Extraction system for apparatus for the layer-by-layer formation of three-dimentionsl objects, and associated methods and controller

An apparatus for the layer-by-layer formation of three-dimensional objects, the apparatus comprising a gas extraction system and an enclosed working space from which gas is to be extracted, wherein the working space is enclosed by side walls, a ceiling and a working surface and comprises a working space inlet to allow gas to enter into the working space, wherein the working surface comprises a build bed surface in which a layer of the object is formed, and

• wherein the gas extraction system comprises:
• a primary conduit comprising a first primary inlet open to an environment external to the working space and, a first interfacing inlet, and a primary outlet connectable to an external extraction source so as to suction gas from the primary conduit
• a first secondary conduit comprising a first secondary inlet in fluidic communication with the working space for extracting gas from the working space, and a first secondary outlet in fluidic communication with the first interfacing inlet;
• a second secondary conduit comprising a second secondary inlet in fluidic communication with the working space, and a second secondary outlet, and further wherein:
• (a) the primary conduit further comprises a second interfacing inlet in fluidic communication with the second secondary outlet, or
• (b) the gas extraction system further comprises a confluent portion having first and second ends, wherein the first secondary outlet and the second secondary outlet are in fluidic communication with the first end of the confluent portion and arranged so as to combine the flows from the first and second secondary outlets into the confluent portion, and wherein the first interfacing inlet is in fluidic communication with the second end of the confluent portion, so as to receive the combined flows from the confluent portion;
• wherein the gas extraction system further comprises a flow controller configured to control the flow of gas from the working space into the first and second secondary conduits and from the first and second secondary conduits into the primary outlet of the primary conduit, wherein the first and second secondary inlets are located in the ceiling of the working space, each facing an area at or near opposite ends of the build bed surface.

A method for extracting gas from the working space of an apparatus for the layer-by-layer formation of three-dimensional objects the method comprising:

• (a) extracting gas from the working space via a secondary conduit, the secondary conduit comprising a secondary inlet and a secondary outlet, the secondary inlet receiving gas from the working space;
• (b) moving the gas from the secondary conduit via the secondary outlet to a primary conduit via a first interfacing inlet of the primary conduit;
• (c) extracting the gas from a primary outlet of the primary conduit by operating an external extraction source connected to the primary outlet;
• (d) suctioning, by operating the external extraction source, a flow of gas from an environment external to the working space into the primary conduit via a primary inlet of the primary conduit that is open to the environment external to the working space, such that the gas extracted from the primary conduit in step (c) is a mixture of gas extracted from the working space via the first interfacing inlet and gas suctioned from the external environment to the working space via the primary inlet;
• and
• (e) operating an internal flow control device located in the secondary conduit to control the flow of gas through the secondary conduit.