Reply To: My build

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As I mentioned I had been hoping to get the machine expanded back out to 36″ x 46″ this weekend. Turns out my office was a bigger mess than I anticipated. I managed to get 3/4 of it cleaned (still have one corner full of electronics to sort through) and made enough room I was able to bring the 4′ x 4′ tabletop in and put the MPCNC on top of it in it’s current configuration.

I also made headway on my needle cutter which is what really got me excited about the MPCNC in the first place when I learned about it here. I made my first cuts in foam with it but am still working on fine tuning the needle length and motor speed.

Most people building these have been using servo testers to control the speed…but that seemed silly to me since the RAMPS can control servos and motor ESC’s take a servo signal. So I first built up a fake servo tester from a spare arduino and a 10k pot to confirm things were working…then dug in on trying to use the RAMPS to control the cutter. Turned out to be easier than I expected!

I’m actually running Marlin RC-6 on my MPCNC, the Marlin team has done a lot of work on the LCD code and it works so much better in RC6 that the older release vicious provides was driving me crazy. So I brought the configs over to RC6 and then dug in on adding a custom MPCNC menu to the LCD for functions I want quick access to when doing CNC work. I’m still working on the menu – right now it just has an option to set the x/y/z positions to 0 (so I don’t have to reset the RAMPS to do that) and options for controlling the needle cutter motor. I plan on adding some other useful functions like “Raise Z 10” and “Move Z to zero” – if anyone has any suggestions on other functions it would be nice to have on a MPCNC custom menu please let me know! The changes I made are on github in my “mpcnc” branch of Marlin here: Once it’s more tested and I have all the functions I want in the MPCNC menu I’ll make a .zip for people who are scared of github to try 😉

Anyway, controlling the needle was easy. It’s just a M280 command like “M280 P0 S0” P sets the “port” and I’ve got my ESC plugged into the 1st (Marlin starts counting from 0) servo port – the one closest to the reset button) S sets the “angle” of the servo valid values are 0-180. To use my setup I have to first give a “Needle off” which is “M280 P0 S0” that starts the RAMPS outputting it’s lowest PWM signal for the servo. That wakes up the ESC for the needle motor – but doesn’t power the motor up yet. I can then do a “Needle Low” (or medium or high) from the menu which does a “M280 P0 S90” giving it the equivalent of 50% throttle. Medium does “M280 P0 S135” and high does “M280 P0 S180” currently those are my only three choices but I need to adjust them.

I’m working on trying to add a “Needle speed” option which lets you use the LCD knob to pick a value – but that’s a bit trickier to implement and not ready yet.

Still, I was able to get the needle going and make a few test cuts which has me really excited. Now I just need to expand the machine to it’s originally intended size so I can start cutting full 20″x30″ sheets of foamboard with it!