3D printers are the staple for quick and cheap prototyping nowadays. I am one of those fortunate enough to own a 3D printer, courtesy of an Instructables contest.
There are still a lot of improvements to be made with 3d printing technology. One such improvement is having non-volatile memory such that a 3d printing job can be resumed after it is accidentally turned off or if the SD card is accidentally removed.
Whether it is caused by a sudden power outage or a rude roommate, we would always have to restart a 3d print from scratch (even if it is 90% finish, sadly) and this is especially annoying for long or difficult prints.
Step 1: Tape Down the 3d Print
Once the build plate has cooled down, the object has little to no adhesion to the build plate anymore. So if you're not fortunate to catch the print shut off while the plate is still warm, we need to ensure the print job doesn't move. Take a generous amount of tape and tape off the brim of your 3d print to the build plate.
Step 2: Measure the Printed Height
To resume our print to where it was, we need to find out where it stopped. There's two ways of knowing this and I'm sure you're only ever going to do it one of the ways.
(1) Measure the height with a measuring tape and find the height in mm.
(2) if you're a masochist, you will count every single layer printed. It is visible to the human eye, just very tedious and long to do. It's not worth it, trust me.
Step 3: Convert Height to Number of Layers
Now, since I trust that none of you actually counted the individual layers, we're just going to employ a neat technique to find the number of layers. Back to junior high math class:
"The printed height is 35mm. The height of each layer is 0.15mm per layer. How many layers are printed?"
(Answer is 233 layers)
You can find the height of each layer in the print setting you have for the gcode. By default the unit is mm per layer.
Step 4: Slicing Your Prints Manually
First, let's verify that the layer height is indeed at 233 layers when it stopped. Open your slicer, mine is Cura and switch to layer view and view everything up to the 233th layer. If it looks the same as what you have physically then it's probably right or around that height. It's hard to tell precisely since you're only getting a resolution to 1mm which is around 7 layers.
Then open the gcode in a text editor. Don't use notepad. I use sublime text since I have it around for coding. You can also use notepad++. Delete the lines in between ;layer:0 and ;layer:233. It's a huge file so it might take a while to traverse. Save the new file with a new file name just in case we overshoot and want some old deleted layers printed.
Then as a final sanity check, open up the new gcode in your slicer and view the free floating print
Step 5: Rinse. Wash. Repeat
If your layer height estimate isn't fully accurate you're gonna see it printing in mid air or colliding with old layers. Immediately abort the print and change the gcode file accordingly (by adding or subtracting layers) until you get just the write amount.
Good luck hitting the Goldilocks zone!