mesh grid, I trying everything and doesn't work good. UPDATE



  • Hello folks,

    Okay, I have made new delta style printer, printable radius 160mm, and using Bl Touch sensor for my probe.

    Endstop: sensorless homing, works perfect.

    Firstly I started calibrating. I measured all the required values, and start kalibrating with G32. Using 7 factors calbrate, 12 of peripheral points and 3 of halfway points.
    After calibrating I use new values into my config.g file and start first test print. Small cube 40x40x10.
    The print quality is really surprising, dimensions almos perfect + -0,1mm.
    Start testing with the largest objects, I noticed that on the right side from the center prints too high and left too low.

    Okay, I started to read about mesh grid. I read everything I was able to find, all guides and other people problems with mesh grind. But its not work for me.

    step by step:

    First. Restart printer. Use G28 to home, Then use G29 and start mesh grind.
    After successful measurement I got a map. Map automatic save in sys folder.

    Slicer Start g. code.

    G28
    G29 S2
    G1 Z10 F5000
    G30
    G29 S1

    And start print, But nothing how bad it was and stayed, on the right side from the center prints too high and left too low. I tried to re-calibrate everything, re-measure it. It feels like he does not use the map, do not reimburse height errors. I have no more ideas where the problem. Only I can print only very small objects in the center of the pad.

    Heightmap perfectly shows left is too high, in right side too low, but when I print do not compensated
    I Need help, friends!

    2_1541338066576_heightmap.csv 1_1541338066575_config.g 0_1541338066575_bed.g


  • administrators

    @vyckaa said in mesh grid, I trying everything and doesn't work good.:

    Start testing with the largest objects, I noticed that on the right side from the center prints too high and left too low.

    That's a classic sign of effector tilt. The effector is tilting by varying amounts depending on XY position. Because the BLTouch is offset form the nozzle, tilt alters the height difference between the BLTouch and the nozzle. This changes the effective trigger height.

    Mesh bed compensation won't help, because it will be affected in the same way by effector tilt.

    These are the things you can do:

    1. Eliminate or at least reduce the effector tilt. The main causes are described at https://duet3d.dozuki.com/Wiki/Calibrating_a_delta_printer#Section_Make_sure_your_build_is_accurate. It helps to mount a bulls-eye spirit level on the effector so that you can see the tilt.

    2. Measure the trigger height of the BLTouch at each probe point used in your bed.g file, and add H parameter corrections to the G30 commands in bed.g to allow for the varying trigger height. See https://duet3d.dozuki.com/Wiki/Calibrating_a_delta_printer#Section_Adding_trigger_height_corrections_to_the_bed_g_file.

    3. Use a different type of Z probe, one that uses the nozzle itself as the probe, such as Smart Effector, Precision Piezo, or FSRs or piezos under the bed supports.



  • Thank you for answer.
    But i don't know what can I do more... auto calibrate G32 every time it shows practically the same values M666 and M665.

    Which parameter specifies the effector tilt?? Endstop adjustments?


  • administrators

    @vyckaa the effector tilt is cased by mechanical construction of the machine. As David says using a bulls eye spirit level will help to visualise effector tilt. If you have different trigger heights across the bed after calibrating everything else out then you can use the H parameter as described by David here:

    Measure the trigger height of the BLTouch at each probe point used in your bed.g file, and add H parameter corrections to the G30 commands in bed.g to allow for the varying trigger height. See https://duet3d.dozuki.com/Wiki/Calibrating_a_delta_printer#Section_Adding_trigger_height_corrections_to_the_bed_g_file.


  • administrators

    @t3p3tony said in mesh grid, I trying everything and doesn't work good.:

    @vyckaa the effector tilt is cased by mechanical construction of the machine. As David says using a bulls eye spirit level will help to visualise effector tilt. If you have different trigger heights across the bed after calibrating everything else out then you can use the H parameter as described by David here:

    Measure the trigger height of the BLTouch at each probe point used in your bed.g file, and add H parameter corrections to the G30 commands in bed.g to allow for the varying trigger height. See https://duet3d.dozuki.com/Wiki/Calibrating_a_delta_printer#Section_Adding_trigger_height_corrections_to_the_bed_g_file.

    ...except that there is a bug in current and most if not all previous firmwares: H corrections on G30 commands don't work if your Z probe uses deployprobe.g and retractprobe.g commands. Fixed in the forthcoming 2.02RC4 release.



  • I try it. I have made corrections for each point from the center point. But nothing new, also bad. I try negative and positive values but same sh .. Remaining to wait for the update..



  • Update:

    Hello folks,

    Sorry for poor english! 🙂

    After RC4 update I try all H corrections and every thing what i found but nothing news...

    I printed calibration models for delta who can show tower position + individual diagonal rod, but every thing is perfect.

    Remeasure all values, but I don't found errors.. All cariages and effector produced according to my individual order with high precision cnc machines.

    bottom and top plates cut from stainless steel with a coordinate laser. All frame have high precision.

    When I try marlin and repetier firmwares, and after all calibrations I got identical error with all three firmware (SEE PHOTO) even at the same points.

    yet again I don't know from what get start. 😞

    0_1543258749987_to high to low.png

    0_1543258890495_error.jpg


  • administrators

    It's almost certainly caused by your use of a Z probe (bltouch) that is offset from the nozzle, combined with effector tilt that varies with XY position. I suggest you mount a bulls eye spirit level on the effector so that you can see the tilt. You can also establish whether this is the problem by measuring the bltouch trigger height at several different XY positions, for example one on the "too high" side and again on the "too low" side.



  • Thank you for answer,
    Ye, I believe, this is a mechanical error. Okay, my bulls eye spirit is coming after order when i get it I will be able to accurately measure it.

    But yes I get different heights from the XY position, but how to repair it, without mechanics corrections?
    I used corrections H and I measured them as follows:

    1. Home axis.

    2. jog the head down to the center of the bed and set 0.1 mm gap with calibration metal tape.

    3. Send G92 Z0 to define that height as Z=0

    4. Nozzle up 10mm (G1 Z10)

    5. Send G30 S-1

    6. I got center point trigger heigh: 1.085 mm

    then go home: G28.
    And I repeat all 5 steps for all Bed.g calibration points.

    After measurements:

    Center 1.085

    Trigger heighs
    P0 1.056
    P1 1.239
    P2 1.334
    P3 1.193
    P4 0.963
    P5 0.796
    P6 1.048
    P7 1.215
    P8 1.004

    The formula: CENTER TRIGGER HEIGH - P0.....P8 TRIGGER HEIGH = CORRECTION

    P0 1.056 ...... 0.029
    P1 1.239 ...... -0.154
    P2 1.334 ...... -0.249
    P3 1.193 ...... -0.108
    P4 0.963 ...... 0.122
    P5 0.796 ...... 0.289
    P6 1.048 ....... 0.037
    P7 1.215 ...... -0.13
    P8 1.004 ...... 0.081

    But it did not help or was even worse. Maybe I'm doing it badly? Perhaps a bad formula?

    I also estimate and calculate the sensor shift from the nozzle XY position and I adjusted the coordinates to get the exact calibration point trigger height.


  • administrators

    Looks like you've used the wrong sign on your H parameters. The H value at a point should be (trigger height at that point) - (trigger height at centre).

    Note, using H-corrections may sort out the calibration, but you will not be able to use mesh bed compensation, because that doesn't know about trigger height variation. But well-built deltas don't normally need mesh bed compensation anyway, provided that the bed is flat.


 

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