It’s common for people to use a low-end spindle on a Probotix Comet CNC. The LinuxCNC software can turn the spindle on and off, but not control the speed or direction.
The G-code for turning a spindle on is M3, but that command alone will not work. It needs a non-zero speed parameter. For example:
will turn the spindle on. To turn it off use M5.
As always, stay safe.
Personal notes on how to get the LinuxCNC software that comes with the Probotix Fireball Comet CNC to find your personal library of G-code files.
The Probotix Comet controller software (AXIS) by default looks for extra G-code files in /home/probotix/emc2/nc_files.
If one does not wish to store files there, one can edit the /home/probotix/configs/Comet/Comet.ini to point it to the directory of choice.
Change the PROGRAM_PREFIX parameter to point to the directory of choice. (As always, please back up files before hacking them.)
This will allow one to, for example, load a standard preamble with the G-code:
or otherwise allow one to create a library of useful routines.
These are my notes on starting and stopping the Probotix Fireball Comet CNC mill.
I’m not kidding about danger. There is one cardinal rule.
The motor control box must never have power without the AXIS control software running.
The AXIS control software (the Comet icon on the desktop) must and I repeat must be running before power is applied to the stepper motor control box, and must remain running as long as power is applied to the stepper motor control box.
Why This Is Important
The motor control box translates signals from the computer’s parallel port into motion and spindle control. The AXIS software controls the signals to the parallel port. If the motor control box is powered on before the AXIS software is running, or the AXIS software is exited before the motor control box has been powered off, then the parallel port and thus the motor control box will be thrown into an unknown, unpredictable, and uncontrolled state and the mill can start operating by itself.
Think about how dangerous this is:
- The spindle can start without warning and the red emergency stop button will not be operable. (I had this happen to me.)
- The motors can start moving without warning and the red emergency stop button will not be operable. These motors are powerful and can crush fingers.
A powerful uncontrolled robotic cutting tool is not something to leave to chance.
Now that I’ve beat that horse to death, here are the steps to safely start up and shut down a Comet:
- Start the computer
- Double click on the Comet program icon and leave it running.
- Power on the controller box.
- Ensure the emergency stop button on the machine is out (off). Twist the knob to reset it.
- Turn on the (virtual) machine power on. Push F2 or click on the orange power button icon on the top tool bar of the AXIS software.
- Use Home All button to put the CNC into a known state.
- Use the machine to make all manner of wonderful creations.
- Turn off the controller box.
- Exit the AXIS (Comet) program. You can use the X in the upper right-hand corner.
- Turn off the computer. In the top right hand corner of the screen there is a power symbol. Click on this to bring up the menu and select Shut Down….
If you ever need to restart LinuxCNC power off the stepper motor controller box first. The motor control box must never have power without LinuxCNC running. (Did you think that I was done beating that horse?)
I have had problems having LinuxCNC crash when trying to restart it. If this happens, reboot the computer. There is a power symbol in the top right corner of the screen. Click on this to bring up the menus and select Restart….