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Improving initial z height repeatability

Discussion in 'General Questions' started by Lance Weston, Jul 24, 2021.

  1. Lance Weston

    Lance Weston Active Member

    Jun 2, 2018
    Likes Received:
    The initial z height starts from zero with steppers turned off. When turned off the zero point will change when the steppers are turned on as they move from their micro stepped position to the nearest indent.

    Start by heating the bed to 10C hotter than I use. This is to allow time for the temp to reach the surface of the bed. Now do a home which is not accurate because the steppers are at the nearest indent and the switches have hysteresis.so the inaccurate home will not change Set absolute mode and turn the fans off. Now move the bed up from home and then home the bed. This will lock the bed to the micro stepped home which should be 16 times more accurate, since the bed is hot already there will not be enough time to turn the steppers off and they will remain in the correct home position. I have commented out robo leveling, but if you use it the bed is at full temp and the results should be more accurate. Next move the bed into printing position so that when the hotend reaches temp it can print immediately and have the minimum drip. Allow the bed to go back down to 60C while the hot end is heated to printing temperature. When the hot end hits temp immediately draw a line down the left side of the bed arriving where the slicer will start the print. Retract. This way there will be no drips across the print. At this point the print will start immediately following the hotend purge line.finish.

    This should be the best order of commands for a good print.

    ;heatup of bed
    M190 S70
    ; set to millimeters
    ; home
    ; set absolute mode
    ; turn off fans
    ; move bed down 230mm
    G1 Z230 F300
    ; Home
    ; zero extruder
    G92 E0
    ; Robo Leveling
    ; move bed to printing position
    G1 Z0.3
    ;non blocking heatup of bed
    M140 S60
    ;heatup of extruder
    M109 S210
    ; print 160mm priming line
    G1 Y-160 E10.0 F500
    ; Retract
    #1 Lance Weston, Jul 24, 2021
    Last edited: Jul 28, 2021

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