Abstract: Example systems relate to recoater movement. A non-transitory machine readable medium may contain instructions executable by a processor. The instructions may include instructions to change an action of a recoater in response to a determination that the recoater has reached a first location of a build area comprising build material. Instructions may further include instructions to lift the recoater in response to a determination that the recoater has reached a second location of the build area. Instructions may additionally include instructions to move the recoater over the second location at the lifted position, wherein the second location includes a build-up of the build material.

Abstract: In one example, a powdered build material supply system for additive manufacturing includes a supply deck, a dispenser to dispense a ribbon of powdered build material on to the supply deck, and a spreader to spread powdered build material from the ribbon over a work area adjacent to the supply deck.

Abstract: According to one aspect, there is provided apparatus for forming a layer of build material for three-dimensional printing. The apparatus comprises a spreader to spread a volume of build material to form a layer of build material on a build platform, wherein at least one end of the spreader is to remain a constant distance from a build material retaining wall in proximity to at least one edge of the build platform as the spreader is moved over the surface of the build platform, and further wherein at least a portion of the spreader is below the top of the retaining wall.

Abstract: In some examples, preheat three-dimensional (3D) printer build material can include a heating plate of a 3D printer to preheat build material from below the build material, where the heating plate is located adjacent to a build platform of the 3D printer, and a heater-spreader carriage of the 3D printer to preheat the build material from above the build material and spread the preheated build material from the heating plate to the build platform.

Abstract: In an example, a method of fusing a 3D object layer with a stationary energy system positioned and a carriage that casts a shadow onto the work area includes, with one pass of the carriage moving over the work area at a constant speed, dispensing a liquid fusing agent onto a first layer of build material in a pattern corresponding to an object slice such that the exposure time of the patterned build material is unequal across the first layer and, with another pass of the carriage moving over the work area in the same direction and at the same constant speed as the first pass, spreading the next layer of build material over the first layer such that the exposure time of the patterned build material in the first layer is made equal across the first layer.

Abstract: In order to have ensure a proper dosing of a 3D printing system, it is disclosed a feeding mechanism for feeding build material to a surface that comprises: a receptacle to receive build material; and an outlet of the build material having a substantially quadrilateral opening with a first dimension and a second dimension orthogonal to one another; the outlet further comprising a third dimension orthogonal to the first dimension and the second dimension defining the height of the outlet, and the feeding mechanism being to selectively feed build material from to the receptacle through the outlet onto a surface as the feeding mechanism moves along a travel direction over the surface, being such travel direction parallel to the first dimension of the outlet, the feeding mechanism further comprising an actuator to modify the magnitude of at least one of the second dimension or the third dimension outlet.

Abstract: In some examples, with respect to feature protection for three-dimensional printing, a three-dimensional model of a three-dimensional object to be printed may be ascertained. A determination may be made as to whether a configuration of a three-dimensional model feature of the three-dimensional model matches a removable feature configuration from a set of removable feature configurations. Based on a determination that the configuration of the three-dimensional model feature of the three-dimensional model matches the removable feature configuration from the set of removable feature configurations, the three-dimensional model feature may be removed from the three-dimensional model to generate a modified three-dimensional model.

Abstract: Some examples include a fusing system for an additive manufacturing machine including a carriage movable across a build zone along the x-axis, a thermic source mounted to the carriage, and a roller mounted to the carriage adjacent to the thermic source. A longitudinal section of an exterior surface of the roller is exposed to indirect heat from the thermic source. The roller is controlled to rotate during and outside of a spreading operation of the build material. The carriage is to maintain the roller within a radiative heat transfer area of the thermic source.

Abstract: In order to have ensure a proper dosing of a 3D printing system, it is disclosed a feeding mechanism for feeding build material to a surface that comprises: a receptacle to receive build material; and an outlet of the build material having a substantially quadrilateral opening with a first dimension and a second dimension orthogonal to one another; the outlet further comprising a third dimension orthogonal to the first dimension and the second dimension defining the height of the outlet, and the feeding mechanism being to selectively feed build material from the receptacle through the outlet onto a surface as the feeding mechanism moves along a travel direction over the surface, being such travel direction parallel to the first dimension of the outlet, the feeding mechanism further comprising an actuator to modify the magnitude of at least one of the second dimension or the third dimension outlet.

