[BUG] M48 produces weird result with FT_MOTION

[vovodroid]

Did you test the latest bugfix-2.1.x code?

Yes, and the problem still exists.

Bug Description

When FT_MOTION is enabled M48 reports huge and weird deviation:

Without FT_MOTION:

BTT SKR 3, BTT Microprobe

Bug Timeline

No response

Expected behavior

M48 reports the same result

Actual behavior

M48 reports different results

Steps to Reproduce

Enable FT_MOTION, perform M48

Version of Marlin Firmware

bugfix-2.1.x, 28/01/26

Printer model

No response

Electronics

BTT SKR 3, BTT Microprobe

LCD/Controller

No response

Other add-ons

No response

Bed Leveling

ABL Bilinear mesh

Your Slicer

None

Host Software

None

Don't forget to include

• A ZIP file containing your Configuration.h and Configuration_adv.h.

Additional information & file uploads

Marlin.zip

[narno2202]

It's not a surprise with a Biqu Microprobe and FT_MOTION enabled. FT_MOTION is currently not disabled for M48 gcode. If FTM_HOME_AND_PROBE is disabled (your case), there is no TERN_(FT_MOTION, FTM_DISABLE_IN_SCOPE()); line in M48.cpp. You can do a PR or if you want, I can do it

[Nuck-TH]

Fix in PR may not be all to it - with FT_MOTION enabled and regardless of FTM_HOME_AND_PROBE, i get spurious outliers during probing test that aren't there when FTM is disabled.

Here are some tests - first 3 with FTM on(FTM_HOME_AND_PROBE enabled, fix is not applied), latter 3 with it off:

