Your filament jammed. There are several reasons why this might happen but it’s hard to know the actual cause without a lot more information.
Do you know what sort of material was being used to print?
Cura LulzBot Edition has a set of recommended profile settings for materials that they have profiled on their printers. This is usually a good “starting point” … but I usually find even these benefit with a bit of tweaking.
There is a “hobb” gear on the print-head … this is the thing that feeds the filament into the extruder. There is an adjustable (sprint-tensioned) “idler arm” that applies pressure on the filament to keep it snug against that hobb gear to help it feed.
If that is too tight… it can chew up filament. If it’s too loose… the filament will slip. I typically set mine to roughly 1/3rd of the tension possible (anything close to around 1/2 tension is probably ok).
Next up is temperature. When you use the Cura software it needs to know what type of filament is being used. This matches the filament to a printing profile meant for that filament type. It is how it knows what temperatures to use for the print nozzle (as well as several other things). If the filament wasn’t warm enough, it wont want to extrude easily and can jam.
Next up are “retractions” and this one is often to blame. I’ll try to explain what this means…
The filament feeding into the print-head is cold and solid. It is pushed into the “hot end” where it heats to printing temperate and takes on the gooey liquid state. As the machine is printing (laying down filament) is continues to push filament into the hot end and extrudes it. But what happens when it gets to the end of that printed segment and needs to move to some other area of the part to continue printing? If it were to just “move” without doing anything… that soft gooey-liquid filament would continue to ooze out of the nozzle during the non-printing move. This results in “stringing” (very fine filaments – almost like spider-web – are left behind). To reduce this stringing & oozing, the printer “retracts” by running the hobb gear backward a short distance. The purpose of this is to relieve pressure so that the filament wont continue to ooze.
When I print PLA (probably the easiest type of material to use), I find the retractions should be just 1mm … or maybe 1.5mm.
If you set retraction values in Cura to be too high, two things happen…
- You can end up pulling air into the extruder (which wont damage anything) but that air heats up. As it heats up it expands. So when you start to print again, it can create a bubble which “pops” and it ends up spitting out a bit of filament. Again… no harm is done to the printer, but it doesn’t leave a very nice finish on your part.
- If your part has lots of short segments that results in frequent retractions, the hobb gear ends up moving back and forth over the same short bit of cold filament so many times that the gear starts tearing up the filament. It gouges a wear-mark in the side of the filament and gets stuck… and now you have a filament jam.
Check the teeth in the hobb gear and make sure they are clean. The cold filament wont stick to the teeth… so a few puffs from a can of compressed air will easily clean them. But if those teeth are jammed with filament then the hobb gear wont grip the filament and it will start slipping.
How to check Retraction settings:
When you are on the “Prepare” panel of Cura LulzBot Edition (along the top you’ll see a the words “Prepare” and “Monitor”) the right side of the prepare window has the filament and print settings. Make sure “Print Setup” is using “Custom” (not “Recommended”) because if you use Recommended then all the settings are hidden from view.
In the “Custom” view, scroll down to the section that says “Material” and this is where you can see the retraction setting. The setting you care about is “Retraction Distance” (for PLA that should be less than 2mm … and I usually find that 1mm works best on my printers).
The value below that is “Maximum Retraction Count”. For some strange reason most of my profiles have this default to “99” (which is a terrible idea). I set it to 10 (and I reduce it even more if I have problems). There is one more value called the “Minimum Extrusion Distance Window” and for me that default to 2mm.
What it means:
If my “minimum extrusion distance window” is set to 2 and my “maximum retraction count” is set to 10, then it means the printer is counting how many times the print job orders a retraction over any given “2mm” long length of cold filament (this is before it goes into the hot-end). If the hobb gear has to run over that same bit of filament MORE than 10 times… then any additional retractions will simply be ignored. (Because excessive retractions will chew up the side of the filament and result in a jam). Setting this value to the default of 99 is … lunacy (if your hobb gear grinds over the same short length of filament 99 times… you will surely have a jam). Just occasionally I’ll print a problematic material that is particular soft (PVA is like this) and even 10 is too much.