How to use this mould making tool:

• Start with only the 'Axis' and 'Master' showing.
• Go to the 'Master' tab, use the tool at http://jsfiddle.net/Riham/yzvGD/embedded/result/ to convert your master STL in to two lists of 'points' and 'triangles' (AKA 'faces'), and paste these lists in to the relevant sections.
• Rotate the master to the desired orientation, and translate it to be approximately centred on the origin.
• Now show the 'Sprue' and 'Riser', and in the Sprue/Riser tab size/position them on the master.
• Now show the 'Mould Bottom' and 'Mould Top', and hide everything else.
• In the Mould tab resize the mould so that it surrounds the master
• Save the 'Mould Bottom' and 'Mould Top' separately and you're done!