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Clarification of Cura start.gcode for nozzle height please


jonjude
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Posted · Clarification of Cura start.gcode for nozzle height please

Hi,

More on Z settings ...

When I look at the start.gcode added by Cura to GCode, I see the explanation :

 

" .....

; if your prints start too high, try changing the Z0.0 below

; to Z1.0 - the number after the Z is the actual, physical

; height of the nozzle in mm.

.......

G1 Z0.0 F{max_z_speed} "

But if I put Z to be a positive number it'll increase the distance between nozzle and print plate, no ?

Can some explain please ? How does a +ve value reduce nozzle-plate gap ?

Salutations

JonJude

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    Posted · Clarification of Cura start.gcode for nozzle height please

    The Z0.0 referrers to the "G92 X0 Y0 Z0 E0"

    It changes the actual "zero point" compared to the end stop, right now it says "0" is exactly the endstop. With Z1.0 you say that the endstop is 1.0mm above the bed. However, I'm not sure if that will work correctly...

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    Posted · Clarification of Cura start.gcode for nozzle height please
    The Z0.0 referrers to the "G92 X0 Y0 Z0 E0"

    It changes the actual "zero point" compared to the end stop, right now it says "0" is exactly the endstop. With Z1.0 you say that the endstop is 1.0mm above the bed. However, I'm not sure if that will work correctly...

    It works great. I've been only adjusting my bed height there for a while now. I don't use a screw adjustment anymore. It's easier and more accurate/consistent. Plus you get to see the actual variations in height that happen.

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    Posted · Clarification of Cura start.gcode for nozzle height please
    The Z0.0 referrers to the "G92 X0 Y0 Z0 E0"

    It changes the actual "zero point" compared to the end stop, right now it says "0" is exactly the endstop. With Z1.0 you say that the endstop is 1.0mm above the bed. However, I'm not sure if that will work correctly...

    It works great. I've been only adjusting my bed height there for a while now. I don't use a screw adjustment anymore. It's easier and more accurate/consistent. Plus you get to see the actual variations in height that happen.

    But do you use a firmware that always stops on endstops or only when homing?

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    Posted · Clarification of Cura start.gcode for nozzle height please
    The Z0.0 referrers to the "G92 X0 Y0 Z0 E0"

    It changes the actual "zero point" compared to the end stop, right now it says "0" is exactly the endstop. With Z1.0 you say that the endstop is 1.0mm above the bed. However, I'm not sure if that will work correctly...

    It works great. I've been only adjusting my bed height there for a while now. I don't use a screw adjustment anymore. It's easier and more accurate/consistent. Plus you get to see the actual variations in height that happen.

    But do you use a firmware that always stops on endstops or only when homing?

    Latest Marlin I think. Uploaded through your builder. Software endstops enabled and Endstops only for homing. How does this affect it?

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    Posted · Clarification of Cura start.gcode for nozzle height please
    Latest Marlin I think. Uploaded through your builder. Software endstops enabled and Endstops only for homing. How does this affect it?

    It means you can move trough the endstop with G1 commands. If you don't have "Endstops only for homing" enabled, then you cannot move beyond the endstop. This is the default in the Cura firmware, to protect your machine.

    This means that with the default Cura firmware, you cannot adjust the Z in the startcode if your bed is too low, only when it is too high.

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    Posted · Clarification of Cura start.gcode for nozzle height please
    Latest Marlin I think. Uploaded through your builder. Software endstops enabled and Endstops only for homing. How does this affect it?

    It means you can move trough the endstop with G1 commands. If you don't have "Endstops only for homing" enabled, then you cannot move beyond the endstop. This is the default in the Cura firmware, to protect your machine.

    This means that with the default Cura firmware, you cannot adjust the Z in the start code if your bed is too low, only when it is too high.

    I see, so unless your height is adjusted too close via the stops or you have the corner cut off you can't do it.

    In my case I have the corner of the platform cut off and my setting is G92 Z-0.48

    I adjust this up or down by +/-0.04 or +/-0.08 to give a tighter or looser start

    Even without a cut off corner you could probably adjust your initial homing to about -0.2 with the screw or whatever and do it through GCode from there.

    I'm a definite fan of this method, I don't need to adjust it often anyway. I have an optical endstop for Z too now so maybe that is giving a more consistent homing as well.

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    Posted · Clarification of Cura start.gcode for nozzle height please

    Hi, yes I see then what Owen means :

    ** when I start printing, and it seems too high I click manually the Z axis to reduce nozzle-plate gap (i.e. click the plate upward)

    ** If I have to click lets say, 5 times, to get the right height, that corresponds to what, 0.5mm ?

    ** So I'd have to put G92 Z-0.5 to have the gap closed for me (no hands on intervention)

    That sound right ?

    Thanks for the responses,

    Regards,

    JonJude

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    Posted · Clarification of Cura start.gcode for nozzle height please

    Yep, that's right.

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    Posted · Clarification of Cura start.gcode for nozzle height please
    ** If I have to click lets say, 5 times, to get the right height, that corresponds to what, 0.5mm ?

    ** So I'd have to put G92 Z-0.5 to have the gap closed for me (no hands on intervention)

    each 'click" is 0.06mm, as far as I know (1 turn is 3mm, and I was able to count 50 clicks per turn)

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