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Add ability to set z-offsets of both nozzles
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Description

While the machine is idle, you can only set the z-offset of extruder 1. Mid print, when it's using extruder 2, you can adjust extruder 2's z-offset, though only relative to its current value.

In the meantime, if someone could share the M commands to use in the cura console to set both z-offsets.

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T1: Test task

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matth created this task.Dec 14 2018, 11:53 AM
matth triaged this task as Normal priority.

M851 might help:

http://marlinfw.org/docs/gcode/M851.html

@marcio can probably explain the way the offsets are working better than I can. I think there may be some information in other tickets on this workboard too.

matth added a comment.EditedDec 14 2018, 12:26 PM

I tried adding the T0 or T1 and then setting them, but the LCD only displays the setting I put in for T0:

T0 M851 Z-.45
T1 M851 Z-.5

Then when I go and check the z-offset, it says -0.45. I then switch the nozzle by typing in T0 into the console, then check the z-offset, still says -.45. I don't know how to check if the z-offset for extruder 2 is changed, since it only displays the offset for extruder 1.

marcio added a comment.EditedDec 14 2018, 12:59 PM

There is not a separate Z-offsets for T1. There is one Z offset which applies for T0, then there is the dual nozzle offset that determines the position of the second nozzle relative to the first. If you are finding that the Z-offset is incorrect for T0, you can adjust the Z-offset. But if the Z-offset is incorrect for T1, then you must adjust the nozzle offset, which is a separate thing. If you try adjusting the Z-offset while printing with T1, you might fix things for the T1, but T0 will now be incorrect. Adjusting the offsets on a dual-nozzle printer using M851 would be very difficult because of the way the Z-offset interacts with the Nozzle Offset.

There is a special screen that shows up when the printer is moving. That is a new screen called "Adjust Offsets". What that screen does is it allows you to nudge the currently printing nozzle in any direction, while the print is running. The idea is that you observe the first layer and nudge the nozzle up and down until the first layer looks correct. Then, you wait until it changes to the other color. Set "Adjust Nozzles Together" to "No" and now adjust the second color so it looks good.

This screen modifies both the Z-offset and the nozzle offsets, depending on which nozzle is printing and whether the "Adjust Nozzle Together" button is checked. It is not modifying the Z-offset or the Nozzle Offset, it modifies both. This is why it only shows a relative, rather than absolute value. Once you are satisfied, if you really want to see the raw for "Z-offset" and "Nozzle Offset", you can stop the print and go to the "Z-Offset" or "Nozzle Offsets" screen to see what values were placed there.

I would just like to be able to set the z-offset for the extruder 2 when not printing. I don't like the idea of being able to change that only in mid-print.

marcio added a comment.EditedDec 19 2018, 11:36 AM

@matth: There is no Z-offset for the second extruder in Marlin. But if you want to change that nozzle relative to the first nozzle, you can modify the Nozzle Offset (when not printing)

marcio closed this task as Resolved.Dec 20 2018, 12:37 PM
marcio claimed this task.

In the latest Marlin, the offset screen now has a checkbox that when checked will show the true Z-offset and Nozzle Offset. I am closing this issue since this new feature gives advanced users the option of understanding how the Z-offset and Nozzle Offsets are being adjusted.