Hi,
This is the order that you should do the levelling:
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The “Auto Z-Align”, this runs the Z axis up to the top bumps stops and back down again. This should get the X axis cross bar that the extruder moves on level within about half a millimetre. If not you would need to investigate why it isn’t.
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“Auto Levelling” - this does the 16 point calibration.
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Z axis offset - put a sheet of paper under the nozzle just before it goes down and adjust in small increments until the nozzle is just “scratching” the paper as you slide the paper around then save. Make sure you do hit save and wait a few seconds for it to save and don’t just hit back.
If you ever allow the two Z axis motors to turn separately you’ll need to do the “Auto Z-Align” again, and if you ever do the Auto Z-Align for any reason you must redo the 16 point Auto Levelling.
In theory once set correctly you should not have to do the z axis offset adjustment again unless you replace the extruder nozzle.
Before you do any of the above I would check two things:
- Make sure the heat block securing screw isn’t loose. While the extruder is cold move the z-axis up about half way to get good access and slip the silicone boot off the heat block at the extruder. Try turning the heat block with your fingers, if you can turn it or move it up or down the screw has come loose. Refer to the following picture:
This photo is from when I had the extruder disassembled but will give an idea of what I’m talking about. The screw I’m referring to normally goes through the hole just below the extruder tip in my photo, and I have the screw sitting in the housing to show where it screws in. From memory it’s a 2mm allen head screw.
If this is loose the extruder nozzle will be able to move up and down while printing, this will keep messing your z axis offset up and cause inconsistent first layers.
- When you do the z axis offset make sure there is no filament in the extruder and no bump of solid filament stuck to the tip of the nozzle. If there is a bump on the nozzle it will cause you to set the z axis offset too high when you do the paper scratch test.
After you’ve done this initial calibration you’ll probably need to make fine adjustments based on actual print jobs where you look at the first layer. I’ve actually made my own simple test print exactly for this purpose here:
https://www.printables.com/model/571686-octagon-tower-test-print
Try printing this with your usual print settings and watch as the first layer goes down, cancelling the print after the first layer is finished.
If the nozzle is too close to the bed you’ll get a rough and scratchy feeling surface caused by the nozzle digging into adjacent material it has printed. If it’s a lot too close it will start to bubble up on the underneath as well. Do the z-axis offset adjustment again and increase the value by 0.02mm and try again. (A more positive value is higher from the bed)
When it is correct the first layer should feel quite smooth to the touch and be nice and uniform without any gaps.
If the z axis offset is too high you’ll start to see gaps between the lines and/or parts of the first layer will start to lift off the bed and not stick properly.
I’d generally increase the height in around 0.02mm increments until the rough scratchy surface becomes smooth, then increase it by about another 0.02mm and that should be good. If you start with it too high, reduce it in 0.02mm increments (being careful to not go down to the point where you can’t move the sheet of paper) until the first layer becomes a bit rough and scratchy then go back up by 0.02mm.
Z axis offset is a critical adjustment - it needs to be within about +/- 0.04mm to get a good first layer.
