Z leveling with probe mysteries ?????

BernieG

The worst part is that, at some point, it was working, more or less.

OK, I was having problems achieving properly G32. I thought it was my probe, working on 5 volts instead of 12. So I changed it, rewired so that the new one is properly working on 12 volts, with the signal at 4.5V. I tested on an Arduino before plugin it on the printer, and everything works as expected. BUT NOTHING CHANGED, so the probe is not the problem!

What happens is that, when I run a G32 command, it starts Ok with the first couple of rows, then it start pushing/crashing into the bed. I must add that before I level X axis and bed with a digital level box, and I have less than 1/10 of a degree of error.

here is the last attempts reasults:

12:34:02.634: Info:Autolevel matrix reset
12:34:23.811: Info:Resetting Z correction
12:35:15.719: Z correction disabled (2)
12:35:20.150: Z-probe:9.04 X:-4.99 Y:10.00
12:35:26.253: Z-probe:9.08 X:-4.99 Y:46.24
12:35:32.386: Z-probe:9.15 X:-4.99 Y:82.49
12:35:38.520: Z-probe:9.11 X:-4.99 Y:118.74
12:35:44.669: Z-probe:9.15 X:-4.99 Y:155.00
12:35:51.575: Z-probe:9.51 X:33.74 Y:10.00
12:35:57.914: Z-probe:9.55 X:33.74 Y:46.24
12:36:04.284: Z-probe:9.62 X:33.74 Y:82.49
12:36:10.655: Z-probe:9.61 X:33.74 Y:118.74
12:36:17.041: Z-probe:9.64 X:33.74 Y:155.00
12:36:24.120: Z-probe:9.65 X:72.50 Y:10.00
12:36:32.004: Z-probe:15.67 X:72.50 Y:46.24

As you can see, the measures looks normal, then suddenly it press onto the bed to find more than 6 mm difference, which is just impossible! Note that I made sure to remove/disable any pre-existing correction.

I am certainly doing something wrong in my settings, but I am unable to pinpoint what, exactly. Here is the relevant part of my configuration.h

// #################### Z-Probing #####################
#define Z_PROBE_Z_OFFSET 0
#define Z_PROBE_Z_OFFSET_MODE 0
#define UI_BED_COATING 0
#define FEATURE_Z_PROBE 1
#define Z_PROBE_BED_DISTANCE 10
#define Z_PROBE_PIN ORIG_Z_MIN_PIN
#define Z_PROBE_PULLUP 1
#define Z_PROBE_ON_HIGH 0
#define Z_PROBE_X_OFFSET 30
#define Z_PROBE_Y_OFFSET 0
#define Z_PROBE_WAIT_BEFORE_TEST 0
#define Z_PROBE_SPEED 4
#define Z_PROBE_XY_SPEED 250
#define Z_PROBE_SWITCHING_DISTANCE 3.52
#define Z_PROBE_REPETITIONS 5
#define Z_PROBE_HEIGHT 1.20
#define Z_PROBE_START_SCRIPT ""
#define Z_PROBE_FINISHED_SCRIPT ""
#define Z_PROBE_REQUIRES_HEATING 0
#define Z_PROBE_MIN_TEMPERATURE 150
#define FEATURE_AUTOLEVEL 1
#define Z_PROBE_X1 1
#define Z_PROBE_Y1 1
#define Z_PROBE_X2 160
#define Z_PROBE_Y2 1
#define Z_PROBE_X3 1
#define Z_PROBE_Y3 160
#define BED_LEVELING_METHOD 1
#define BED_CORRECTION_METHOD 0
#define BED_LEVELING_GRID_SIZE 5
#define BED_LEVELING_REPETITIONS 5
#define BED_MOTOR_1_X 1
#define BED_MOTOR_1_Y 1
#define BED_MOTOR_2_X 170
#define BED_MOTOR_2_Y 1
#define BED_MOTOR_3_X 170
#define BED_MOTOR_3_Y 170
#define BENDING_CORRECTION_A 0
#define BENDING_CORRECTION_B 0
#define BENDING_CORRECTION_C 0
#define FEATURE_AXISCOMP 1
#define AXISCOMP_TANXY 0
#define AXISCOMP_TANYZ 0
#define AXISCOMP_TANXZ 0

Hoping you can help me here, as for now, I am stuck with this and unable to use bed leveling.

