Question 1
A car company has a requirement of 100,000 hubcaps for their car assembly operation annually. A hubcap is a cover for the wheel hub of a motor vehicle, and is largely a non load bearing part, and made with metallic alloys or non-metallic materials. A typical hubcap (dimensions not important) is shown in the Figure, which costs about $7 per part. Using the principles of manufacturing processes and with the assistance of the Table provided:
a) Provide a list of 5 design considerations (geometry, finish, mechanical properties, etc.) for manufacturing a hubcap for automobiles. Based on your considerations, recommend i) material, and ii) manufacturing process to be used to manufacture the hubcaps. Provide clear criteria (cost, properties, density, formability, shape, complexities, etc.) to support your choice of material/manufacturing process.
b) For the selected manufacturing method, show (i) necessary material preparation, (ii) the design of the mould or tooling using a freehand sketch, and (iii) stepwise details of processing and finishing operations used to manufacture the hubcaps.
Figure. A generic hubcap used in a motor vehicle (highlighted).
Table: Cost and Properties of Engineering Materials.
Question 2
1. Define the bulk deformation process of Extrusion, and list the 2 main types of extrusion. Explain the relationship between Ram Stroke and Ram Pressure in the 2 main forms of extrusion, and describe the major factors that influence Ram Pressure? List and explain briefly the different defects in extrusion products, and describe how these defects can be minimized?
2. Define the phenomenon of Springback in sheetmetal forming, and provide a detailed explanation of the methods used to compensate for springback in finished sheetmetal products.
3. Why are the parts manufactured using powder metallurgy of near net shape? For mixtures of dissimilar metal powders, explain how (a) blending/mixing, and (b) compaction are carried out before sintering. Explain how (i) blending/mixing and (ii) compaction steps influence the (a) sintering step and (b) porosity development in the processed part.