Z Endstop homing problem

Hi,
Thank you for allowing me access to this group;
I need help in resolving a Z axis endstop settings.
I’m building a custom 3d printer and using marlin firmware, main board is BTT SKR 1.4 Turbo, optical endstops blasini on all three axes.
Bed is moving from top to bottom.
Here is the picture explaining where I put the locations of endstops, and where is my desired home for all three axes.
The X and Y seems to be homing fine, going in the right direction, and stoping when endstop is triggered;
I'm having problem with Z axis; when homed it goes up in the right direction, the endstops triggers when it passes thru but then it keeps on going up, it doesn't tell the motors to stop.

This is what it looks right now:

#define X_MIN_ENDSTOP_INVERTING false // Set to true to invert the logic of the endstop.
#define Y_MIN_ENDSTOP_INVERTING false // Set to true to invert the logic of the endstop.
#define Z_MIN_ENDSTOP_INVERTING false // Set to true to invert the logic of the endstop.
#define X_MAX_ENDSTOP_INVERTING false // Set to true to invert the logic of the endstop.
#define Y_MAX_ENDSTOP_INVERTING false // Set to true to invert the logic of the endstop.
#define Z_MAX_ENDSTOP_INVERTING false // Set to true to invert the logic of the endstop.
#define Z_MIN_PROBE_ENDSTOP_INVERTING false // Set to true to invert the logic of the probe.

#define INVERT_X_DIR true
#define INVERT_Y_DIR false
#define INVERT_Z_DIR false


#define X_HOME_DIR 1
#define Y_HOME_DIR -1
#define Z_HOME_DIR 1

#define X_MIN_POS 0
#define Y_MIN_POS 0
#define Z_MIN_POS 100
#define X_MAX_POS X_BED_SIZE
#define Y_MAX_POS Y_BED_SIZE
#define Z_MAX_POS 0


Thanks in advance

Sounds like you have made the typical error when you have a machine where the bed moves up and down

An end stop at the top of travel is Z min. ie it is the minimum distance from the hotend to the bed

Same with moves
a Z+ move should move the bed down, increasing the distance from the hotend to the bed
a Z- move should move the bed up, decreasing the distance from the hotend to the bed

So #define Z_HOME_DIR 1 is wrong change it to -1 then check the movement directions are correct

Edited 1 time(s). Last edit at 02/27/2022 09:39PM by Dust.

I tried that, changed to min and -1 but it goes into opposite direction, it goes down; not up when homing;
I changed the Z endstop to MAX back and it is going in the right direction now, but still won't trigger the endstop; I found somewhere that changing #define HOMING_BUMP_MM { 10, 10, 10 }
in the configuration_adv.h file would do the trick but I don't know to which value to change, because I already changed the default settings to #define HOMING_BUMP_MM { 5, 5, 2 }
#define HOMING_BUMP_DIVISOR { 2, 2, 4 }
I also uncommented the #define ENDSTOPS_ALWAYS_ON_DEFAULT but it has no effect.

Invert your Z direction

Find #define INVERT_Z_DIR if it is set to true make it false and vice versa

I did that and it is going in the wrong direction. Maybe some option needs to be commented? For example I'm not using probe but maybe this needs to be uncommented?
/**
* Enable this option for a probe connected to the Z-MIN pin.
* The probe replaces the Z-MIN endstop and is used for Z homing.
* (Automatically enables USE_PROBE_FOR_Z_HOMING.)
*/
#define Z_MIN_PROBE_USES_Z_MIN_ENDSTOP_PIN

And what about this? Maybe something here?
// Mechanical endstop with COM to ground and NC to Signal uses "false" here (most common setup).
#define X_MIN_ENDSTOP_INVERTING false // Set to true to invert the logic of the endstop.
#define Y_MIN_ENDSTOP_INVERTING false // Set to true to invert the logic of the endstop.
#define Z_MIN_ENDSTOP_INVERTING false // Set to true to invert the logic of the endstop.
#define X_MAX_ENDSTOP_INVERTING false // Set to true to invert the logic of the endstop.
#define Y_MAX_ENDSTOP_INVERTING false // Set to true to invert the logic of the endstop.
#define Z_MAX_ENDSTOP_INVERTING false // Set to true to invert the logic of the endstop.
#define Z_MIN_PROBE_ENDSTOP_INVERTING false // Set to true to invert the logic of the probe.

step 1) check moment directions are correct, not homing. change with INVERT_Z_DIR , check + direction first as cant go less than start position.

a Z+ move should move the bed down, increasing the distance from the hotend to the bed
a Z- move should move the bed up, decreasing the distance from the hotend to the bed

step 2) set Z_HOME_DIR -1

This is a physical parameter of your machine, it is at the min position, set it to min, don't change it without moving the endstop.


step 3) check endstop triggered state with M119. manually with a bit of cardboard change its state and recheck. Ensure it says Open when the End stop it not being activated, and triggered when it is.

Edited 1 time(s). Last edit at 03/01/2022 12:03AM by Dust.

Okay
This is how it went :
Checked the directions + and -, they where inverted (Z+ did not move the bed down but up) so changed the INVERT Z DIR to true.
Then I checked the M119. I put a small screwdriver in the optosensor and checked the M119, Zmax was triggered. When nothing was in the optosensor, the M119 said Zmax is open.

Must have been I made some mistake in the previous steps, don't know how, but tried it again with M119 (making sure the + goes down and - goes up) it turns out that no the Zmax endstop is always triggered, no matter if something is put in the optosensor or not

Could you post a wiring diagram for your optic-sensor .

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Computer Programmer / Electronics Technician