Workshop Technology
Aluminium is the best material for making patterns because it is

All of the listed here
Corrosion resistant
Easy to work
Light in weight

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Workshop Technology
A jolt machine is used to

Produce uniform packing of sand in the mould
Ram the sand harder at the pattern face with decreasing hardness towards the back of the mould
Produce uniform sand hardness throughout the mould
Ram the sand harder at the back of the mould and softer on the pattern face

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