I have a working MPCNC build! I’d like to express my thanks to Ryan and everyone on these forums, which I consulted constantly throughout the build. I bought the hardware kit (sans electronics) from here but used a Mega and RAMPS1.4 board from Aliexpress I had sitting around. I am running the Marlin firmware and Octoprint running on a Pi as a host. I’m using A4988 Pololu driver boards which only support 1/16 steps, so I had to recompile the firmware after setting the value for DEFAULT_AXIS_STEPS_PER_UNIT to {100, 100, 400, 100} in Configuration.h. I’m using a dual-endstop setup. Working volume is 24 x 24 x 5.5. I use Fusion with the guffy postproccessor.
Some adventures I had:
- The first time I plugged in the Mega/RAMPS board, I was greeted with grey smoke. I made the mistake of not checking the pin-outs on the stepper driver boards, and plugged all five of them in backwards, so all 5 were destroyed instantly.
- This also burned up the 5V regulator on the Mega. After replacing the regulator and stepper drivers, the Mega still works.
- I printed everything with PETG out of habit since that's what I commonly use. I think this has resulted in a gantry assembly that flexes more than it would with PLA. I'm going to try reprinting those parts with PLA to see what happens.
- The arm on one of my endstops fell off without me noticing, leading to a very exciting homing process featuring lots of grinding and clunking. I probably should have expected that from a $0.50 endstop switch. I will upgrade to better ones.
- I know, it's too tall. I'm going to shorten it. I don't ever plan on using it as a 3D printer.
- Movements weren't initially that smooth owing to the rough coating on the conduit. It has already started to wear smoother in some spots. I plan to run it in big squares for a while to wear the rails in.
- I over tightened all the bearings. Listen to Ryan when he says not to do that. I loosened everything up.
- I initially had some random Z plunges into the work piece, even though speeds and feeds were well below the maximums. I lowered my Z current limit in the stepper driver and moved the spindle power cord away from the stepper wires. It hasn't happened again. I also tune my tool paths in fusions to eliminate all the Z movements during adaptive clearing of a pocket.
- I also had missed steps on Y in my initial runs. My steppers were extremely hot (defined as "can only hold hand on it for 10 seconds before pulling away") so I lowered all the current limits and haven't had that problem again since. The steppers are now warm but not hot.
- I have significant stretch in the belts due to the zip ties. I'm not convinced it matters given the good results I'm getting.
Hopefully this wasn’t too wordy. Thanks Ryan for all of this awesomeness!
