The Ender 3 is one of the most hacked-on 3D printers in the maker world, but converting one into a working CNC mill is a genuinely ambitious build that touches on mechanics, firmware, and tooling all at once. This project (E3CNC) goes well beyond a simple spindle swap — it runs on Klipper with a custom plugin, which is an unusual and interesting choice since Klipper is typically a 3D printer firmware. Adapting it for milling means dealing with toolpath generation, spindle control, and rigidity compensation that the original printer was never designed for.

The standout detail is the 3D printed touch probe for workpiece alignment. Touch probing is a fundamental CNC skill — knowing exactly where your stock sits in machine coordinates is what separates a successful cut from a broken endmill — and seeing it implemented on a budget-printed frame is a great teaching example of how to bring "real" CNC techniques into a hobby-grade build.

For anyone who already owns an Ender 3 collecting dust, or who wants to understand the practical engineering tradeoffs between additive and subtractive machines (rigidity, axis loads, chip evacuation, coolant), this is a much richer watch than the typical factory-floor CNC demo.