G31 and mesh, need help

  • Hello, I just finished my CoreXY ...

    This is not the first for me, but always under Marlin.

    So I just jumped and I use for the first time Duet3D.

    I just made my first pieces with. But, I find myself with a worry ... I use a BLTouch and I have to change constantly the values ​​of my probe (G31 P25 X-24 Y-10 Z0.79) a shot, it is Z1, once Z0.95 and now Z0.79 and yet I do not change anything in my setup and the printer turned on. It's always the same room I print, a test cube. For me, it remains a real mystery!

    Another thing, I programmed the compensation of the bed, at the beginning of printing, my printer makes a mesh of the bed (very long) ...

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    then prints. I'm not sure that this is really effective, because I'm not sure that the image acquired during this mesh is used for compensation, it makes me think more of a test. I think that I have certainly forgotten something or I do not use the right option and yet I see my 2 axes Z moved on the same layers. In addition, the surface of my cube is not completely of equal shape?

    In addition the result of the survey seems huge! My bed is a bed 300X300 from ED3 240 VAC which normally is of good quality.

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    Thank you once again to you ...

  • also the since it gets higher in the middle and lower on the side that could indicate x gantry sagging under the weight.

  • @veti I'm not sure I understood everything ...

    But by creating this Macro, it gives me that! 😎

    0_1554060051874_Capture d’écran 2019-03-31 à 21.16.16.png

  • wow where did that 0 come from.
    even ignoring the 0 you have a range of 0.1mm for the same point.

    this points to a mechanical problem in your machine. assuming the probe is ok.

    can you post a picture of your printer?

  • @veti I was inspired by a HyperCube, but I redesigned all the pieces.

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  • are those carbon rods? that would explain it.

    try changing them for aluminium rods if you dont want to use normal linear motion shafts.

  • also not related. those steel core belts can cause problems and can stretch over time.
    have a look at GATES-LL-2GT

  • @veti No, they are aluminum bars of 12 specially designed to receive IGUS linear bearings ... Moreover, all my axes are of this kind.

  • with the carriage in the middle and about 1 mm above the bed press on it from the top and see if you can make the nozzle touch the bed.

  • @veti Yes, by performing the test and with a high pressure, the nozzle touches the bed.

  • thats my guest. maybe someone else can weigh in as well.

    i would try with with standard bowden carriage to minimize the weight of the carriage and see if that improves the situation.

  • @veti Oui, merci. Je vais voir cela.

  • Another thing very strange. When I print now my test cube to continue my adjustments ... Only the skirt of the cube prints correctly and adheres well to the bed (outline that I put to 20 mm voluntarily for the tests). The cube does not adhere to it, or the first layer is mediocre. I did the test at different places in the bed and the result is the same!

  • administrators

    A few suggestions:

    1. Are you probing with the bed hot or cold? It may change shape significantly when hot.

    2. BUT if you probe with the heater on, there is a possibility that the magnetic field form the bed heater may affect the BLTouch. I think that's unlikely with a 240V bed because the currents are low. Still, it might be worth trying the effect of adding parameter B1 to your M558 command, to turn off the heater during probing.

    3. The bed seems to have a significant Z offset over most of the surface. How are you homing Z? It's probably best to home it using the BLTouch at the centre of the bed.

    4. The bed also appears to have a significant tilt in the Y direction. To help you adjust the levelling screws, see https://duet3d.dozuki.com/Wiki/Using_the_manual_bed_levelling_assistant.

    5. The humpback shape across the X axis suggests that the X gantry is sagging under the weight of the print head.

  • Hello and thank you for your answer.

    Small precision, my printer worked under Marlin (twenty pieces) before and I had not detected any problem of this type.

    I tried to test the leveling of the bed, without the heating of the bed ... it does not change anything!

    I removed the mesh from the board in config.g and installed the Bed_Levelling_Assistant (Confi.g and Bed.g)

    I did 3 tests (G32) one behind the other, without adjusting the screws of my bed, and the result is not the same each time and I say to myself that it is certainly not normal ...

    0_1554144032805_Capture d’écran 2019-04-01 à 20.40.14.png

    I love all DUET3D equipment and I admit that despite the problems I encounter (certainly because of my inexperience) it is for me already excellence and I am eager to find out in detail.

    Thank you.

  • Moderator

    What do you have in your bed.g file?

    Have you actually done a test print to verify what a first layer will look like?

    Try printing this as a test to compare the effects of the software leveling attempts.


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