How to recover from a stopped mid print

Hello, I was printing a fairly large object. I went out for a short while, when I came back the printer had stopped for about 3 minutes. I don't know how or if I can re-start the print from where it stopped, so I had to re-print the whole thing from the beginning. What a waste of material and time.
For future reference, how do I do that? (re-start from where it left off.) I think someone in the house open the window next to the printer caused a sudden temperature drop, thus the printer stopped. I use Marlin and pronterface on a purse i3.

Edited 2 time(s). Last edit at 03/02/2018 03:12PM by rich1812.

You can measure the height and the head position at which the print stopped. Then take a copy of the GCode file and strip out from the start of the file all the GCodes up to the point at which the print stopped. You can get most of the way there by looking for the G1 Z commands that move the head up to each new layer, or for the new layer comments if your slicer generated them. Having found the start of the correct layer (G1 Znn where nn is the height of the top of the last complete layer plus the layer height), work out how which GCode commands for that layer it printed before it stopped, and remove those too.

Finally, if you sliced the file using absolute extrusion coordinates, you need to insert a G92 Enn command , where nn is the E value on the last G1 command you removed.

You now have a file that you can print, provided that you first home X and Y, preheat the extruder and bed, turn on any print cooling fans that you need, set the print head at the correct height, and send G92 to tell the firmware what height it is at.

If all that sounds difficult and tedious (it is), next time use Duet electronics and RepRapFirmware. It saves a resume file on the SD card automatically when the print paused for any reason, including a pause due to a heater fault.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Yes the resume in RRF is great. However it might be as easy to remove the part completed model from the bed. File off the top layer so its flat. Measure the height you reached then reslice the model cutting it so that you print the bit that did not complete. Now bond them together.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

Thans for the reply.
Sounds complicated. I read about measuring the height etc. I was hoping for a easier way out. I am lazy. I guess there isn't a easier "magic". I will give Duet electronics a try.