The build platform on the MakerBot Replicator Z18 3D Printer has two parts: a flat, sturdy aluminum base, and removable plastic tops called Build Plates. Build Plates for the MakerBot Replicator Z18 reduce downtime when printing multiple large models. The ability to switch out Build Plates allows you to immediately move on to your next print, while setting aside your most recent print for careful removal later on.