Core XY Won't stop homing at endstop

I have an Airwolf Axiom printer that I'm trying to write new firmware for. I'm using Marlin 2.07 on VS Code. It is a Core XY machine where it homes at front, left with the build plate at the bottom of travel, that is, X min, Z min, Z Max. That is where the endstops are. All 3 axes move in the proper direction on Pronterface. X,Y and Z also home in the right direction. It uses the Z Min Plug for the probe.

X an Y home and trigger the endstops and stop as they should. Z, however moves to the end of travel and crashes into the bottom (away from the nozzle). The Z Max endstop triggers but doesn't stop the stepper. Oddly enough, when I trigger the leveling probe connected to the Z Min pin while it is homing Z, it stops the stepper and shows the Z axis as homed on the LCD (it displays zero and stops flashing). Also, if I change #define Z_HOME_DIR 1 to #define Z_HOME_DIR -1 ,it homes in the opposite direction (up) and if I manually trigger the Z Max endstop switch it stops and shows Z as homed on the LCD. All the endstops trigger properly manually with M119. Also the wiring is correct as it all works properly on the original closed source firmware.

So the problem seems to be the wrong endstop limit switch triggers when homing. I want to make the appropriate change in firmware and not change the wiring. I'm sure this is possible since I was trying to set up the firmware a few months ago and got it past this point. Unfortunately I didn't document my changes well enough and I can't remember what I did before. It's probably a simple setting I'm missing.

Anyone have any ideas?
Thanks

Sorry, I had that backwards. I wrote

Also, if I change #define Z_HOME_DIR 1 to #define Z_HOME_DIR -1 ,it homes in the opposite direction (up) and if I manually trigger the Z Max endstop switch it stops and shows Z as homed on the LCD.

meant to say

" Also, if I change #define Z_HOME_DIR -1 to #define Z_HOME_DIR 1 ,it homes in the opposite direction (up) and if I manually trigger the Z Max endstop switch it stops and shows Z as homed on the LCD.

Quote
jspring111
I have an Airwolf Axiom printer that I'm trying to write new firmware for. I'm using Marlin 2.07 on VS Code. It is a Core XY machine where it homes at front, left with the build plate at the bottom of travel, that is, X min, Z min, Z Max. That is where the endstops are. All 3 axes move in the proper direction on Pronterface. X,Y and Z also home in the right direction. It uses the Z Min Plug for the probe.

Hi jspring111, wen you say Z move in the proper direction did you mean that, after homing, it goes down when you jog in positive direction?

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Luca

CoreXY custom (LF Mark1) 395x360x350 - Mega (clone per ora..) + RAMPS1.4 + 4xA4988 + 4 Nema17 17HS4401 - HotEnd V6 clone con ugello da 0.4mm - RepRapDiscount - Display LCD 2004 Smart Controller - Firmware MK4duo 4.2.9 - Repetier-Host 2.1.6

When I say Z moves in the proper direction, I mean when I move the axes in Pronterface, they move in the correct direction. This is before homing. When I try to home the axes,they also move in the correct direction toward the endstops (X min, Y min and Z max).

The problem is that I can't get it to home because, even though the endstop limit switch is triggered when the bed gets down to the bottom of travel, it ignores it and keeps moving the bed down until it crashes into the bottom of the printer. The stepper starts skipping and makes a bad noise until I hit the reset switch.

Please disregard the above

Is the Zmax endstop at the physical top or bottom of the Z axis?

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

It's at the bottom of the printer, when the bed is all the way down. That's because it's a Core xy Machine. Confusing on Pronterface since their Z arrow indicating + points up, not down.

Direction is always from the print's perspective. The bed surface is Z=0 and as the nozzle gets higher (or bed gets lower), Z is increasing. How do you locate the bed surface? Are you using a probe, specifying an offset, or ?

The home position is defined by the locations of the endstops. The origin is defined by the ordinate values you set after homing. You can put either anywhere, but you must always use right hand rule coordinates to match the CAD software and the slicer or your prints will come out mirrored. Putting the Z endstop at the Zmax position will require you to wait however long it takes the bed to go all the way down and come all the way back up each time you print. There may be good reason to do that depending on how your Z axis works, but it doesn't always make sense to do that. Endstops are ignored in some (all?) firmwares when the printer isn't specifically homing. So you can (not that you'd want to) put the Z endstop in the middle of the Z axis and then specify the offset and it will work fine. Since you have to locate the bed to start printing, why not put the Z endstop at Z=0? Then the bed won't have to travel so far for homing...

I find that setting the printer's origin to the center of the bed is very convenient because it makes it easy to use different slicers and guarantees that prints will be made at the center of the bed.

I wrote some blog posts on this topic:
[drmrehorst.blogspot.com]
[drmrehorst.blogspot.com]
[drmrehorst.blogspot.com]

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]