Converting a Mini Five-Axis CNC Mill to Run From a Raspberry Pi

CNC stands for “computer numerical control” and so it should be obvious that a CNC mill requires a computer to run. But that is more complex than it may sound. You need a computer to create g-code based on toolpaths and the CNC mill itself needs to be able to interpret that g-code to coordinate the movement of the motors. The CNC mill can interpret g-code using either a dedicated computer or a microcontroller. To upgrade their mini five-axis CNC mill, dgouws123 took the first route and got LinuxCNC running on a Raspberry Pi.

LinuxCNC is a popular open-source CNC control software package. It reads g-code files and tells the CNC tool (mill, lathe, plasma cutter, etc.) exactly how to move its motors. In most cases, the computer running LinuxCNC is not capable of interfacing with the CNC machine’s motors directly. Instead, it communicates with the CNC machine’s own control board. LinuxCNC does all the heavy lifting of g-code interpretation and works out actual motor movement commands, while the CNC machine’s controller does the low-level work of interfacing with the motors and sensors.

In this case, dgouws123 had a used Minitech Mill gifted by their father. When they received that mill, it came with an old Windows 7 PC running Mach3 software that communicated with the mill’s controller through parallel ports. That proved to be unreliable, which is why dgouws123 sought out an upgrade.

That hardware for that upgrade consists of a Raspberry Pi 4 Model B single-board computer, a Mesa7i76e FPGA controller board, five Cloudray DM542S stepper drivers (one for each axis), and two beefy power supplies (one for the Mesa7i76e and one for the stepper drivers). LinuxCNC runs on the Raspberry Pi and tells the Mesa7i76e how to move the motors.

In the Instructables tutorial, dgouws123 goes into great detail on wiring and setup. They even explain the kinematic configuration, which is an important detail for five-axis CNC machines that three-axis operators may not know about. Unlike a three-axis machine, a five-axis machine may have multiple ways of reaching a given point. The kinematic configuration determines how it should move to avoid collisions and to achieve the desired cuts. That depends on the geometry of both the work piece and the machine itself, so proper configuration is crucial.

Finally, dgouws123 wraps up the tutorial with instructions on how to generate compatible g-code using Fusion360’s CAM (computer-aided manufacturing) capabilities. If you have this mill or one like it, then dgouws123’s information will be invaluable.