Abstract: In an example, a printing apparatus may include, a rotatable shaft, a removable drum mounted on the shaft and a fixing element to fixedly couple the removable drum to the shaft, so that the removable drum is to rotate with the shaft. The printing apparatus may also include a heater, a printing apparatus satellite component located adjacent to the removable drum and engageable with the removable drum and a controller. The controller may be to receive a command to prepare the removable drum for removal; and in response, control the shaft to rotate the removable drum; control the heater to heat the removable drum while it rotates; and control the printing apparatus to engage the satellite component of the printing apparatus with the removable drum while it rotates.

Abstract: A positioning device to control the position of a print agent applicator comprises a mount to support a print agent applicator at a load point on the mount; an actuator coupled to the mount to apply a driving force at an actuation point on the mount; and a guide mechanism to guide the mount and supported print agent applicator, under the driving force, to translate along a predetermined path towards a printing drum to form an engaging contact between the print agent applicator and the printing drum.

Abstract: A print apparatus is disclosed. In an example, the print apparatus comprises: a photoconductive surface to receive a latent image representative of an image to be printed onto a printable substrate; a plurality of print components, each print component having a surface movable relative to the photoconductive surface, wherein a current or voltage is to be applied between the print component surface and the photoconductive surface; and processing circuitry to: measure a current or voltage between each print component surface and the photoconductive surface; responsive to detecting a deviation in the measured current or voltage from a reference current or voltage in respect of any of the plurality of print components, determine that there exists a defect associated with the photoconductive surface; and determine, based on the amount of deviation of the measured current or voltage from the reference current or voltage, an indication of the size of the defect.

Abstract: In an example of the disclosure, an imaging oil is applied upon a photoconductor surface. An element is brought into contact with the imaging oil at the photoconductor surface. The element has a first refractive index that is within a predefined tolerance of a second refractive index of the imaging oil. The photoconductor surface is exposed to light emitted by a writing component. The light passes through the element and the imaging oil.

Abstract: A printing drum for a liquid electrophotographic printing system which comprises a photosensitive surface and a heating device mounted to the printing drum. The heating device heats the photosensitive surface of the printing drum to a predetermined temperature.

Abstract: Disclosed is a liquid electrophotographic printing apparatus that comprises a developer roller, a cleaning member to contact the developer roller with a contact force and a force adjustment arrangement to adjust the contact force.

Abstract: A positioning device to control the position of a print agent applicator comprises a mount to support a print agent applicator at a load point on the mount; an actuator coupled to the mount to apply a driving force at an actuation point on the mount; and a guide mechanism to guide the mount and supported print agent applicator, under the driving force, to translate along a predetermined path towards a printing drum to form an engaging contact between the print agent applicator and the printing drum.

Abstract: A liquid electro-photographic printing system, comprising: a binary ink developer assembly, a power supply arrangement, a switching arrangement, and a controller. The binary ink developer assembly includes a plurality of members defining a flow path for a printing fluid containing charged particles, the plurality of members including a first member and a second member that are arranged to generate an electric field therebetween, the first member having a plurality of segments. The power supply arrangement continuously provides a supply of voltages during a print operation, the voltages including a first voltage and a second voltage having a different voltage level from that of the first voltage.

Abstract: In an example, a method includes rotating a print apparatus component to be cleaned about a first rotational axis. A cleaning element having a cleaning surface in contact with the print apparatus component may be driven such that the cleaning surface has a component of motion which is parallel to the first rotational axis in a contact region. A relative velocity of the cleaning element and the print apparatus component may be varied during a cleaning operation.

Abstract: In one example of the disclosure, a developer system includes a housing and a developer roller. A first electrode and a second electrode are disposed in the housing, the first and second electrodes to create an electrical charge to cause transfer of printing fluid to a developer roller surface. The developer roller is rotatably connected to the housing. The developer includes a surface, a bearing to support and enable rotation of an axle attached to the developer roller, and a plurality of stop pins. The plurality of stop pins are connected to the housing. The stop pins are to support the bearings and to establish target distances between the developer roller surface and the first electrode and second electrodes.

