Autoleveling Z_PROBE_HEIGHT and distance from bed

entr04y · June 2015

I'm using firmware version 0.92.3 downloaded 3-4 days ago.

I have a Cartesian printer where the bed is fixed and X, Y, and Z are on a gantry which moves up and away from the bed as the print progresses. I am using a capacitance sensor which is triggering at ~3mm from the bed and the distance from the bed to the tip of the nozzle is 1.5mm when the sensor triggers. My Z Endstop configuration is:

#define ENDSTOP_PULLUP_Z_MIN false

#define ENDSTOP_Z_MIN_INVERTING false

#define MIN_HARDWARE_ENDSTOP_Z false

#define ENDSTOP_PULLUP_Z_MAX true

#define ENDSTOP_Z_MAX_INVERTING true

#define Z_HOME_DIR 1

#define MAX_HARDWARE_ENDSTOP_Z true

#define min_software_endstop_z false

#define max_software_endstop_z false

And my Probe setup is this:

#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 1

#define Z_PROBE_X_OFFSET 0

#define Z_PROBE_Y_OFFSET 0

#define Z_PROBE_WAIT_BEFORE_TEST 0

#define Z_PROBE_SPEED 2

#define Z_PROBE_XY_SPEED 150

#define Z_PROBE_SWITCHING_DISTANCE 1

#define Z_PROBE_REPETITIONS 10

#define Z_PROBE_HEIGHT -1.5

#define Z_PROBE_START_SCRIPT ""

#define Z_PROBE_FINISHED_SCRIPT ""

#define FEATURE_AUTOLEVEL 1

#define Z_PROBE_X1 0

#define Z_PROBE_Y1 0

#define Z_PROBE_X2 369

#define Z_PROBE_Y2 0

#define Z_PROBE_X3 369

#define Z_PROBE_Y3 328

#define FEATURE_AXISCOMP 0

#define AXISCOMP_TANXY 0

#define AXISCOMP_TANYZ 0

#define AXISCOMP_TANXZ 0

I'm a bit confused as to the correct value for Z_PROBE_HEIGHT.

From what I understand, the Z_PROBE_HEIGHT should be set to a value of 1.5, but I am confused as to whether the firmware wants that as a negative value or a positive value for my situation. I've been using a negative value, but I wanted to verify that is correct as I am running into another issue.

When I run the auto level routine (G28, G32 S2) it does it's thing and then when it is done moving Z to 0 puts the nozzle at 3mm above the print bed. I've tried M502, M500, M501 to reset everything in the EEPROM, is there somewhere else I need to check where that 3mm offset might be coming from?

Thanks!

Repetier · June 2015

In your case -1.5 should be the correct value.

G32 is not supposed to replace homing and also does not stop at z=0. If in doubt do a G28 after autoleveling and check again. If you had 1.5 instead of -1.5 you have your 3mm difference. It either starts at height where it started or does a zmax homing depending on printer type/parameter. M50x do not change autoleveling settings.

entr04y · June 2015

Ok, I have it set to -1.5, and that is what it has been the last few times I've tried it.

Here is exactly what I have been doing:

M502 (repetier hosts says "auto leveling disabled")

M500

M501

Power off and on the arduino

G28

G1 Z5

G32 S2 (matrix is updated, repetier host says "auto leveling enabled")

G28

G1 Z0

At the end of the above sequence, the head is 3mm from the build plate, every time.

If I set a z offset in slic3r of -3mm the print starts at the correct height, so I guess that's good enough, I'd just like to understand why zero is being set to +3mm by auto leveling. I'm also issuing a G28 as the first command of every print.

At the very least, M502 disables auto leveling according to repetier host. I'll give it another try and add M321 S2 and M322 S3 to clear everything out before I do the G32 S2 and see if that makes a difference. Are there any other commands that I should issue to make sure I'm starting from a "clean" slate?

Thanks!

Repetier · June 2015

Could you please try -4.5 instead of -1.5 and see if it makes a difference. Unfortunately I have no cartesian printer with z probe for testing myself.

At least I would expect the error to get 0 if it was -3 before if that variable has the influence it should have. If nothing changes I know at least where to look for.

entr04y · June 2015

Thanks, I'll give that a shot... I've got a couple other issues I'm working out so it may be a day or two before I get back to this.

entr04y · June 2015

Ok, so I played with it a bit. It looks like for my printer I need Z probe offset to be a positive number. I set it to +1.5 and its coming out perfect now. I had tried that before, and gotten different results, but I must have had something else misconfigured at the time.

A separate issue is that while trying this stuff I was having an issue getting G32 to run. I figured out eventually it was because with an offset of -4.5 the max z-probe - bed distance was greater than what I had set for it. While trying to figure that out I set the Z length about 10mm longer than I have travel for (the measurement was coming out negative, so I thought it just needed room for the math) and when I ran G32 it blew right past the sensor trigger (I watched the light come on as it did this) and crashed into the bed. I would think that during a G32, if the sensor gets triggered it should stop at that point.

Autoleveling Z_PROBE_HEIGHT and distance from bed

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