Abstract: An apparatus may, in an example, include a build platform to receive a dose of build material and a build material spreader to spread the dose of build material over a length of the build platform wherein lateral portions of the build material spreader have a diameter smaller than a medial portion of the build material spreader.

Abstract: In an example, a method includes acquiring, at a processor, object model data for an object to be generated in additive manufacturing, the object model data representing the object as a plurality of polygons. A virtual object space enclosing the object may be inspected from a plurality of discrete source points in a plane. For each of a plurality of distances from each source point, it may be determined if a polygon face is encountered, and if so, a counter may be set based on whether the polygon face is oriented towards the source point or away from the source point. Based on a content of the counter, it may be determined if a volume enclosed between two distances from a source point is a volume of the object.

Abstract: It is disclosed a 3D printing system and a build material spreading method for a 3D printer that comprises: moving a spreader in a first pass in a first direction over a pile of build material at a first separation distance from a dosing surface thereby sweeping a first amount of build material; modify the first separation distance by the distance adjustment unit to a second separation distance; and moving the spreader in a second pass in a second direction towards the build surface to sweep a second amount of build material in a direction towards the build surface.

Abstract: In an example implementation, a method of fusing a 3D object layer includes, with a non-scanning, stationary energy system positioned over a work area, simultaneously irradiating the entirety of the work area uniformly with fusing light, wherein a carriage casts a shadow onto a portion of the work area and prevents fusing light from irradiating the portion of the work area when positioned between the fusing light and the work area. The method includes, with a first pass of the carriage from a first side to a second side of the work area, spreading a first layer of build material and dispensing a liquid fusing agent onto the first layer such that exposure time to the fusing light is unequal across the first layer, and with a second pass, returning the carriage to the first side.

Abstract: According to one example, there is provided a method of distributing build material in a 3D printing system. The method comprises moving a build material support positioned below a hopper, the movement to cause build material stored in the hopper to be deposited on the build material support, and moving a recoater to spread build material from the build material support over a build platform to form a layer of build material thereon, and to return any excess build material back to the build material support.

Abstract: According to one aspect, there is provided apparatus for forming a layer of build material for three-dimensional printing. The apparatus comprises a spreader to spread a volume of build material to form a layer of build material on a build platform, wherein at least one end of the spreader is to remain a constant distance from a build material retaining wall in proximity to at least one edge of the build platform as the spreader is moved over the surface of the build platform, and further wherein at least a portion of the spreader is below the top of the retaining wall.

Abstract: A retractable shade disposed between build material and a lamp facilitates uniform thermal processing across the length of a build bed by blocking emitted radiation from the lamp during movement of the pen across the build bed.

Abstract: A 3D print material shut-off apparatus includes a discharge opening isolator, disposed in a first region of a 3D printer and a print material hopper including a discharge opening at a bottom portion of the print material hopper to discharge a print material from the print material hopper in a second region of the 3D printer adjacent to the first region. The discharge opening isolator is to occlude the discharge opening of the print material hopper when the print material hopper is in the first region.

Abstract: In some examples, a lid of a build material carriage of a three-dimensional (3D) printer can include a lid covering an opening of the build material carriage while the lid is in an engaged position, and a mechanism to keep the lid over the opening of the build material carriage while the lid is in the engaged position, where the lid uncovers the opening of the build material carriage when the build material carriage is moved to receive build material via the opening during a build material fill process such that the lid is in a disengaged position.

Abstract: It is disclosed a 3D printing system and a build material spreading method for a 3D printer that comprises: moving a spreader in a first pass in a first direction over a pile of build material at a first separation distance from a dosing surface thereby sweeping a first amount of build material; modify the first separation distance by the distance adjustment unit to a second separation distance; and moving the spreader in a second pass in a second direction towards the build surface to sweep a second amount of build material in a direction towards the build surface

Abstract: In one example, a refill control system to control the flow of powdered build material to a dispenser to periodically refill the dispenser with powdered build material. In one example, the refill control system includes a container to hold powered build material and a valve operable between a closed position to block a flow of powdered build material from the container to the dispenser and an open position to not block the flow of powdered build material from the container to the dispenser. The container is movable from a first position to a second position to connect the container to the dispenser and from the second position to the first position to disconnect the container from the dispenser.