BLTouch + RRP Configurator. Bad mechanincs or bad config?



  • Generated a config for DIY i3 Rework with BLTouch .

    Probe is offset enough to clear the bed in x axis, if I home the printer and start the auto-probing the generated config will deploy the probe from the origin (Xmax, Ymax, Zmin) and move straight for the first probe point.

    This causes the tip from the probe to extend below the bed and crash into the side as it moves to the first probe point.

    Removing M98 Pdeployprobe.g ; deploy mechanical Z probe from bed.g it works as the probe is still deployed at the first probe point.

    As far as I can tell the tip of the probe needs be able to extend past bed surface to probe it, and if the offset causes it to clear the side of the bed then this is inevitable and the configurator shouldn't generate the deploy line in bed.g? Or maybe adding a move to a safe z-height before deploying the probe and moving to the first probe point is a better approach if it affects other types of probes?

    Other than that it worked a treat with the Maestro board.



  • you need to increase the H parameter of your M558

    https://duet3d.dozuki.com/Wiki/Gcode#Section_M558_Set_Z_probe_type


  • administrators

    @bearer said in BLTouch + RRP Configurator. Bad mechanincs or bad config?:

    As far as I can tell the tip of the probe needs be able to extend past bed surface to probe it,

    Correct.

    and if the offset causes it to clear the side of the bed then this is inevitable

    If you declare the XY offset correctly in your G31 command, and your G31 probe points in bed.g are all inside the bed, then it won't try to probe beyond the edges of the bed.

    and the configurator shouldn't generate the deploy line in bed.g?

    The configurator should not generate deploy/retract commands in bed.g when using bltouch. It should for other types of probe. We'll get it fixed.



  • @veti said in BLTouch + RRP Configurator. Bad mechanincs or bad config?:

    you need to increase the H parameter of your M558

    https://duet3d.dozuki.com/Wiki/Gcode#Section_M558_Set_Z_probe_type

    For that to work the value needs to be almost half my Z height as the move from Xmax, Ymax, Zmin to Xmin, Ymin, Zdiveheight has quite the shallow angle at any reasonable value for dive height.

    I can't see any other reasonable solution than to remove the probe deployment from bed.g or have the move to the first probe point first raise Z to dive height, then traverse to Xmin, Ymin. Doing it in a single move can result in a crash for oddball machine configuration with excessive probe offsets.



  • @veti said in BLTouch + RRP Configurator. Bad mechanincs or bad config?:

    what about not using the zmin endstop and using the probe for zmin?

    the probe has nothing to hit at home position, it clears the bed off the X axis.

    @dc42 said in BLTouch + RRP Configurator. Bad mechanincs or bad config?:

    @bearer said in BLTouch + RRP Configurator. Bad mechanincs or bad config?:

    The problem is if printer is homed, the probe is already off and below the bed. Initiating the probing then results in a crash, the actual probing skips the points the probe cannot reach.

    If you are doing a straight G30 probe (for example, to home Z) then it's up to you to position the probe in the XY plane before probing. Typically you would do a G1 XY move to bed centre before the G30.

    I just hit the Bed Autocompensation button in DWC. It told me it cannot do before homing printer, so I home printer and hit the button again. Probe deploys and crashes, but as you indicated the config has been incorrectly generated and resolving that should prevent future users seeing the same issue.

    However splitting the initial move into z and x,y moves might not be a bad idea in general?



  • what about not using the zmin endstop and using the probe for zmin?


  • administrators

    @bearer said in BLTouch + RRP Configurator. Bad mechanincs or bad config?:

    The problem is if printer is homed, the probe is already off and below the bed. Initiating the probing then results in a crash, the actual probing skips the points the probe cannot reach.

    If you are doing a straight G30 probe (for example, to home Z) then it's up to you to position the probe in the XY plane before probing. Typically you would do a G1 XY move to bed centre before the G30.

    If you are doing G30 probes with XY coordinates as is usual in bed.g, then I repeat, if you declare the probe XY offset correctly in your G31 command, and your G31 probe points in bed.g are all inside the bed, then it won't try to probe beyond the edges of the bed. If it does try to probe outside, then you haven't set up the XY offset in G31 correctly, or the XY coordinates in your G30 commands are outside the bed limits. Or perhaps you haven't set up the M208 XY limits correctly, so that after homing X and Y the X0 Y0 point isn't where you want it (which is usually either the centre of the bed, or one corner). See https://duet3d.dozuki.com/Wiki/Centering_the_bed_or_setting_the_bed_origin.



  • Morning gremlings made my reply into an edit:/

    In any case I think we can call it case closed if the configurator will be changed to exclude the deploy commands for BLTouch. 👍


 

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