Abstract: According to an example, an apparatus for a three-dimensional printing system comprises a chamber, an actuator, and a controller. The chamber comprises an opening towards the top of the chamber to receive a container having an openable base and the container is to contain a build cake, wherein the chamber further comprises a platform movable below the opening that is to receive the build cake when the base of the container is opened. The actuator is to move the platform within the chamber, and the controller is to position the platform at a build cake receiving position such that when the container base is opened, the build cake drops onto the platform generating a shock wave that is transmitted into the build cake.

Abstract: In example implementations, an apparatus includes a build platform and a cap. The build platform has an opening on a top surface to fill a build material storage unit. The cap is inserted into the opening to seal the opening. A top surface of the cap and the top surface of the build platform have a uniform thermal conductivity when the cap is inserted into the opening.

Abstract: In example implementations, an apparatus includes a build platform and a cap. The build platform has an opening on a top surface to fill a build material storage unit. The cap is inserted into the opening to seal the opening. A top surface of the cap and the top surface of the build platform have a uniform thermal conductivity when the cap is inserted into the opening.

Abstract: In example implementations, an apparatus includes a build platform and a cap. The build platform has an opening on a top surface to fill a build material storage unit. The cap is inserted into the opening to seal the opening. A top surface of the cap and the top surface of the build platform have a uniform thermal conductivity when the cap is inserted into the opening.

Abstract: In example implementations, an apparatus includes a build platform and a cap. The build platform has an opening on a top surface to fill a build material storage unit. The cap is inserted into the opening to seal the opening. A top surface of the cap and the top surface of the build platform have a uniform thermal conductivity when the cap is inserted into the opening.

Abstract: A mixer unit is described, comprising a support, a mixing container which includes a mixing device, and first and second load cells mounted on opposed sides of the mixing container between the mixing container and the support. The mixing container is to receive and mix unfused build materials for a 3D printing system from at least two different sources. The mixing container is mounted to the support in a manner constraining to vertical movement and such that all vertical forces from the mixing container pass through the load cells to the support. In this manner, a vertical force of the mixing container acting on the support is measured to weigh the contents of the mixing container. A method of mixing unfused build materials for a 3D printing system in a predefined weight ratio using the mixer unit is also described.