This project has a few components, the first being the base mill that I converted. I started with a Proxxon MF 70, which is a relatively small manual mill with a pretty weak spindle motor. It has the advantage of being all all metal with a sturdy cast iron base however, and it small size makes it more suitable for storage in a small space. 

Converting this mill to CNC has been done enough that there are many kits available as well as some 3d printable options. For the x and y axes I chose to print some nicely designed motor mounts that I found by claustonnesen on Thingiverse. These also increased the y travel distance over the stock mill. For the z axis I designed my own stepper motor mount in order to make space for the large spindle motor I planned to add. This meant I had to offset the motor position and use a belt for the z axis. All of the axes include switches to prevent the machine from moving beyond its limits.

The spindle motor from the machine is a large brushless motor repurposed from an electric skateboard that I built in highschool. The VESC speed controller is also from that project and allows for a bunch of control schemes. The VESC is set to control the speed of the motor with a potentiometer and the Hall sensors in the motor. In this scheme the ESC will adjust the supplied current to regulate the motor speed regardless of the load on the spindle. The ESC is also configured not to exceed the maximum current that the power supply is capable of providing. 

To give feedback on the motor speed I use an arduino inside the spindle housing and a hall effect sensor that measures the rotational frequency of magnets on the spindle shaft. Although there are two magnets pictured, only one faces the correct way to trigger the sensor and the other is there for balance, this way the Arduino does not have to record 2x the speed. There is a 3:1 ratio from the spindle to the motor with a 36v power supply and a 180 KV motor. I was aiming for a top speed around 20K rpm with these basic stats but I have seen speeds slightly higher than that on the current version. 

The project makes use of a generic 3 axis CNC controller I bought on Amazon and which I interface with using Universal G-code Sender on my laptop. The G-code is generated using Fusion 360's CAM tool which I was not familiar with before starting this project. I have started to use the CAM tool more and I am trying to get more familiar with it so I can mill parts for future projects. I make use of the CNC controller's emergency stop function with a button that is wired to the top of the enclosure of the machine, which is a 3d printer enclosure I found that has convenient double doors on the front. The enclosre also has built in lighting which is also really nice to have. The machine is screwed into a large block of plywood under the bottom of the enclosure for added stability and to prevent it moving around.