Abstract: In some examples, a build material recycling device of a three-dimensional (3D) printer can include an upper chamber including an inlet and a material separator coupled to the inlet, a classifier coupled to the upper chamber, and a lower chamber coupled to the classifier, where the classifier is located between the upper chamber and the lower chamber.

Abstract: Printers and associated printer maintenance methods and apparatus are disclosed. An example printer includes a build material dispenser to dispense build material onto a work area; a contaminant filter to receive at least some of the build material from the work area, the contaminant filter being structured to filter contaminants from the build material received; and a drawer including the contaminant filter, the drawer to enable the contaminant filter to be removed for cleaning.

Abstract: In some examples, an apparatus includes an optical sensor to detect a material in a printing system, a light transmissive layer to pass light to the optical sensor, and a wiper actuatable to wipe a surface of the light transmissive layer to remove particles of the material away from the surface of the light transmissive layer.

Abstract: In some examples, a build material recycling device of a three-dimensional (3D) printer can include an upper chamber including an inlet and a material separator coupled to the inlet, a classifier coupled to the upper chamber, and a lower chamber coupled to the classifier, where the classifier is located between the upper chamber and the lower chamber.

Abstract: According to one aspect there is provided a build material processing apparatus for a 3D printing system. The system comprises a sieve to sieve build material, the sieve to receive a flow of build material, a vibrator mechanism to vibrate the sieve at a resonant frequency. A controller is provided to determine displacement characteristics of the sieve, determine, based on the displacement characteristics, a fill state of the sieve, and control a flow of build material to the sieve based on the determined fill state.

Abstract: A 3D printing system comprises a pressure system to provide a negative pressure and a hopper having a first opening to receive powder to be used for printing, wherein the powder is received in an open state of the first opening. The hopper has a second opening to guide air from outside the hopper to inside the hopper and has a third opening connected to the pressure system so as to provide for a negative pressure inside the hopper, the negative pressure to overcompensate for the air receive through the second opening such that a pressure being lower when compared to an ambient pressure of the hopper is generated inside the hopper.

Abstract: An example of an apparatus is provided. The apparatus includes a container to store a powder. The apparatus includes a flow generator to move a gas to the container. The flow generator is to move the gas at a first velocity and a second velocity, the first velocity to fluidize the powder in a fluidized state, and the second velocity to pass through stationary powder in a powder pack. The apparatus includes pressure sensors to measure pressures in the container. The apparatus includes a measurement engine in communication with the pressure sensors, wherein the measurement engine is to calculate a mass of the powder based on a fluidized pressure differential and based on a pack pressure differential.

Abstract: A selectable drive printing device includes a feedshaft to selectively drive a print drive system and a scan drive system, and a shifter to selectively shift a drive selector assembly of the selectable drive printing device between a scanning system drive position wherein the scan drive system is driven and a printing system drive position wherein the print drive system is driven. The shifter is coaxially and rotatably coupled around the feedshaft. Further, the shifter selectively drives the print drive system and the scan drive system based on an angular position of the shifter about the feedshaft.

Abstract: In an example, a lift mechanism may include a linkage to engage with a pick arm, a crank switchably disposed in a first position and a second position, and a swingarm to move the crank from the first position to the second position. The linkage may move the pick arm from a raised position to a lowered position when the crank moves from the first position to the second position.

Abstract: In an example, a lift mechanism may include a linkage to engage with a pick arm, a crank switchably disposed in a first position and a second position, and a swingarm to move the crank from the first position to the second position. The linkage may move the pick arm from a raised position to a lowered position when the crank moves from the first position to the second position.

Abstract: A selectable drive printing device includes a feedshaft to selectively drive a print drive system and a scan drive system, and a shifter to selectively shift a drive selector assembly of the selectable drive printing device between a scanning system drive position wherein the scan drive system is driven and a printing system drive position wherein the print drive system is driven. The shifter is coaxially and rotatably coupled around the feedshaft. Further, the shifter selectively drives the print drive system and the scan drive system based on an angular position of the shifter about the feedshaft.