>>> M48 P10 V4 X24 Y24
SENDING:M48 P10 V4 X24 Y24
M48 Z-Probe Repeatability Test
Positioning the probe...
Bed X: 24.00 Y: 24.00 Z: 0.18
1 of 10: z: 0.185 Mean: 0.184750 Sigma: 0.000000 Min: 0.185 Max: 0.185 Range: 0.000
2 of 10: z: 0.185 Mean: 0.185000 Sigma: 0.000250 Min: 0.185 Max: 0.185 Range: 0.000
3 of 10: z: 0.184 Mean: 0.184750 Sigma: 0.000408 Min: 0.184 Max: 0.185 Range: 0.001
4 of 10: z: 0.185 Mean: 0.184688 Sigma: 0.000370 Min: 0.184 Max: 0.185 Range: 0.001
5 of 10: z: 0.185 Mean: 0.184700 Sigma: 0.000332 Min: 0.184 Max: 0.185 Range: 0.001
6 of 10: z: 0.185 Mean: 0.184792 Sigma: 0.000366 Min: 0.184 Max: 0.185 Range: 0.001
7 of 10: z: 0.185 Mean: 0.184786 Sigma: 0.000339 Min: 0.184 Max: 0.185 Range: 0.001
8 of 10: z: 0.185 Mean: 0.184844 Sigma: 0.000352 Min: 0.184 Max: 0.185 Range: 0.001
9 of 10: z: 0.185 Mean: 0.184833 Sigma: 0.000333 Min: 0.184 Max: 0.185 Range: 0.001
10 of 10: z: 0.132 Mean: 0.179575 Sigma: 0.015778 Min: 0.132 Max: 0.185 Range: 0.053
Finished!
Mean: 0.179575 Min: 0.132 Max: 0.185 Range: 0.053
Standard Deviation: 0.015778
>>> M48 P10 V4 X24 Y24
SENDING:M48 P10 V4 X24 Y24
M48 Z-Probe Repeatability Test
Positioning the probe...
Bed X: 24.00 Y: 24.00 Z: 0.19
1 of 10: z: 0.187 Mean: 0.187250 Sigma: 0.000000 Min: 0.187 Max: 0.187 Range: 0.000
2 of 10: z: 0.187 Mean: 0.187250 Sigma: 0.000000 Min: 0.187 Max: 0.187 Range: 0.000
3 of 10: z: 0.138 Mean: 0.170750 Sigma: 0.023334 Min: 0.138 Max: 0.187 Range: 0.049
4 of 10: z: 0.188 Mean: 0.175000 Sigma: 0.021507 Min: 0.138 Max: 0.188 Range: 0.050
5 of 10: z: 0.187 Mean: 0.177300 Sigma: 0.019779 Min: 0.138 Max: 0.188 Range: 0.050
6 of 10: z: 0.187 Mean: 0.178958 Sigma: 0.018432 Min: 0.138 Max: 0.188 Range: 0.050
7 of 10: z: 0.185 Mean: 0.179821 Sigma: 0.017196 Min: 0.138 Max: 0.188 Range: 0.050
8 of 10: z: 0.184 Mean: 0.180344 Sigma: 0.016144 Min: 0.138 Max: 0.188 Range: 0.050
9 of 10: z: 0.185 Mean: 0.180833 Sigma: 0.015284 Min: 0.138 Max: 0.188 Range: 0.050
10 of 10: z: 0.185 Mean: 0.181225 Sigma: 0.014547 Min: 0.138 Max: 0.188 Range: 0.050
Finished!
Mean: 0.181225 Min: 0.138 Max: 0.188 Range: 0.050
Standard Deviation: 0.014547
>>> M48 P10 V4 X24 Y24
SENDING:M48 P10 V4 X24 Y24
M48 Z-Probe Repeatability Test
Positioning the probe...
Bed X: 24.00 Y: 24.00 Z: 0.19
1 of 10: z: 0.129 Mean: 0.129000 Sigma: 0.000000 Min: 0.129 Max: 0.129 Range: 0.000
2 of 10: z: 0.186 Mean: 0.157375 Sigma: 0.028375 Min: 0.129 Max: 0.186 Range: 0.057
3 of 10: z: 0.185 Mean: 0.166417 Sigma: 0.026462 Min: 0.129 Max: 0.186 Range: 0.057
4 of 10: z: 0.185 Mean: 0.171000 Sigma: 0.024253 Min: 0.129 Max: 0.186 Range: 0.057
5 of 10: z: 0.132 Mean: 0.163150 Sigma: 0.026778 Min: 0.129 Max: 0.186 Range: 0.057
6 of 10: z: 0.184 Mean: 0.166625 Sigma: 0.025650 Min: 0.129 Max: 0.186 Range: 0.057
7 of 10: z: 0.185 Mean: 0.169214 Sigma: 0.024580 Min: 0.129 Max: 0.186 Range: 0.057
8 of 10: z: 0.184 Mean: 0.171063 Sigma: 0.023507 Min: 0.129 Max: 0.186 Range: 0.057
9 of 10: z: 0.149 Mean: 0.168583 Sigma: 0.023245 Min: 0.129 Max: 0.186 Range: 0.057
10 of 10: z: 0.147 Mean: 0.166450 Sigma: 0.022962 Min: 0.129 Max: 0.186 Range: 0.057
Finished!
Mean: 0.166450 Min: 0.129 Max: 0.186 Range: 0.057
Standard Deviation: 0.022962
>>> M493 S0
SENDING:M493 S0
Fixed-Time Motion disabled
>>> M48 P10 V4 X24 Y24
SENDING:M48 P10 V4 X24 Y24
M48 Z-Probe Repeatability Test
Positioning the probe...
