Bl Touch measures not precise

zecchi

Hi, I'm new in the forum.
I've a core XY printer , with duet 2 wifi.

I've tried to setting up a chinese Bl Touch, but I've had a huge problem: when I send G30 command more times the printer stops each time at a different height.
I've noticed that issue because printer sometimes prints very close to the bed and other times very hight from it.

What I've already tried:

set in homez a "double homing", first time the printer probes fast , the second slower.
repetitivity test and these are the results (very bad ) :

I don't know what I can do , may be a Bl Touch's problem?
Bl Touch is configured with a 240ohm resistor. In firmware it's configured like this:

Thanks to all ,
Alex

PaulHew

Morning, what version of BLTouch is it? 2, 3, 3.1?
If it is a V2 or V3 you do not need to cut the link or use a resistor, both of mine are connected directly with no issues whatsoever.

First suggestion is to update to the latest 2.04 non RC firmware.

To calculate my Z offset, I take 5 - 10 readings, then find the average, then use that for my G31.

HTH
Paul

dc42

Are you probing with heaters on or off? The magnetic field from some bed heaters in particular interferes with BLTouch. You can add the B1 parameter to your M558 command to turn of heaters temporarily during probing.

aidar

Trigger value of 500 is not good for bltouch as well, use P25 in G31 command.

zecchi

@PaulHew unfortunately I don't know the Bl touch version. This is mine :

There is a method to understand the Bl touch version?

Anyway, I want to update the board to the latest (no RC) firmware as you said.

Thanks

zecchi

@dc42 I've tried both, with heater on and heater off. No changes.

Thanks

zecchi

@aidar ok, I will change it. P500 was set as default.

Thanks

Veti

that looks like a clone
Genuine BLTouch have a QR code on PCB

clones are know to be inaccurate

PaulHew

Have to agree with Veti, that is definitely a clone.

AntClab BLTouch have plastic pins, not metal. Also they have a plug that plugs into the Touch as opposed to being directly soldered.

Get an original is my advise.

Veti

or build something like this.
https://www.thingiverse.com/thing:3303618
that is what i am using

zecchi

@Veti unfortunately when I bought I didn't think about this :'(.

zecchi

@Veti very interesting , is it precise as is shown in the video?

Veti

@zecchi
yes and its not prone to interference like the bltouch. it is not as compact