homing issues...

[dos]

i've come across some issues recently that i can only chalk up to a bug, unless there is something i am missing.

if i try and home x with an axis width of 0 to 230 (M208 X0:230), if the printer has the carriage roughly <= half of the x axis width then homing works as expected. however, if the carriage is at a starting point beyond the half way point, say X200, rather than traveling in the negative direction towards the end stop it travels in the positive direction until it crashes into the end of the gantry.
here is my x homing sequence:

G91               ; relative positioning ; line 1 - comment added for post clarity
G1 H2 Z5 F6000    ; lift Z relative to current position ; line 2 - comment added for post clarity
G1 H1 X-230 F1800 ; move quickly to X axis endstop and stop there (first pass) ; line 3 - comment added for post clarity
G1 H2 X5 F6000    ; go back a few mm ; line 4 - comment added for post clarity
G1 H1 X-230 F360  ; move slowly to X axis endstop once more (second pass) ; line 5 - comment added for post clarity
G1 H2 Z-5 F6000   ; lower Z again ; line 6 - comment added for post clarity
G90               ; absolute positioning  ; line 7 - comment added for post clarity

additionally if i home successfully and then home again, it will have random behavior which appears to be a result of skipping over lines in the homing sequence, or rather not waiting for the previous process to complete before continuing. for example, z will lift (line 2) and will move x into the positive direction (due to skipping lines 3 & 4?) and then it will slowly go back towards the end stop (line 5). i have also seen where it runs through all the steps in order but when told to return to the end-stop (line 3) it will only move back a few millimeters and zero out in the center of the gantry without ever hitting the end-stop.

this same phenomena happens when homing all as well.

i have a video of the phenomena that shows the issues first hand. the steps performed are:

• home x
• home all
• move x less than 50% of bed width
• home all

unfortunately i can not attach a video larger than 4mb because this is 2003 apparently.

[engikeneer]

@dos what board are you using? Firmware version and config.g? What are you using for endstops and how have you got them wired up/mounted?

To me, your 'skipping over lines' sounds like you have some interference/poor connections on your endstop. I think the board is reading the endstop as already triggered when it executes line 3.

[dos]

@engikeneer
i'm using a duet 3 mini, with the latest rr firmware. i have normally closed switches wired that are rigidly mounted to the chassis and gantry. your theory of "interference/poor connections" wouldn't account for the the x traveling in the wrong direction when trying to home. if the wiring or switch was broken then it wouldn't attempt to home at all due to as you said it failing open. everything was running just fine until the other day when this problem just started occurring all of a sudden. for giggles i will replace the endstop but have zero faith that will fix the issue. this definitely looks to be a a faulty duet 3 board.

[Phaedrux]

@dos said in homing issues...:

G1 H2 X5 F6000

The H2 will allow it to move back even if it's not homed. Try removing the H2 on the back off moves for X. If it doesn't move anymore than it thinks it's already triggered.