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

dc42

It looks like the trigger height is decreasing with every probe. The most likely cause of this is that when the probe triggers and Z movement is stopped abruptly, the Z motors are unable to stop immediately. So they overshoot, leaving the print head lower than the firmware thinks it is.

To test this theory, try reducing the probing speed, which is the F parameter in M558. You currently have F100, so try F50.

Another possibility is that you have the Z acceleration too high or the motor current too low, so that when you command Z to move back up 5mm, steps are lost during the initial acceleration. To test this, try reducing the Z acceleration in the M201 command. You currently have Z120, so try Z60.

droftarts

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

It looks like the trigger height is decreasing with every probe.

Isn't the trigger height increasing with each probe? Newest is first, oldest last. That's what had me stumped.

8:24:50 PM Stopped at height 0.595 mm
8:24:39 PM Stopped at height 0.582 mm
8:24:32 PM Stopped at height 0.570 mm
8:23:49 PM Stopped at height 0.553 mm
8:23:40 PM Stopped at height 0.540 mm

Ian

apex2011

@dc42 I tried both of these suggestions one at a time. I am still receiving the same result.

6:19:38 PMG30 S-1
Stopped at height 0.452 mm

6:19:29 PMG30 S-1
Stopped at height 0.438 mm

6:19:01 PMG30 S-1
Stopped at height 0.423 mm
6:18:54 PMM120

6:18:50 PMG30 S-1
Stopped at height 0.410 mm

6:18:29 PMG30 S-1
Stopped at height 0.382 mm

6:18:17 PMG30 S-1
Stopped at height 0.368 mm

6:18:08 PMG30 S-1
Stopped at height 0.357 mm

6:17:57 PMG30 S-1
Stopped at height 0.340 mm

6:12:57 PMG30 S-1
Stopped at height 0.315 mm

6:12:42 PMG30 S-1
Stopped at height 0.298 mm

apex2011

Thank you everyone that has given me input, I am very confused with this. I've been messing with the M558 Line. It now reads every 2 stop heights the same.

Here is what I changed it to M558 P9 H6 F80 T6000 A10 S0.005 B1 R0.5

8:33:00 PMG30 S-1
Stopped at height 0.510 mm

8:32:51 PMG30 S-1
Stopped at height 0.510 mm

8:32:42 PMG30 S-1
Stopped at height 0.507 mm

8:32:33 PMG30 S-1
Stopped at height 0.507 mm

8:32:24 PMG30 S-1
Stopped at height 0.507 mm

8:32:13 PMG30 S-1
Stopped at height 0.505 mm

8:32:00 PMG30 S-1
Stopped at height 0.505 mm

8:31:47 PMG30 S-1
Stopped at height 0.498 mm

8:31:37 PMG30 S-1
Stopped at height 0.498 mm

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.