Thanks!

Roko

Your probing coordinates look odd based on your settings. Are your offsets correct?
How did it print before using bed levelling?(just curious).

BernieG

Roko said:

Your probing coordinates look odd based on your settings. Are your offsets correct?
How did it print before using bed levelling?(just curious).

I believe they are correct. I have been testing my bed centering, and adjusted offset accordingly. What looks strange to me, is that it seems the probe offset seems to NOT be taken into account.

It was printing pretty well before print leveling, I just got tired to have to adjust the bed so often to get it level.

Repetier

From the output it surely makes no sense to have 6mm difference here. Question is why does firmware think this. Did it (a) go up 6mm after the last good measurement or (b) did it go down 6mm more then before? (a) would be an error and we would need to find out why and how this could happen. (b) means a hardware reason like a heated bed being on making an inductive probe return different results or some other thing. Don't know your printer to guess here.

BernieG

Repetier wrote
From the output it surely makes no sense to have 6mm difference here. Question is why does firmware think this. Did it (a) go up 6mm after the last good measurement or (b) did it go down 6mm more then before? (a) would be an error and we would need to find out why and how this could happen. (b) means a hardware reason like a heated bed being on making an inductive probe return different results or some other thing. Don't know your printer to guess here.

Thanks for your answer. What is happening is (b).
My printer is an Anet A8, I have a 0.8 mm PEI on top of the Aluminium bed, which is NOT on when I attempt to setup bed leveling. The Probe is Omron TL-Q5MC1-Z.

You say "or some other thing". What other things should I be looking for?

What I see looks like different results, that is the led light sometimes goes on at what I believe is a normal distance, like +-2mm above the bed, but sometimes it goes on AFTER touching the bed, and sometimes not at all!

Could it be some wrong settings on my side, or something faulty on the electronic side?

Repetier

From your description it is in any case a hardware related issue as you have a led indicator that shows when it triggers.

Since it is a inductive probe you should have bed disabled when measuring. I think in 1.0 I even disable it actively when probing, but not sure if that was in public version or for a vendor. Also it might measure differently depending on the area of metal below. If you can make it less sensitive so it needs to go closer to bed. That would normally help with accuracy. If they are hyper sensible there are just too much electric fields that can influence it.

BernieG

Thanks for your answer. Is there a GCode command to disable the bed? Anyway, I will look how to do that, and hope it makes all the difference.

I have not seen a way to make it less sensitive. If this does not work, would there be probes you would recommend over the one I have?

BernieG

Well, I believe I solved it, and report my findings here as it might be usefull to others: I went from 4 mm/s as probe speed to 2 mm/s.

#define Z_PROBE_SPEED 2

That's it! So, yes, it IS hardware related, it's just that, between the probe and the controler, communication might be a bit slow...

here is my last, successful, attempt at G32:

