Abstract: Examples relate to methods of printing a 3D printed tamper evident security structure for protecting a feature; the method comprising repeatedly: depositing a layer of build material; doping one or more than one region of the layer of build material using a dopant to influence a respective electrical attribute of one or more than one region associated with a graph of the structure; and agglomerating one or more than one selected portion of the layer of the build material, including the one or more than one doped region of the layer of build material, to form progressively the graph with a predetermined measurable electrical characteristic.

Abstract: In example implementations, a powder level sensor is provided. The powder level sensor includes a capacitive sensor, a processor, and a cleaning mechanism. The processor is communicatively coupled to the capacitive sensor. The processor interprets a measurement of the capacitive sensor to detect a layer of residual build material on a surface of the powder level sensor. The cleaning mechanism may be communicatively coupled to the processor. The processor activates the cleaning mechanism to remove the layer of residual build material on the surface of the powder level sensor.

Abstract: Examples relate to methods of printing a 3D printed tamper evident security structure for protecting a feature; the method comprising repeatedly: depositing a layer of build material; doping one or more than one region of the layer of build material using a dopant to influence a respective electrical attribute of one or more than one region associated with a graph of the structure; and agglomerating one or more than one selected portion of the layer of the build material, including the one or more than one doped region of the layer of build material, to form progressively the graph with a predetermined measurable electrical characteristic.

Abstract: Techniques for controlling moisture content of build material in a three dimensional printer are provided. An example system includes a build material vessel to contain the build material and receive a flow of air, and a humidifier to adjust the humidity of the air flowing into the build material vessel. The system also includes one or more sensors to determine a dew point of the air flowing into the build material vessel. The humidity level of the air flowing into the hopper is controlled by the humidifier to maintain the dew point at a level that will prevent condensation of water inside the build material vessel.

Abstract: Examples of a 3D printing apparatus arranged to perform a print operation using build material, and methods of operating such a 3D printing apparatus, are described. In one case, a 3D printer is arranged to perform a print operation using build material whilst a build material temperature sensed by the printer is below a threshold temperature of the build material. The printer is arranged to obtain a threshold temperature indicator in advance of a respective print operation.

Abstract: A system for manufacturing three dimensional objects can include logic to detect, for at least one vessel, a moisture content level corresponding to a build material residing in the at least one vessel. The logic can also adjust a humidity level and a temperature of a gas and a conditioning agent applied to the at least one vessel, wherein the humidity level and the temperature are based on the moisture content level and a temperature of the build material residing in the at least one vessel. Additionally, the logic can initialize manufacturing a three dimensional object with the build material from the at least one vessel in response to detecting the moisture content level of the build material residing in the at least one vessel is within a predetermined range.

Abstract: An apparatus and method for performing a print operation on a 3D printer (110) are described herein. A 3D printing apparatus comprising a 3D printer (110) is arranged to perform a print operation using build material from a build unit (120) unless a value that identifies a first build material stored in the build unit in a first register, which is set according to an initial build powder fill operation of the build unit (120) by a powder management station, is different from a value in a second register, which is set according to the initial build powder fill operation, or modified in response to, or following, a subsequent opening of the build unit (120).

Abstract: In an example, an apparatus is described that includes a non-resistive heat source, a thermally conductive face, and a temperature detector. The thermally conductive face has a controlled long-wave infrared emissivity and is in thermal contact with the non-resistive heat source. The temperature detector is positioned to detect a temperature of the thermally conductive face.

Abstract: In example implementations, a powder level sensor is provided. The powder level sensor includes a capacitive sensor, a processor, and a cleaning mechanism. The processor is communicatively coupled to the capacitive sensor. The processor interprets a measurement of the capacitive sensor to detect a layer of residual build material on a surface of the powder level sensor. The cleaning mechanism may be communicatively coupled to the processor. The processor activates the cleaning mechanism to remove the layer of residual build material on the surface of the powder level sensor.

