4th axis scale factor (steps per degree)

Hi, I have a new 1100MX and I bought the 4th axis driver kit (stepper driver) and wired up a small ebay 4th axis with a er32 collet.

I just want to learn what the 4th is all about in CAM and in practice before buying into the other more expensive options.

The little 4th is working but the scale is off. I am using the 4" rotary table option available by selecting a radial box in path pilot. I changed the scale in the 4" axis to the correct value in an ini file for the tormach 1100MX But I don't think it was updating. I tried a bunch of edit, restart combinations. I found some similar questions like this for the 440s and the 770s but each seems to have a specific case that complicates the answer. It sounds like the harmonic drive of the 4" might make it more difficult to edit this scale factor. Maybe I should use and edit the 6/8" scale to run this?

Does anyone know the easiest and exact place to edit this scale? Do you need to restart with each change? or can I make edits and check accuracy without the whole reboot.

Also Is the scale factor simply steps per degree?

Any help greatly appreciated!!! Thank you.






.

Ok found how to update steps per degree. Chose to use the 4" rotary table selection from user interface.

Go to ~/tmc/config/common/4th_axes.inc
Go to the line that says "SCALE = " under the 4-inch table section; it will be around line 34. The original SCALE value is commented out with a "#". You can restore it at any time by deleting the "#" and commenting out the current value. Then you need to restart the entire machine for the changes to take effect.

I can confirm this is the proper place to edit the Steps Per Degree.

Some math to help out future people setting up their own 4th axis.

Micro Steps = Driver Pulses / Steps Per Revolution of motor

(micro steps * motor steps per rev * total gear reduction) / 360 = steps per degree

For example... i used a 200 step motor with 1000pulses on the driver and a 50:1 harmonic.

1000 / 200 = 5 Micro Steps
(5 * 200 * 50 ) / 360 = 138.888888 steps per degree

So i would enter 138.888888 as the SCALE of the 4th axis

The microarc Tormach has setup for 141.666666 around 51:1... not sure how they hit that total gear reduction.