Magnetic Bed V2 and Calculating Z offset


I have a lulzbot taz pro that has been sitting around for almost a year. I recently purchased the magnetic flex bed to replace the original bed that the taz pro came with. I’ve completed the installation of the magnetic flex bed V2 and I would like to do a test print. I am not familiar with the process of leveling the bed or calculation the z offset for this type of printer. Could someone assist me in understanding how to 1. level the bed and 2. How to calculate the z offset correctly. I do want to mention that the toolhead that is currently installed is the 0.5mm HE Toolhead. According to the forums the option to automatically calculate the z offset is only for the dual extruder toolhead. Any assistance would be appreciated.



You don’t need to re-level the bed, that’s handled automatically by the printer by touching the four washers at the corner. Provided you have a good clean nozzle, it’s a non-issue.

For my Pro running with the magnetic flex bed, the new z offset is -0.30mm, with the glass bed it was about -1.2mm. That offset is where the print surface is relative to the top of the washers, so changing out your toolhead won’t change your offset, since the nozzle is automatically zeroed off of the washer.

You change that z offset in the advanced settings menu, but I would recommend starting by setting it to -0.10mm, then starting a simple test print. As the test print is running, go into the “nudge nozzle” in the menu while printing and nudge it down by the 0.01mm increment until the lines on the first layer start to touch. With the 0.5mm HE toolhead, you shouldn’t have much issue seeing the layer lines, just do something with a big enough base that it has time to even out between each little nudge downward. I’ve noticed that the pro seems to take a couple seconds to process the nudges downward (in contrast to the Taz 6’s instant z offset adjustment), so do it just a little at a time. After you back out of that menu, it will ask if you want to save. You do want to save, unless you made things worse.

The offset talked about with the dual is to correct for offsets between extruder 1 and 2, nothing else.

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When I replaced the bed on my TAZ 6, the Z-offset went from approximately -1.2 to 0.3 (a difference of 1.5). See the Final Notes.

Hi Wrathernaut,

Thank you for the assistance. I was able to set the z offset to -.10 and make manual adjustments as you suggested. It turns out the z offset works best at -0.3 after doing 1x1 cube test print at -0.1, -0.2, -0.3.

My issue is resolved.

Hi B-Morgan,

I am curious to know. Per my comment below, I found that my z offset was best at -0.3. Could you help me understand why yours would be so drastically different at + 0.3? Maybe due to you using the TAZ 6 and a different bed, than the magnetic bed? Would the tool head make a difference as well?



The Z-offset value reflects the difference between the mechanically triggered Z-min endstop and the actual bed surface. The mechanical X-min, Y-min, and Z-min endstops are tested with a G28. The corner washers used to establish “levelness” of the bed are tested with a G29 which is not strictly needed.

On the TAZ 6 (and I assume the TAZ Pro), the tip of the nozzle is used to trigger the Z-min endstop, as long as you do another G28 after changing the tool head, the relationship between the Z-min endstop and the nozzle is the same. The TAZ 6 dual-extruder V3 comes with an “adapter” that fits over the Z-min switch which changes its physical location in relation to the bed surface. I believe the TAZ Pro originally came with a Dual extruder tool head and I don’t know exactly how the Z-min endstop was designed.

The actual value of the Z-offset isn’t important. What is important is that the nozzle never “touches” the bed surface (or worse, attempts to position itself “below” the bed surface). The Z-offset is adjusted up or down to make sure this doesn’t happen but more importantly, how the filament is deposited on the bed surface can be fine tuned with this value. The value of Z in the gcode generated from the slicer should never be less than or equal to zero.

The installation guide for the Magnetic Bed V2 sold me to adjust the initial Z-offset by +1.5 which is what I did. I then did some fine tuning based on the how the first layer was deposited and I think my +0.3 turned into +0.27. Your -0.3 is an acceptable value if you are happy with your first layer.