A 3D printing system comprising at least one build unit in which 3D objects can be generated by a 3D printer, a management system to control the 3D printing system, a 3D printer and a material processing unit in which processing operations can be performed on the build unit, the management system comprising: a processor configured to: obtain status data from at least some of the elements of the 3D printing system, including obtaining status data relating to a build unit inserted into a 3D printer or a material processing unit of the system, the status data relating to the build unit comprising an identifier of the build unit; obtain data relating to a print job to be printed; determine, from the obtained data, a schedule of operations to be performed by elements of the 3D printing system and; generate control data to allow enforcement of the determined schedule, wherein the processor is to generate control data that includes: the identifier of the build unit, an identifier of either the 3D printer or the material processing unit intended to process the identified build unit; and an indication of whether the identified build unit may be used at the current time; and send or make available the generated control data to at least one of the 3D printer and material processing unit; and wherein the 3D printer or the material processing unit into which the build unit is inserted is configured to perform a check against the control data prior to processing the build unit inserted thereinto to ensure that it is in compliance with the control data, and the 3D printer or the material processing unit into which the build unit is inserted is not to perform operations which are not in accordance with the control data. a processor configured to: obtain status data from at least some of the elements of the 3D printing system, including obtaining status data relating to a build unit inserted into a 3D printer or a material processing unit of the system, the status data relating to the build unit comprising an identifier of the build unit; obtain data relating to a print job to be printed; determine, from the obtained data, a schedule of operations to be performed by elements of the 3D printing system and; generate control data to allow enforcement of the determined schedule, wherein the processor is to generate control data that includes: the identifier of the build unit, an obtain status data from at least some of the elements of the 3D printing system, including obtaining status data relating to a build unit inserted into a 3D printer or a material processing unit of the system, the status data relating to the build unit comprising an identifier of the build unit; obtain data relating to a print job to be printed; determine, from the obtained data, a schedule of operations to be performed by elements of the 3D printing system and; generate control data to allow enforcement of the determined schedule, wherein the processor is to generate control data that includes: the identifier of the build unit, an identifier of either the 3D printer or the material processing unit intended to process the identified build unit; and an indication of whether the identified build unit may be used at the current time; and send or make available the generated control data to at least one of the 3D printer and material processing unit; and wherein the 3D printer or the material processing unit into which the build unit is inserted is configured to perform a check against the control data prior to processing the build unit inserted thereinto to ensure that it is in compliance with the control data, and the 3D printer or the material processing unit into which the build unit is inserted is not to perform operations which are not in accordance with the control data. send or make available the generated control data to at least one of the 3D printer and material processing unit; and wherein the 3D printer or the material processing unit into which the build unit is inserted is configured to perform a check against the control data prior to processing the build unit inserted thereinto to ensure that it is in compliance with the control data, and the 3D printer or the material processing unit into which the build unit is inserted is not to perform operations which are not in accordance with the control data.