Steven Tran
Manufacturing engineering Engine block By Steven Tran
Steven Tran
Victa 2 stroke engine block Introduction The engine block is an important component of the engine in any machinery as it houses majority of the engine components allowing it to function properly. The engine block is designed with key requirements: high strength and cost. Mass production of engines requires methods to c hoose most appropriate materials and quickly manufacture with least cost involved. The engine block studied in this report is identified as to what material it is composed of and the manufacturing process it undergoes to achieve the final result. These manufacturing processes are performed in order from sand-casting to drilling and threading. Material used The Victa 2 stroke engine block was built from Cast iron. Many manufacturers use cast iron due to its relatively high abundance and ease of manufacture which relates to lower costs. Its high strength property influences the lasting life o f the vehicle whereas as its high heat resistivity prevents it from deformation when the vehicle is in operation.
Figure 1.
Manufacturing processes of engine block (in order)
1. Sand casting The grainy surface texture of the engine block is a result from the process of sand casting. This is performed by packing sand/clay to form a mold around a desired pattern in a flask. It is necessary for the mold to consist of gating system, pouring cup, riser and Sprue. The pouring cup funnels melted iron to the sprue preventing air from entering the casting which then enters the gate (filling up the mold. The purpose of the riser is to feed liquid metal to the shrinking casting as it cools preventing a number of defects. . The metal is allowed to solidify before Kalpakjian, S., Schmid, S.R. 2011, Manufacturing Engineering and separating it from the sand cast. The big Technology, Prentice Hall, pp 10-7. cylindrical crank hole and the bearing housings evident in the figure 1(a) were also formed during the sand casting by inserting a specific core pattern into the mold to create such cavities. Sand casting is performed widely by many manufacturers since it can be done quickly and at low costs, considering the ability to continuously reuse the mold. Hence this reasons for why most engine blocks are completed through sand casting. 2. Milling By observing the evenly cut edges of the engine block and the silver lining on the thread entrance, milling proc ess is evident. The outer edges which were milled flat enable the engine block to be easily placed in a fixture so other components can be machined.
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Milling is performed by cutting away the material (metal) using a multiple-tooth cutter rotating past the work piece. Milling can be done on different axis. This ranges between flat, angular or curved. In the case of the Victa engine block, face milling straightened or flatten the surface as well as carved out the thin edges. Milling is another commonly used in the industry as it can be operated by a computer, making cutting very accurate. The high speed rotation enables it to perform the task at a reasonably fast rate hence reasons as to why this process is used for mass production. 3. Drilling With the outer edges milled, the engine block can be placed in a fixture. The small holes such as the thread/screw hole is initially drilled using different drill bits of different sizes for different diameters. Drill bits of different sizes rotating at speeds 20-60m/min for iron run through the engine block producing the holes. As previously mentioned, cylindrical crank case was not drilled considering it impractical to drill a
hole of such size. Drilling is another process commonly implemented in manufacturing as it is quick and easy. However when drilling the i nsides are not smooth or constant in thickness, this problem is resolved by boring.
4. Boring Boring operates with a pre-existing hole in which case was created during the sand cast or the drilling. Greater accuracy of the diameter of holes in the engine block is achieved through boring rather than drilling. Accuracy of the holes is a necessity in manufacturing the engine block for example, the piston chamber needs to be of great accuracy and smoothness so that the piston pumps efficiently and is not damaged by the walls of the chamber. A smoother finish is also obtained from boring hence can be seen in the crank case and the
combustion chamber.
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5. Threading After the smooth finish from boring, the small holes which are designated for bolts are threaded. This is achieved by using internal threading tools called “taps” (a cylindrical piece with threads at one end). The internal threads are created by turning the tap in a clockwise motion into the hole.
Critical and non- critical parts of the engine block Critical: - Piston chamber - Crank shaft
Non-critical: -
Screw holes
Conclusion
The Victa 2 stroke engine block was manufactured by the processes of sand casting iron, milling, drilling and boring. These processes are cost efficient methods to produce quality products for customers.
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Index
Boring..........................................................................................................................2,3
Cast iron......................................................................................................................1
Drilling.........................................................................................................................2
Milling……………………………………………………………………………………………………………………. 2
Reference th
Kalpakjian, S., Schmid, S.R. 2011, Manufacturing Engineering and Technology, 6 edn , Prentice Hall. Wikipedia. 2011, ‘Sand Casting’, viewed 4 September 2011, Custom part, 2008, ‘ Milling’, viewed 7 September 2011, http://www.custompartnet.com/wu/milling Pictures of engine block provided by Rohan Guruji
