Issues with custom delta printer / RRF 2.05.01

I am experiencing very strange issue with one delta printer – based on Kossel design. It was working fine with RRF 2.05, until the bearings of the belt idler wheels got damaged. I changed the wheels as well as updated the firmware to RRF 2.05.1, but the calibration currently provides not repeatable results. It seems the diagonal length with every calibration increases ?

4:13:41 PMM666
Endstop adjustments X-0.26 Y1.40 Z-1.14, tilt X0.17% Y-0.02%
4:13:37 PMM665
Diagonals 284.257:284.257:284.257, delta radius 148.710, homed height 281.298, bed radius 110.0, X -0.316°, Y -0.251°, Z 0.000°
4:13:26 PMG32
Calibrated 9 factors using 17 points, deviation before 0.017 after 0.013

4:09:38 PMM666
Endstop adjustments X-0.33 Y1.48 Z-1.16, tilt X0.24% Y-0.02%
4:09:34 PMM665
Diagonals 284.224:284.224:284.224, delta radius 148.704, homed height 281.299, bed radius 110.0, X -0.347°, Y -0.297°, Z 0.000°
4:07:28 PMG32
Calibrated 9 factors using 17 points, deviation before 0.018 after 0.013

4:02:25 PMM666
Endstop adjustments X-0.19 Y1.36 Z-1.16, tilt X0.12% Y-0.03%
4:02:19 PMM665
Diagonals 283.880:283.880:283.880, delta radius 148.590, homed height 281.294, bed radius 110.0, X -0.312°, Y -0.237°, Z 0.000°
4:02:04 PMG32
Calibrated 9 factors using 17 points, deviation before 0.015 after 0.014

3:58:32 PMM666
Endstop adjustments X-0.17 Y1.35 Z-1.18, tilt X0.11% Y-0.06%
3:58:29 PMM665
Diagonals 283.705:283.705:283.705, delta radius 148.535, homed height 281.288, bed radius 110.0, X -0.309°, Y -0.225°, Z 0.000°
3:56:11 PMG32
Calibrated 9 factors using 17 points, deviation before 0.018 after 0.015

3:50:57 PMM666
Endstop adjustments X-0.23 Y1.43 Z-1.20, tilt X0.17% Y-0.06%
3:50:54 PMM665
Diagonals 283.518:283.518:283.518, delta radius 148.482, homed height 281.296, bed radius 110.0, X -0.331°, Y -0.244°, Z 0.000°
3:44:36 PMG32
Calibrated 9 factors using 17 points, deviation before 0.016 after 0.014

3:29:03 PMM666
Endstop adjustments X-0.15 Y1.32 Z-1.17, tilt X0.08% Y-0.05%
3:28:59 PMM665
Diagonals 282.511:282.511:282.511, delta radius 148.180, homed height 281.289, bed radius 110.0, X -0.312°, Y -0.202°, Z 0.000°
3:28:30 PMG32
Calibrated 9 factors using 17 points, deviation before 0.031 after 0.015

3:20:59 PMM666
Endstop adjustments X-0.28 Y1.51 Z-1.23, tilt X0.23% Y-0.11%
3:20:54 PMM665
Diagonals 279.692:279.692:279.692, delta radius 147.458, homed height 281.288, bed radius 110.0, X -0.383°, Y -0.230°, Z 0.000°
3:20:28 PMG32
Calibrated 9 factors using 17 points, deviation before 0.056 after 0.016

Calibration of the diagonal rod lengths only works well if you can probe well outside the normal print radius. I suggest you change to 8 factor calibration.

Incorrect tower steps/mm, which can be caused by loose belts or pulleys, can cause calibration to adjust the diagonal rod length.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].