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