Ruida Controller Z Axis Motion And Focus Distance Setup

Another LightBurn forum discussion helped me work through how the Z Axis motions should work. This is a lightly edited mashup of several of my comments and builds off a discussion concerning the proper setup of the axis homing / direction settings; the starting point concerns whether the “up” jog arrow should make the platform go up or down.

It may be a matter of definitions and the consistency thereof.

An earlier comment in the thread said “The Machine’s Z-Axis operates in the wrong direction!”, so I had (erroneously) suggested flipping the Direction Polarity control to reverse it, which made it move in the other (wrong) direction when homing.

Knowing that, I suggested restoring Direction Polarity for the correct homing direction, then flipping Invert Keypad Direction reverse both the keypad and LightBurn directions.

If that does not sort the directions out the way you want, then it’s not clear how to proceed.

The Focus Distance parameter determines how far the U (or Z) axis moves from its default position after the focus pen / switch trips: it adds distance and can only be positive. Mine arrived at 0.0 mm and remains that way.

That default position comes from the U (or Z) axis parameter Home Offset controlling the backoff distance from the switch trip point. Mine is at 10.1 mm, which positions the nozzle 18.5 mm from the material and puts the focal point at the surface.

I think the intent is to have the vendor determine Home Offset to make the focus switch work correctly with a minimum mechanical backoff, then add Focus Distance to match the actual lens focal distance. The settings on my machine came from OMTech, but I don’t regard them as unalterably correct.

For my Sherline CNC mill, jogging “up” increases the distance between the tool and the table by raising the spindle.

For my MakerGear M2 3D printer, jogging “up” increases the distance between the nozzle and the platform by lowering the platform.

In both cases, the “up” button corresponds to an increasing distance.

I think the idea behind the Ruida’s setup parameters is to put the just-homed Z axis origin at the platform surface, with the jog buttons (and LightBurn’s motions) then raising the focus point to the surface of the material by lowering the platform: positive numbers increase the distance.

With that in mind, picking the Invert keypad direction setting so that the up button makes the platform go down is correct: it increases the distance from the initial home position. That should also make positive Z steps increase the distance (away from the work) and negative steps decrease it (into the work), which seems sensible.