Using Z-offset from Marketplace in Cura for Ultimaker 2+

[squodeler 0]

Newbie here, trying to understand just how the z-offset (by ahoeben/afieldofview) works.  Please bear with me being long-winded.

 

Running Cura 4.6 with the z-offset plugin.

 

Suppose I level and physically set the bed to, say, 0.2 mm below the nozzle.

I print some PLA with z-offset = 0 in Cura UI.

Now I want to use PETG, so I use the plugin in Cura UI to set a z-offset of, say, +0.25 mm.

So now Cura is telling the printer that, physically, 0.45 mm below the nozzle is the Z=0 position.

I print a model.

If I run the same gcode again, does the printer know to set the bed 0.2 mm below the nozzle, before running the gcode to change the z-offset, to set the bed 0.45 mm below the nozzle again?

If so, the absolute altitude of the bed following calibration (the 0.2 mm value) must be stored somewhere and used to initialize the Z axis.  Is this done by the firmware before the gcode is run?

If not, how does the printer driver avoid stepping the bed lower each time the gcode is run?

 

Explanation appreciated.  This community is appreciated.

[ahoeben 1,955]

8 hours ago, squodeler said:

If I run the same gcode again, does the printer know

Any and all offset created by the plugin is reset when the printer is "homed". The printer is homed on the start of every new print.

 

Your printer uses "stepper motors". These can rotate by very precise increments, but they do not "know", nor can they meassure, their current angle. As a result, all the printer "axes" can move by a certain distance very precisely, but when started the printer has no idea where each of the axes are. When homing, each of the axes touches on a "known" position, and from there on all relative moves are added up so the printer knows where each axis is.

 

The plugin "plays" with the internal knowledge of where the "0" for the Z axis is. It stays in the modified state until the z axis is homed again.

 

As an aside: bold text is normally used for emphasis. You emphasized your whole post, as if you were shouting the whole thing. Please don't; it is not necessary.

[squodeler 0]

@ahoeben

 

Thanks.  I guessed that was the case.  The bold text was an accident.   Fast response appreciated.