13637318
Description
Flashcards by Lily Chapman, updated more than 1 year ago
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Created by Lily Chapman
over 6 years ago
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| Question | Answer |
| Key steps in casting | 1) Melt the metal 2) Pour into a mould 3) Let molten metal freeze 4) Remove from mould |
| Advantages of casting | - Creates relatively complex geometries - Can create both internal and external shapes - Produces very larges shapes - Can be suited to mass production (if the geometry is less complex) |
| Disadvantages of casting | - Material limits mechanical capabilities - Poor dimensional accuracy and surface finish - Excess material - Safety issues |
| What are the two forms of mould? | Open mould and closed mould |
| Closed mould casting | Has a complex geometry, requires a gating system leading into the cavity. |
| Features in a closed mould casting | - Risers: A reservoir built to prevent cavities due to shrinkage - Core: Used to create an internal cavity - Runners: Connected channels that transport the molten metal |
| What is an expendable mould process? | The mould must be destroyed in order to remove the casting |
| What is a permanent mould process? | -One where the mould can be reused many times - Open moulds used |
| How does volume to surface ratio affect the casting? | A casting with a higher volume-to-surface area ratio cools and solidifies more slowly than one with a lower ratio |
| How do you minimise the effects of shrinkage? | Design the riser to have a larger volume-to-surface area ratio so that the main casting solidifies first |
| Solidification shrinkage | Shrinkage of a cylindrical casting during solidification and cooling. Causes a reduction in level of the casting |
| Directional solidification | The regions most distant from the molten metal should freeze first. To do this Locate sections of the casting with lower V/A ratios away from the riser, so freezing occurs first in these regions. |
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