DonStauffer
Posts: 12
Joined: Tue Sep 05, 2017 5:23 pm

Global Z offset and "babystepping"

Mon Jan 08, 2018 10:06 pm

My CR-10S is running Marlin 1.1.7, which has a feature called babystepping. When a print starts, I can double click the console knob on my CR-10S, and then adjust nozzle height real-time.

My understanding of babystepping is that when I use it and get a perfect first layer height, I should update the global Z offset in Simplify3D on the GCode tab, by adding the babystep value to it. That's assuming my Z offset (M851) is set correctly. After that, the next time I print with that profile on that printer, assuming the probe hasn't moved relative to the nozzle, and that I haven't changed the Z offset, little or no babystepping should be required to get the same perfect layer height.

Do I understand this correctly? Because that's not what's happening most of the time. I have to babystep various amounts, in varying directions, each print. Updating the global Z offset in Simplify3D doesn't do what I expect. I can still usually get a good print, but I don't understand.

Why might this be?

DonStauffer
Posts: 12
Joined: Tue Sep 05, 2017 5:23 pm

Re: Global Z offset and "babystepping"

Mon Jan 08, 2018 11:26 pm

Rethinking, the real question is "Why was I able to babystep -1.20 mm (down) without the nozzle being below the surface of the glass?" My layer height was 0.196 (which is 0.2 times 98% for the first layer).

User avatar
DarthRevan
Posts: 479
Joined: Wed Feb 18, 2015 8:29 am

Re: Global Z offset and "babystepping"

Tue Jan 09, 2018 2:33 pm

Good question,

If your first layer height is 0.196 and you're able to jog/step the Z down -1.20 then the probing value is leaving too large of a gap between your nozzle and your bed.

In my experience you're ultimately looking for a gap of about the thickness of a piece of paper when discerning nozzle and bed gap prior to any adjustments for first layer height. I'd recommend using one tool exclusively for playing with your nozzle height. Changing multiple variables at once often leaves you scratching your head as to what caused the outcome you desired. :geek:

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