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HELP !! Auto-Level, Z Homing, CobbleBot = Total Headache!!!

pmanpman
in Questions & Answers
PLEASE, PLEASE give me a step by step answer.  I cannot go on reading and guessing - I may throw the printer out of the window !!!!

OK.  I have spent almost a few weeks trying to make this work.  Without z probing and auto leveling, using a min endstop the printer prints quite OK, but I have to manually recalibrate before each print.

So using z probe:

1.  I have a CobbleBot Basic (yeah, I know!!).
2.  Installed Z-probe (inductive sensor) - at Z-min pin, and moved endstop to z-max endstop.
Q1.  What EXACTLY is "Z-probe height"?  My probe tip is ABOVE level of hotend end nozzle.  There to many definitions of "Z Probe Height".  The image here http://www.repetier.com/documentation/repetier-firmware/z-probing/ shows this:


but my set up is this:


In the FIRST case the Z probe triggers before nozzle is near bed, and will prevent nozzle from approaching bed to print.  Unless z probe is a retractable mechanical probe.  Do the calculations change.
2b.  No matter what I do, I get a value of 30 added to my z height?  Is this because the formula needs to change????


3.  I choose 3 position z probing.  I can actually do the z probing, and my probe triggers fine and the three positions are measured.  
Q2:  BUT the routine stops after the last point, and it does not go back up to calculate the z height.

4.  Q3:  How do I measure z height from bed to max endstop.  It just is not working, and my prints always start with a bed crash.

5.  Q4: What is the "zero" for starting a print?  Without a z MIN endstop how does the printer know what position to start the print.

I need help !!!!!!! Soon !!!!!!!!    :-)

Comments

  • RepetierRepetier
    Make sure bed coating is set to 0
    your definition for z probe height is the same. The image just shows the point where it triggers. The fact that your probe does not touch bed makes no difference.

    You need to run G32 AFTER G28 homing. So we know z position old before probing. G32 S2 will then measure the difference and modify z length accoridingly. After G32 S2 check with M114 if position should be correct. Be aware that you need to change probe height in eeprom to have an effect! After probing you can change zlength until your height fits. Then change z probe height by the value you needed to correct for next G32 run.

    Make sure
    Endstop distance after homing for z is maybe 5 mm, so you can move at zmax without hitting zmax endstop when moving left(right. This is important

    For prints you have the normal G28 and zero is taken from z length since we know we can go so much down.


    ENDSTOP_(X|Y|Z)_BACK_ON_HOME
  • pmanpman
    edited January 2016
    Thank you for your replies.

    1.  So I have to set z length manually.  I thought that G32 will automatically run a z height up to the max endstop.

    "Endstop distance after homing for z is maybe 5 mm, so you can move at zmax without hitting zmax endstop when moving left(right. This is important"

    This I dont get.  The Repetier firmware goes to max endstop and then moves down a little, and then moves up slowly to hit and stay at the endstop.  The endstop is fully triggered constantly until next move command.  
    So you are saying after it adjusts the z max I should make it go back down 5mm????  How is this done automatically as part of the homing routine???

    ""and zero is taken from z length since we know we can go so much down""

    So this "zero" is set manually by me by adjusting z length/height??  This is again guess-work.  It is not optimal.

    Can we write code use the z probe to define the distance above the bed?  Since my nozzle is set 0.1mm above bed when probe triggers, this is my starting print height.   This is not  like z min endstop.  It just is code to go down till probe triggers.
    If you tell me how to code this, I can try !!  Seriously.

    Also, what is ENDSTOP_(X|Y|Z)_BACK_ON_HOME ......it is on the bottom of your message.
  • pmanpman
    Any answer?
  • RepetierRepetier
    ENDSTOP_Z_BACK_ON_HOME is what you should set to5 to move it 5 mm down after homing to z so endstop is not triggered any more (this can be changed in eeprom as well I think, but not sure).

    I also said you run
    G28 
    so you have a valid z position with current z length
    and then run
    G32 S2
    to correct z length. As it already nows start z it can compute z length without z max homing again. That is all.

    Assuming z probe height is not set correctly I then said you could adjust z length manually. From the value of change you know the error in z probe height. So if you change then z probe height by the change the next G32 sould lead to correct z length without manual interference.
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