Idex Bed.g



  • Hi I think I am having trouble with my Idex bed file. I have an Idex with separate Z motors, one on each end of the X U axis.

    Therefore I have a bed.g file that firstly tries to balance the z motors then does a bed compensation.
    The reason I say I might have an issue is that if I rerun the bed compensation staright after running the bed compensation then the z alignment is up to .2mm out so the z motors realign themselves again. the bed.g file is below, comments really welcome.

    ; bed.g
    ; called to perform automatic bed compensation via G32
    ;
    ; generated by RepRapFirmware Configuration Tool on Sun Feb 26 2017 13:25:00 GMT+0000 (GMT Standard Time)
    G90 ; Set to Absolute Positioning
    G29 S2 ; Clear the height map
    M561 ; Clear any Bed Transforms
    T0 ; Ensure Tool 0 is selected
    G28 ; Home All

    ;Mesh bed levelling
    M208 X296 S0 ; Reset axis maxima to allow probe to get to x250

    ;Adjust LeadScrew
    M671 X-54:354 Y100:100 S5 ; define lead screw positons
    G30 P0 X13 Y100 Z-99999 ; probe point near first lead screw
    G30 P1 X270 Y100 Z-99999 S2 ; probe point near second lead screw

    ;Adjust LeadScrew
    M671 X-54:354 Y100:100 S3 ; define lead screw positons
    G30 P0 X13 Y100 Z-99999 ; probe point near first lead screw
    G30 P1 X270 Y100 Z-99999 S2 ; probe point near second lead screw

    M557 X5:276 Y10:200 S45 ; 267 44 Define mesh grid

    ; Probe the bed
    G29 ; Probe

    G1 Z5 ; Raise Head
    G1 X0 Y0

    M208 X250 S0 ; Reset axis maxima to normal


  • administrators

    It's often necessary to run the side-to-side bed levelling more than once, because the effect of adjusting the leadscrews on the bed tilt isn't quite the same as theory predicts. The important thing is that when you run it multiple times, the corrections it makes are smaller each time.

    If it consistently under-corrects, use the M671 F parameter to force an over-correction.



  • Hi dc, as you can see from the bed.g I run the leadscrew correction 3 times, and yes it goes down each time, for instance I get readings such as
    first correction difference 0.3
    second correction difference 0.08
    third correction 0.02

    but the issue arises if I run the bed.g as above, then I run it immediately again, then I am back to having say a 0.3 difference on the first shot.

    I don't know why that is occurring as I would expect a 0.02 difference or below.


  • administrators

    When you run it the second time, does it apply 0.3mm correction to both leadscrews, or to just one? If it's applying it to both leadscrews then it's just trying to correct a Z=0 position error. This is most likely happening because you home Z at bed centre, and bed centre differs in height from the two probe point in bed.g by 0.3mm. Your height map file may confirm that.


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