Superficially, it is easy to think about converting a 3D printer into a CNC machine. After all, they both do essentially the same thing. They move a tool around in three dimensions. Reducing this to practice, however, is a problem. A CNC tool probably weighs more than a typical hotend. In addition, cutting into solid material generates a lot of torque.
[Thomas Sanladerer] knew all this, but wanted to try a conversion anyway. He had a few printers to pick from, and he chose a very sturdy MendelMax 3. He wasn’t sure he’d wind up with a practical machine, but he wanted to do it for the educational value, at least. The result, as you can see in the video below, exceeded his expectations.
The resulting device can work wood, acrylic, and even aluminum. This required a few changes to the printer, though. A lot of the MendelMax is 1 mm sheet metal. [Thomas] replaced a lot of parts with beefy 3D-printed parts and MDF. He also reduced the Y axis travel a bit to make the bed more stable. The software was essentially left unchanged but has some configuration changes that he explains.
The first incarnation used an inexpensive rotary tool as a spindle. However, the stress on the tool would cause it to fail after a bit of use. [Thomas] got a 48 V spindle motor and a matching power supply that works well.
The results are good, although not perfect. [Thomas] still wants to switch out some belts and strengthen the Z axis more. Still, it looks pretty useful. We aren’t sure all 3D printers would be as easy to stiffen as much as the MendelMax. Still, this build proves that it can be done, at least for some printers.
A more common approach is to use your 3D printer to build a CNC machine. Of course, converting the other way (that is, CNC to 3D printer) is almost trivial. Another option is to mount a LASER which doesn’t have torque problems. Of course, you might have safety issues, but that’s another hurdle to clear.