Z Probe Trigger Height G30 S-1 height changing every probe

apex2011

As a temporary measure I've backed up my config and reverted back to manual leveling. I have yet to successfully print since switching to the Duet board. Hopefully this gets me going.

dc42

Let us know how you get on. I notice that you are currently losing about 0.0025mm every other probe attempt, which at the 400 microsteps/mm you are using is 1 microstep. This gives me an idea about what may be happening.

dc42

@apex2011, how do you have the Z motors connected to the Duet?

apex2011

I followed this document (Step 10) https://duet3d.dozuki.com/Guide/Ender+3+Pro+and+Duet+Maestro+Guide+Part+1:+Wiring/37

Modified the plug so it would connect directly to the Duet without re-terminating.

apex2011

@dc42 I decided to take everything back to step one and go through the entire process again in case I missed something. I am still getting the same issue where the probe reads a different value every time

Turbo

@apex2011 What's your current on the z motors? it definitely sounds like you're losing a step.

apex2011

@Turbo Sorry if this is a dumb question but how do I confirm this?

Turbo

@apex2011 in your config.g file, you'll have a line that looks like this:

M906 X1000 Y1000 Z1000 E850:850 I50 ; Set motor currents (mA) and motor idle factor in per cent

the z value is what you're after, and should be around 800 or so.

apex2011

@Turbo ah OK, that is
M906 X800 Y800 Z800 E900 I30 ; set motor currents (mA) and motor idle factor in per cent

Turbo

okay so current looks fine. you could try bumping up by a factor of 50 to 100 and see if you get any changes, but I'm not sure about that one.
you could also adjust the electromagnet on the bltouch by tightening/loosening the allen screw on top, again, not sure, but im throwing things out there that might help.

apex2011

@Turbo thanks! I'll give those a try

Phaedrux

Also might help to check the tension on your V wheels on the Z carriage. Check the lead screw nut as well to see if it's loose in its mount or something. Check the lead screw coupler too. And Z motor mount.

It was asked earlier, but are you testng with the bed warmed up? Have you PID tuned the bed heater? Running the bed heater in bang-bang mode can cause the heating plate to flex slightly as it cycles current through it. Hard to probe a moving target.

apex2011

@Phaedrux I just checked the tension on the V wheels, it looks good, there's no play on the rail. I have done PID tuning. I have been testing with the bed cold

Phaedrux

Firmware version?

apex2011

@Phaedrux Firmware 2.03 (2019-06-13b2)
Web 1.22.2

apex2011

I tried updating to 2.05.1, same issue unfortunately.

apex2011

I had a spare BLTouch so I just tried installing it with new wiring in hopes that was the issue, it wasn't. I must be doing something wrong or missing something but I can't seem to find what it is.

Phaedrux

@dc42 said in Z Probe Trigger Height G30 S-1 height changing every probe:

Let us know how you get on. I notice that you are currently losing about 0.0025mm every other probe attempt, which at the 400 microsteps/mm you are using is 1 microstep. This gives me an idea about what may be happening.

I'm not sure what else to check for. Perhaps DC42 has an idea?