Bad Repeatability with BLTouch

[palmhoej]

I have fitted my two printers (Creality CR-10 S5 & Tronxy X5s) with a BL Touch censor and Duet 2 Wifi. Same story for both printers, but i will only give example from one:

When i am running the following script:

M401
G30 P0 X250 Y250 Z-9999
...... (repeat 10x times probing in the same spot)......
G30 P09 X250 Y250 Z-9999 s1

i get the following result:
G32 bed probe heights: -0.275 -0.245 -0.130 -0.255 -0.265 -0.248 -0.255 -0.250 -0.220 -0.287, mean -0.243, deviation from mean 0.041

Is this acceptable? 0.16mm difference between the outliers is almost half the height of one filament layer.

Following settings have been used:

; Z-Probe
M574 Z1 S2 ; Set endstops controlled by probe
M307 H3 A-1 C-1 D-1 ; Disable heater on PWM channel for BLTouch
M558 P9 H5 F80 T2000 ; Set Z probe type to bltouch and the dive height + speeds
G31 P500 X-45 Y-5 Z0.35 ; Set Z probe trigger value, offset and trigger height
M557 X15:195 Y15:195 S40 ; Define mesh grid

Its the same story for the other printer, which makes me think that i am doing something wrong.

[oliof]

You could try reduing the dive speed to see if the results improve.

M558 P9 H5 F80 T1000

[palmhoej]

I halfed it once, with no result, but just for the fun of it, i did it again:

G32 bed probe heights: 0.178 0.280 0.183 0.288 0.155 0.207 0.293 0.183 0.288 0.165, mean 0.222, deviation from mean 0.055

A little bit better, but not acceptable: 0,123mm between the max and minimum. And know it is so slow that you barely can see it moving.

[dc42]

Are you probing with heaters on? If so, adding the B1 parameter in your M558 command in config.g may help.

[palmhoej]

No heaters or hotends are turned on. But i added the B1 parameter and it did not help (it actually got worse, but i think thats just random error in the diviation, not because i added the B1):

G32 bed probe heights: 0.115 0.202 0.322 0.117 0.122 0.210 0.322 0.217 0.317 0.190, mean 0.214, deviation from mean 0.079

[MortarArt]

Complete side point here, but what I currently do with my printers, because I have constant repeatability issues, is I edit the gcode to delete re-homing for prints, especially when printing the same part repeatedly.

I've considered seeing if I can figure out a way to have a check box in the web UI to enable / disable re-homing when pressing the "print another" button.

[palmhoej]

The problem is i have a CR-10 S5, which means it can print 500x500mm prints... but it is impossible to get such a big surface flat enough, so i need the bed mesh to compensate for this (or tell me where i need to level the surface).

[Veti]

is it a clone? because they are less accurate.

[gavatron3000]

My genuine smart bltouch has repeatability below 0.03. I had some issues which I found to be my z jerk was too high. I assume was during the z axis retract move causing it for me.

[3Dreamer]

@palmhoej Hi, was there any progress? I've the same problem, and I've made some test about that:
https://forum.duet3d.com/topic/11093/bltouch-m558-accuracy-test-strange-behaviour