Abstract: In some examples, a controller is to receive a measurement of an electrical property of an oscillation control system from a sensor, determine, based on the measurement of the electrical property, a frequency of oscillation of a structure vibrated by the oscillation control system in the system, the vibration of the structure to cause passage of a portion of a material through the structure, and estimate a level of a remaining portion of the material at the structure based on the determined frequency of oscillation of the structure.

Abstract: An interlock circuit comprises a plurality of semiconductor switching units electrically connected or connectable in series in a supply line, a plurality of control units electrically connected to the plurality of semiconductor switching units, and a trigger unit electrically connected to the plurality of control circuits. Each control unit activates or deactivates a corresponding semiconductor switching unit in response to trigger signal received from the trigger unit.

Abstract: Examples relate to methods of printing a 3D printed tamper evident security structure for protecting a feature; the method comprising repeatedly: depositing a layer of build material; doping one or more than one region of the layer of build material using a dopant to influence a respective electrical attribute of one or more than one region associated with a graph of the structure; and agglomerating one or more than one selected portion of the layer of the build material, including the one or more than one doped region of the layer of build material, to form progressively the graph with a predetermined measurable electrical characteristic.

Abstract: Some examples include a thermal imaging assembly, comprising a thermal sensor having a field of view and optics, an emitting source to validate the optics in the field of view, an emitter storage to selectively house the emitting source outside of the field of view, and a carrier to move the emitting source between the emitter storage and the field of view.

Abstract: Some examples include a thermal imaging assembly, comprising a thermal imaging device including a thermal sensor, a transistor to generate heat, a thermal jacket forming a cavity to house the thermal imaging device, the thermal jacket forming a space around the thermal imaging device, the thermal jacket thermally coupled to the transistor to transmit heat generated by the transistor to the cavity, and an insulative shell disposed around the thermal jacket to maintain a temperature of the thermal imaging device within the insulative shell.

Abstract: In an example, an apparatus is described that includes a non-resistive heat source, a thermally conductive face, and a temperature detector. The thermally conductive face has a controlled long-wave infrared emissivity and is in thermal contact with the non-resistive heat source. The temperature detector is positioned to detect a temperature of the thermally conductive face.

Abstract: A system for manufacturing three dimensional objects can include logic to detect, for at least one vessel, a moisture content level corresponding to a build material residing in the at least one vessel. The logic can also adjust a humidity level and a temperature of a gas and a conditioning agent applied to the at least one vessel, wherein the humidity level and the temperature are based on the moisture content level and a temperature of the build material residing in the at least one vessel. Additionally, the logic can initialize manufacturing a three dimensional object with the build material from the at least one vessel in response to detecting the moisture content level of the build material residing in the at least one vessel is within a predetermined range.

Abstract: Certain examples described herein relate to build units that are physically connectable to at least one host apparatus of an additive manufacturing system. A build unit comprises at least one controllable device useable in an object building operation. In certain examples, the at least one device is controllable according to first control instructions originating from the at least one host apparatus when the build unit is physically connected to the at least one host apparatus. In certain examples, the at least one device is also controllable according to second control instructions generated independently of the at least one host apparatus when the build unit is not physically connected to the at least one host apparatus.

Abstract: Techniques for controlling moisture content of build material in a three dimensional printer are provided. An example system includes a build material vessel to contain the build material and receive a flow of air, and a humidifier to adjust the humidity of the air flowing into the build material vessel. The system also includes one or more sensors to determine a dew point of the air flowing into the build material vessel. The humidity level of the air flowing into the hopper is controlled by the humidifier to maintain the dew point at a level that will prevent condensation of water inside the build material vessel.

Abstract: A power regulation circuit including an input from an alternating current (AC) power supply, a load element connected to the AC power supply input, a dummy power resistor connected in parallel with the load element, and a controller to dynamically control power to the load element and to the dummy power resistor in response to a variation in the power consumption of the load element.

Abstract: In an example, a print device comprises: a heat pump (102) to extract heat from a fluid source to produce cooled fluid and to transfer the heat from the fluid source to heat a print material (108), wherein the cooled fluid is used to cool a component (106) of the print device.