X / Y Drift On RADDS

  • First off let me state that I am not using a Duet board, but a RADDS board running RepRapFirmware. Not having issues with the wiring or anything like that though so I figured this was probably the best place to discuss my RRF settings.

    I am having a problem with X / Y drift on one specific print. The drift is extremely consistant. It moved about 0.2mm in X and Y every layer in the same direction almost like it was sliced that way. I can print test prints and every other model I have tried print fine. Someone had suggested I lower my acceleration and jerk on FreeNode, but that did not seem to help. What I am wondering is what are sane values in RRF for a catrician printer. I copied many of my settings from the Prusa i3 example config. Here are my current settings for movement:

    M201 X500 Y500 Z15 E800 	; Accelerations (mm/s^2)
    M203 X15000 Y15000 Z4000 E3000 	; Maximum speeds (mm/min)
    M566 X300 Y300 Z200 E200 	; Max Jerk (mm/min)
    M208 X300 Y300 Z300		; set axis maxima 300x300x300
    M208 X0 Y0 Z0 S1		; set axis minimum 0x0x0
    M92 X200 Y160 Z800		; Set axis steps/mm
    M92 E1672	               	; Set extruder steps per mm

    Any help is greatly appreciated

  • administrators

    Discounting slicer bugs, I can see a few possibilities:

    1. Drift is caused by loose pulleys.

    2. Drift is caused by excessive speed, acceleration or jerk settings. If this is the case, the drift will be by a multiple of 4 full steps every time. You can work out whether this fits what you observe.

    3. Drift is caused by firmware not generating all the steps. If this is the case, if you run M122 after drift has occurred, the "Step errors" field in the Move section of the report should be non-zero.

    4. Drift is caused by the firmware sending step pulses faster than your drivers can handle. This is quite likely to happen if you use DRV8825 drivers. You can use the M569 command to increase the step pulse width (which also increases the minimum step pulse interval) to avoid this.

    HTH David

  • I am using the DRV8825 drivers. What T value do your recommend for M569?

  • administrators

    AFAIR you need about 2 microseconds for those drivers.

  • yeah the drv8825 spec sheet says at minimum 1.9 microseconds. I set it to 2.

  • Well that did not do it either.

    M122 does not show any step errors:

    Recv: MaxReps: 4, StepErrors: 0, FreeDm: 46, MinFreeDm 40, MaxWait: 154696ms, Underruns: 661, 0

    Regarding option 2, does any of these settings seem excessive for a Cartesian printer?

    M201 X500 Y500 Z15 E800 	; Accelerations (mm/s^2)
    M203 X15000 Y15000 Z4000 E3000 	; Maximum speeds (mm/min)
    M566 X300 Y300 Z200 E200 	; Max Jerk (mm/min)

  • administrators

    A max speed of 15000 (250mm/sec) might be excessive, especially on the Y axis if it is a moving bed. Try 6000. A max Z speed of 4000 may also be too high depending on your Z steps/mm. Accelerations and jerk look ok to me.

  • Going back to the first post, if everything else prints fine, then it has to be the model itself and/or the way it was sliced. There is nothing alarming in the speeds accels or jerk settings. I presume your slicer lets you set the actual print speeds?

  • Well now I am really confused. Last night I marked all the pulleys and steppers with pen so I could see if any were slipping and none of them have moved. I also lowered the acceleration and jerk to a quarter of what I listed above and tried printing the part. The normally 2 hour print took over 8 hours and still messed up exactly as it had before. I am using Simplify3d as a slicer. I have tried both version 3.1.1 as well as the new 4.0.0. The only other thing I can think to check is if my belts are slipping, but the drift is only like 0.2mm per layer. I am at a loss.

  • administrators

    Did you lower travel speed too? Also it might be worth increasing the driver step timing to 3us.

  • No I did not, but with the size of the print and the acceleration I had set there is no way it got even close to that speed.

  • Sounds like you ruled out everything but S3D.

  • administrators

    How much drift would 4 full steps be on your printer?

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