In some 3D printing systems, after printing, powder must be recovered from the build unit, and
transported to the storage tanks so that it can be sieved and then loaded again for the next job. To
perform this, multiple circuits of pipes are needed from volume to volume.
With the introduction of new materials and the option of switching from one to another, it is
important to guarantee that the system is clean from the previous material before loading the new
one to ensure quality and that the printed parts will have the expected mechanical properties.
Currently the process used to clean is to use vacuum to try to transport all the powder out of the
circuit, but it is not 100% effective, the only way to guarantee this it to dissemble all pipes and
hoses to check if there is powder inside.
This disclosure is to present a system that would tell the user if there is powder left in the system
and exactly where it is using simple temperature sensors and a heater, eliminating the need of
disassembling everything and wasting time. It would consist of sensors installed along the pipes
and tubes that would monitor the temperature of that segment. Vacuum would be used to try and
transport the powder out as it is done now but with the add in of knowing the temperature evolution
of each segment. Checking which segments took longer to go back to ambient temperature would
tell the user where the powder is.
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INC, HP, "PIPING POWDER DETECTION SYSTEM", Technical Disclosure Commons, (May 14, 2019)