TwoTrees TS2 20W newbie autofocus confusion

Hi-
I am a total noob.
The TS2 (10W or 20W) has a z-axis autofocus. I installed the TS2 macros to focus, but I am confused how they work. Specifically, how do I trigger the TS2 to use the probe to autofind the focus point? Wouldn’t that point would be Z0?

From there, TwoTrees provide some macros that should be helpful but seem to assume the engraver already knows the point where the laser is in focus at the surface of the object.

The first macro is called Z lift 20mm. The gcode for this macro is G1 Z20. This is where my confusion begins. It seems it should move the z-axis up 20mm. It is unclear where the starting point is, however. Shouldn’t there be something to define the zero point?

The second macro is Engrave. The gcode is:
$HZ
G91
G1 Z0

I have no idea what the $HZ means. The G91 tells to move from the current position (again, doesn’t it need to know the starting position?). G1 Z0 should move the z-axis by zero(?). Doesn’t this just mean don’t move?

Last confusion (for now!): If I want to autofocus on a small object, like a dog tag, won’t the z-axis probe miss the object completely?

Thanks in advance,
-Bob

I don’t have any familiarity with your specific machine but can provide some insight on the g-code.

The meaning of “G1 Z20” could depend on the state of the controller. Under G90 that would mean absolute Z20 position. Under G91 it would mean move +20mm on Z axis.

Yes. This assumes that some Z0 has been established.

This means home the Z-axis.

This means use relative motion.

Yes. This will move the laser 0 mm on the Z relative to current position. Note sure what the value of this whole thing is but it seems to me that the main purpose is homing.

Does Z-axis home high or low? Meaning is it far from the material or close to the material? And what is position of Z after homing?

If autofocus is accomplished with a Z-axis probe that triggers onto the material then yes, this would be a problem. There are ways of defining material height that is based off of an absolute z-home position but that’s a different story entirely.

Superb! Thank you for your prompt and comprehensive reply. That seems to work nicely. Did a test engrave and Wow! this thing burned through 1/8 balsa on the engrave test.

Moral: focus matters.

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Focus is a huuuge deal! Glad you’re up and running - thanks for the solve @berainlb

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