How to home (G28) midprint and resume?

lazy_mosquito

I want to do a colorchange with my duet 0.85 in the middle of a print. I can pause at the right place, but because i have a rather big delta printer with a fidly filament change it is almost impossible to change my filament without moving the printhead. My solution was to insert a G28 command after the break in the g-code; so it would center it again before resuming print. but after the g28 command it homes indeed but stops and tells me the print is finished. Somebody another idea how i can rehome my head again after filament change in midprint?

Phaedrux

What firmware version?
What do you have in homedelta.g?
What do you have in pause.g and resume.g?

lazy_mosquito

@phaedrux
RepRapFirmware for Duet 1.26.1 (2020-02-09b1)
homedelta.g:
G91 ; relative positioning
;*** Slow homing has been configured. Change F180 to F1800 below when your configuration is working
G1 S1 X1305 Y1305 Z1305 F3600 ; move all towers to the high end stopping at the endstops (first pass)
G1 S2 X-5 Y-5 Z-5 F1800 ; go down a few mm
;*** Slow homing has been configured. Change F180 to F360 below when your configuration is working
G1 S1 X10 Y10 Z10 F180 ; move all towers up once more (second pass)
G1 Z-5 F2400 ; move down a few mm so that the nozzle can be centred
G90 ; absolute positioning
G1 X0 Y0 F3600 ; move X+Y to the centre

no pause.g
no resume.g

Phaedrux

I'm not sure how exactly it will behave when pause and resume macros are missing. But this is what the config tool generates for pause and resume for a delta. It saves the current print position and then parks and then resume will restore that print position.

; pause.g
; called when a print from SD card is paused
;
; generated by RepRapFirmware Configuration Tool v3.2.3 on Tue Jun 08 2021 13:01:27 GMT-0600 (Central Standard Time)
M83            ; relative extruder moves
G1 E-10 F3600  ; retract 10mm of filament
G91            ; relative positioning
G1 Z5 F360     ; lift Z by 5mm
G90            ; absolute positioning
G1 X0 Y0 F6000 ; go to X=0 Y=0

; resume.g
; called before a print from SD card is resumed
;
; generated by RepRapFirmware Configuration Tool v3.2.3 on Tue Jun 08 2021 13:01:50 GMT-0600 (Central Standard Time)
G1 R1 X0 Y0 Z5 F6000 ; go to 5mm above position of the last print move
G1 R1 X0 Y0          ; go back to the last print move
M83                  ; relative extruder moves
G1 E10 F3600         ; extrude 10mm of filament

You can make adjustments to that if you wish as well.

lazy_mosquito

@phaedrux
This would work in a normal situation, it works on my Prusa. But on the Prusa it is very easy to change the filament without moving the printhead, which is almost impossible with my delta printer.
The problem is, that the printer will restore its position from the existing,moved, coordinates, but when the head is moved by replacing the filament, the printer has lost its absolute position and will go back to the wrong position, that's why I would like to home it first. In that way, I can reposition the head back in a known position and start from there.
My printer has rods of 72 cm, which makes that any force you put on the arms easily overpowers the holding force of the steppermotors, specially with my extruder. It works very well but is a pain to load new filament.

Phaedrux

@lazy_mosquito said in How to home (G28) midprint and resume?:

that's why I would like to home it first.

Yes I understand. Add a G28 to the resume macro.

lazy_mosquito

@phaedrux
Thanks already for your answer.
I would expect it behaves similarly to adding it directly in the code.

But I will first try to invoke it via the pause and the resume macro and sees if it makes a difference instead of invoking it directly in the g-code.

i just create the macro's and invoke them manually after the prints pauses?

Phaedrux

@lazy_mosquito said in How to home (G28) midprint and resume?:

i just create the macro's and invoke them manually after the prints pauses?

No, when you create a pause.g and resume.g macro file in the /sys folder they will get called when you manually pause and resume the print with the buttons automatically.

o_lampe

@phaedrux
I'm not aware that RRF 1.26 already had the 'restore position' feature?

@lazy_mosquito
Can you add a bracket to the printer frame (bed respectively) were you park&lock the effector before filament change?

lazy_mosquito

@lazy_mosquito
Can you add a bracket to the printer frame (bed respectively) were you park&lock the effector before filament change?

Thats an option i was also thinking about, but more complex to achieve compared to code.

Phaedrux

@o_lampe said in How to home (G28) midprint and resume?:

I'm not aware that RRF 1.26 already had the 'restore position' feature?

Ah yes, I hadn't thought about that. I'll have to dig to see when that was implemented. I took it for granted that it was already present.

dc42

@o_lampe said in How to home (G28) midprint and resume?:

I'm not aware that RRF 1.26 already had the 'restore position' feature?

The restore position feature was introduced in 2014 AFAIR, several years before rrf 1.26 was released.