z0 doesn't change height when changing Z-Probe height

Paranoid

Hi

I have done Z probing for a long time but decided to finetune it a bit more after upgrading to 1.0.3.
Something strange I'm noticing is that when I change Z-Probe height before running G32, afterwards it doesn't change the nozzle height at Z0. I've tried finding an answer on the forum but didn't find one that works.

I have Z max end stop, an inductive sensor and this plastic PEI sheet on my bed (which has already been set in EEPROM)

The procedure I follow:
- disable autolevel and distortion correction
- home x, y, z
- move z to z10
- G32 S2
- update new printer height in printer settings
- check z0

I've had my Z-probe height as 2.324mm while following the standard z probing guide in the repetier documentation. After checking z0, I noticed it was off by 1.75mm (too low). So I changed my Z-probe height in EEPROM to 4.074 and repeated the procedure. Distortion correction has been disabled permanently to get the Z0 right, so that shouldn't have an influence.
After doing this again, nothing changed. z0 remains at the same height.

What am I doing wrong?

Repetier

From repetier.ino

G32 S<0..2> P<0..1> - Autolevel print bed. S = 1 measure zLength, S = 2 Measure and store new zLengthyou have S2 so it should run to z max and update. Did you check zlength in eeprom before and after the command or even better modify it first so it must change.

You have update height as extra steps. What do you do there?

Have you rehomed before testing z=0?

Paranoid

Hi

I checked zlength before and after and it is updated, although always around the same value as stated in the OP. Around 367.xx in my case. But it is updated none the less.

The height update I mentioned is only in repetier host in printer settings, don't think this really does anything but update the work space in the host.

I always rehome z before testing the new z0.

You say G32 S2 runs to zmax? I always home everything first, lower z to a position close to bed and let it run G32. It doesn't home to zmax again automatically.

Paranoid

I used to bypass this via the bed coating thickness but when having finetuned my distortion correction all my first layers were messy in layer height. This is why I want to properly have my z probe height defined so that hopefully solves the issue.

Repetier

Ok, there are 2 variants depending on bed leveing method, so yours is this

        if(s != 0) {

            // at origin rotations have no influence so use values there to update

            Printer::zLength += currentZ - Printer::currentPosition[Z_AXIS];

            //Printer::zLength += /*currentZ*/ plane.z((float)Printer::currentPositionSteps[X_AXIS] * Printer::invAxisStepsPerMM[X_AXIS],(float)Printer::currentPositionSteps[Y_AXIS] * Printer::invAxisStepsPerMM[Y_AXIS]) - zRot;

            Com::printFLN(Com::tZProbePrinterHeight, Printer::zLength);

        }

it changes z based on difference between measured and theoretical z position. In earlier versions it did physically measure. One of the things driving me crazy - all these mods to make users happy. So not z max homing is ok.

Repetier host value is just so host known z position after homing. Not necessary what firmware assumes. But if you use 
G1 Z0
it will always send the absolute position and then both are in sync.

Paranoid

Thanks for the explanation. So actually if I change Z-probe height, then according to the calculation it should change the z positioning accordingly. The strange thing it doesn't seem to happen. Possibly I'm missing something?

Can you suggest a short workflow for me to try to identify a possible mistake I'm making here?

MartinH

can you share your configuration.h, it might help to hi lite any problems.

Paranoid

Absolutely. Here it is:
https://pastebin.com/nyqZCedL

Any help is appreciated.

Paranoid

Something I forgot to ask in OP: when changing Z-probe height in EEPROM, is it necessary to redo the whole autoleveling process (G32)?

EDIT: after trying myself I believe the answer here is yes.

Also, I think I find the solution. After reading about the zmax homing above, I tried just doing G32 S2 from zhome instead of lowering it myself. I have tried different Z-probe height settings like this and I can actually finetune it now!

So, the proper workflow is:
- Home X,Y
- Home Z
- G32 S2
- G1 Z0
- Check Z0 height

After that it's just a matter of adjusting Z-probe height according to the nozzle position at Z0.

I have reduced the number of measurements to test this so I'll do some more finetuning the next couple of days.
If I don't come back with follow up questions, you can consider this solved  

In any case, thanks for the good communication!

MartinH

Paranoid said:

Thanks for the explanation. So actually if I change Z-probe height, then according to the calculation it should change the z positioning accordingly. The strange thing it doesn't seem to happen. Possibly I'm missing something?

Can you suggest a short workflow for me to try to identify a possible mistake I'm making here?

are you changing the value in config.h or direct in the eeprom?

looked over your configuration.h and all looks good.

Repetier

Actually in your original post you said already home x,y,z so I assumed you did that already.
Apart form this you are right. Changing z probe height requires a redo of G32 S2 to adjust z length. In effect it changes z length by the change of z probe height.

Paranoid

MartinH said:

are you changing the value in config.h or direct in the eeprom?

looked over your configuration.h and all looks good.

Yes, always changing things directly in EEPROM. I hardly ever change values in configuration.h anymore apart from major firmware updates. Thanks for the help!

Paranoid

Repetier said:

Actually in your original post you said already home x,y,z so I assumed you did that already.
Apart form this you are right. Changing z probe height requires a redo of G32 S2 to adjust z length. In effect it changes z length by the change of z probe height.

Indeed, I also did that before. The thing that changed is that I don't lower the head to e.g. Z10 before starting G32 S2. Also afterwards I don't do Zhome for checking the Z0 position as you suggested. My feeling is that one of these two factors somehow have something to do with the issue I had.
Thanks for your assistance!