Method and device for conveying particulate material during the layer-wise production of patterns

A method comprising:

• forming three dimension objects comprising the steps of:
• 1) providing a device for conveying particulate material comprising:
• a) a reservoir;
• b) a spreader unit;
• and
• c) a plurality of particulate material conveying systems including a first particulate material conveying system having a screw conveyor and a second particulate material conveying system having a screw conveyor;
• 2) forming a first layer of the three dimension object by a layer forming step comprising:
• a) conveying the particulate material out of the reservoir into the spreader unit with at least the first particulate material conveying system;
• b) spreading the particulate material unit unto a build platform with the spreader;
• and
• c) conveying excess particulate material that was fed to the spreader unit back into the reservoir after the step of spreading;
• and
• 3) forming a second layer of the three dimensional object by a layer forming step by repeating steps 2a, 2b and 2c;
• wherein the steps 2a and 2c of conveying takes place in a closed conveying circuit that includes the plurality of particulate material conveying systems.