Questions about BL Touch on Ender 3



  • I recently installed a BL Touch on my Ender 3. I wish I had done it sooner but I have a couple of questions. I am not able to set the X and Y offsets for leveling, there are no settings for these on the printer itself, only for the Z offset. I have sent M851 X-44 Y-7 and M500 commands to the printer and the reply is only OK, Z-2.92 and no offset when I level. I have put the same commands in the Gcode of a print and still no offset. I have tried different versions of Marlin and got the same results. Could it be that either Marlin or my printer can't do it? I am still using the 8 bit board, I tried three of the 4.2.7 boards and they all froze while printing so I went back to the original board.
    Another question, if I run the leveling will it remain in affect for multiple prints as long as I don't turn the printer off or do I need to do it when I start every print? It takes almost 6 minutes due to checking 25 points, I could go back to older firmware that only checks 9 points.



  • I did some more checking and without the offset the probe measures too close to the edge (and other places) which are higher or lower than where the nozzle is 44mm away. I uploaded a picture that shows the first layer where some places the nozzle is too close to the bed and there is almost no filament and other places where the nozzle is too high for the filament to adhere. There really is that much difference in a 44mm distance that the BL Touch cannot allow for unless the probe measures where the nozzle will be. I went back to the 1.1.6 firmware that only probes 9 locations instead of the 25 that 1.1.9 does and it is an improvement (but I wish it could be better) which means it just happens to probe where the height 44mm away is close to the same as where the nozzle is. 20210831_145113 (Small).jpg



  • Hey Yolanda, I have noticed that my aluminum bed is not very flat, neither is the Creality glass surface (the bottom of the glass is actually a little flatter than the top), I really like the magnetic flexible building surfaces but they aren't very flat either. When I print, even with the BL Touch doing a 25 spot leveling, the ends of the print may be smashed on the bed and the middle barely touching. Most of the time I use .2mm layers. Marlinfw.org shows how to do X and Y probe offsets with M851 and it can be done in uncompiled firmware but my printer doesn't acknowledge it either way, even after trying 3 different versions of firmware. I bought a new aluminum bed and it was more warped than the original. I have "flattened" the aluminum bed somewhat by putting paper shims between it and the flexible building surfaces, maybe that's the best I can do. I am a bit of a perfectionist, maybe that's the problem.



  • hi, @m9mitch From your description, the following advice may help you.1. After installing BL-Touch, there is no X and Y offset, only Z offset; 2. Normally, the newly installed BL-touch needs to be adjusted and compensated. If there is no problem with the subsequent printing, there is no need to adjust.


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