Finishing a print that failed due to nozzle clog (can one avoid initial z-calibration?)
 
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Finishing a print that failed due to nozzle clog (can one avoid initial z-calibration?)  

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Aw Mac 3
(@aw-mac-3)
Active Member
Finishing a print that failed due to nozzle clog (can one avoid initial z-calibration?)

When I checked my printer this morning, the nozzle was continuing to move in space above the first 5-or-so mm it had been printing when I left last night. The nozzle had clogged at some point during the night. Now it's unclogged and ready to print, but I don't want to start anew -- I want to learn how to restart a print when this happens.

According to some sites, like here and here, the way to do this is to hack the gcode by deleting instructions for those layers that have already been laid. Great. Done. All well and good (perhaps -- I haven't tried).

But I know that as soon as I Print from SD with my new file, it's going to run a z calibration step to obtain its 9 points and that will run the nozzle through my partial print (and throw and error to boot). 

Is there a better was than hacking gcode to restart a failed print or in any case avoid the initial z calibration step? Thanks.

 

Best Answer by --:

You don't want to have the startup gcode that calls for a mesh level (or even a home) when you do this ... and if you have powered off the printer, or bumped the plate or extruder, you are basically out of luck anyway because then you must home the printer.  

Posted : 05/08/2019 2:05 pm
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(@)
Illustrious Member
RE: Finishing a print that failed due to nozzle clog (can one avoid initial z-calibration?)

You don't want to have the startup gcode that calls for a mesh level (or even a home) when you do this ... and if you have powered off the printer, or bumped the plate or extruder, you are basically out of luck anyway because then you must home the printer.  

Posted : 05/08/2019 3:04 pm
Aw Mac 3
(@aw-mac-3)
Active Member
Topic starter answered:
RE: Finishing a print that failed due to nozzle clog (can one avoid initial z-calibration?)

Thanks, Tim. Luckily there power has remained on and the plate and extruded are as they were except for the removal and replacement of the filament.

I found the code for "G28 ; home all axes" I assume that should be deleted/commented out. Are there other commands in the gcode for a mesh level? Here is the starting code for print:

; generated by PrusaSlicer 2.0.0+ on 2019-08-04 at 17:40:04

;

; external perimeters extrusion width = 0.45mm
; perimeters extrusion width = 0.45mm
; infill extrusion width = 0.45mm
; solid infill extrusion width = 0.45mm
; top infill extrusion width = 0.40mm
; first layer extrusion width = 0.70mm

M107
M190 S65 ; set bed temperature and wait for it to be reached
M104 S215 ; set temperature
G28 ; home all axes
G1 Z7 F5000 ; lift nozzle
; Filament gcode
M109 S215 ; set temperature and wait for it to be reached
G21 ; set units to millimeters
G90 ; use absolute coordinates
M82 ; use absolute distances for extrusion

Posted : 05/08/2019 3:13 pm
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(@)
Illustrious Member
RE: Finishing a print that failed due to nozzle clog (can one avoid initial z-calibration?)

I'd need to see the entire gcode ... and by experience will recommend you just restart the print.  I've lost 36 hours to print failures. Painful, but not worth losing another 36 hours because of an offset caused by thermal drift, part shift, or part lift from the bed cooling for too long.

 

Posted : 05/08/2019 4:29 pm
vintagepc
(@vintagepc)
RE: Finishing a print that failed due to nozzle clog (can one avoid initial z-calibration?)

Depending on the part you may be able to just cut the object in the slicer at the Z height it failed at, print the remaining part by itself with a brim (if needed) and glue it on top of the bottom part. 

Did that just the other day with a similar situation.

Posted : 05/08/2019 5:02 pm
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