Homed vs actual start of print - different?

I home, then disable steppers and and level my bed to the nozzle, it is touching the bed everywhere.

Then I go to print and its about 1mm in the air. Why would these two be different?

... can you post the start lines of your G-code until the first "G1" moves?

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

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Thank you for your response. I've included both Slic3r and Cura, as I've used both recently.

Slic3r:
G28 ; home all axes
G1 Z5 F5000 ; lift nozzle

Cura:
;Sliced at: {day} {date} {time}
;Basic settings: Layer height: {layer_height} Walls: {wall_thickness} Fill: {fill_density}
;Print time: {print_time}
;Filament used: {filament_amount}m {filament_weight}g
;Filament cost: {filament_cost}
;M190 S{print_bed_temperature} ;Uncomment to add your own bed temperature line
;M109 S{print_temperature} ;Uncomment to add your own temperature line
G21 ;metric values
G90 ;absolute positioning
M82 ;set extruder to absolute mode
M107 ;start with the fan off
G28 X0 Y0 ;move X/Y to min endstops
G28 Z0 ;move Z to min endstops
G1 Z15.0 F{travel_speed} ;move the platform down 15mm
G92 E0 ;zero the extruded length
G1 F200 E3 ;extrude 3mm of feed stock
G92 E0 ;zero the extruded length again
G1 F{travel_speed}
;Put printing message on LCD screen
M117 Printing...

... and now look at the first "G1"-moves of the printing part - somewhere there should be this 1mm-lifting or differenzing ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Viktor - excuse my ignorance. Where might I find that G1 Code?

... look at the start of the lines - the printer moves the printhead with "G0" commandos and move and extrude plastic with "G1" commandos.

So you can check, to which exact positions the head is moved by the code ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Quote
sirvancelot112
I home, then disable steppers and and level my bed to the nozzle, it is touching the bed everywhere.

Then I go to print and its about 1mm in the air. Why would these two be different?

If you home your steppers you establish the known position for them in terms of steps/partial steps. If you disable the steppers, as you said you did, you have now lost that established position from homing. I can't say I'm surprised your printing 1mm above the bed if you didn't home the steppers again prior to starting the print as the stepper motor has potentially moved to a full step despite homing from a partial step.

... what's the "length" of a full-step? - with my machines it's something between 0.05mm and 0.3mm ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Not totally positive. I was able to fix the issue by changing my Z Offset to -0.6.

I've created an attached an image that explains the issue. I masked the issue by changing the Z offset but it has made the first layer a real crapshoot. I'd like to find the root cause.

PDBeal - I home before pulling any print from the SD card and it homes again as part of the GCode. I left that detail out.