13:26:25.264: Z-probe:9.43 X:10.00 Y:20.00

13:26:42.296: Z-probe:9.53 X:10.00 Y:60.00

13:26:59.420: Z-probe:9.66 X:10.00 Y:100.00

13:27:16.677: Z-probe:9.80 X:10.00 Y:140.00

13:27:34.038: Z-probe:9.85 X:10.00 Y:180.00

13:27:51.981: Z-probe:9.54 X:52.50 Y:20.00

13:28:09.105: Z-probe:9.66 X:52.50 Y:60.00

13:28:26.356: Z-probe:9.77 X:52.50 Y:100.00

13:28:43.730: Z-probe:9.90 X:52.50 Y:140.00

13:29:01.194: Z-probe:9.96 X:52.50 Y:180.00

13:29:19.185: Z-probe:9.53 X:95.00 Y:20.00

13:29:36.326: Z-probe:9.68 X:95.00 Y:60.00

13:29:53.600: Z-probe:9.80 X:95.00 Y:100.00

13:30:10.998: Z-probe:9.92 X:95.00 Y:140.00

13:30:28.489: Z-probe:9.99 X:95.00 Y:180.00

13:30:46.515: Z-probe:9.56 X:137.49 Y:20.00

13:31:03.686: Z-probe:9.71 X:137.49 Y:60.00

13:31:20.992: Z-probe:9.84 X:137.49 Y:100.00

13:31:38.429: Z-probe:9.96 X:137.49 Y:140.00

13:31:55.957: Z-probe:10.03 X:137.49 Y:180.00

13:32:13.974: Z-probe:9.51 X:180.00 Y:20.00

13:32:31.100: Z-probe:9.67 X:180.00 Y:60.00

13:32:48.368: Z-probe:9.81 X:180.00 Y:100.00

13:33:05.755: Z-probe:9.93 X:180.00 Y:140.00

13:33:23.257: Z-probe:10.00 X:180.00 Y:180.00

13:33:27.767: plane: a = 0.0007 b = 0.0029 c = 9.3999

13:33:27.783: Transformation matrix: 1.000000 0.000000 -0.000747 -0.000002 0.999996 -0.002906 0.000747 0.002906 0.999995

13:33:27.783: CurrentZ:10.04 atZ:10.10

13:33:28.162: Info:Autoleveling enabled

I don't know if a maximum difference of 0.6 mm is bad, but it seems a lot more consistent with my bed than 6 mm, that's for sure!

Repetier

It first look it looks consistent and like a rotated bed, so exactly what it targets to correct.

0.6mm is much in the sense of could not print good without correction. It will also keep the z axis moving a lot. So also it now gets corrected automatically it would improve if you correct the bed a bit manually. The less you have to correct the better.

BernieG

Repetier said:

It first look it looks consistent and like a rotated bed, so exactly what it targets to correct.

0.6mm is much in the sense of could not print good without correction. It will also keep the z axis moving a lot. So also it now gets corrected automatically it would improve if you correct the bed a bit manually. The less you have to correct the better.

yes, thanks, thought I would do so, I should be able to have less difference, maybe around 0.3, which is still a lot, but that bed is far from perfect.

BTW, did I understand correctly if I believe the correction is applied to the first 5 or 6 layers, then diminish to the point there is no correction at all after a few more layers?

Repetier

No, the correction from G32 is just rotational correction applied over whole distance. But your result looks like rotational correction. Test same region with repetier-host and correction enabled to see how good it is after correction.

What you mean is distortion correction G33 which is only working correctly in 1.0 which you can not use due to size limits.

BernieG

Just wanted to let you know that Autolevel is now working perfectly well. I setup the bed better, so now I have less than 0.3 mm difference between extremes. I can see the Z motors moving a bit during long straight lines, so I see it's working.

I still have a little problem I can't figure out: When doing Home Z (G28 Z), I see the nozzle and probe going down slowly, the probe sensing the height and stopping the motion down, so it looks OK. But then the nozzle is moving up a little bit, going down again, then pressing on the Bed, going up a bit more, going down faster into the bed!

So it looks like the first movement down is not really taken into account, as I have to set a Z offset of 1.8 mm to avoid scratching the bed surface when printing!

Is there values to adjust in EEPROM to avoid this?

Thanks!

Repetier

Bed coating increased could make it go not that much down. Not sure what is taken into account in 0.92.9. The first 2 down moves are normal z homing. Then it might go back a bit and adds some corrections from rotation and bed coating. Just to be sure - you have NO z-min endstop and use z probe also as z-min right? Because that is how z min homing with z probe has to work.

BernieG

Repetier wrote
Just to be sure - you have NO z-min endstop and use z probe also as z-min right? Because that is how z min homing with z probe has to work.

Yes, that's correct.

I will try adding some bed coating.