Bed X: 24.00 Y: 24.00 Z: 0.18
1 of 10: z: 0.184 Mean: 0.184000 Sigma: 0.000000 Min: 0.184 Max: 0.184 Range: 0.000
2 of 10: z: 0.184 Mean: 0.184000 Sigma: 0.000000 Min: 0.184 Max: 0.184 Range: 0.000
3 of 10: z: 0.184 Mean: 0.184000 Sigma: 0.000000 Min: 0.184 Max: 0.184 Range: 0.000
4 of 10: z: 0.184 Mean: 0.184000 Sigma: 0.000000 Min: 0.184 Max: 0.184 Range: 0.000
5 of 10: z: 0.184 Mean: 0.184000 Sigma: 0.000000 Min: 0.184 Max: 0.184 Range: 0.000
6 of 10: z: 0.184 Mean: 0.184000 Sigma: 0.000000 Min: 0.184 Max: 0.184 Range: 0.000
7 of 10: z: 0.184 Mean: 0.184000 Sigma: 0.000000 Min: 0.184 Max: 0.184 Range: 0.000
8 of 10: z: 0.185 Mean: 0.184063 Sigma: 0.000165 Min: 0.184 Max: 0.185 Range: 0.000
9 of 10: z: 0.184 Mean: 0.184056 Sigma: 0.000157 Min: 0.184 Max: 0.185 Range: 0.000
10 of 10: z: 0.184 Mean: 0.184050 Sigma: 0.000150 Min: 0.184 Max: 0.185 Range: 0.000
Finished!
Mean: 0.184050 Min: 0.184 Max: 0.185 Range: 0.000
Standard Deviation: 0.000150
>>> M48 P10 V4 X24 Y24
SENDING:M48 P10 V4 X24 Y24
M48 Z-Probe Repeatability Test
Positioning the probe...
Bed X: 24.00 Y: 24.00 Z: 0.18
1 of 10: z: 0.184 Mean: 0.184000 Sigma: 0.000000 Min: 0.184 Max: 0.184 Range: 0.000
2 of 10: z: 0.184 Mean: 0.184000 Sigma: 0.000000 Min: 0.184 Max: 0.184 Range: 0.000
3 of 10: z: 0.184 Mean: 0.184000 Sigma: 0.000000 Min: 0.184 Max: 0.184 Range: 0.000
4 of 10: z: 0.184 Mean: 0.184000 Sigma: 0.000000 Min: 0.184 Max: 0.184 Range: 0.000
5 of 10: z: 0.184 Mean: 0.184000 Sigma: 0.000000 Min: 0.184 Max: 0.184 Range: 0.000
6 of 10: z: 0.184 Mean: 0.184000 Sigma: 0.000000 Min: 0.184 Max: 0.184 Range: 0.000
7 of 10: z: 0.184 Mean: 0.184000 Sigma: 0.000000 Min: 0.184 Max: 0.184 Range: 0.000
8 of 10: z: 0.184 Mean: 0.184000 Sigma: 0.000000 Min: 0.184 Max: 0.184 Range: 0.000
9 of 10: z: 0.183 Mean: 0.183917 Sigma: 0.000236 Min: 0.183 Max: 0.184 Range: 0.001
10 of 10: z: 0.184 Mean: 0.183925 Sigma: 0.000225 Min: 0.183 Max: 0.184 Range: 0.001
Finished!
Mean: 0.183925 Min: 0.183 Max: 0.184 Range: 0.001
Standard Deviation: 0.000225
>>> M48 P10 V4 X24 Y24
SENDING:M48 P10 V4 X24 Y24
M48 Z-Probe Repeatability Test
Positioning the probe...
Bed X: 24.00 Y: 24.00 Z: 0.18
1 of 10: z: 0.184 Mean: 0.183500 Sigma: 0.000000 Min: 0.184 Max: 0.184 Range: 0.000
2 of 10: z: 0.184 Mean: 0.183750 Sigma: 0.000250 Min: 0.184 Max: 0.184 Range: 0.001
3 of 10: z: 0.184 Mean: 0.183834 Sigma: 0.000236 Min: 0.184 Max: 0.184 Range: 0.001
4 of 10: z: 0.183 Mean: 0.183688 Sigma: 0.000325 Min: 0.183 Max: 0.184 Range: 0.001
5 of 10: z: 0.184 Mean: 0.183750 Sigma: 0.000316 Min: 0.183 Max: 0.184 Range: 0.001
6 of 10: z: 0.184 Mean: 0.183792 Sigma: 0.000303 Min: 0.183 Max: 0.184 Range: 0.001
7 of 10: z: 0.184 Mean: 0.183822 Sigma: 0.000290 Min: 0.183 Max: 0.184 Range: 0.001
8 of 10: z: 0.183 Mean: 0.183750 Sigma: 0.000331 Min: 0.183 Max: 0.184 Range: 0.001
9 of 10: z: 0.183 Mean: 0.183639 Sigma: 0.000443 Min: 0.183 Max: 0.184 Range: 0.001
10 of 10: z: 0.184 Mean: 0.183675 Sigma: 0.000434 Min: 0.183 Max: 0.184 Range: 0.001
Finished!
Mean: 0.183675 Min: 0.183 Max: 0.184 Range: 0.001
Standard Deviation: 0.000434

[narno2202]

With #28314 FT_MOTION is disabled during repeatability test.

[dbuezas]

Mmmm why would we need to disable ftmotion at all? This sounds more like a bug to fix than a limitation of ftmotion (like it used to happen with homing and probing)