Linear particle accelerators (LINACs) are fundamental to modern particle physics. At CERN, linear accelerators are at the very core of the accelerator chain and serve as the main source for ion and proton beams. Despite their importance for experimental particle physics, very few teaching aids have been available to demonstrate the underlying principles in a hands-on fashion to high school students. This is why the 3D-printed LINAC was developed. Scope of the project At its core, the 3D printed LINAC is a fully functional model to demonstrate how charged particles can be accelerated in oscillating electric fields. In the model, a graphite coated ping pong ball is accelerated through a plexiglass tube using a custom-built switch. Minimal equipment is needed: A 3D-printer for the main parts, an Arduino for controlling the accelerator, some standard electronic components, and a plexiglass tube. A list of the required materials is provided, along with the construction manual.