another option, which i've done before, is to first remove the partial print from the bed.. sounds counter intuitive, i know. then measure the thickness of it with some calipers and figure out the height, and use the 'sink into bed' feature in Cura and drip it down that far. slice the model and give the print a go. the print should start off at about where you left off and finish cleanly. once it finishes, use some gorilla glue or something similar to glue the two parts together and clamp it down if you can.
one thing you can do here, if you'd like to make sure it's as close of a match as possible, is after it's printed about 5 layers or so, stop the print and remove it from the bed (be sure to let it cool as to not warp it). line it up and see if you've chosen the right height to start the print at, it should line up closely with your earlier print. if it's too small, decrease the stat layer height, if it's too big, increase it. by stopping it early, you won't waste much extra material by printing it all if you don't match it up just right.
by doing it this way (by not printing directly on the previous print), you can have more control over what comes out and have less of a chance at messing up your previous print, with the compromise of using glue. also, if the previous print stopped in a weird spot on the last layer, it would give you a chance to sand it all down smooth to make clean contact.
i guess another method could be to figure out the height that it printed so far, divide it out by the thickness of the layers, and go into the gcode and remove the entire first section (after the start code) up to that layer. you might need to add some code yourself to be sure you don't run the head into your model, but it should be able to continue roughly where it left off, assuming your measurements are correct. with this method, you'd be dealing with the same kind of mess up chances as gr5's method.
since in that print, you have those two circles in the middle of it, you might be able to locate where they are, model up or import something small and try to line it up there, and start printing there. it might help you to line up the print head to the right height without immediately starting on the edge, where it would be visible. you'd know after a layer or two if you guessed the height correctly, and then either peel off or sand off that one or two layers before actually continuing the print. oh, and remember that if it's still on the bed, you can use the +Z/-Z movements to move the head close to or touching the most recent layer to try to guess the height without calipers.
good luck, be sure to post back as to what worked and how well it turned out!
You can definitely do it. Joris has posted some recommendations recently - I think over on google groups. You should definitely try even if you fail as you will eventually succeed.
The quick explanation is you just cut out most of the gcode and rerun it. The trick is knowing which part to cut out, and also moving the z to the right spot and so on.
I think Joris is one of those who grabs the z coupler and clicks it a few times to adjust the z axis while printing. So if you go a little high you can fix it quickly. But if you go too low you will have trouble.
Personally I would home the z, then move the Z up and up until it is the right height. I would turn off steppers and check the height carefully and then when I think I know the right height within .2mm I would know where to edit the gcode. I would add a gcode to move the bed lower than when you stopped so that when it moves to the start of the print it doesn't bump your print.
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