The object is then machined, the process of machining is critical; it describes the exact shape and geometry of the connecting rod along with the tolerances. The machining process includes the grinding of the side surfaces, broaching of crank and piston ends, the drilling of the bolt holes and tapping is also conducted at this stage. The machining of the object is followed by the machine fracture splitting groove, which comprises of the fracture splitting, assembly of the connecting rod, followed by final round of machining. This final round of machining includes the finish grinding of the side faces, the final drilling of the crank and piston pin ends, and the milling of the bearing positioning grooves. After implementation of these steps, the connecting rod has attained its shape and geometry. The insertion of the crank end bearing shells is conducted, followed by the insertion of the small end bearing bush. The honing of the crank and piston pin bushes is conducted, which shall bring reduce the surface roughness. The object is then inspected against the recommended standards (Bruce, 1997). The description of the cracking process has been stated as under, The automobile industries have explored latest procedure for the fabrication and manufacturing of the connecting rod. The process is regarded as reasonable, and provides appropriate shape and geometry. The process is commonly employed for high performance engines, and "the connecting rods are fabricated as single part through precision forging". Material Compatibility The application of the connecting rod is driven by its material of construction. The automobile industries normally fabricate the connecting rods from high-strength material. The connecting rod is exposed to high temperature, and undergoes series of thermal shock. The high strength materials shall provide strength to the component; such materials are suitable for cars having high horsepower and speed. Forged grade alloy is commonly preferred for the fabrication of the connecting rods, the material is composed of nickel and molybdenum and small percentage of manganese, the added composition improves harden-ability and prevents the formation of the "stable oxide". During the manufacturing process of the connecting rod, Copper is added in improve the toughness of the component. The connecting rods are commonly produced from wrought steel bar, this undergoes "extensive deformation during cogging and rolling of the original ingot; and creates the inclusion stringers and thus places of weakness". As per observations, the connecting rod manufactured from wrought steel has dimensional and reliability issues, it has been traced that the variance is based upon the "direction of the piece's rolling and forming history". Material deformation is lower for the parts manufactured from powder forged material, and "therefore mechanical properties of these materials changes significantly, and influences the fatigue resistance positively; the mechanical properties of such materials are improved through better surface finish and finer grain size". Within automobile industry difference of manufacturing practices are common, connecting rods are produced from powder forged material, because "alloying elements such as manganese sulphide increases rod machine-ability, as a route to cost control", and alloys are used for the fabrication of the connecting rods because "better properties as a route to an optimized design and lower cost, thus balancing the performance-cost equation"; the copper is employed as the alloying agent (Kalpakjian, 1997). Fig. Tools for tightening of bolts mounted on connecting rod. Fig. Lathe machine for machining purpose. Fig. Machine designed for manufacturing of connecting rod. Fig. Honing machine Fig. Bearings of connecting rod installed at crankpin and crosshead location. References 1. Kalpakjian & Schmid. Manufacturing Engineering and Technology. Addison-Wesley Publication. 2000. 2. Bruce Gregg et al. Modern Materials and Manufacturing Processes. US Imports & Phipes Publication. 1997. 3. Kalpakjian. Manufacturing Processes for Engineering Materials. Addison-Wesley Publication. 1997. 4. Mikell P Groover. Fundamentals of Modern Manufacturing. Wiley Publication. 1996. 5. GE Thyer. Computer Numerical Control of Machines. Butterworth-Heinemann. 1991. Read More