BL-touch randomly deploys

Zynch

I'm having an issue with the bl-touch probe randomly deploying and then instantly retracting. Right now, I have to disconnect the probe before printing as it caused the probe to crash into the print before.
I believe it starts doing it when the extruder heater is running.

All of the cables in my printer are shielded (besides the first and last 2-3 cm), with the shields going to a ground point. Besides that the only notable thing I can think of is the cables are a bit on the longer side at about 5 m (the printer is my old cnc that I slapped an extruder on). The cable for the bl-touch is 5-wire 0.34 mm2.

I was originally using a cheap clone, but replaced it with a genuine one. The only difference I could tell is that the clone had a more "distinct" movement, and the genuine one feels a bit sluggish.
Also with the genuine I cannot run the bed mesh, as it will fail to deploy after a dozen or two points.

Everything is running on a Duet3 MB 6HC (no sbc) with the following commands:

Config:

; Z-Probe
M950 S0 C"io7.out"                       ; create servo pin 0 for BLTouch
M558 P9 C"^io7.in" H5 F120 T6000         ; set Z probe type to bltouch and the dive height + speeds
G31 P500 X34 Y0 Z1.677                   ; set Z probe trigger value, offset and trigger height
M557 X15:385 Y10:190 S20                 ; define mesh grid

Deploy probe:

M280 P0 S10

Retract probe:

M280 P0 S90

I've been dealing with this for a while, and it's driving me crazy.

jay_s_uk

@zynch you may be better off using a toolboard to run everything off at the extruder, which would reduce the long cable runs

Hernicz

@zynch BLTouch wire too close to exruder stepper wire.

Zynch

@jay_s_uk said in BL-touch randomly deploys:

@zynch you may be better off using a toolboard to run everything off at the extruder, which would reduce the long cable runs

At the moment, I'd rather try solving it without doing a bunch of changes and rewiring.

@hernicz said in BL-touch randomly deploys:

@zynch BLTouch wire too close to exruder stepper wire.

They do run next to each other in the cable chain, but there's no other practical way to route the wires. Which is the reason why I went with everything having it's own shielded cable.

mikeabuilder

I had this same problem, including the cable chain. And it was caused by crosstalk between the motor wires and the BL touch wiring. I proved it with a temporary bypass cable for the motor. with the bypass cable, the problem went away. My solution was to separate the cables some inside the cable chain. In my case I had two flat cables laying next to each other the whole run through the cable chain. Shoving them around a bit inside the chain to separate them a little solved the problem.

Hernicz

@mikeabuilder I did the same. I've put every other cable between the two like a sandwich