Modified Marlin Firmware CNC To Printer

thingiverse

Modified Marlin firmware for the original CR-10 mainboard. UPDATE: The Creality CR-10 board DOES work. I had forgotten to short out the limit switch pins. I just used 2 pin jumpers to fool Marlin into thinking that the switches are there. Also need to disable software endstops. Then just send a G92 X0 Y0 Z0 to home. This and other useful commands can be saved as a gcode file to the SD card for preparing the machine without the need for a laptop. A return to home would be G0 X0 Y0 Z0. I may also make changes to the LCD status screen to get rid of the bed and nozzle icons and add a laser icon in place of the fan. This project had started out as an attempt to use a spare CR-10 mainboard to control a 3018 Woodpecker-based CNC / Laser engraver. I soon found out that because the woodpecker's stepper drivers VREF is set at 11.2V, and the board runs off of 24V, that the CR-10 board was not going to cut it. The stepper motors would not budge!!! I abandoned the woodpecker board that came with the engraver for several reasons. It doesn't support variable spindle speed or laser PWM control although it claimed to. When viewed on my scope, the laser output waveform looked nothing like a TTL or PWM signal. It was actually a sawtooth waveform. Even when a M3 S255 command was sent the peak to peak voltage was 0.2 volts. Plus, the board was not designed correctly. While M3 did turn on the spindle, when in laser mode M3 turned the laser OFF. This is totally backwards and also a serious safety risk. As it turned out M5 turned on the laser. The laser also remained ON after powering the unit on until M3 (backwards!!!) was sent. Throw it in the garbage!!! Upon further inspection and after enabling PWM in the GRBL firmware, the only change was a voltage increase in said waveform. Pin D11 did produce PWM signals but as a function of spindle RPM as explained in the firmware comments ... and in 1000 steps. This wouldn't work for software that sets full laser power with M3 S255. I found a new GRBL control board that includes manual jog buttons, a LCD and SD support here https://www.ebay.com/itm/3-Axis-0-9J-USB-GRBL-Control-CNC-Engraving-Machine-Board-GRBL-Offline-Controller/163440050537?_trkparms=aid%3D333200%26algo%3DCOMP.MBE%26ao%3D1%26asc%3D20190129125700%26meid%3Dad06f9548e2848d4b7aff1ef2ebf613a%26pid%3D100752%26rk%3D1%26rkt%3D12%26sd%3D152944279794%26itm%3D163440050537&_trksid=p2047675.c100752.m1982 The Marlin firmware's main.cpp has been modified to include the M3/M5 commands on the FAN port. It works and behaves in the same manner as sending a M106/107. I also included a custom boot screen. While my CR10 to CNC failed, this modified firmware will allow GRBL-flavored gcode to be processed by a 3D printer, so that part was a success. The M3/M5 commands can now be recognized by Marlin for laser engraving. I see no reason why the modified main.cpp cannot be applied to just about any printer running Marlin. Just copy the file into your source code. The changes made are in the switch() function that examines incoming gcode commands. The fan section of the switch function is where the new commands reside. In addition, 2 new struct() functions were added for M3/M5 and mimic PWM fan operation.