Abstract: A print apparatus component to be cleaned is rotated about a rotational axis. A cleaning element having a cleaning surface in contact with the print apparatus component is rotated. The cleaning element is oscillated in a direction parallel to the rotational axis. Rotation and oscillation of the cleaning element are varied according to a predetermined function to remove a residue from the print apparatus component.

Abstract: A method of printing images in a liquid electrophotographic printer is provided. In an example, the method includes measuring at least one current associated with an image development unit of the liquid electrophotographic printer. A first time at which a peak occurs in the measured current is determined; the first time indicates that a printing substance is transferred from a point on a developer roller of the image development unit to a photo imaging member of the liquid electrophotographic printer at a first location within the image development unit. A second time at which said point on the developer roller is expected to contact the cleaner roller within the image development unit is calculated and, at the second time, a voltage applied to the cleaner roller is controlled to reduce the potential difference between the cleaner roller and the developer roller.

Abstract: A liquid electro-photographic printing system, comprising: a binary ink developer assembly, a power supply arrangement, a switching arrangement, and a controller. The binary ink developer assembly includes a plurality of members defining a flow path for a printing fluid containing charged particles, the plurality of members including a first member and a second member that are arranged to generate an electric field therebetween, the first member having a plurality of segments. The power supply arrangement continuously provides a supply of voltages during a print operation, the voltages including a first voltage and a second voltage having a different voltage level from that of the first voltage.

Abstract: In an example of the disclosure, a print apparatus component to be cleaned is rotated about a rotational axis. A cleaning element having a cleaning surface in contact with the print apparatus component is rotated. The cleaning element is oscillated in a direction parallel to the rotational axis. Rotation and oscillation of the cleaning element are varied according to a predetermined function to remove a residue from the print apparatus component.

Abstract: In one example of the disclosure, a developer system includes a housing and a developer roller. A first electrode and a second electrode are disposed in the housing, the first and second electrodes to create an electrical charge to cause transfer of printing fluid to a developer roller surface. The developer roller is rotatably connected to the housing. The developer includes a surface, a bearing to support and enable rotation of an axle attached to the developer roller, and a plurality of stop pins. The plurality of stop pins are connected to the housing. The stop pins are to support the bearings and to establish target distances between the developer roller surface and the first electrode and second electrodes.

Abstract: In an example, a method includes collecting (102) print agent from a print agent reservoir to form a print agent layer on a first print agent transfer member (204). The print agent layer may be transferred (104) directly from the first print agent transfer member to a second print agent transfer member (206), where the print agent layer may be heated (106). The print agent layer may be applied (108) directly from the second print agent transfer member to a substrate.

Abstract: In an example, a cleaning station comprises a wiper blade to scrape cleaning fluid across a surface of a component of a print apparatus. A suction pump is to remove a cleaning fluid from a surface of the component of the print apparatus. A sensor is to determine the thickness of cleaning fluid on a surface of the component of the print apparatus. A controller is to vary a suction pressure of the suction pump based on measurements of the sensor.

Abstract: In an example of the disclosure, an imaging oil is applied upon a photoconductor surface. An element is brought into contact with the imaging oil at the photoconductor surface. The element has a first refractive index that is within a predefined tolerance of a second refractive index of the imaging oil. The photoconductor surface is exposed to light emitted by a writing component. The light passes through the element and the imaging oil.

Abstract: A method of printing images in a liquid electrophotographic printer is provided. In an example, the method comprises measuring at least one current associated with an image development unit of the liquid electrophotographic printer. A first time at which a peak occurs in the measured current is determined; the first time indicates that a printing substance is transferred from a point on a developer roller of the image development unit to a photo imaging member of the liquid electrophotographic printer at a first location within the image development unit. A second time at which said point on the developer roller is expected to contact the cleaner roller within the image development unit is calculated and, at the second time, a voltage applied to the cleaner roller is controlled to reduce the potential difference between the cleaner roller and the developer roller.

Abstract: In an example, a cleaning station comprises a wiper blade to scrape cleaning fluid across a surface of a component of a print apparatus. A suction pump is to remove cleaning fluid from a surface of a component of a print apparatus. A sensor is to determine the thickness of cleaning fluid on a surface of a component of a print apparatus. A controller is to vary a suction pressure of the suction pump based on the measurements of the sensor.