Ivan Miranda’s 3D-Printed CNC Mill Is Capable of Cutting Steel

A CNC mill is a machine tool that is capable of automatically cutting a three dimensional part out of a chunk of solid material. Most metal parts are either made from stamped and formed sheet metal or they’re milled. CNC mills are traditionally very big, very heavy machines. They have to be in order to be rigid enough to withstand the forces involved without any deflection, which would result in poor precision. Most often, they’re made from heavy steel or iron. But YouTuber Ivan Miranda was able to build a 3D-printed CNC mill that is capable of cutting steel.

As with most other machine tools, rigidity is the most important characteristic of a CNC mill’s frame. That’s usually achieved by making the frame and all of the movement components as solid as possible. A typical 3D printer’s hardened rods, for example, would deflect under the loads a CNC mill is subjected to. So 3D-printing the parts for a CNC mill is generally considered unwise — they’re just not strong enough. But Miranda has proved that it is indeed possible, despite common wisdom. He doesn’t say what kind of tolerances he is able to achieve with the machine, but the milled aluminum parts look nice and have finishes that don’t show any obvious signs of chattering.

Miranda’s CNC mill is constructed a bit like an oversized 3D printer, which makes sense given that 3D printing is one of his areas of expertise. The box frame was made mostly from aluminum extrusion tubes connected together with 3D-printed brackets. The X and Y axes are actuated by stepper motors with 1:19 planetary gears connected by huge HTD 5M belts. The Z axis is actuated by a stepper motor via a ball screw. The spindle is just a typical handheld router. In his tests, Miranda was able to cut aluminum at a depth of 1mm and a feed rate of 800mm/min. More impressively, he was even able to cut mild steel—though he doesn’t specify the feeds and speeds used for that. For serious work, a traditional CNC mill would be far more practical, but Miranda’s 3D-printed CNC mill looks great for hobby work.