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30 Cards in this Set
- Front
- Back
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Manufacturing |
To make or process a raw material into a finished product |
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3 fundamental ways to create objects |
Subtractive Formative Additive |
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Subtractive |
The process where a volume of material is worked to reduce its physical size into the shape/geometry of the desired object - milling, carving, filing |
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Formative |
A volume of material is worked to change its shape (e.g by applying heat and force) to that of the desired object, such as squeezing, pressing or pouring into a mould |
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Additive |
The process whereby material is added selectively to build up the object into the desired geometry |
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Metal categories |
Ferrous Non ferrous |
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Ferrous metals |
Mainly made of iron with smaller amounts of other metals or elements added in order to give the correct properties Almost all are magnetic and can be picked up with magnets These metals rust or oxidise if not treated as they contain irom |
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Non ferrous metals |
All other metals - don't contain iron Not magnetic, can't be attracted by magnets, metals don't oxidise as they don't contain iron E.g- Al, Cu, Pb, Zn, Sn (tin) |
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Pure metals |
Consist of a single element, so metal only, most common - Al/Cu/Zn/Fe/Pb/Sn/gold/silver |
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Metal alloy |
A mixture of 2 or more pure elements Pure metals sometimes lack certain required properties, so to create these properties a number of pure metals are combined together |
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Phase |
A form of material having characterisitc structure and properties A form of material with identifiable composition, definable structure, and distinctive boundaries which separate it from other phases E.g- solid/gas/liquid |
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Equilibrium phase diagrams |
Map the natural tendencies of a material/material system to show the equilibrium for all possible conditions Most common is temperature-composition |
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Primary variables for phase diagrams |
Temperature Pressure Composition |
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Degree of solubility |
Determines properties I - Two metals completely soluble in each other II - Two metals soluble in liquid state and insoluble in solid state III - Two metals soluble in liquid state and partially soluble in solid state |
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Eutectic alloy |
Composition where solidus and liquidus are at the same temperature |
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Casting of metals |
Process in which molten metal flows by gravity or other force into a mould where it solidifies in the shape of the mould cavity Name of part made in the process |
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Casting steps |
1) Melt the metal 2) Pour it into mould 3) Let it freeze 4) Remove from mould |
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Casting Advantages |
Can create relatively complex component geometries - sacrificial moulds Can create external/internal shapes Some casting processes are net shape, others are near net shape Can produce very large parts Some casting methods are suited to mass production- less complex component geometries |
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Casting disadvantages |
Different disadvantages for different casting processes Limitations on mechanical properties Poor dimensional accuracy and surface finish for some processes Excess material used in casting process that need to be reused Safety hazards to workers due to hot molten metals and related environmental problems |
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Parts made by casting |
Large parts/components mponents Small parts/componentsCasting usually performed in a foundry by foundrymen Casting usually performed in a foundry by foundrymen |
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Large parts/components |
Engine blocks for automotive vehicles, wood burning stoves, machine frames... |
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Small parts/components |
Dental crowns, jewellery, pots, pans statuettes... |
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2 types of casting mould |
-open mould = container in shape of desired part -closed mould = mould geometry is more complex and requires gating system (passageway) leading into the cavity (the geometry of the part) |
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Cores in moulds |
Core held in place in mould cavity by chaplets Possible chaplet design Casting with internal cavity |
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Categories of casting process |
Expendable mould processes - mould destroyed (sacrificial) to remove casting Permanent mould processes - mould can be reused many times to produce many castings |
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Expendable mould processes |
Mould materials- sand, plaster... Advantages- complex component geometries possible Disadvantages- production limited by mould manufacture time |
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Permanent mould processes |
Mould materials- metal, ceramic refractory material (less common) Advantages- reusable, higher production rates Less complex geometries (need to open mould) |
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Heating metal |
Furnace is sufficient for casting Heat required is sum of- 1) heat to raise temperature to melting point 2) heat of fusion to convert solid to liquid 3) heat to raise molten metal to desired temperature for pouring |
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Pouring the molten metal |
Metal must flow into all regions of the mould including the main cavity, before solidifying- depends on: Pouring temperature Pouring rate Turbulence |
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Rate of freezing |
Depends on heat transfer into mould and thermal properties of metal |
