Abstract: In one example a method of generating a three-dimensional object in a 3D printing system using a fusing agent of a first colour and a build material having a second colour different from the first colour, and a detailing agent, comprises obtaining object model data describing an object to be generated, and determining a first portion of the object to be generated to have the second colour. The method comprises determining object generation instructions to generate the object by defining a gap region of a layer of build material that is to correspond to the first portion of the object to have the second colour on which no agents are to be applied, a band of detailing agent on a layer of build material immediately adjacent to the gap region to define an outer limit of the gap region and therefore a boundary of the first portion of the object, and a fusing agent region on a layer of build material adjacent to the gap region on which fusing agent is to be applied.

Abstract: A method includes receiving an object model describing a geometry of a three-dimensional, 3D, object for printing by a 3D printer, and build material data indicating a selected build material to be used in printing the 3D object by the 3D printer. A volume to surface area ratio of the object model is calculated. In response to the volume to surface area ratio being greater than a first predetermined threshold value for the selected build material, it is determined that printing the 3D object by the 3D printer from the selected build material is expected to result in a defect in the 3D object.

Abstract: In one example a method of additive manufacturing includes obtaining object model data and colour data. The object model data describes at least portion of an object to be generated in additive manufacturing using a build material having a first colour and a fusing agent having a second colour different from the first colour. The colour data describes an intended colour of at least portion of the object to be manufactured by additive manufacturing. The intended colour is substantially the first colour, the second colour or a colour therebetween. The method includes determining object generation instructions to apply the fusing agent to a first region of a layer of the build material. The first region of the layer corresponds to portion of the object and the instructions are to apply fusing agent at a contone level such that the colour of the portion of the object corresponding to the first region of the layer of build material is substantially the same as the intended colour as described by the colour data.

Abstract: An example method of generating three-dimensional objects is disclosed. Object generation instructions to generate the object may be determined by defining a shell region of a layer of build material corresponding to the first portion of the object having a first color, and defining a fusing agent region on a layer of build material adjacent to the shell region on which fusing agent of a second color is to be applied and specifying an amount of colorant to be applied to the shell region wherein the object generation instructions specify application of fusing agent and colorant such that, when the layer of build material is heated using a heat source, the fusing agent region of the build material melts due to energy absorbed from the heat source and the build material of the shell region melts due, at least in part, to energy transfer from the fusing agent region.

Abstract: An apparatus comprises a processor and a machine-readable storage medium storing machine-readable instructions executable by the processor. The machine-readable instructions comprise instructions to cause the processor to create 3D print data including data defining one or more objects to be printed in a build chamber of a 3D printer and data defining, in addition to the one or more objects, a shield to be printed to shield the one or more printed objects in the build chamber to reduce heat dissipation to an outside of the build chamber. The shield is designed depending on a thermal behavior of the build chamber and/or depending on a thermal behavior of the one or more objects to be printed.

Abstract: In one example a method of generating a three-dimensional object in a 3D printing system using a fusing agent of a first colour and a build material having a second colour different from the first colour, and a detailing agent, comprises obtaining object model data describing an object to be generated, and determining a first portion of the object to be generated to have the second colour. The method comprises determining object generation instructions to generate the object by defining a gap region of a layer of build material that is to correspond to the first portion of the object to have the second colour on which no agents are to be applied, a band of detailing agent on a layer of build material immediately adjacent to the gap region to define an outer limit of the gap region and therefore a boundary of the first portion of the object, and a fusing agent region on a layer of build material adjacent to the gap region on which fusing agent is to be applied.

Abstract: An apparatus is described which comprise a material mixer to provide build material from at least a first build material supply and a second build material supply to a build unit of a 3D printer. The first build material and the second build material are mixed according to a mixing ratio. The apparatus further comprises a processor to determine the mixing ratio based on inputs indicating at least print job characteristics and material constraints.