Tutorial: Recover and restart a failed print.

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satoer
Posts: 436
Joined: Mon Oct 01, 2012 8:00 pm
Location: Netherlands

Tutorial: Recover and restart a failed print.

Post by satoer »

Don’t you just hate it, after a really long print the software crashes or the nozzle gets clogged before the print has finished? A waste of time and filament.
Well after several failed prints I have found a solution to restart the print from the point it has been failed. I’m sure I’m not the only one here so I thought I shared my experience with you guy’s.

There are several reasons a print can fail, some are easy to recover some needs some adjusting and calculations.
Before you start a print job, save the G-code. If Repetier host crashes you won’t be able to recover without the G-code. So if you’re planning to start a really long print, save the G-code.

If you need to recover from a software crash or some kind of USB connection loss, you need to home the extruder again. So, it’s advisable to slice the object in a way that it’s not below the aluminum X-beam in the home position(you can move the 3D object with the right mouse button). This way the partially printed object won’t get hit. If you need to recover from a extruder failure like a clogged extruder you don’t have to home the extruder again.

So in case of a software crash you need home the extruder. Repetier host is pretty stable in my experience, but I’ve had a crash when I was scrolling through the virtual layers from a complex high polygon model while printing it. If it crashes, the software probably hangs and won’t respond to mouse clicks. But you still have the ability to read the last layer that it’s been working on before the crash. Write that down and quickly terminate and restart Repetier host. Reconnect and heat the print bed before it cools down too much. Now home the X axis. After that home the Y axis. Now you need to home the Z axis, but before you do this, inspect the printer carefully that it won’t hit the partially printed object with a printer part if you home it. If it has no clearance to home the extruder’s Z axis, you’re fucked and need to print the whole print again.

If you’re able to home the Z, you are in luck. Home the Z and after that move the Z axis/extruder above the printed object. This is very important!

Now we have to calculate the layer height that the printer has to restart from. If you’re able to write down the layer it was working on before the crash its easy: [Layer height] x [last layer] so if you’re layer height is 0,15mm and the last layer it’s been working on was 351 the calculated layer height is 0,15 x 351 = 52,65
If you need to recover from a extruder failure it’s a bit more work. Press the stop button, and immediately heat the print bed again (before its cools down). Never restart repertier host! Or you have to re-home again.

After that you need to get the extruder unclogged without removing the hot end from the extruder carriage. Otherwise after reassembling it won’t align exactly in its original position. So if you manage to unclog the extruder you’re good to go. If you accidentally push the extruder trough the steps, re-home the X axis. There probably a lot of unprinted layers below the printed object. So you need the move the extruder (with the software arrows in repertier host!) carefully down until it almost hits the last printed layer (extreme little space between the extruder and printed object). You can read the Z position above the Z control arrows. This is the layer height you need to restart from.

Now you need to edit the G code. Open the G code in a word processor. Don’t use the G code editor from Repetier host, because it sucks to remove a large amount of G code with that program.

Search for a large amount of lines where the Z is as close to the calculated or measured Z as possible. Ignore the lines where sometimes the desired Z height is mentioned. These are probably hops.

Example:
Image

Now search back to the first “M101” code before the lines with Z(line height). This is the code for the new layer. Now you have to delete all the G-code above that: Move the cursor before the “M101” and press [SHIFT] + [CTRL] + [HOME] this will select everything above the “M101” ( in a word processor, this won’t work in Repetier host) with the selection press [DEL] now save the G-code and load it in repetier host. Heat the extruder and slide the speed slider all the way back to the slowest setting. Extrude some fillament to get the nozzle filled. Make sure the extruder is heigher than the printed object!

Now put some good luck charms on and around your printer, praise the lord Reprap almighty and put your fingers crossed. Press the play button. Hold your hand on the USB cable ready to pull it out if something goes wrong.

Now the printer restarts the print from the point it has been failed. After several layers you can turn the speed up again. It probably needs some post processing afterwards because I think it’s almost impossible to create an invisible seam since you don’t know the exact point of failure in the Gcode. Better this than redo the whole print!
Last edited by satoer on Tue Jun 11, 2013 3:36 pm, edited 1 time in total.
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TyRGeN
Posts: 13
Joined: Thu Nov 01, 2012 4:06 pm

Post by TyRGeN »

Thanks satoer once again an excellent advice !

killejano
Posts: 92
Joined: Mon Apr 01, 2013 7:23 pm

Post by killejano »

I found out an easy way of getting closer to the right spot. Outer loops are allways at a lower feed rate so look for the feed rate after you have found the right layer. First there's a slow feedrate for outer loops then a M103 in between and the other loops and yet again a M103 in between the inner loops and infill. If your print stopped at mid infill just pick a spot somewhere in the infill to begin. Just delete all the above code.

And remember you can home z anywhere on the table. x and y don't have to be home while homing z so there should be room allmost allways to do this.

satoer
Posts: 436
Joined: Mon Oct 01, 2012 8:00 pm
Location: Netherlands

Post by satoer »

And remember you can home z anywhere on the table. x and y don't have to be home while homing z so there should be room allmost allways to do this.
Yes, why didn't I think of that. Of course.
My Felix 1.5 printed designs on Thingiverse
E3D V6 Hot end upgrade for your Felix
Tweezer bracket for your Felix
Led bar upgrade for your Felix

Makron
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Joined: Wed Mar 20, 2013 1:29 pm

Post by Makron »

Hail SATOER !!!

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