Finer adjustments to z offset?

Is there a way to do finer adjustments of the z offset? I’m having issues with first layers because the nozzle is just a tad too close, but if I raise it up .05 it’s too high. My other printers let me adjust by .01. I’m more familiar with GRBL than I am with Marlin, I am aware that Marlin is a very heavily modified GRBL but my experience lies in CNC and not 3D printing. Any help is appreciated.

At a USB console (Luban or Octoprint) type G1029 D -x.xx where -x.xx is how far you want the nozzle to go down. Negative down, positive up. Remains until you next calibrate. You can adjust as much as you like but has to be under 1mm at a time!

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Awesome thanks! Helped a lot!

If you are interested and careful this is how I level, its at the end of the post.

Lots of levelling info and just wish Snapmaker would take the fact that their leveling process does not match the printing process seriously.

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I’m about to do a linear guide rail modification that someone posted on the facebook group. They also made the brackets too, so for now I took off the glass bed (haven’t done the IR mod yet anyway) and I’m going to see if it will help with the flatness of the bed. I doubt it will do anything for the center of the bed, only the outer edges. I’m hoping the biggest benefit will be that the carriages become less prone to coming loose on the Y axis and eliminate any possibility of the front/back wobble. Mine has yet to do this but I’m not going to wait for it to happen.

Have to say the biggest benefit I saw was moving to glass. The glass works as it’s flat so you just have to sort out the slopes and even though you can easily move the front and back of the bed, when printing they stay quite constant. I have thought tightened the rail carriages to reduce wobble. Glass also ment that the difference between the Snapmaker probing and printing locations could be sorted with nozzle height as it was only slope that was being adjusted, not humps and bumps. If you remove the wobble the humps and bumps of the bed will still exist and the miss-aligned leveling will not sort that.

Oh yeah, I only took the glass bed off to do this rail mod. I’m putting it back on in conjunction with the linear rail guides. With those 2 combined I wonder how flat I can get it to be.

Here’s a way to finely adjust the Z offset on the J1 (only in the positive direction) without having to manually change it for each print - mine was too close and grinding the platen and this fixed the problem:

Do the bed levelling procedure but place a piece of folded aluminum foil over each contact circle on the bed (number of folds is up to you but a single fold, measuring 0.03mm fixed me right up!)

This fools the machine into thinking the bed is just that small amount higher. The foil is only there during the bed levelling procedure - remove it afterward!

I wonder if G1029 d(z-offset) works on j1