Solutions to Core XY printer success



  • Hi, I have just spent some months building a CoreXY printer from scratch using rails with a print volume of 500X500X500 mm and have just succeeded (after a huge effort) in tuning the printer and getting a good quality print.
    I would like to thank all of the contributors to this forum for the information and also the RepRap community for all the work put in. Without them I would not have succeeded. I have just observed the forum and this is my first post.
    I would like to put a few items of information on this post which may help others on their journey:

    1. I had problems right at the end in getting a good first layer. I was getting a lot of stippling on the first layer. Changing temperature, layer height and extrusion widths did nothing to solve it. The problem turned out to be simple. During the tuning process I used the same print over and over and did not clean the bed after each print. I was using PETG for tests and adhesion is not generally a problem. A clean with Isopropyl alcohol solved the problem. I am using a flexible buid plate from Wham Bam using PEX.
    2. The live Z for tuning first layer height which is available on the Prusa Original MK3 is not available on RepRap firmware. Baby stepping implemented on the DWC does not seem to work. Here is my solution :
      Using M206 does change the end stop ie M206 Z0.05 effectively moves the bed coordinates to lower the extruder head. If you want to lower further you need M206 Z0.10 and so on . I have made a series of macros to move the head up and down. I have made a simple square print to fine tune my Z height. Once OK I send a M500 to store it in EEPROM. In my print start up code I use M501 to read the value back. If you use mesh bed compensation the M206 commands seem to have no effect during the print so I do my tuning prior to printing. Once tuned the setting seems to remain OK.
    3. Initially I used a non temperature compensated inductive Z probe which drifted too much with temperature so I replaced it with a genuine BL touch probe. Thanks again for the post by Betrue3D for the invaluable informatin. I had a few consitency problems which turned out to be not a probe problem but how I mounted the probe. The probe mount has to be closely associated with the hotend tip and to that end I printed a custom cooling shroud for the hotend with ribs which engate with the hotend heat sink and I directly printed the BLtouch mount onto the shroud. The relationship between the hotend and the probe now remain constant. I do however do all of my calibration with the hotend at temperature. I also set my trigger threshold to 500 to make sure that I don't get inconsistent triggering due to electrical noise.
    4. Make sure that the Z homing point is exactly the same place as one of the mesh bed leveling probe points. I had a bed crash in the middle of the bed which caused a dimple in the print bed (the homeall.G made by the configurator swapped Z with the Y axis which caused the problem). I happened to home on this dimple but did not probe on this point. The bed mesh compensation map varied considerably in height until I moved the home and probe to the same point (in the middle and away from the dimple) As a check , irrespective of how level your bed is, the home and probe point on the mesh bed should always be close to zero.
      Hope the above may helps someone on their journey to 3D printing success.


  • Fantastic, thank you for all the tips.



  • My solution for #2 is to use a finely adjustable Z=0 endstop. I previously used a lever/cam/microswitch arrangement and recently switched to a differential screw adjustment and opto interruptor that moves the bed by 100 um per full turn of the screw. I can easily make small adjustments without overshoot.


  • administrators

    @Willo47 said in Solutions to Core XY printer success:

    The live Z for tuning first layer height which is available on the Prusa Original MK3 is not available on RepRap firmware. Baby stepping implemented on the DWC does not seem to work. Here is my solution :
    Using M206 does change the end stop ie M206 Z0.05 effectively moves the bed coordinates to lower the extruder head. If you want to lower further you need M206 Z0.10 and so on . I have made a series of macros to move the head up and down. I have made a simple square print to fine tune my Z height. Once OK I send a M500 to store it in EEPROM. In my print start up code I use M501 to read the value back. If you use mesh bed compensation the M206 commands seem to have no effect during the print so I do my tuning prior to printing. Once tuned the setting seems to remain OK.

    Baby stepping does work, but it respects the M208 limits. So if you set the M208 Z min to 0 then you can't babystep down by more than the first layer height.

    It's common to home using the Z probe; in which case fine adjustment to the Z=0 position is done using the G31 Z parameter.


Log in to reply