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

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

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Workshop Technology
The diaphragm moulding machine is used to

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

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