DUPLO Train Tunnel – Modular Cardboard Extension

This model allows you to easily create a tunnel for a DUPLO train setup using a simple and flexible design. The tunnel consists of two identical arch pieces that only need to be printed twice. A piece of cardboard is then inserted between the arches, forming the body of the tunnel. This approach makes it possible to adjust the tunnel length freely, depending on the size of the cardboard you use. The recommended width of the cardboard is approximately 36 cm to ensure a proper fit. The cardboard is simply pressed or slotted between the printed arches, so no glue or additional tools are required. The result is a lightweight but stable tunnel that can be assembled quickly and modified at any time. Thanks to this modular construction, the tunnel can also be taken apart just as easily. The arches and cardboard can be separated within seconds, making the whole setup very compact and convenient to store when not in use. PLA and PETG works well for printing, and standard settings such as 0.2 mm layer height and moderate infill are sufficient. The design is straightforward and optimized for easy printing without supports. Thicker cardboard will improve stability, especially for longer tunnels.