http://www.z-corp.com
To get the idea check this place. For your high tolerances of the 6x6x6 I think you would have to find a place that makes 3-d prints of powdered metal.

3d printing is the state of the art for rapid prototyping. One of these machines would be great for producing blanks to then take moulds from. Or using powdered metal systems to produce the moulds directly for poured resins.

They could not be used to replace the steel moulds for injection moulding. These steel moulds need to be clamped together with a force between 200 and 750 tonnes to with stand the presures involved! They need to be made from very strong steel.

You might be able to use a metal mould from one of these printers to replace the aluminium moulds used for low pressure injection. The problem is that it would probably cost more than getting an aluminium mould made using conventional CNC milling technology.

A lot of the cost involved in getting a mould manufactured is in the design. The puzzle parts have to be redesigned to be suitable for the process, the moulds themselves go through a difficult cycle of design, flow and heat dissipation analysis, redesign... This is a very specialised area.

Some rapid prototyping processes are getting near the point where the parts made are directly useable straight from the machine. You could design a puzzle and have the parts produced to build it directly! Obviously this will be very expensive for a long time to come, but I like the idea of a puzzle replicator sitting somewhere!

Prices are starting to fall, these z-tech printers start at about $30000 + training + installation + tax. That sound a lot but it is about the same as the first colour laser printers. Maybe one day everyone can have a replicator next to there desktop!

Max

My current favourite dream machine is this offering from Japan

http://www.autostrade.co.jp/english/e_darts_eng.html

At only $25000, it is cheaper and than 3d printers. It is also faster and easier to use. And it is almost silent. Would be great to have one for making mould blanks!

Max