BLTouch failed to raise probe only in some points of the plate

[dnasini]

Basic Information:

Printer Model: Ender 5Plus
MCU / Printerboard: SKR mini E3 v3
klippy.log

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Describe your issue:

During last days I did some basic maintenance to my printer like:

• replacing plastic angle supports with metallic one
• adding additional metallic plates in angles to improve rigidity
• fixing the two lead screws a little bit bended

To do all this stuff I had to move the printer from his location and move it back once done. During this period I did a couple of prints without any issue. Since during last intervention I had to remove the plate, once all have been reassembled I decided to perform a new bed leveling using the Klipper macro.
I have configured the coordinates for the bed screws and use the BLTouch to probe the four screw positions and adjust when necessary. The process starts with homing the axis and then start probing the four point starting from the Front Left angle. Once the probe reaches the angle, deploys the pin and after a second retract it (no bed movement at all) and returns the error “BLTouch Failed to raise probe”. I tried twice with same result. Power cycle all the system didn’t fix the problem.

To fix the lead screws i created two decouplers similar to this one using 5 small magnets (6mm x 3mm). At the beginning, my suspect was some magnetic interferences with the BLTouch so I disinstalled both of them but the problem still remains

It sounds to be a problem related to the “position” on the plate where I try to use the probe. In the inner part of the bed , the BLTouch does its work but when I specify a part of the bed close or near to the border it fails. It happen always in the front part of the bed and less on the rear.
I don’t think is something related to the BLTouch itself since I replaced it with a spare one with same result.

BLTouch was working fine in the past, a couple of weeks ago I did twice the bed leveling with macro and a couple of Bed Mesh with 49 points without any issues.

Honestly I don’t have any clue about the potential root cause of this issue, any idea or suggestions?

Thank you for your support
klippy.log (558.1 KB)

[dnasini]

Well, maybe I found a little clue to the root cause. 90% of faulty probes are at borders of the bed and 100% in the front. In all those spots the wired cable is “tensioned” and straight. So I tried cutting the plastic zip ties and let it loose. This way I succeed to have a full bed leveling out of 3, the other 2 were fine till the last point (Front right).

Tomorrow I’ll try re-cabling it and let him more loose

[YaaJ]

Try with the pullup activated on the sensor pin :

sensor_pin = ^PC2

[mykepredko]

@dnasini has the BL Touch sensor_pin defined as PC2 in their klippy.log:

[bltouch]
sensor_pin = PC2
control_pin = PA1
x_offset = -35.9
y_offset = -7.8
speed = 3.4
pin_up_touch_mode_reports_triggered = False
z_offset = 2.750

If you look at the schematics for the SKR mini E3 v3 that he is using, PC2 is given the Reference Designator Z-STOP and when you look at the schematic for the Z-STOP pin, you find that it already has a 10k pullup on it:

I think the more cromulent question to @dnasini is “Why are you using PC2 for the BL Touch sensor instead of PC14 which is specified for PROBE on the board?”

[YaaJ]

Had the problem today…
A Octopus and a microswitch (not a OC or OD transistor), with a 1 meter 2-wire cable. The pin is also pulled to +3.3V by a 10k onboard resistor. Couldn’t get it to work properly until I activated the internal pullup (50k usually) ; most of the time read triggered (inverted input). Activated the internal pullup, just to see what happens ; 10k // 50k = 8.3k ; did the trick, pulling up a tiny bit more solved the problem.
Most likely a wiring issue (cable length, routed close to the steppers cables, poor contacts, EMI, etc. to be investigated for better reliability)
Costs nothing, always worth testing.

[dnasini]

@mykepredko

I think the more cromulent question to @dnasini is “Why are you using PC2 for the BL Touch sensor instead of PC14 which is specified for PROBE on the board?”

Hi Mikepredko, I use BLTouch for Z-Homing and that’s why I’ve specified PC2. I have two SKR mini E3 v3 boards on two separate printers and both are pinned the same way. They have been working fine in this setup for more than an year doing Z-Homing, Bed Leveling and meshing without any issue.

On this printer (Ender 5 Plus) the wiring had worked fine for more than 6 months, then I upgrade it to Mercury One.1 (CoreXY project) and re-cabled all wires to better fit the upgrade and it had worked fine for more then a month. Now is showing this issue.

Googling potential route causes, I found that similar issues could be caused by loose connectors so I tried to cut all zip ties that fix the cable to the frame and something changed. It doesn’t mean it is fixed, just a previous systematic fail now has success. Today I try to re-cabling all wires and better accommodate the path

[dnasini]

@YaaJ

Try with the pullup activated on the sensor pin :

sensor_pin = ^PC2

Hi YaaJ, I gave it a try with same behaviour

[Sineos]

@dnasini

In all those spots the wired cable is “tensioned” and straight. So I tried cutting the plastic zip ties and let it loose. This way I succeed to have a full bed leveling out of 3, the other 2 were fine till the last point (Front right).

It seems you have already given the answer yourself.

[dnasini]

@Sineos

It seems you have already given the answer yourself.

Yes, I can confirm it was a cabling issue

I remove the plastic spiral that kept cables all together. I replaced it with a nylon sleeve that keeps cables all together but is extremely flexible. At the same time I gave more “length” to the BLTouch cable and that makes the solution

I succeed to perform 6 bed leveling processes in a row so sounds it has been fixed

Thx everyone for suggestions and support

[mykepredko]

Personally, I would recommend that you use the pins made available on the motherboard for the BL Touch rather than selecting others.

The pin electronics of the BL Touch (and various clones/work a likes) are not defined and there is a loose standard that they follow when connected to a main controller board.

I’ve seen a number of cases where somebody connecting to pins other than the defined ones have led to problems but disappear when the specified pins are attached. Similarly, I always cringe when I see the knee-jerk reaction of turning on the pull up of a pin if it doesn’t work without understanding the electronics or even taking a cursory look at the schematics of the boards involved.

Great news that you found your problem and you’re back up and running!