Initial drawings for the tool are published here:

The cost for the production of one heated mould is approximately $300aud / $200usd

No other tools are required to produce a brick, however shredding your plastic, using an extruder to fill the mould, and mechanical assistance to close the mould will speed up production. Early experimental bricks were made by standing on the mould to close it.

I'm currently building a mechanical ram and jig with components I had on hand, as I only need one of them to produce bricks from several moulds. I'm using mechanical compression with the intent of measuring the stroke, and resistance from the viscous plastic, so as to document this for more efficient machines later down the track.

Full details about the project will eventually be published here:

My objective broadly in the project is to enable more people to be able to build formwork suitable for sustainable building techniques, in particular Rammed Earth, which enables more energy efficient buildings, with low embodied energy. Formwork manufacturing is one of two primary barriers to producing Rammed Earth structures. The second is labour intensivity. I aim to produce number of robotic and mechanical aids, designed to work with this formwork, to reduce the labour requirements.