To replace the DC motors I ordered three (3Nm 4.2A) stepper motors, drivers and power supply from Longs ebay shop. With their German warehouse the my order arrived within the week.
Later that same day I started connecting every up and I was ready for my first test. For testing I again used my favourite CNC program, LinuxCNC.
With the DC motor under control I started to do my first integration test. The original setup (see my IronMan post) used a unconventional way of turning a rotation into a linear motion, instead of rotating the leadscrew it was rotating the nut. Since I had the all the parts for this setup I thought I would give this a try.
In the photo's below you'll see the DC motor on the back with its shaft poking through the (original metal plate, yes its a bit rough but this is a test setup remember). The motor shaft is connected to the 24mm leadscrew nut via a belt and pulley system (40:30 ratio). I used some nuts and bots to connect the lot to my gantry.
Motor shaft poking through the metal plate
Belt and pulley with 40:30 ratio
Bolted down to the gantry
For the first (see video below) test I just used my Arduino in combination with a small joystick to generate the PWM and DIR signals for the driver. Aligning the motor and leadscrew was more difficult than I thought it would be. For the test in the video I simply used a clamp to hold the leadscrew in place.
After some more testing I still was not happy with the performance, the leadscrew/nut showed a lot (1 or 2 mm) of backlash. Next up was the belt drive test. I build a structure from some left over multiplex to hold the motor and the bearings in place and attached the smallest pulley (20 teeth) I had.
Wauw.... 10000mm/min that's fast!!. Of course going fast is fun and it looks cool but can it also go slow? The next day I started the slow test and at first it looked good, 100mm/min and even slower was possible, but I wanted to know if at these low speeds there was stil enough power to actually mill so I started using my hand to supply some back pressure........ "what's that funny smell?". That funny smell was my motor driver burning up, apparently it wasn't build for this purpose.
It's a shame, after finally getting the motors to work with DE0 Nano and Linux CNC I was really happy, but I think this these motors are not suitable for my final system. Of course some current limiters can protect the driver but I want a better solution for this system..... to be continued
