Materials and Processes Homework, Chapter 8
Review Questions
Deborah Williams
10052014

1. Die casting needs more machining, 2 types, less likely are the shell process and the Shaw Process. 2. Wax and plaster of paris, jelly, sand. Shell molds use sand and plastic resin. Polystyrene in evaporative casting process. 3. Draft or taper 4. When metal solidifies from liquid it shrinks in inches/feet depending on metal. You have to leave enough extra metal to allow for shrinkage and machining. 5. Cores are the center (void) of a part. Used to produce a desired cavity. Mostly by compacting a sand mixture into the core box and curing it. 6. A crane hook needs to be able to safely handle a lot of weight, so I would use steel because it is stronger than cast iron and cast iron is a lot more brittle. 7. I would choose grey cast iron because the housing is a non-weight bearing part, it just needs to keep grease in and dirt out. The cast iron would be much cheaper to make and it doesn’t need to be remachined after either. Reducing production and labor cost. 8. I would use the shell process of sand casting. It will be much less expensive to make the molds, they can be re-used, and there would be no machining afterwards providing labor savings. 9. Used with permanent molds to make a shell of metal in the mold. Metal is poured in and allowed to solidify for a certain amount of time, used for hollow parts, not necessarily for strength. 10. Centrifugal casting 11. Investment casting; very accurate, significant production rates possible, can use lower temp metals, i.e. Aluminum, zinc, tin and some bronzes. 12. Shell process is the one I would choose because if you need more the mold has a long shelf life, it can be automated reducing labor costs and ferrous and non-ferrous metals can be used. 13. The cupola furnace is used to melt cast iron for foundry work. It uses coke for fuel, and refractory brick and a sand bed for lining. Electric furnaces are also used where electricity is cheaper than fossil fuel. 14. Gas-fired crucible or air furnaces. Larger, reverberatory-type gas-fired furnaces are also used. 15. Cranes, ladles, fork trucks lifting devices and sometimes troughs. 16. It gets reconditioned by machine and prepared for reuse. It gets crushed, screened, magnetically separated and impinging of sand grains against a wear plate at high velocity the dust is vacuumed assay and the clean sand is transported to hoppers for reuse. 17. To protect from the heat involved with working with molten metal and also help protect coming in contact with the molten metal in case there is an explosion. 18. Use proper radii, cooling rates will be different in a thinner section, needs to be as uniform as possible. Use fillets, use an odd number of spokes. 19. Sand was not sorted well enough and the risers where either not used or not filled. There could also be a problem with releasing the gasses. 20. Cold chamber machines have a separate melting and holding furnace; used for higher temps needed to melt metals. The hot-chamber machines has a submerged gooseneck injector and plunger. This type has an oil-fired or gas-fired furnice with a cast iron pot for melting and holding the metal; used for the lower melting point metals like zinc-based and tin-based alloys.