Slow Sagging Death at End of Job

[rymnd]

Came across a strange failure behavior yesterday:

At the end of a job, the arms slowly sank down until the effector crashed into the finished part. The filament also seemed to fully retract through the bowden and popped out of the EZstruder. I was away from the printer at the time and didn't catch it in action, but from my Octoprint timelapse, it seemed that this happened over the course of ~5 min. When I came back to the printer, the hotend/heatbed were both up, so it appears that the job finished appropriately, and the sagging failure occured post-job. I also heard a buzzing sound from the extruder stepper, but it wasn't moving. The oddest thing (to me) about the sag is that when everything's normally powered off, the weight of the carriages/effector aren't enough to make the whole thing sag downwards.

Extruder Temp: 227
Heatbed Tempt: 90
Printer mods: xnaron-style magnetic arms
Print mode: via SD card
Firmware: Latest via Seemecnc
Slicer: Cura 14.03
Timelapse video: https://dl.dropboxusercontent.com/u/108 ... 020720.mpg (VLC player might be easiest way of looking at last few frames)

I'm thinking this might be one of those once-in-a-blue-moon failures, but if anyone else has seem something similar, I'd appreciate the insight.

Thanks for your time!

[guanu]

if you could, post your start and end gcode from cura, also have you printed that file before?

what can cause the retract forever is if there was not a G92 E0, but rather a G1 E0 (making it try to bring the extruder back to 0 from all the filament that has been already extruded).
I have seen this problem before with cura not starting a file with a G92 E0 and if you do prints back to back, the first E command it sends will bring the filament back from where it was since it was not reset.

[rymnd]

if you could, post your start and end gcode from cura, also have you printed that file before?

what can cause the retract forever is if there was not a G92 E0, but rather a G1 E0 (making it try to bring the extruder back to 0 from all the filament that has been already extruded).
I have seen this problem before with cura not starting a file with a G92 E0 and if you do prints back to back, the first E command it sends will bring the filament back from where it was since it was not reset.

Huh, interesting! So, I had to prematurely end a job right before this one. Maybe that was part of it? This was the first time I've printed this file, though I've printed a couple of times through the new Cura.

I have had repeated issues successfully printing w/ gcode from Cura 14.03/Kisslicer across the USB from Octoprint. The job will at times just pause in the middle and stop moving. As a result, I now usually print via SD card if I'm using paths generated from the new Cura or Kisslicer.

start g-code

Code: Select all

;Sliced at: {day} {date} {time}
;Basic settings: Layer height: {layer_height} Walls: {wall_thickness} Fill: {fill_density}
;Print time: {print_time}
;Filament used: {filament_amount}m {filament_weight}g
;Filament cost: {filament_cost}
;M190 S{print_bed_temperature} ;Uncomment to add your own bed temperature line
;M109 S{print_temperature} ;Uncomment to add your own temperature line
G21        ;metric values
G90        ;absolute positioning
M82        ;set extruder to absolute mode
M107       ;start with the fan off
G28 X0 Y0  ;move X/Y to min endstops
G28 Z0     ;move Z to min endstops
M106 S125
M42 P6 S125
G1 Z15.0 F{travel_speed} ;move the platform down 15mm
G92 E0                  ;zero the extruded length
G1 F200 E3              ;extrude 3mm of feed stock
G92 E0                  ;zero the extruded length again
G1 F{travel_speed}
;Put printing message on LCD screen
M117 Printing...

end gcode:

Code: Select all

;End GCode
M104 S0                     ;extruder heater off
M140 S0                     ;heated bed heater off (if you have it)
M106 S0
M42 P6 S0
G91                                    ;relative positioning
G1 E-1 F300                            ;retract the filament a bit before lifting the nozzle, to release some of the pressure
G1 Z+0.5 E-5 X-20 Y-20 F{travel_speed} ;move Z up a bit and retract filament even more
G28 X0 Y0                              ;move X/Y to min endstops, so the head is out of the way
M84                         ;steppers off
G90                         ;absolute positioning

Looks like the G92 E0 is where you say it should be.

[guanu]

ok, it doesnt look too bad, but a few things I would change are in the start gcode, remove the following lines:
G28 X0 Y0 ;move X/Y to min endstops
G28 Z0 ;move Z to min endstops

and replace them with:
G28

you only want the single G28 to home all the towers, same goes with the end gcode, remove the G28 X0 Y0, and replace it with just a G28

and to be on the safe side, and make it easier for repeating prints, I'd still throw a G92 E0 on a line below your G28 in your end gcode
but otherwise yea, it looks like it should only retract a total of 6mm after a print job.

Other things you can do:
repalce the end gcode M106 S0 with M107 (what this does is turn off your fan, but might as well give it a proper shut off rather than a value of 0)
remove the M42 P6 S0 from the end gcode
remove the M42 P6 S125 from start gcode (these are triggering pin 6, which is fan 2... not used)

hopefully cleaning up the start/end gcode could help for any future problems...

[rymnd]

ok, it doesnt look too bad, but a few things I would change are in the start gcode, remove the following lines:
G28 X0 Y0 ;move X/Y to min endstops
G28 Z0 ;move Z to min endstops

and replace them with:
G28

you only want the single G28 to home all the towers, same goes with the end gcode, remove the G28 X0 Y0, and replace it with just a G28

and to be on the safe side, and make it easier for repeating prints, I'd still throw a G92 E0 on a line below your G28 in your end gcode
but otherwise yea, it looks like it should only retract a total of 6mm after a print job.

Other things you can do:
repalce the end gcode M106 S0 with M107 (what this does is turn off your fan, but might as well give it a proper shut off rather than a value of 0)
remove the M42 P6 S0 from the end gcode
remove the M42 P6 S125 from start gcode (these are triggering pin 6, which is fan 2... not used)

hopefully cleaning up the start/end gcode could help for any future problems...

Thanks for the suggestions! Appreciate the insight!

I had the M42 P6 commands because I have extra fans on the effector connected to pin 6