The Mass Fabricator is an end-game Industrial Craft 2 machine. It requires 1,000,000 EU to generate a single item, UU-Matter. UU-Matter can be used to craft many different items, including some that are otherwise unattainable (such as Iridium Ore and water and lava source blocks). Sending a redstone signal to the Mass Fabricator will stop it from consuming power.
A Mass Fabricator can be provided with Scrap to lower the amount of EU required to produce one unit of UU-Matter by a factor of six. This means the Mass Fabricator only requires 166,666 EU to generate one UU-Matter.
Currently, the Mass Fabricator, the Oil Fabricator, and the Terraformer are the only machines that are capable of accepting High Voltage from an HV Transformer or MFSU directly. The Mass Fabricator will explode if provided with Extreme Voltage (a packet greater than 512 EU/t), such as that from a Nuclear Reactor, or if provided with more than 500,000 total EU in a single tick.