Pathpilot 4th axis

Hello!
I’m new here and am hoping someone can help me out. I don’t know much about programming or Linuxcnc. I have a Tormach 440 running on Pathpilot...completely stock as it comes from Tormach. I’d like to run a 4th axis on this mill but have no idea where to start. I have the stepper driver and 4th axis but have no idea where to start. I’ll need a lot of hand holding so hope I don’t catch too much grief.
Thanks in advance, Scot

I would start with a basic question
is your 4th axis from Tormach or a 3rd party/DYI one?
Do you know the details for the Driver (ie, model) and the stepper (usually 1.8 deg per step, but 0.9 are also out there)

The first thing is how to add control signals for the 4th axis. since it uses a Leadshine MX3660 as it's main controller and this is a 3 axis controller

If I read the MX3660 and the 440 hal file correctly is it outputing Step/Dir on pins 8/9 of the DB25. that in turn is going to the Outputs 3(step) and 4(dir)

So if you wired those to the Step/Dir of your stepper driver along with gnd (depending on your driver)?
You also need to connect 48V power to the driver

You'll likely need to tweak the hal file and set the SCALE to your steps per rev for your motor/driver combo

This is high level of course but from what i see in the INI/HAL files and the MX3660 manual it should be a start.

anyway, that is a start

Hello and thank you for the reply! It is a DIY 4th axis with a standard 200 step/rev motor and 21:1 reduction. I think I can figure out how to wire up the driver using your info and my limited experience. But, the INI/HAL files and such are above my head. Is there a tutorial somewhere that explains how to access the inner working of Pathpilot? I have seen a video or two were someone modifies settings but I’d be concerned about creating a mess and ending up with a non-functioning machine.

I'm thinking if all you do is edit
tmc/configs/tormach_mill/tormach_mill_base.ini

find the [AXIS_3] section at the bottom
change
SCALE=400
to what ever you're setting your driver to in steps

before you anychanges make a backup of the file your changing
cp /home/operator/tmc/configs/tormach_mill/tormach_mill_base.ini /home/operator/tmc/configs/tormach_mill/tormach_mill_base.ini.bak for example

editing the base config will make it work for all tormach mills.
you can edit the specific file also for the 440

you'll probably have to tweak the SCALE to get the value that works best.
i really haven't looked at how the scale works on a angular axis since I don't have one.

Thank you, again. I will give it a look later this week...overly busy with work right now! It’s highly likely I will be back with more questions.

I am close to seeing if this will work. In the .ini files, I see the “scale” value and I understand it to be steps per degree for a rotary axis. There is also a mysterious “harmonic_scale” value right below the scale value. I looked through the part of the LinuxCNC documentation that talks about the scale setting but I don’t see anything about harmonic_scale. Anyone know what this is?

Looking at the source code and tormach website that is the Duality Lathe Option. Scale is for normal 4th axis.

Thank you once again! I will try scale and harmonic_scale and see what happens. Which .ini file should I make the change in?

I am having some trouble with the stepper motor. It will turn in one direction but not the other. I am not yet sure why. If it becomes necessary to check or change, how do you verify the assignment of output 3 to step and output 4 to direction? Where are these values assigned?

Unless you want it to apply to all mill configs you would do the one that's specific to your will . example tormach_440_specific.ini and add the config items you want to override the base config tormach_mill_base.ini

the motor config for the pins would be in the hal file.
look for a line like this in the spefic.ini file for which hal file
[HAL]
HALFILE = tormach_mill_mesa_440.hal << you would edit this one

I am having trouble finding this hal file. Can you tell me where it lives?